Is Sound Deadener a waste of time (money) on an old Convertible?

So I got my '65 Caddy Drop Top back on the road after installing the suspension and dropping in a LS motor. This is California, so I doubt that the top will ever be up.

While doing the swap, I ripped out the carpet as I had to raise the drive line tunnel quite a bit. We use the Dynamat Dynapad as a carpet pad to start with as it makes a great carpet pad.

The stereo gear that is going into the car is;
(2) JL 12TW-D8s in the trunk parallel wired to 2 ohms run by a VX100/1i
A set of JL three-ways in the front kicks, doors and the tweeters are in the dash run off a VX800/8i
Fiio M11 to hold the music

I have a pair of W7-12s that I was going to use, but the trunk on this big ol car got filled up quickly with the air system and two group 34s. The trunk shown in the photo below will be redone as everything was temp installed for fitment and I have two 3-gallon air tanks, one of them with the compressor inside to replace the shown 5 gallon tank and hopefully gain back some room.

This car has HUGE thick flat steel panels everywhere, so my question is;
* Being a convertible, should I be adding sound deadener to the inside of the door skins, under the Dynapad and off course the complete trunk?

And of course which one (ones?) as there are so many now, Dynamats, Rattletrap, Nick's Resonix and even Mobile Solutions has their own line now.

BTW, I met Nick out at Mobile Solutions earlier this year and wanted to talk with him about this particular subject, but as usual Bryan had us running and running and running! I even missed the end of the final night as I had a business meeting set that evening.


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I think you would still benefit from some reasonable application. The dynamat will help more than anything at blocking road noise. Apply the damping on the most unsupported panels. The floor is usually corrugated enough that CLD doesn't help that much there, but definitely on the doors and any large unsupported panels. But apply sparinginly I really don't think it will make a huge difference in a convertible. I recommend NIck's Resonix as he is directly supporting all of us hobbyists and his material I assume is derived from the old Sound Deadening Solutions product which was the best. However I have found most of them work about the same the primary difference being which once is thicker as they are sold by square area so its real easy to reduce the thickness and sell for a lower price.

God that's a great looking car, always wanted a convertible, especially a land yacht convertible. Love my '92 Deville which has now transitioned from lame old car to vintage classic. Not a convertible though.

Preston, thanks, that is pretty much what I was thinking.

I will be adding Dynamat Extreme under the DynaPad as the floors do have some pretty big flat areas.

I just ordered up 20 SF of Nick's Resonix squares to place on the door skins and the sides of the trunk.

BTW, that's NOT a Caddy in your sig pic!

I just re-read my post and wanted to clarify - MLV (thick vinyl) and/or dynapad ie something with a sound barrier component will make a bigger difference than the CLD (dynamat). I assumed you already had the dynapad.
i think that's true for most cars actually, we all got so carried away with dynamat type products, but I think there is more to be gained with sound barriers and absorbers.

When I did the install in my wife's truck (2016 Tacoma, 6x9 front door speakers and dash tweets), I only treated just the front doors with MLV and CLD. I figured since the rear speakers are disconnected, there wouldn't be any benefit of treating the rears.

It now sounds like the rear windows are cracked open a bit because we hear more noise from the rear than in the front. I will be pulling those door panels off soon to treat them also.

The moral of the story is, treat everything you can, because it will make a difference.

I did all the normal deadening stuff to my big Bronco that has a think canvas soft top. I made before and after measurements, I reduced road noise by 6db at 35mph, and 5db at 60mph. I suspect that if I had done RTA measurements at the same time it would show the most improvement at higher frequencies. The vehicle became much more enjoyable to drive.