Where to add sound deadening mat? For adding door speakers and under carpet

[traut811]

Good morning everyone.

I pulled the lower door panels off my '67 C10 and found out someone cut holes for a 6x9 speaker with what appears to be a hammer and chisel, probably the reason a carpet lower panel was added to cover it. I'm making patch panels now to fix all the ugliness, to turn around and cut holes for a 6.5" door speaker. I would like to add sound deadening material inside the door.

Where all is recommended to put this? I know I need right behind the door speaker, but do I line the entire inside of the door, outer and inner skin? I plan to do under the carpet as well, and I guess up the back wall also. I ordered 50sqft of the 50mil kilmat this morning so hope to tackle it this weekend.

Thanks in advance for any advice or suggestions.

[sick472]

Sound deadening mat like that is very good at reducing sheet metal vibrations. Think about adding a piece of chewed bubble gum to the surface of a drum set cymbal...it will kill the sound. It does little to absorb free sound like carpet would. With that said, a piece of sound mat added in the center of the larger open areas will yield the bulk majority of the results. This has never stopped me from adding it pretty much from corner to corner in the cabs. But, for door inners, I'd keep it to a minimum. Inside the lower inner door panel is the first place to add it due to the vibrations from the speakers and then, maybe, to the lower section of the outer door skin. I advise the lower section only...You can imagine what would happen on a real hot day and the mat decides to let go and goo into your window mechanisms. Maybe the Kilmat brand is not prone to this as I have always used the poor-man's sound mat...Peel & Seal Roofing. At any rate, full coverage in your doors is not necessary, or anywhere else for that matter. I did cover the entire floor and firewall of my 72, because it's addicting to put down and just looks so cool...I hope I never have to take it up! lol

[cj847]

In my opinion........(I realize that a lot of people cover the entire surface)

You need to cover the areas that are unsupported. It does nothing in a corner where two pieces are welded together or where a floor support is welded to the floor or where the metal has a significant bend (ie > 45 degrees).

I did my whole truck with probably 20-30 feet. Mainly pieces 8" x 8" or 8" x 12" placed in the center of unsupported areas like under the seat, between floor supports, where floor meets firewall, etc. On the doors I used a couple of big pieces and covered most to the outside surface that was easy to reach and easy to get a roller against. I didn't think about the inside half of the door, I'll need to do that next time iI have the door panel off. Get the surface as clean as possible so the adhesive can bond.

Sounds like you just recently got he truck? Be sure to vacuum out the bottom inside of the door and make sure the weep holes are open in the bottom of the doors.

[traut811]

Thank you both for the replies, and great advice. Just my thoughts, but I figured a piece against the outside door skin, inside the door directly behind the speaker would deaden whatever is coming off the speaker right there. If I should do the inside of the inside skin as well I will tackle that.

Good call on if the stuff fails, I don't necessarily know if there would be any advantage of doing much more than a small area just around the speaker which is why I ask.

Makes perfect sense about the unsupported areas needing it the most. 50sq ft of the kilmat was only $60 or so, which was a lot cheaper than the dynamat. It had great reviews and saw people on here talking about it so going to give it a shot. If I have extra, I have a '69 Z/28 project that's dead at this moment I'll save it for.

I got the truck a couple years ago out of Long Beach CA. I made a taillight fuel filler for it, need to put barnwood in the bedfloor, ridetech coilovers are finished and front sway bar, need to do the rear sway bar still, bought a Sniper EFI for it almost a year ago and haven't put it in yet, and have all of this audio stuff that I'm just now getting around to doing. It isn't much, just 6.5" door speakers, 2x 3.5" tweeters that I'll put in the center dash, little 400w sub for the speakers and a powered 8" sub under the seat. It had no sound inside before so just to have some tunes.

One more question to add- it looks like there's a thick rubber coating of some sort inside the cab that has factory paint over it. I guess this needs to be scraped off the best I can? Almost looks like a bedliner or something, but you can flake edges off with your fingers. It might have been from someone over the last 50 years also, who knows.

