Apr. 14, 2025
Performance: 1/5
Teao Product Page
Difficulty of Installation: 1/5
Overall Value: 2.5/5
Materials
Our ResoNix Stage-1 sound deadening door kit is very straightforward and would be what your average layman thinks sound deadening a door involves. So, a door is typically made out of 3 layers. The outer skin, the inner skin, and the door panel. The outer skin and door panel are the most important, so this is what we are going to focus on for the Stage-1 door treatment recommendation. First, I recommend treating the small gap between the outer door skin and the crash bar with butyl rope. This will help provide extra stability to the outer door skin for minim cost and effort.
Next up, how much sound deadener to use on your door? I recommend utilizing 3.5, maybe 4 square feet of ResoNix CLD Squares on the outer door skin. Once the outer door skin is treated, it is time to seal up the inner door skin access holes. For the Stage-2 recommendation, how much sound deadening to use on the inner skin isn’t really on the table. Our Stage-1 kit doesn’t include the appropriate material to do this (CLD is only okay to seal up holes with if they are smaller and non-service points. Larger access holes are not to be sealed with CLD). You can use ABS, PVC, etc, but this portion is on you if you are only going with our Stage-1 kit. If using a PVC plastic or other semi-rigid material to seal up these holes, it is suggested to apply some ResoNix CLD onto the center of the access hole covers.
Next up is the door panel itself. Door panels are typically very flimsy and resonant. That said, this area is LESS important if you are only doing this for regular driving situations, so how much sound deadening to use on your door panel will vary depending on your exact use and goal. When doing a Stage-1 application, only apply CLD to the very large/flat pieces of the door. For sound system installations, this is just as, if not more important than the outer door skin, so plan this out well to get the most out of the limited materials you have. Treat the large flat areas with most priority, but be sure to focus on areas around the speaker, as well as any areas of the panel that are multiple overlapping layers that can rattle/buzz against each other.
Before you go over those seams with CLD, treat the gaps with ResoNix Butyl rope to decouple the layers from one another to prevent them from rattling against one another. Remember, larger single pieces are much more effective than multiple small pieces. Do not waste your time/material on pieces that are smaller than say 12 square inches or less when doing a Stage-1 installation. Once this is complete, you can then apply the ResoNix CCF Strips to the outer perimeter of the speakers if you are doing a sound system upgrade. If you are just doing this for general driving purposes, you can skip this unless you want to improve your stock sound system.
Our Stage-1 door treatment will definitely yield a good improvement, but will most likely not be satisfactory for the more die-hard enthusiasts. It is quick and easy to do. Do to being relatively inexpensive, quick, and offering a decent improvement, I’d say it is a relatively okay value. Me personally, I suggest doing our Stage-2 at minimum considering I HIGHLY suggest doing this once, and doing it right. The more you disassemble your car, the more you diminish its integrity.
Performance: 3/5
Difficulty of Installation: 2/5
Overall Value: 5/5
Materials
Our ResoNix Stage-2 Door Sound Deadening Kit is very straightforward. A door is typically made out of 3 layers. The outer skin, the inner skin, and the door panel. The outer skin and door panel are the most important, so this is what we are mostly going to focus on for the Stage-2 door treatment recommendation. How much sound deadening, acoustic absorbers, and how much should you use for our Stage 2 recommendation?
First, I recommend treating the small gap between the outer door skin and the crash bar with butyl rope. This will help provide extra stability to the outer door skin for minimal cost and effort. Next up, I recommend at least 50%, but preferably more coverage of CLD on the outer door skin. If you are ONLY applying sound treatment for the sake of quieting down your car, you may start approaching diminishing returns at around 30% coverage, but for a sound system, this “25%-rule” goes out the window due to the excess pressure in the door from the speakers. Remember, larger singular pieces perform better than multiple smaller pieces.
Once the outer door skin is treated, it is time to seal up the inner door skin access holes. For the Stage-2 recommendation, how much sound deadener to use on the inner skin isn’t really on the table. Our Stage-2 kit doesn’t include the appropriate material to do this (CLD is only okay to seal up holes with if they are smaller and non-service points. Larger access holes are not to be sealed with CLD). You can use ABS, PVC, etc, but this portion is on you if you are only going with our Stage-2 kit. If using a plastic or other rigid material to seal up these holes, it is suggested to apply ResoNix CLD onto the access hole covers.
Next up is the door panel itself. Door panels are typically very flimsy and resonant. That said, this area is LESS important if you are only doing this for regular driving situations. In these cases, only apply CLD to the very large/flat pieces of the door, and you will want to more so focus on the outer door skin. For sound system installations, this is just as, if not more important than the outer door skin. Treat the large flat areas with most priority, but be sure to focus on areas around the speaker, as well as any areas of the panel that are multiple overlapping layers that can rattle/buzz against each other.
Before you go over those seams with CLD, treat the gaps with ResoNix Butyl rope to decouple the layers from one another to prevent them from rattling against one another. Once the CLD application is finished, apply full coverage of ResoNix Fiber Mat to the door panel. Be careful to leave screw holes open and unobstructed. Once this is complete, you can then apply the ResoNix CCF Strips to the outer perimeter of the speakers if you are doing a sound system upgrade. If you are just doing this for general driving purposes, you can skip this unless you want to improve your stock sound system.
Optional Upgrade: Add a box of ResoNix Lockout sound absorbing material, or even its big brother, ResoNix Guardian, and apply this over the ResoNix CLD Squares sound deadening material that you installed onto the outer door skin inside of the door cavity. This will help absorb the rear wave of the door-mounted midbass driver and lower distortion from resonance, as well as absorb outside noise that is entering the vehicle.
Performance: 4/5
Difficulty of Installation: 3/5
Overall Value: 3.5/5
Materials
Our ResoNix Stage-3 Door Sound Deadening Kit is very similar to our Stage-2 suggested kit. The main difference is the addition of more CLD coverage, but also the upgrade from the original ResoNix CLD Squares, up to the ResoNix Mega CLD Squares for better performance on outer door skins, flat sections of door panels, and on block-off plates. The next difference is the addition of ResoNix Guardian applied on top of the CLD that is inside of the door cavity on the outer door skin.
The Stage-3 suggested sound deadeing kit for doors is very straightforward. A door is typically made out of 3 layers. The outer skin, the inner skin, and the door panel. The outer skin and door panel are the most important, so this is what we are mostly going to focus on for the Stage-3 door treatment recommendation. First, I recommend treating the small gap between the outer door skin and the crash bar with butyl rope. This will help provide extra stability to the outer door skin for minim cost and effort.
Next up for the Stage-3 suggested kit, 80% or more coverage of ResoNix Mega CLD Squares on the outer door skin. Remember, larger pieces perform better than multiple smaller pieces. Next up, installing the ResoNix Guardian on top of the CLD on the outer skin. Use 3 square feet, or up to 100% coverage per door. More coverage is better, and focus on the area directly behind the speaker first and work your way out.
Once the outer door skin is treated, it is time to seal up the inner door skin access holes. Our Stage-3 kit doesn’t include the appropriate material to do the actual sealing of the access holes. CLD is only okay to seal up holes with if they are smaller and non-service points. Larger access holes are not to be sealed with CLD. You can use ABS, PVC, etc, but this portion is on you if you are only going with our Stage-3 suggested kit. If using a plastic or other rigid material to seal up these holes, it is suggested to apply ResoNix CLD onto the access hole covers. How much sound deadening to use on the access hole block-off plates depends on how resonant they are. I typically just do 100% coverage.
For our Stage-3 suggested kit, go for full coverage, and spot treat any areas you may deem important on the inner door skin. No need for 100% coverage with this suggested kit on the inner door skin. It is also important to use a gasketing material on your block-off plates (and speaker baffles if applicable) as this will help fully seal off the block-off plates. I would suggest using ResoNix CCF Decoupler 7 or CCF Decoupler 3F or 3S for this the block-off plate and speaker baffle sealing to the inner door skin. If you have other places to use CCF7, that’s what I would suggest. I personally use CCF Decoupler 7 for block off plates and backside of speaker baffles where they meet the inner door skin, and CCF3S and/or CCF3F as a speaker mounting gasket.
Next up is the door panel itself. Door panels are typically very flimsy and resonant. This area is just as, if not more important than the outer door skin. Treat the large flat areas with CLD with most priority, but be sure to also put special focus on areas around the speaker, as well as any areas of the panel that are multiple overlapping layers that can rattle/buzz against each other. On the materials list for the Stage-3 suggested kit, we have 10 ResoNix CLD Squares listed to accompany the 20 ResoNix Mega CLD Squares. This is for installation on the door panel ONLY IF the door panel would be too difficult to install the ResoNix Mega CLD Squares due to stiffness of the aluminum constraining layer.
