Sound deadening?

[cgreen]

I just ordered 100 sq ft of Fatmat and should be putting it in next week. I plan on doing the rear wall with a single layer and a layer on the plastic piece that goes up just the back window. I also plan on doing the doors, as the back one has no sound deadening at all. I am into car audio and want to improve midbass. Have any of you guys sealed up the door by adding thin metal in the open areas and then deadening over it? I plan on putting a layer of deadener on the door and one on the door panel because it buzzes like crazy. I am going with 4 8's ported behind the reat seat and want to be able to crank it without buzzzing.

 

[3500GMC]

You'll notice a big difference. It'll go a long way to lower the resonant frequency of the cabin. Probably the best thing is to dampen heavily around the drivers in the doors (add mass) as this should help with the buzz. Most component sets are infinite baffle (requires no enclosure per se) and like to be well sealed to the mounting surface, no air leaks, keeps the wave cancellation from happening... Unless you weld the metal in, it may add to the buzz problem.

 

[cgreen]

I have Peerless mids with Pioneer tweets in the frond doors and Dayton 4 inch mid/full ranges in the rear door. I am thinking about taking thr plastic off and leaving it off because it is buzzing with just the Dayton 4's going. what I have seen people do is put this expanded metal over the open areas of the door and used the sound deadener over that. my sub- stage will be 4 Elemental designs 8's off a Avionixx amp that does 580 watts at 1 ohm. They will ported tuned to right at 30 hz. I am going deaden the rear wall then the rear doors and see what just the 4's sound like and see if sealing the doors might help enough to justify it.

 

[3500GMC]

I'm surprised you need more midbass in a truck/car application. Usually the tin can exaggerates the frequencies from around 120 to say 250... Hmm.

I bet the 8 inchers will almost automatically handle the midbass freqs even tuned at 30... unless you roll them off sharply (24db octave) with an active crossover.

I have found that less is more in good sounding audio. I don't know what you are shooting for though.

 

[juddspaintballs]

You can just as easily use 1/4" underlayment board to fill the holes, hold it in with a few dabs of caulking or glue, and then deaden over that. It won't rattle and there's no welding required. Before you do that, though, I'd deaden the exterior door skin from the inside of the door. That is the panel that will resonate the most and transmit the most road noise into the cabin (with the exception of the roof) because it is a large "flat" area that can easily vibrate. Cover about 1/3 of that door skin with deadening material and it'll eliminate the issue.

 

[cgreen]

You can just as easily use 1/4" underlayment board to fill the holes, hold it in with a few dabs of caulking or glue, and then deaden over that. It won't rattle and there's no welding required. Before you do that, though, I'd deaden the exterior door skin from the inside of the door. That is the panel that will resonate the most and transmit the most road noise into the cabin (with the exception of the roof) because it is a large "flat" area that can easily vibrate. Cover about 1/3 of that door skin with deadening material and it'll eliminate the issue.

I've done about 2/3 of the rear door tonight and that's about all I can reach. I'm not going to spend a lot of time on the rears, the front is where I want to really make the mids shine. I plan on upgrading to Dayton 6.5's up front later on and they should sound awesome with the doors sealed and deadened. I also put a sock in the air vent at the back of the cab, that should allow air to flow but cut down on road noise. I drove through NC last week with nothing on the rear wall and road noise was horrible.