Installing Sound Deadening/Insulation in 66' Mustang (what to get, how to do trunk)

[SadbutTrue 10+ year member]

(cliffnote version at bottom)

Okay, so I've spent all day reading sounddeadenershowdown.com (and browsing it, second skin, and fatmat to compare prices).

I was initially going to get just a roll of Fat Mat and call it a day, but after my research it seems that the Fat Mat is a so-called 'damper' material (similar to the 'Damplifier' product on Second Skin and CLD tiles from sounddeadenershowdown.com, among others). These sites say that covering more than 25% of panels with these damping material yields diminishing results.

I was told by a guy that does classic mustang restomods (and hence installs a lot of systems in these cars) that ~100 sq. ft. is sufficient for the entire car.

Correct me if I'm wrong, but the above information has led me to believe that A) 100 sq. ft. of Fat Mat may be excessive (since 100 sq. ft. is enough to cover the whole car, but more than 25-50' sq feet probably will just be excess weight and not help much with noise reduction) and B) that in order to get the best results, I need to pair it with an vinyl blocker (AKA 'MLV' on most these sites) and possibly a foam (CCF).

Sooo... (I apologize for the book //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif )...

I *believe* that it is in my best interest to order ~50 sq. feet. of Fat Mat, and then 65-100 sq feet of an MLV and CCF (each). The best deals I can find on these quantities would be about $80 for the Fat Mat, and $70 for about 67 sq. feet. of MLV and CCF (each, from sounddeadenershowdown.com). This ends up being around $220 plus shipping - on the high end of what I want to spend, but doable. If 50' isn't enough for the Fat Mat, I could get 100 square feet for $130, but i don't want to go over $300 total for insulating materials.

First question: Does all of that sound good and reasonable? Any flaws in the logic? Overkill? Missing anything?

Next...

My Mustang is built with no real barrier between the back of the rear seat and the trunk. Right now, for safety reasons (to prevent a fire from the gas tank from reaching the cabin), there is a sheet of aluminum between the trunk and cabin.

The system I am installing will include at least 1 subwoofer (probably a single 12" since I already have one, but possibly dual 10's instead). There is no room in the cabin for it, so it has to be in the trunk in some capacity.

My original plan was to cut a hole in the aluminum to accomodate my subwoofer's box, put some extra insulation around the box (between it and the aluminum), and then put insulation on the cabin-side of the remaining aluminum sheet - and completely ignore any soundproofing in the trunk itself.

Since the sub would be blasting directly into the rear seat, it would seem that soundproofing the trunk wouldn't really benefit much... plus my Mustang's trunk would more difficult than most modern cars to apply sound deadening too because the surfaces aren't neat and flat. Doing this would also dramatically reduce the amount of insulation needed (not sure if the 100 sq. ft. amount includes the trunk or not).

So... is that a good idea?

Cliffnote version:

1. Would 50 square feet of Fat Mat (serving as a 'damper'), 70 sq. feet of MLV, and 70 sq. feet of CCF be enough to properly deaden/insulate a 1966 Mustang coupe?

2. Can I avoid soundproofing the trunk by placing my sub in the barrier between the trunk and my cabin, and just insulating around the sub and on the barrier itself?

Thanks! //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif

Click to read more...

 

[SadbutTrue 10+ year member]

No one?

 

[keep_hope_alive Premium Member]

Avoid Fatmat. Trust me. Go with Rammatt BXT instead (for almost the same price). Fatmat isn't worth the cheap price. I learned the hard way on that too. BXT II is great stuff.

How much to use depends on your goals. 100% coverage will provide better results and improve transmission loss. A MLV layer decoupled from the floor (key point) is the only way to really snuff out road noise - note you do need 100% coverage for any barrier. Don't neglect the doors - major source of road noise there - and they need to be sealed up to be quiet (dead air space). So 100% coverage on the doors with holes sealed up (sheet metal with screws then deadener overtop). For the MLV you'll need to measure the sq. ft. of the floor and ****** hump, and firewall, and wheel wells.

If you fire the sub into the cabin and not into the trunk, you don't need to deaden the trunk. Note that no new or old cars have flat trunks, all of them are curved and time consuming.

You need to stiffen up the panel around the sub - as much as possible. Stiffen the box as much as possible. a layer of sheet metal will resonate. i'd weld some square steel tubing for additional stiffness around the sub box.

 

[SadbutTrue 10+ year member]

So should I ditch the sheet metal altogether (maybe replacing it with wood or another material)? Or will stiffening the box, insulating the contact between the box and sheet metal (and the top of the sheet metal itself, with special attentio nto where it mounts to the car) be enough?

Do you think I should expect tons of rattles from the springs and stuff within the seat (since the sub will be blasting right through that)?

I see you didn't mention CCF... is that considered unnecessary or less beneficial?

 

[Anthony Collova 10+ year member]

The better that material the less you need.

100 sq feet of fat mat would yield similar results (provided it sdid not fail and melt off the panel) as maybe - 25 sq feet of a real CLD vibration mat.

More is always better, but not always as efficient. In fact it is pretty much guaranteed that the close you get to 100% coverage (with any brand) the more money you spend per given incriment of measurable results.

Mass is king for reducing airborne noise however so if you use a barrier that is loaded up with a foam decoupler, you wil lbe doing very well.

My suggrestion, stay away from fat mat, and stick with

Dynamat Extreme

Raammat BXT II

SDS

Hushmat

Or my products.

ANT

 

[SadbutTrue 10+ year member]

The better that material the less you need.100 sq feet of fat mat would yield similar results (provided it sdid not fail and melt off the panel) as maybe - 25 sq feet of a real CLD vibration mat.

More is always better, but not always as efficient. In fact it is pretty much guaranteed that the close you get to 100% coverage (with any brand) the more money you spend per given incriment of measurable results.

Mass is king for reducing airborne noise however so if you use a barrier that is loaded up with a foam decoupler, you wil lbe doing very well.

My suggrestion, stay away from fat mat, and stick with

Dynamat Extreme

Raammat BXT II

SDS

Hushmat

Or my products.

ANT

Thats another thing I was curious about... what materials do I need to be concerned about melting? I live in the San Fernando valley, where outside temperatures can hit 110 pretty easily during summer (leading to some ridiculously hot in-car temps).

Also, do you have an opinion on the trunk/aluminum panel idea?

 

[keep_hope_alive Premium Member]

i can tell you that Fat mat won't be sticking to your car within a year of any temps