Before you go over those seams with CLD, treat the gaps with ResoNix Butyl rope to decouple the layers from one another to prevent them from rattling against one another. For a Stage-3 installation, I typically end up with about 50% coverage on a typical door panel. That said, door panels vary drastically. Some will require and be able to have 100% coverage easily installed. Others will be difficult to do more than 25% due to the construction of the door panel.
Once this is done, go over all clips and other small areas and treat with ResoNix Butyl Rope to prevent these small pieces from rattling and buzzing. Once the CLD application is finished, apply full coverage of ResoNix Fiber Mat to the door panel. If Fiber Mat 45 fits without too much compression, use it. If it’s too tight of a fit, use Fiber Mat 25. Be careful to leave screw holes open and unobstructed. Once this is complete, you can then apply the ResoNix CCF Strips to the outer perimeter of the speakers if you are doing a sound system upgrade. If you are just doing this for general driving purposes, you can skip this unless you want to improve your stock sound system.
Performance: 4.5/5
Difficulty of Installation: 3.5/5
Overall Value: 3/5
Materials
The ResoNix Stage-4 Door Sound Deadening Kit is pretty much identical to Stage-3, but with a couple of extra easy steps. The main difference is we are suggesting the addition of the ResoNix CCF Decoupler 3S, ResoNix CCF Decoupler 3F, and the ResoNix Barrier. The CCF Decoupler 3S will be used to help even further isolate small parts of a door to prevent rattles and buzzes. This can be used on door handles, door light housings, clips, wire harnesses, and more. The CCF Decoupler 3F will help with gasketing on the speaker baffle, and other areas that need structure while still being decoupled.
The ResoNix Barrier will be used to create custom block-off plates to seal the inner door skin access holes. In most situations, it is better than using typical 1/8” ABS plastic as it will resonate less since you can give it shape and structure and the material is naturally inert. If you can use 3/8” ABS, PVC, or Acrylic, that in conjunction with CLD will be better, but it is very rare to be able to fit that on the inner door skin of modern car doors without preventing proper installation of the door panel. So, if your door can fit that and you have the tools to make the block off plates properly, use that instead of the ResoNix Barrier, unless you value the time savings that using the ResoNix Barrier will net you. Typically, it takes me about 20 minutes per 2 doors to do block off plates with ResoNix Barrier. With thicker plastic, it takes about 2 hours for the two doors for various reasons such as needing to make the shape perfect for fitment, applying more material, creating a seal, drilling holes, etc.
If you have an inner door skin with a 3-dimensional shape to it, it becomes even more difficult to do with plastic since you have to heat mold it. This is where ResoNix Barrier REALLY comes in handy. With ResoNix Barrier, all you have to do is trace out the shape, cut it out with heavy duty scissors, drill your holes, use riv-nuts if that’s your style (I personally do) and install it. Shape and trim the material if need be.
Also, I suggest going full coverage Of ResoNix Mega CLD Squares on the outer door skin, and as much coverage as possible with whatever version of CLD Squares you can get away with on the door panel. Another tip, at this level you should be really trying to fill out the inside of your door panel with as much ResoNix Fiber Mat as possible. Having pockets of air is performance left on the table.
Stage-1
Performance: 2.5/5 without sunroof, 1.5/5 with sunroof
Difficulty of Installation: 2/5
Overall Value: 3.5/5 without sunroof, 2/5 with sunroof
Materials
Our ResoNix Stage-1 sound deadening kit for roofs is also very straightforward and would be what your average layman thinks sound deadening a roof would involve. Roofs are typically much more straight forward than doors as you only need to worry about the roof skin and its support beams as opposed to 3 or more layers like a door. The Stage-1 recommended kit will achieve two things. First, it will help improve transient response from low frequencies being produced from your sound system, and it will also help reduce resonance from driving. It’ll also drastically lessen the intensity from rain impacting your roof. All of these differences will be very obvious in most vehicles. As mentioned, it’ll be more drastic in cars without sunroofs, but still noticeable in cars that feature a window overhead.
First step is to drop the headliner. Most vehicles only require you to remove the A/B/C Pillars, grab handles, sun visors, overhead lights, and any overhead consoles in order to do this. Once it is dropped, you should be able to complete your work without even needing to completely remove the headliner from the interior, which can get tricky in some vehicles without creasing it.
Once the headliner is dropped, use the ResoNix Butyl Rope to help bridge the gap between parts of the roof skins support beams and the roof skin itself. This will help stabilize the roof skin. Up next, apply ResoNix CLD Squares. When not doing full coverage, it is important to space pieces out evenly, starting application from the center of the resonant panel, in this case, the roof skin. Remember, larger pieces are much more effective than multiple smaller pieces.
Tip: Put the edge of the CLD just a hair over the roof support beams. This will further utilize the supports to help stabilize the roof skin. Do not fully cover them. Just overlapping by 3/4″ is fine.
Optional Upgrade: Use ResoNix Mega CLD Squares sound deadening material instead of the original CLD Squares to get even better resonance control performance on the roof.
Performance: 3.5/5 without sunroof, 2/5 with sunroof
Difficulty of Installation: 2.5/5
Overall Value: 4.5/5 without sunroof, 2.5/5 with sunroof
Materials
Our ResoNix Stage-3 sound deadening kit for roofs only changes one thing from Stage-2 for a roof installation. The application of more CLD Squares to target 80% or more coverage is the only difference. The additional CLD Squares will help further reduce resonance of the roof skin. The higher coverage is going to be especially beneficial in sound system installations where the “25% coverage rule” goes out the window since there are outside forces acting on the panels instead of just typical mechanical energy transfer from normal driving.
The addition of ResoNix Fiber Mat takes this install to the next level since it introduces sound absorption (and even thermal insulation) into the mix, AND can even provide further stability for the roof skin. Wind noise generated overhead is typically over 250Hz. ResoNix Fiber Mat does an excellent job at absorbing these frequencies, so a large majority of noise that you hear from overhead will be absorbed before it even reaches you. For sound absorption purposes, you want the thickest material possible without compressing it too much, or ideally not compressing it at all. If you can fit Fiber Mat 45 without compressing it more than 30%, go for it. In my experience, almost all headliners can be installed very easily with Fiber Mat 45 installed.
How much sound deadening and sound absorber should you use if you have a sunroof? If you have a car with a sunroof, especially one that is large relative to the size of the roof, just do your best. Get the most coverage you can without impeding the function of the sunroof and its parts. Stage-3 is as far as I would recommend going. Anything more than that is probably a waste. Thankfully, glass does much better than thin sheet metal at blocking sound and being non-resonant, so you have that going for you.
Performance: 1/5 for most modern sedans, 3/5 for older vehicles, and 2/5 for some larger modern trucks (F150, Silverado, etc)
Difficulty of Installation: 2/5
Overall Value: 1/5 for most modern sedans, 2/5 for older vehicles, and 2/5 for some larger modern trucks (F150, Silverado, etc)
Materials
Our ResoNix Stage-1 suggested sound deadening kit for floors is in my opinion, not really worth it in MOST vehicles considering the amount of work it will require. In some older vehicles or vehicles like Jeep Wranglers, it may be much easier and more beneficial. But the amount of work required relative to the performance makes this a low value. If your car is already stripped for one reason or the other, than this is quick and easy. But starting with a completed and assembled interior of a vehicle will make this a lot of work for a small benefit.
So, how much sound deadener for our Stage-1 floor recommendation? The Stage-1 suggested kit is just 25-30% coverage of ResoNix CLD Squares sound deadening on the floor. This will help more on older vehicles and trucks with flat floors since they have less strength and rigidity in the floor pans vs modern sedans. This will help a bit with drone, which is usually caused by exhaust and road noise exciting the floor pans and causing them to resonate. This will help handle that. Remember, larger pieces will perform better than multiple smaller pieces, and focus on the flat areas that are resonant. Not the strong areas that have support from dips, curves, bends, or bumps.
Optional Upgrade: Switch to ResoNix Mega CLD Squares sound deadening material for even better performance.
Performance: 2.5/5 for most modern sedans, 4/5 for older vehicles, and 3.5/5 for some larger modern trucks (F150, Silverado, etc)
Difficulty of Installation: 2.5/5
Overall Value: 2.5/5 for most modern sedans, 4/5 for older vehicles, and 4/5 for some larger modern trucks (F150, Silverado, etc)
Materials
Our ResoNix Stage-2 suggested sound deadening kit for floors is a pretty large leap in performance and product amount. But there is not much point in doing anything in between what Stage-1 is, and what this Stage-2 recommendation is. Just like in the Stage-1 recommendation, we are going to start with ResoNix CLD Squares sound deadener material. This time, we are going to do a minimum of 50% coverage, but aim for 75% coverage or more if possible. How much coverage I suggest will really depend on how resonant your floor is. The larger/flatter the floor is, the more coverage I recommend. Remember, focus on the large flat areas more than the structured areas, and use larger single pieces as opposed to multiple smaller pieces to get the most performance.