[Accelo]

"thick rubber coating of some sort inside the cab that has factory paint over it"
For sure GM installed it.
Poor man's dynamat is all.
Rick

[sick472]

Any chance that the rubber coating your talking about is the factory tar-like under carpet soundproofing? It's die cut from flat material about 1/10" thick and will take form to the floor pan rather nicely over time. Here is a photo of my new stuff going in. There is a piece for under the seat that is not shown in my pic. Over time this stuff could stick pretty good to the floorboards.

Depending on how far you are taking the restoration of the cab, you could leave it as it is soundproofing rather well if it is stuck down (damping vibrations). I would have to scrape it up and inspect for rust, rust removal (if neeed), lay down a heavy coat of paint, and apply the new mat.

[HO455]

Originally Posted by sick472

Any chance that the rubber coating your talking about is the factory tar-like under carpet soundproofing? .

Nope is was a spray on undercoating product. That after 50 years only half of it is still stuck and the other 50% will fight you all the way to remove it.

[traut811]

HO455 has it. Looks more like a thick undercoating that is somewhat textured. Some of the stuff was peeling up and picked off with my finger, but looks like the rest will put up a really good fight trying to remove it.

I haven't pulled the carpet (yet). The plan was to just do the inside of the doors for right now while I have a section cut out for patches, then do the cab floor when I replace the carpet and seat.

The truck is actually really solid. I have not found rust on it yet luckily.

[sick472]

I have used air chisels on a low pressure setting with a wide chisel to speed up the removal of undercoating-like goo. It works best in cold temps so that the goo is more brittle and less sticky and you just have to be careful not to get carried away and cut though the sheet metal. I do have an oscillating multi-tool that has a scrapper blade, but I have not tried it on jobs like this. It could work well, but cold and brittle may be the key as well. Otherwise, on a HOT summer day and a hand scraper!

[traut811]

Originally Posted by sick472

I have used air chisels on a low pressure setting with a wide chisel to speed up the removal of undercoating-like goo. It works best in cold temps so that the goo is more brittle and less sticky and you just have to be careful not to get carried away and cut though the sheet metal. I do have an oscillating multi-tool that has a scrapper blade, but I have not tried it on jobs like this. It could work well, but cold and brittle may be the key as well. Otherwise, on a HOT summer day and a hand scraper!

That sounds like a fun time.
If the whole inside of the door doesn't need sound deadening mat, at least I shouldn't have to remove it all I suppose. It scares me pushing around on the inside of the outside door skin but I'll try to remove what I can around the speaker area. I have one of those scraper blades also so may give it a whirl here.

[LS short box]

I used some Dyna Mat "like" inside the doors. My doors had some GM spray on under coating inside the door. It was rock hard and chipped off with a little effort.
Here's a pic of my cab insulation.

[71longbed-brew]

80 mil Kilmat works pretty well
Its available on Amazon

[ricurt69]

On a 72 I dyna mated the doors. The problem was one door was original and has I guess a factory hard rough inner surface. It was not long before it all ended up falling to the bottom of the door. One door was a repo and the Mat stuck and is still on there years later. Would not be very easy to try and sand / scrape the inner door and maybe causing damage. Anyone encountered this?

[notsolo]

Not sure what would have been used inside the doors, but 50 yr old undercoating comes off with some kerosene and a scraper, spray bottle wait scrape and repeat. I don't think anything will stay or stick in there unless it's removed.

[ricurt69]

On the inside of the door skin where it would normally go. I did the whole interior before new carpet etc.

[Richard]

Originally Posted by sick472

I have used air chisels on a low pressure setting with a wide chisel to speed up the removal of undercoating-like goo. It works best in cold temps so that the goo is more brittle and less sticky and you just have to be careful not to get carried away and cut though the sheet metal. I do have an oscillating multi-tool that has a scrapper blade, but I have not tried it on jobs like this. It could work well, but cold and brittle may be the key as well. Otherwise, on a HOT summer day and a hand scraper!

I use a flap wheel on my dull, worn out oscillating multi-tool blades to make a chisel tip just for this purpose. Saves some time and money. Removing at room temp seems to work best.

[LNP]

I used Lizard Skin sound deadening and the ceramic to stop the road heat on my floor before installing my carpet.