From here, we are going to apply ResoNix Fiber Mat. Most vehicles will require Fiber Mat 25 under the carpet in order to fit the carpet back in, especially modern sedans, but some may be able to fit the Fiber Mat 45, which will perform much better if it can indeed fit. If it doesn’t fit, don’t sweat it and stick with Fiber Mat 25. In most cases, you will be sticking this on top of the CLD directly, and preferably with 100% coverage. Be sure to not cover any wires, modules, mounting holes/posts, or anything else that may require service in the future.
If you are not doing 100% coverage, focus on areas that are closest to the source of the noises you are hearing. Transmission tunnels, rear seat areas, rear floors in trucks with loud exhaust, etc. If your vehicle features a carpet that has a backing that is hard, you can stick the Fiber Mat directly to the back of the carpet if you desire, which will leave the floor fully and easily serviceable in the future.
Optional Upgrade: Switch to ResoNix Mega CLD Squares sound deadening material for even better performance.
Performance: 0.5/5 for modern vehicles, 2.5/5 for vintage vehicles
Difficulty of Installation: 1/5 once access is gained to the firewall. Gaining access to the firewall will vary drastically in difficulty from vehicle to vehicle.
Overall Value: 0.5/5 for most modern vehicles. 2/5 for most vintage vehicles.
Materials
Our Stage-1 recommendation for firewall and hood treatment focuses on the basics to provide a noticeable improvement in noise reduction and thermal insulation with minimal effort and cost. Please note, the Stage-1 suggestions for the Hood & Firewall are not very effective to where I personally would find it worth it for a modern vehicle. For vintage vehicles, this is a different story since they have hoods and firewalls that are not nearly as structural and insulating, and a Stage-1 installation can still yield noticeable results.
Starting with the interior side of the firewall, apply ResoNix CLD Squares to cover approximately 50% of the surface area. Focus on large, flat sections for maximum effectiveness. If you’re up for an extra step, you can also treat the engine side of the firewall, although this is optional at this stage.
For the underside of the hood, remove the OEM hood liner carefully to expose the metal surface. Apply ResoNix CLD Squares to cover about 50% of the area, again concentrating on the larger, flatter sections. Once installed, replace the OEM hood liner. This application will help dampen resonance and help reduce some engine noise transmitted through the hood.
The optional upgrade to ResoNix Mega CLD Squares offers superior damping performance due to its thicker constraining layer and higher mass. If you desire greater noise reduction and are willing to invest a bit more, this upgrade is worthwhile.
Performance: 2.5/5 for modern vehicles, 3.5/5 for vintage vehicles.
Difficulty of Installation: 2/5 once you have access to the firewall.
Overall Value: 3/5 for modern vehicles, 4/5 for vintage vehicles.
Materials
Our Stage-2 recommendation builds upon Stage-1 by adding sound-absorbing and thermal-insulating layers to both the firewall and hood. This stage offers noticeable improvements, especially for vintage vehicles with less factory insulation. For modern vehicles, while the benefits may be more subtle, those seeking a quieter and cooler cabin will still appreciate the enhancements. To me, this is where the juice starts becoming worth the squeeze for modern vehicles. (I have had many customers reach out after doing this treatment on modern vehicles and were very happy with the end results).
Firewall (Interior Side):
Begin by applying 50% coverage of ResoNix CLD Squares to the interior side of the firewall, focusing on large, flat areas prone to vibration. Next, apply a full 100% coverage layer of ResoNix Fiber Mat over the CLD-treated areas. The Fiber Mat serves as an excellent sound absorber and thermal insulator, reducing airborne engine noise and heat transfer into the cabin.
Firewall (Engine Side):
This will be easier and much more worthwhile on vintage vehicles. Not so worth while on modern vehicles. On the engine side of the firewall, apply 50–100% coverage of ResoNix CLD Squares, depending on accessibility and desired performance. Follow this with a 100% coverage layer of ResoNix Fiber Mat Silver, which is designed to withstand the harsh conditions of the engine bay while providing sound absorption, thermal insulation, and a radiant heat barrier layer. A radiant heat barrier is different and separate from a thermal insulator in that it primarily reflects radiant heat rather than absorbing and slowing down conductive heat transfer, which is the function of a thermal insulator.
Hood:
Remove the OEM hood liner to expose the underside of the hood. Apply 50–100% coverage of ResoNix CLD Squares, concentrating on larger, flatter sections for maximum effectiveness. Then, install a full 100% coverage layer of ResoNix Fiber Mat Silver. If there is no OEM hood liner, adding the Fiber Mat Silver is highly recommended to enhance sound absorption and thermal insulation. Reinstall the OEM hood liner if present.
Optional Upgrade:
Upgrading to ResoNix Mega CLD Squares will provide superior damping due to their thicker constraining layer and higher mass, making it a worthwhile investment for those seeking greater noise reduction.
Performance: 3/5 for Modern Vehicles. 4/5 for Vintage Vehicles
Difficulty of Installation: 2.5/5 once you have access to the firewall.
Overall Value: 3.5/5 for modern vehicles with louder engines. 4/5 for vintage vehicles.
Materials
In Stage-3, we take a more comprehensive approach to sound deadening and thermal insulation, suitable for vehicles requiring extensive treatment—particularly vintage models with minimal factory insulation. For modern vehicles, this stage also offers significant improvements for those seeking optimal cabin comfort.
Firewall (Interior Side):
Apply 75–100% coverage of ResoNix Mega CLD Squares to the interior side of the firewall for maximum vibration damping. Follow this with a full 100% coverage layer of ResoNix Fiber Mat to absorb sound and insulate against conductive heat transfer. Then, add a 100% coverage layer of ResoNix Barrier to block any remaining noise and thermal transfer into the cabin. In practice, it is best to do CLD, then Fiber Mat, and then Barrier, but if it is easier to do CLD, then Barrier, then Fiber Mat, it wont be the end of the world.
Firewall (Engine Side):
This step is optional and more beneficial for vintage vehicles. Modern vehicles often have adequate factory insulation on the engine side, making additional treatment less impactful. If you choose to proceed, apply 75–100% coverage of ResoNix Mega CLD Squares on the engine side of the firewall. Then, install a full 100% coverage layer of ResoNix Fiber Mat Silver. The Fiber Mat Silver not only provides sound absorption and thermal insulation but also acts as a radiant heat barrier, reflecting radiant heat away from the cabin.
Hood:
This is only for hoods that are very flat and has plenty of working tolerance to add thick materials, as ResoNix Guardian will not be easy to bend, and is very thick. Optional if you need it to be able to contour to bends easier, swap ResoNix Guardian for ResoNix Lockout.
Remove the OEM hood liner if present to expose the underside of the hood. Apply 75–100% coverage of ResoNix Mega CLD Squares, focusing on large, flat areas for maximum effectiveness. Then, install a full 100% coverage layer of ResoNix Guardian. This material absorbs sound, insulates against heat, and blocks sound, protecting both the hood’s paint and reducing engine heat and sound entering the cabin.
Note: Reinstall the OEM hood liner over the ResoNix materials if possible. While not strictly necessary, it can provide additional protection and insulation.
Performance: 4/5 for Modern Vehicles with louder engines, and 5/5 for Vintage Vehicles
Difficulty of Installation: 3.5/5 once you have access to the firewall
Overall Value: 1.5/5 for modern vehicles, 2.5/5 for vintage vehicles
Materials
In Stage-5, we aim for the ultimate in sound deadening and thermal insulation for your vehicle’s firewall. This level is typically reserved for vintage vehicles undergoing restoration or for enthusiasts seeking the highest level of cabin comfort and noise reduction. For modern vehicles, the marginal gains may not justify the extensive effort and cost, but if you’re striving for perfection, this is the way to achieve it.
Firewall (Interior Side):
Firewall (Engine Side):
This step is optional and primarily recommended for vintage vehicles, as it can be very challenging on modern vehicles due to space constraints and accessibility. If you choose to proceed:
Note: Hood treatments conclude at Stage-3. No further treatments are recommended for the hood in Stage-5.
By following this sequence—CLD, then Guardian (or Lockout), then Fiber Mat, then Barrier—you achieve the most effective combination of vibration damping, sound absorption, thermal insulation, and noise blocking for your vehicle’s firewall.
Installation Considerations:
Applicability to Modern Vehicles:
While Stage-5 provides the highest level of sound deadening and thermal insulation, modern vehicles may not experience substantial benefits over Stage-4 due to existing factory treatments. Carefully consider whether the additional effort and cost align with your desired outcomes.
By investing the time and resources into a Stage-5 firewall treatment, you’re committing to the highest standards of automotive comfort and performance. Whether you’re restoring a vintage classic or enhancing a modern vehicle, this comprehensive approach will provide unmatched reductions in noise and heat, elevating your driving experience to new heights.
Final Thoughts:
By tailoring your sound deadening and thermal insulation efforts to the specific needs of your vehicle, whether it’s a modern model with adequate insulation or a vintage car requiring significant upgrades, you can achieve a quieter, cooler, and more comfortable driving experience. Stage-5 represents the pinnacle of what’s possible, offering the most comprehensive solution for reducing noise and heat in your vehicle.
Performance: 1/5
Difficulty of Installation: 1/5
Overall Value: 2.5/5
Materials
Our ResoNix Stage-1 sound deadening door kit is very straightforward and would be what your average layman thinks sound deadening a door involves. So, a door is typically made out of 3 layers. The outer skin, the inner skin, and the door panel. The outer skin and door panel are the most important, so this is what we are going to focus on for the Stage-1 door treatment recommendation. First, I recommend treating the small gap between the outer door skin and the crash bar with butyl rope. This will help provide extra stability to the outer door skin for minim cost and effort.
Next up, how much sound deadener to use on your door? I recommend utilizing 3.5, maybe 4 square feet of ResoNix CLD Squares on the outer door skin. Once the outer door skin is treated, it is time to seal up the inner door skin access holes. For the Stage-2 recommendation, how much sound deadening to use on the inner skin isn’t really on the table. Our Stage-1 kit doesn’t include the appropriate material to do this (CLD is only okay to seal up holes with if they are smaller and non-service points. Larger access holes are not to be sealed with CLD). You can use ABS, PVC, etc, but this portion is on you if you are only going with our Stage-1 kit. If using a PVC plastic or other semi-rigid material to seal up these holes, it is suggested to apply some ResoNix CLD onto the center of the access hole covers.
Next up is the door panel itself. Door panels are typically very flimsy and resonant. That said, this area is LESS important if you are only doing this for regular driving situations, so how much sound deadening to use on your door panel will vary depending on your exact use and goal. When doing a Stage-1 application, only apply CLD to the very large/flat pieces of the door. For sound system installations, this is just as, if not more important than the outer door skin, so plan this out well to get the most out of the limited materials you have. Treat the large flat areas with most priority, but be sure to focus on areas around the speaker, as well as any areas of the panel that are multiple overlapping layers that can rattle/buzz against each other.
Before you go over those seams with CLD, treat the gaps with ResoNix Butyl rope to decouple the layers from one another to prevent them from rattling against one another. Remember, larger single pieces are much more effective than multiple small pieces. Do not waste your time/material on pieces that are smaller than say 12 square inches or less when doing a Stage-1 installation. Once this is complete, you can then apply the ResoNix CCF Strips to the outer perimeter of the speakers if you are doing a sound system upgrade. If you are just doing this for general driving purposes, you can skip this unless you want to improve your stock sound system.
Our Stage-1 door treatment will definitely yield a good improvement, but will most likely not be satisfactory for the more die-hard enthusiasts. It is quick and easy to do. Do to being relatively inexpensive, quick, and offering a decent improvement, I’d say it is a relatively okay value. Me personally, I suggest doing our Stage-2 at minimum considering I HIGHLY suggest doing this once, and doing it right. The more you disassemble your car, the more you diminish its integrity.
Performance: 3/5
Difficulty of Installation: 2/5
Overall Value: 5/5
Materials
Our ResoNix Stage-2 Door Sound Deadening Kit is very straightforward. A door is typically made out of 3 layers. The outer skin, the inner skin, and the door panel. The outer skin and door panel are the most important, so this is what we are mostly going to focus on for the Stage-2 door treatment recommendation. How much sound deadening, acoustic absorbers, and how much should you use for our Stage 2 recommendation?
First, I recommend treating the small gap between the outer door skin and the crash bar with butyl rope. This will help provide extra stability to the outer door skin for minimal cost and effort. Next up, I recommend at least 50%, but preferably more coverage of CLD on the outer door skin. If you are ONLY applying sound treatment for the sake of quieting down your car, you may start approaching diminishing returns at around 30% coverage, but for a sound system, this “25%-rule” goes out the window due to the excess pressure in the door from the speakers. Remember, larger singular pieces perform better than multiple smaller pieces.
Once the outer door skin is treated, it is time to seal up the inner door skin access holes. For the Stage-2 recommendation, how much sound deadener to use on the inner skin isn’t really on the table. Our Stage-2 kit doesn’t include the appropriate material to do this (CLD is only okay to seal up holes with if they are smaller and non-service points. Larger access holes are not to be sealed with CLD). You can use ABS, PVC, etc, but this portion is on you if you are only going with our Stage-2 kit. If using a plastic or other rigid material to seal up these holes, it is suggested to apply ResoNix CLD onto the access hole covers.
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Next up is the door panel itself. Door panels are typically very flimsy and resonant. That said, this area is LESS important if you are only doing this for regular driving situations. In these cases, only apply CLD to the very large/flat pieces of the door, and you will want to more so focus on the outer door skin. For sound system installations, this is just as, if not more important than the outer door skin. Treat the large flat areas with most priority, but be sure to focus on areas around the speaker, as well as any areas of the panel that are multiple overlapping layers that can rattle/buzz against each other.
Before you go over those seams with CLD, treat the gaps with ResoNix Butyl rope to decouple the layers from one another to prevent them from rattling against one another. Once the CLD application is finished, apply full coverage of ResoNix Fiber Mat to the door panel. Be careful to leave screw holes open and unobstructed. Once this is complete, you can then apply the ResoNix CCF Strips to the outer perimeter of the speakers if you are doing a sound system upgrade. If you are just doing this for general driving purposes, you can skip this unless you want to improve your stock sound system.
Optional Upgrade: Add a box of ResoNix Lockout sound absorbing material, or even its big brother, ResoNix Guardian, and apply this over the ResoNix CLD Squares sound deadening material that you installed onto the outer door skin inside of the door cavity. This will help absorb the rear wave of the door-mounted midbass driver and lower distortion from resonance, as well as absorb outside noise that is entering the vehicle.
Performance: 4/5
Difficulty of Installation: 3/5
Overall Value: 3.5/5
Materials
Our ResoNix Stage-3 Door Sound Deadening Kit is very similar to our Stage-2 suggested kit. The main difference is the addition of more CLD coverage, but also the upgrade from the original ResoNix CLD Squares, up to the ResoNix Mega CLD Squares for better performance on outer door skins, flat sections of door panels, and on block-off plates. The next difference is the addition of ResoNix Guardian applied on top of the CLD that is inside of the door cavity on the outer door skin.
The Stage-3 suggested sound deadeing kit for doors is very straightforward. A door is typically made out of 3 layers. The outer skin, the inner skin, and the door panel. The outer skin and door panel are the most important, so this is what we are mostly going to focus on for the Stage-3 door treatment recommendation. First, I recommend treating the small gap between the outer door skin and the crash bar with butyl rope. This will help provide extra stability to the outer door skin for minim cost and effort.
Next up for the Stage-3 suggested kit, 80% or more coverage of ResoNix Mega CLD Squares on the outer door skin. Remember, larger pieces perform better than multiple smaller pieces. Next up, installing the ResoNix Guardian on top of the CLD on the outer skin. Use 3 square feet, or up to 100% coverage per door. More coverage is better, and focus on the area directly behind the speaker first and work your way out.
Once the outer door skin is treated, it is time to seal up the inner door skin access holes. Our Stage-3 kit doesn’t include the appropriate material to do the actual sealing of the access holes. CLD is only okay to seal up holes with if they are smaller and non-service points. Larger access holes are not to be sealed with CLD. You can use ABS, PVC, etc, but this portion is on you if you are only going with our Stage-3 suggested kit. If using a plastic or other rigid material to seal up these holes, it is suggested to apply ResoNix CLD onto the access hole covers. How much sound deadening to use on the access hole block-off plates depends on how resonant they are. I typically just do 100% coverage.
For our Stage-3 suggested kit, go for full coverage, and spot treat any areas you may deem important on the inner door skin. No need for 100% coverage with this suggested kit on the inner door skin. It is also important to use a gasketing material on your block-off plates (and speaker baffles if applicable) as this will help fully seal off the block-off plates. I would suggest using ResoNix CCF Decoupler 7 or CCF Decoupler 3F or 3S for this the block-off plate and speaker baffle sealing to the inner door skin. If you have other places to use CCF7, that’s what I would suggest. I personally use CCF Decoupler 7 for block off plates and backside of speaker baffles where they meet the inner door skin, and CCF3S and/or CCF3F as a speaker mounting gasket.
Next up is the door panel itself. Door panels are typically very flimsy and resonant. This area is just as, if not more important than the outer door skin. Treat the large flat areas with CLD with most priority, but be sure to also put special focus on areas around the speaker, as well as any areas of the panel that are multiple overlapping layers that can rattle/buzz against each other. On the materials list for the Stage-3 suggested kit, we have 10 ResoNix CLD Squares listed to accompany the 20 ResoNix Mega CLD Squares. This is for installation on the door panel ONLY IF the door panel would be too difficult to install the ResoNix Mega CLD Squares due to stiffness of the aluminum constraining layer.
Before you go over those seams with CLD, treat the gaps with ResoNix Butyl rope to decouple the layers from one another to prevent them from rattling against one another. For a Stage-3 installation, I typically end up with about 50% coverage on a typical door panel. That said, door panels vary drastically. Some will require and be able to have 100% coverage easily installed. Others will be difficult to do more than 25% due to the construction of the door panel.
Once this is done, go over all clips and other small areas and treat with ResoNix Butyl Rope to prevent these small pieces from rattling and buzzing. Once the CLD application is finished, apply full coverage of ResoNix Fiber Mat to the door panel. If Fiber Mat 45 fits without too much compression, use it. If it’s too tight of a fit, use Fiber Mat 25. Be careful to leave screw holes open and unobstructed. Once this is complete, you can then apply the ResoNix CCF Strips to the outer perimeter of the speakers if you are doing a sound system upgrade. If you are just doing this for general driving purposes, you can skip this unless you want to improve your stock sound system.
Performance: 4.5/5
Difficulty of Installation: 3.5/5
Overall Value: 3/5
Materials
The ResoNix Stage-4 Door Sound Deadening Kit is pretty much identical to Stage-3, but with a couple of extra easy steps. The main difference is we are suggesting the addition of the ResoNix CCF Decoupler 3S, ResoNix CCF Decoupler 3F, and the ResoNix Barrier. The CCF Decoupler 3S will be used to help even further isolate small parts of a door to prevent rattles and buzzes. This can be used on door handles, door light housings, clips, wire harnesses, and more. The CCF Decoupler 3F will help with gasketing on the speaker baffle, and other areas that need structure while still being decoupled.
The ResoNix Barrier will be used to create custom block-off plates to seal the inner door skin access holes. In most situations, it is better than using typical 1/8” ABS plastic as it will resonate less since you can give it shape and structure and the material is naturally inert. If you can use 3/8” ABS, PVC, or Acrylic, that in conjunction with CLD will be better, but it is very rare to be able to fit that on the inner door skin of modern car doors without preventing proper installation of the door panel. So, if your door can fit that and you have the tools to make the block off plates properly, use that instead of the ResoNix Barrier, unless you value the time savings that using the ResoNix Barrier will net you. Typically, it takes me about 20 minutes per 2 doors to do block off plates with ResoNix Barrier. With thicker plastic, it takes about 2 hours for the two doors for various reasons such as needing to make the shape perfect for fitment, applying more material, creating a seal, drilling holes, etc.
If you have an inner door skin with a 3-dimensional shape to it, it becomes even more difficult to do with plastic since you have to heat mold it. This is where ResoNix Barrier REALLY comes in handy. With ResoNix Barrier, all you have to do is trace out the shape, cut it out with heavy duty scissors, drill your holes, use riv-nuts if that’s your style (I personally do) and install it. Shape and trim the material if need be.
Also, I suggest going full coverage Of ResoNix Mega CLD Squares on the outer door skin, and as much coverage as possible with whatever version of CLD Squares you can get away with on the door panel. Another tip, at this level you should be really trying to fill out the inside of your door panel with as much ResoNix Fiber Mat as possible. Having pockets of air is performance left on the table.
Stage-1
Performance: 2.5/5 without sunroof, 1.5/5 with sunroof
Difficulty of Installation: 2/5
Overall Value: 3.5/5 without sunroof, 2/5 with sunroof
Materials
Our ResoNix Stage-1 sound deadening kit for roofs is also very straightforward and would be what your average layman thinks sound deadening a roof would involve. Roofs are typically much more straight forward than doors as you only need to worry about the roof skin and its support beams as opposed to 3 or more layers like a door. The Stage-1 recommended kit will achieve two things. First, it will help improve transient response from low frequencies being produced from your sound system, and it will also help reduce resonance from driving. It’ll also drastically lessen the intensity from rain impacting your roof. All of these differences will be very obvious in most vehicles. As mentioned, it’ll be more drastic in cars without sunroofs, but still noticeable in cars that feature a window overhead.
First step is to drop the headliner. Most vehicles only require you to remove the A/B/C Pillars, grab handles, sun visors, overhead lights, and any overhead consoles in order to do this. Once it is dropped, you should be able to complete your work without even needing to completely remove the headliner from the interior, which can get tricky in some vehicles without creasing it.
Once the headliner is dropped, use the ResoNix Butyl Rope to help bridge the gap between parts of the roof skins support beams and the roof skin itself. This will help stabilize the roof skin. Up next, apply ResoNix CLD Squares. When not doing full coverage, it is important to space pieces out evenly, starting application from the center of the resonant panel, in this case, the roof skin. Remember, larger pieces are much more effective than multiple smaller pieces.
Tip: Put the edge of the CLD just a hair over the roof support beams. This will further utilize the supports to help stabilize the roof skin. Do not fully cover them. Just overlapping by 3/4″ is fine.
Optional Upgrade: Use ResoNix Mega CLD Squares sound deadening material instead of the original CLD Squares to get even better resonance control performance on the roof.
Performance: 3.5/5 without sunroof, 2/5 with sunroof
Difficulty of Installation: 2.5/5
Overall Value: 4.5/5 without sunroof, 2.5/5 with sunroof
Materials
Our ResoNix Stage-3 sound deadening kit for roofs only changes one thing from Stage-2 for a roof installation. The application of more CLD Squares to target 80% or more coverage is the only difference. The additional CLD Squares will help further reduce resonance of the roof skin. The higher coverage is going to be especially beneficial in sound system installations where the “25% coverage rule” goes out the window since there are outside forces acting on the panels instead of just typical mechanical energy transfer from normal driving.
The addition of ResoNix Fiber Mat takes this install to the next level since it introduces sound absorption (and even thermal insulation) into the mix, AND can even provide further stability for the roof skin. Wind noise generated overhead is typically over 250Hz. ResoNix Fiber Mat does an excellent job at absorbing these frequencies, so a large majority of noise that you hear from overhead will be absorbed before it even reaches you. For sound absorption purposes, you want the thickest material possible without compressing it too much, or ideally not compressing it at all. If you can fit Fiber Mat 45 without compressing it more than 30%, go for it. In my experience, almost all headliners can be installed very easily with Fiber Mat 45 installed.
How much sound deadening and sound absorber should you use if you have a sunroof? If you have a car with a sunroof, especially one that is large relative to the size of the roof, just do your best. Get the most coverage you can without impeding the function of the sunroof and its parts. Stage-3 is as far as I would recommend going. Anything more than that is probably a waste. Thankfully, glass does much better than thin sheet metal at blocking sound and being non-resonant, so you have that going for you.
Performance: 1/5 for most modern sedans, 3/5 for older vehicles, and 2/5 for some larger modern trucks (F150, Silverado, etc)
Difficulty of Installation: 2/5
Overall Value: 1/5 for most modern sedans, 2/5 for older vehicles, and 2/5 for some larger modern trucks (F150, Silverado, etc)
Materials
Our ResoNix Stage-1 suggested sound deadening kit for floors is in my opinion, not really worth it in MOST vehicles considering the amount of work it will require. In some older vehicles or vehicles like Jeep Wranglers, it may be much easier and more beneficial. But the amount of work required relative to the performance makes this a low value. If your car is already stripped for one reason or the other, than this is quick and easy. But starting with a completed and assembled interior of a vehicle will make this a lot of work for a small benefit.
So, how much sound deadener for our Stage-1 floor recommendation? The Stage-1 suggested kit is just 25-30% coverage of ResoNix CLD Squares sound deadening on the floor. This will help more on older vehicles and trucks with flat floors since they have less strength and rigidity in the floor pans vs modern sedans. This will help a bit with drone, which is usually caused by exhaust and road noise exciting the floor pans and causing them to resonate. This will help handle that. Remember, larger pieces will perform better than multiple smaller pieces, and focus on the flat areas that are resonant. Not the strong areas that have support from dips, curves, bends, or bumps.
Optional Upgrade: Switch to ResoNix Mega CLD Squares sound deadening material for even better performance.
Performance: 2.5/5 for most modern sedans, 4/5 for older vehicles, and 3.5/5 for some larger modern trucks (F150, Silverado, etc)
Difficulty of Installation: 2.5/5
Overall Value: 2.5/5 for most modern sedans, 4/5 for older vehicles, and 4/5 for some larger modern trucks (F150, Silverado, etc)
Materials
Our ResoNix Stage-2 suggested sound deadening kit for floors is a pretty large leap in performance and product amount. But there is not much point in doing anything in between what Stage-1 is, and what this Stage-2 recommendation is. Just like in the Stage-1 recommendation, we are going to start with ResoNix CLD Squares sound deadener material. This time, we are going to do a minimum of 50% coverage, but aim for 75% coverage or more if possible. How much coverage I suggest will really depend on how resonant your floor is. The larger/flatter the floor is, the more coverage I recommend. Remember, focus on the large flat areas more than the structured areas, and use larger single pieces as opposed to multiple smaller pieces to get the most performance.
From here, we are going to apply ResoNix Fiber Mat. Most vehicles will require Fiber Mat 25 under the carpet in order to fit the carpet back in, especially modern sedans, but some may be able to fit the Fiber Mat 45, which will perform much better if it can indeed fit. If it doesn’t fit, don’t sweat it and stick with Fiber Mat 25. In most cases, you will be sticking this on top of the CLD directly, and preferably with 100% coverage. Be sure to not cover any wires, modules, mounting holes/posts, or anything else that may require service in the future.
If you are not doing 100% coverage, focus on areas that are closest to the source of the noises you are hearing. Transmission tunnels, rear seat areas, rear floors in trucks with loud exhaust, etc. If your vehicle features a carpet that has a backing that is hard, you can stick the Fiber Mat directly to the back of the carpet if you desire, which will leave the floor fully and easily serviceable in the future.
Optional Upgrade: Switch to ResoNix Mega CLD Squares sound deadening material for even better performance.
Performance: 0.5/5 for modern vehicles, 2.5/5 for vintage vehicles
Difficulty of Installation: 1/5 once access is gained to the firewall. Gaining access to the firewall will vary drastically in difficulty from vehicle to vehicle.
Overall Value: 0.5/5 for most modern vehicles. 2/5 for most vintage vehicles.
Materials
Our Stage-1 recommendation for firewall and hood treatment focuses on the basics to provide a noticeable improvement in noise reduction and thermal insulation with minimal effort and cost. Please note, the Stage-1 suggestions for the Hood & Firewall are not very effective to where I personally would find it worth it for a modern vehicle. For vintage vehicles, this is a different story since they have hoods and firewalls that are not nearly as structural and insulating, and a Stage-1 installation can still yield noticeable results.
Starting with the interior side of the firewall, apply ResoNix CLD Squares to cover approximately 50% of the surface area. Focus on large, flat sections for maximum effectiveness. If you’re up for an extra step, you can also treat the engine side of the firewall, although this is optional at this stage.
For the underside of the hood, remove the OEM hood liner carefully to expose the metal surface. Apply ResoNix CLD Squares to cover about 50% of the area, again concentrating on the larger, flatter sections. Once installed, replace the OEM hood liner. This application will help dampen resonance and help reduce some engine noise transmitted through the hood.
The optional upgrade to ResoNix Mega CLD Squares offers superior damping performance due to its thicker constraining layer and higher mass. If you desire greater noise reduction and are willing to invest a bit more, this upgrade is worthwhile.
Performance: 2.5/5 for modern vehicles, 3.5/5 for vintage vehicles.
Difficulty of Installation: 2/5 once you have access to the firewall.
Overall Value: 3/5 for modern vehicles, 4/5 for vintage vehicles.
Materials
Our Stage-2 recommendation builds upon Stage-1 by adding sound-absorbing and thermal-insulating layers to both the firewall and hood. This stage offers noticeable improvements, especially for vintage vehicles with less factory insulation. For modern vehicles, while the benefits may be more subtle, those seeking a quieter and cooler cabin will still appreciate the enhancements. To me, this is where the juice starts becoming worth the squeeze for modern vehicles. (I have had many customers reach out after doing this treatment on modern vehicles and were very happy with the end results).
Firewall (Interior Side):
Begin by applying 50% coverage of ResoNix CLD Squares to the interior side of the firewall, focusing on large, flat areas prone to vibration. Next, apply a full 100% coverage layer of ResoNix Fiber Mat over the CLD-treated areas. The Fiber Mat serves as an excellent sound absorber and thermal insulator, reducing airborne engine noise and heat transfer into the cabin.
Firewall (Engine Side):
This will be easier and much more worthwhile on vintage vehicles. Not so worth while on modern vehicles. On the engine side of the firewall, apply 50–100% coverage of ResoNix CLD Squares, depending on accessibility and desired performance. Follow this with a 100% coverage layer of ResoNix Fiber Mat Silver, which is designed to withstand the harsh conditions of the engine bay while providing sound absorption, thermal insulation, and a radiant heat barrier layer. A radiant heat barrier is different and separate from a thermal insulator in that it primarily reflects radiant heat rather than absorbing and slowing down conductive heat transfer, which is the function of a thermal insulator.
Hood:
Remove the OEM hood liner to expose the underside of the hood. Apply 50–100% coverage of ResoNix CLD Squares, concentrating on larger, flatter sections for maximum effectiveness. Then, install a full 100% coverage layer of ResoNix Fiber Mat Silver. If there is no OEM hood liner, adding the Fiber Mat Silver is highly recommended to enhance sound absorption and thermal insulation. Reinstall the OEM hood liner if present.
Optional Upgrade:
Upgrading to ResoNix Mega CLD Squares will provide superior damping due to their thicker constraining layer and higher mass, making it a worthwhile investment for those seeking greater noise reduction.
Performance: 4/5 for Modern Vehicles with louder engines, 4.5/5 for Vintage Vehicles
Difficulty of Installation: 3/5 once you have access to the firewall
Overall Value: 2/5 for modern vehicles, 3/5 for vintage vehicles
Materials
In Stage-4, we enhance the comprehensive treatment of Stage-3 by adding a full layer of ResoNix Barrier to the interior side of the firewall. This stage focuses solely on the firewall to maximize sound deadening and thermal insulation, ideal for vehicles where engine noise and heat are significant concerns.
Firewall (Interior Side):
The recommended order of application is CLD, then Fiber Mat, followed by Barrier. This sequence ensures optimal performance in reducing vibrations, absorbing sound, and blocking heat transfer.
Firewall (Engine Side):
This step is optional and primarily recommended for vintage vehicles, as it can be challenging on modern vehicles due to space constraints and accessibility. If you choose to proceed:
Note: Modern vehicles often have adequate factory insulation on the engine side, so additional treatment here may offer diminishing returns.
Hood Treatments Conclude at Stage-3
Please note that hood treatments are not included in Stage-4. All recommendations for hood sound deadening and thermal insulation conclude at Stage-3.
By focusing intensively on the firewall in Stage-4, you enhance the barrier between the engine bay and the cabin. The combination of ResoNix Mega CLD Squares, Fiber Mat, and Barrier on the interior side of the firewall provides a highly effective shield against engine noise and heat entering the passenger area. For vintage vehicles, the optional engine side treatments further improve these benefits.
Installation Considerations:
Order of Application: Following the recommended sequence of CLD, Fiber Mat, then Barrier will yield the best results. However, if installation constraints require a different order, try to maintain the integrity of each layer’s purpose.
Performance: 4/5 for Modern Vehicles with louder engines, and 5/5 for Vintage Vehicles
Difficulty of Installation: 3.5/5 once you have access to the firewall
Overall Value: 1.5/5 for modern vehicles, 2.5/5 for vintage vehicles
Materials
In Stage-5, we aim for the ultimate in sound deadening and thermal insulation for your vehicle’s firewall. This level is typically reserved for vintage vehicles undergoing restoration or for enthusiasts seeking the highest level of cabin comfort and noise reduction. For modern vehicles, the marginal gains may not justify the extensive effort and cost, but if you’re striving for perfection, this is the way to achieve it.
Firewall (Interior Side):
Firewall (Engine Side):
This step is optional and primarily recommended for vintage vehicles, as it can be very challenging on modern vehicles due to space constraints and accessibility. If you choose to proceed:
Note: Hood treatments conclude at Stage-3. No further treatments are recommended for the hood in Stage-5.
By following this sequence—CLD, then Guardian (or Lockout), then Fiber Mat, then Barrier—you achieve the most effective combination of vibration damping, sound absorption, thermal insulation, and noise blocking for your vehicle’s firewall.
Installation Considerations:
Applicability to Modern Vehicles:
While Stage-5 provides the highest level of sound deadening and thermal insulation, modern vehicles may not experience substantial benefits over Stage-4 due to existing factory treatments. Carefully consider whether the additional effort and cost align with your desired outcomes.
By investing the time and resources into a Stage-5 firewall treatment, you’re committing to the highest standards of automotive comfort and performance. Whether you’re restoring a vintage classic or enhancing a modern vehicle, this comprehensive approach will provide unmatched reductions in noise and heat, elevating your driving experience to new heights.
Final Thoughts:
By tailoring your sound deadening and thermal insulation efforts to the specific needs of your vehicle, whether it’s a modern model with adequate insulation or a vintage car requiring significant upgrades, you can achieve a quieter, cooler, and more comfortable driving experience. Stage-5 represents the pinnacle of what’s possible, offering the most comprehensive solution for reducing noise and heat in your vehicle.
Constrained Layer Damper Sound Deadening Materials, such as our ResoNix CLD Squares, ResoNix Heavy Duty Mega CLD Squares, and ResoNix Lite CLD Rectangles, which many technical hobbyists will refer to as “CLD,” and the general hobbyists and many installers and salesmen refer to in a genericized way as “sound deadener,” is the most common product used to sound treat a vehicle, and is almost always the first major step to the entire process. A CLD features two layers; a visco-elastic (fluid to a degree yet stretchy/snappy like elastic) butyl rubber layer and an aluminum constraining layer on top. Typical CLD’s use a backing paper and are peel-and-stick for their application.
How a Constrained Layer Damper works is for the most part, pretty simple. When the panel that it’s adhered to bends and flexes (resonance), and subsequently, so does the CLD sound deadening material. The aluminum constraining layer provides a stiff reference across the top surface of the visco-elastic butyl. The radius differences that form between the panel that the CLD is adhered to, and the top aluminum constraining layer causes the butyl to stretch, resist, and want to snap back into position. These shear forces generated by the viscoelastic butyl is what “Constrains” the panel to prevent flexing. This process converts the mechanical energy of the panel into minuscule amounts of heat. This conversion of energy is the reduction of resonance that we are looking for.
In car audio, we add larger, more powerful speakers with a lot of power being applied to them to the vehicle. With these more powerful speakers, there is a lot more acoustic energy being introduced into the cabin of the vehicle. The most notable areas for this type of product in a car audio installation would be the door panels, door skins (outer door skin being more important than the inner door skin), trunk lids/hatches, roofs, rear decks and their trim panels, floors, various interior plastic trim panels that will resonate, and anywhere else in a vehicle that is susceptible to resonance. The doors (door panels included) are usually the worst offenders, so let’s focus on those for the example. When you have a speaker mounted to a door, the front wave of that speaker, when installed correctly, is only partially radiated directly forward through the door panel grille and into the cabin. The rest of that front wave doesn’t make it out of that door grille due to the speaker’s dispersion pattern, and that energy must go somewhere.
Now, something to note. Every vehicle is different, and every vehicle will behave differently. Each vehicle and each individuals end goal will require a different amount of CLD and sometimes a different approach to the overall game plan of applying a CLD. This can come down to the locations it’s placed, how much is needed in certain areas, etc. I find that economy cars benefit more from these products than rugged premium and luxury cars. When we work on something like a Toyota or Honda, there is a more noticeable difference when applying a CLD vs. applying CLD to, say, a Mercedes. This is because these higher-end vehicles have much more robust and sturdier parts. That said, I have yet to find a vehicle that I have worked on that wouldn’t benefit from having CLD applied, even considering diminishing returns and time spent on the project. This goes from 80’s Toyotas, all the way up to modern Rolls Royce models. Every vehicle can benefit from a Constrained Layer Damper
This is a much-debated topic by enthusiasts, and as with any other topic often debated by enthusiasts, it is greatly misunderstood. Some people say the rule of thumb is a minimum of 25% coverage, while others say anything more than 25% coverage is a waste of time and materials. Others say 50% coverage is where diminishing returns kick in. Others swear that anything less than 100% coverage is wasting your time. So what gives? Who’s right? Buckle up……. NO ONE. That’s right. A Constrained Layer Damper doesn’t work based on the percentage of the area covered. Constrained Layer Dampers only constrain the parts of the panels that they cover. Think of a CLD sound deadener as a “support” for the panel it is adhered to. Just because you support one area, doesn’t mean the other areas are supported. What this means is there is no magic number for the percentage of coverage before you hit a point where diminishing returns kicks in. This purely comes down to a couple of things.
Part two, this is where things get tricky. I will do my best to make this easy to understand. Some panels are small enough or rigid enough not to require CLD treatment. To not need CLD treatment would require that panel to be small enough to where its weight and stiffness are at a point where its resonant frequency is well above a critical frequency range, and it doesn’t have any ringing. Large, flat panels, on the other hand, will be very resonant and will ring since there is no rigidity, and the resonance frequency is in a critical frequency range. When you treat a large panel and leave areas unrelated, you are essentially creating other “smaller” untreated panels. Are these new “panels” small enough to where they do not resonate, or at least are pushed outside of the scope of the given application and the user’s particular goals? If so, they can be left untreated. But, if that left over area can act as an individual panel that is large enough to resonate at a level that is unacceptable for the goals at hand, then it needs to be treated as such.
Let’s provide an example.
Let’s take two flat panels on a vehicle, say the outer door skin and the roof skin of a large SUV. For the sake of keeping this simple and easy to follow, let’s say the outer door skin is a perfect 10 square feet, and the roof skin is a perfect 100 square feet. Now let’s treat these panels each with 25% coverage. This leaves the outer door skin with a leftover 7.5 Square feet that are untreated and “unsupported,” and it leaves the roof skin with 75 square feet that are untreated and “unsupported.” If you saw any general areas that had about 7.5 square feet that could be treated for resonance control, even if broken up into smaller sections, you’d probably treat it. But if you saw an area with 75 square feet of resonant panels, you’d very well immediately think that this area needs to be treated. Remember, the product itself works as a system, but all of the individual pieces work on their own. The panel has no idea if it has 25% coverage or 85% coverage. But the areas that are left untreated are left to act as their own, resonant panel.
To summarize all of this, resonance is a very complex thing, and every panel size, shape, material, and its given environment will change its behavior. To say you only need X amount to hit diminishing returns is grossly misleading, especially when we consider that everyone’s goals, tolerance, and budgets are different. And that most people chit chatting on the internet do not have a basic understanding of how it works.
True Constrained Layer Dampers only really benefit from 1 layer. Many people on the internet talk about using 2, or sometimes even more layers. Frankly, these guys are wasting their time and materials. To re-cap how a constrained layer damper works, the shear forces generated in the butyl rubber when in between a flexing panel and the constraining layer cause the resistance of panel flex. The aluminum constraining layer provides a stiff reference for the butyl to snap to. Keeping this in mind, a second layer only treats the flex of the first layers’ aluminum constraining layer. This isn’t very beneficial.
Now, notice how I started that last paragraph saying “TRUE Constrained Layer Dampers”? This is because there are CLD products on the market that perform so poorly as an actual constrained layer damper, that their minimal stiffness, and added weight are their main source of panel resonance reduction. For these types of products, yes, more layers will be beneficial, but still will not be as effective as a high quality constrained layer damper, even with these multiple layers. Don’t believe me? Click this link to see testing results that show as such (Coming soon, will write this in once I finish this article)
One more thing about Constrained Layer Dampers, they do NOT block noise. That is right. Nearly EVERY other sound deadener company will claim this about their CLD product, and many hobbyist automotive forum members will say this, but it is just not true. A good Constrained Layer Damper Sound Deadener can most definitely lower the noise floor of a vehicle since it will reduce the amount of noise generated by the resonance of panels, but it will NOT block outside noise from entering the vehicle. Any company claiming this about their product is lying to you. Why it doesn’t block noise is simple. Noise from the outside of the car is transferred through the body of the car, and again radiated out as the same sound. All it is, is energy transfer through molecules. The CLD being coupled to these panels will just transfer the energy as well. While it will technically lower the transfer, it won’t be by anything measurable. This is a totally separate behavior that has nothing to do with the CLD constraining the panel it is adhered to in order to reduce mechanical resonance.
Now, notice how I started that last paragraph saying “TRUE Constrained Layer Dampers”? This is because there are CLD products on the market that perform so poorly as an actual constrained layer damper, that their minimal stiffness, and added weight are their main source of panel resonance reduction. For these types of products, yes, more layers will be beneficial, but still will not be as effective as a high quality constrained layer damper, even with these multiple layers. Don’t believe me? Click this link to see testing results that show as such (Coming soon, will write this in once I finish this article)
The tests conducted are significantly before the point in temperature where any high-quality CLD product would begin to melt. The point of this paragraph, melting is not the only drawback of cheap, low-performing products. Their damping performance drastically declines at higher temperatures, temperatures that your car WILL see, to the extent that they are virtually ineffective.
The second image illustrates the same SAE-J Composite Loss Factor testing conducted at the same facility, but this time for the ResoNix Mega CLD Squares. Although they utilize the same butyl formula and thickness as our original ResoNix CLD Squares, they feature a thicker and significantly stiffer aluminum constraining layer. This modification is evident in its performance—while peak performance is clearly higher, there’s a very noticeable improvement in performance at higher temperatures.
Should the opportunity arise (i.e., if we have a surplus of funds great enough to pay for third-party standardized testing of various products), we plan to run tests on other products at these elevated temperatures to demonstrate this effect. For the time being, our focus is on showcasing how a high-performing product like ours fares under various temperature conditions.
Using sound absorbers to tackle airborne noise problems in vehicles is both a straightforward and efficient method. These products are less expensive than alternatives like noise barriers and offer a clear advantage for anyone looking to improve their vehicle’s sound environment without a hefty investment. This cost-effectiveness makes sound absorbers a perfect choice for most, striking the perfect balance between performance, affordability, and ease of installation.
The real beauty of sound absorbers lies in their installation simplicity. Unlike the relatively complex and tedious installation required for noise barriers (more on this in their own section down below. To sum it up, a non-perfect installation will punish you with unideal end results), sound absorbers can be easily applied without much thought put into perfect coverage, bypassing the need for meticulous precision or extensive prep work. Again, sound absorbers work by allowing sound to pass through them, and converting the sound energy into mechanical and thermal energy. Due to this, you do not have to do 100% coverage with a sound absorber in order to get the benefits, unlike a noise barrier. Whatever you put into it will essentially be what you get out of it. This ease of installation not only makes them more appealing to a wider audience but also minimizes the chance of mistakes negatively affecting the end results. Sound absorbers offer a practical and straightforward solution for vehicle owners seeking to improve the acoustics of their vehicles with minimal hassle.
Installing it is very simple. Just cut to shape with heavy-duty scissors, peel the backing paper, and apply it to the desired surface. As with anything, ensure the surface is clean and clear of dirt, oil, and grease. I prefer to clean the panels with isopropyl alcohol beforehand. You can stick this anywhere you want, so long as it is clear of any moving parts. I do not recommend installing these inside door cavities as an absorber as I worry that window mechanisms can snag the material and cause issues. Same with seat belt areas. But everywhere else, free game.
When cutting ResoNix Fiber Mat, you will sometimes find that it does not perfectly seal, or may not seal at all. First, this is okay. It does not negatively affect the material in any way. The material as a whole can handle anything an automotive installation will throw at it, regardless if the edges are fully sealed or not. What I find causes the edges to seal or not seems to come down to the cutting device used. Some scissors and shears seal it perfectly, others do not.
The general rule of thumb with ResoNix Fiber Mat 0.5″ & 1″, or any sound absorbing material for that matter, is that any application is always increasingly beneficial. Any time you add more of an absorption product, you will absorb more noise. There is one caveat, though. Stuffing it to the point of compression will alter the product’s behavior and shift and change the acoustic absorption properties, usually in a way that is negative to our end goals in the automotive environment. For larger voids such as roofs, quarter panels, etc., only fill them until they are full, but do not add extra to the point that the Fiber Mat compresses. Fiber Mat should remain “lofty” for the best performance. The only time compressing is preferred is when you are using Fiber Mat as a decoupler as well. Light compression of ResoNix Fiber Mat will drastically increase decoupling performance and panel stabilization without having enough adverse effects on absorption to be concerned. Door panels and rear decks come to mind here since these are areas that we are typically very concerned about with panel-on-panel vibration, especially in sound system applications. Obviously, some areas will have to be compressed, at least a little bit. This is okay if some areas are compressed and others are not. We just want to minimize material compression if the end goal is to absorb outside noise. If the goal is decoupling, compress it as much as you want.
We are currently working on a document that will list all of the vehicles that our customers have submitted installation information regarding Fiber Mat fitment. This will be posted here and on the Fiber Mat product pages, and will be updated as customers submit their installations to us, and as we do more installations ourselves.
Regarding picking Fiber Mat 0.5″ or Fiber Mat 1.0″ for your installation in your specific vehicle, that can be hard to say. While we have done many vehicles and customers have submitted information about many vehicles, we still haven’t done most. While we can help guide you based on our experience, it is ultimately up to you to determine which thickness best suits your application. If you have used this product in your vehicle, feel free to us with your year/make/model along with what products you used, where you used it, and how it worked out (if it fit, could fit more, could double up, if there are any OEM materials that need to be worked around or removed, etc). Thanks!
Remember, when it comes to sound absorption fill, but do not compress. So far, in my experience Fiber Mat 45 will be better suited for larger tolerance door panels, rear decks, rear hatch trim panels, quarter panels, roofs, fender liners, etc. Fiber Mat 0.5″ is typically suited for smaller tolerance door panels, pillars, floors, trunk floors, tire wells, etc.
The typical use case for ResoNix Guardian and ResoNix Lockout is inside car doors, subwoofer enclosures, or anywhere else with a flat surface behind speakers that produce a lot of energy. The point here is to absorb the acoustic energy inside the door or enclosure BEFORE that acoustic energy makes it to the door skin or enclosure wall. Since ResoNix Guardian and Lockout’s Hydrophobic Melamine layer absorbs noise, and the Mass Loaded Vinyl layer that’s in ResoNix Guardian helps deflect noise and act as a sacrificial layer for resonance, all before said noise reaches the door skin or enclosure wall, the amount of acoustic energy that even reaches those boundaries is significantly lessened, therefore reducing the overall amount of resonance and vibration that is created.
The second use for ResoNix Guardian is to make use of the floating layer of 1/8″ thick, 1 pound per square foot Mass Loaded Vinyl (MLV) Layer. We haven’t covered noise barriers yet, but this is the first product that makes it extremely easy to install a noise barrier to your vehicle’s roof and vertical sides of larger vans and RV’s. Previously, installing a noise barrier on vertical, or god forbid overhanging surfaces, was difficult, tedious, and not consistently effective. Mechanical fasteners, specific Velcro (that we still offer), or other hoops must be jumped through to install noise barriers, such as Mass Loaded Vinyl or ResoNix Barrier, onto these surfaces. Now, it’s just peel, stick, done. All of this is done with the added benefit of the MLV being fully decoupled and isolated and with the help of acoustic absorption of the Hydrophobic Melamine. In my experience, this use is only applicable for vehicles with very large and flat surfaces, such as vans and RV’s. Otherwise, if your car features complex shapes, ResoNix Barrier is a better option.
The third use for ResoNix Guardian and ResoNix Lockout is for their thermal insulation properties. While Hydrophobic Melamine is an excellent acoustic absorber, it is also a top-tier thermal insulator. So much so, that it is even used in aerospace applications to protect from heat. ResoNix Guardian and Lockout are the ultimate solutions for treating a camper van or RV since you get not only the acoustic benefits but also the thermal insulation benefits. It will help keep heat in when its needed, and heat out when not desired.
What makes them very picky is the fact that a noise barrier ideally needs FULL coverage to be effective. While not having full coverage can still yield some improvement, it will be minuscule compared to full coverage. When you do not have full coverage, sound acoustic energy will travel around and take the path of least resistance right past the noise barrier. Written in our more detailed section, I use this analogy…
Say your annoying and inconsiderate next-door neighbor decides to cut his grass with his obnoxiously loud mower at 7 am on a Sunday while you’re trying to sleep in on your only day off. It just so happens that it was a warm night, and you slept with your window open. The second he fires up that old John Deer of his, it wakes you up. You think to yourself, “Ugh, here we go again. Better close my window and try to get back to sleep”. What happens to your perceived volume of his mower when you close your window halfway? Nothing, right? What about when you close it 90% of the way? Still pretty much no different than with it fully open. What about when you close it pretty much all the way but don’t lock it and have a good seal? Yeah, perceived volume is lower, but not by as much as you had hoped. Your perceived volume of his mower only becomes significantly lower and tolerable when you fully seal that window shut. It’s no different when trying to sound-proof your vehicle.
While this is a very generalized explanation and it’s not as perfectly clear cut as 100% or nothing, this is a good way to look at it and approach it. Any flanking paths will drastically reduce performance. Unlike sound absorbers, you don’t necessarily get out of it what you put into it until you start getting very close to full coverage. One thing I suggest to someone who doesn’t want to do full coverage, is to at least do full coverage of the floor of a vehicle. This allows sound coming from under the vehicle to be deflected to the sides, where you can easily use a sound absorber such as ResoNix Fiber Mat to eliminate it. It will not be as effective, but it is a good in-between.
Another part that makes them picky and selective is that noise barriers need a decoupling layer, ideally on both sides, to isolate them from the vehicle. Noise barriers need to be decoupled from the body of the vehicle and the panels that cover them. Otherwise, the resonance of the body panels will be transferred directly to the noise barrier, which will also resonate and radiate its own noise, rendering the noise barrier mostly ineffective.
ResoNix Barrier is very easy to install. For floors, just remove the carpet, roll it out, contour it to dips, peaks, bends, etc., as tightly as you can, overlap layers and even fold them once over to lock them together to prevent sound from leaking through, and let gravity hold them in place. For vertical surfaces, I prefer to use riv-nuts and stainless steel machine screws with fender washers to hold ResoNix Barrier into place. I do not suggest using Velcro to hold up ResoNix Barrier. The foam will not be able to bear the weight and will rip. The adhesive will also tear the foam apart if you try to remove it. For roofs, this isn’t easy. You can again use mechanical fasteners into the roof braces or can somehow install it directly onto the headliner, but I am not sure how that will hold up as it may be too heavy for a headliner to support. This is where ResoNix Guardian or ResoNix Fiber Mat comes in, making treating the roof much more manageable.
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