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Sound Deadening Doors


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#1 SleeperSaab

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Posted 23 February 2011 - 08:09 AM

Guys, I know I've been going on about sound deadening AND I know there are 100 tutorials here about this, but I posted this on my blog and on a Saab site, so I thought I'd post it here and see what comments I draw. If it's really too lame, delete it. Posted Image

Okay, there are a lot of different schools of thought on how much Dynamat you should use. They say the best bang for buck option is about 25 – 30% coverage and just putting it in the place where resonance and rattles may occur. However, after the 30% the law of diminishing returns applies, which means that the more you put on, the less extra benefit you get. 30% might give you 90% effectiveness, and 100% might give you 100% effectiveness so for the 70% extra spending, you only get about 10% better…

But, I come from the school of overkill and can’t be bothered spending the time to find the exact spots where I should be applying Dynamat, so I just covered as much as I can. On the outer shell of the door, I have covered it at around 100% (there may be slight areas where the mat doesn’t join, but it will still give it full coverage) and on the inner shell of the door, I have sealed up all the service holes and applied to resonant prone areas.

Previously, I have just Dynamatted around the speaker and behind it. This is quite often enough. But, I have to be honest and say that I have found a noticable difference in the way the speaker plays and for that I’m happy to have gone the extra mile.

So, here’s a couple of pictures of the outer skin at 100%…

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And a close up….

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Then, because I like overkill, I have applied a new product that Dynamat puts out called a Dynazorb. It’s designed to specifically absorb the stray frequencies that bounce out of the back of the speaker. I don’t know if it’s really worth the money (around $40 each), but I have had reports from professional installers who have tested it and they say the difference is noticable. I believe them.

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Next I made sure I’d finished with all the wires and tested that the speaker and spacer fit in with the door trim and all that, then Icovered up the service holes. Now, if you don’t use Dynamat, but something similiar, beware that you can still remove it if needed. Dynamat is pretty easy to remove even after a long time, so covering the service holes that hardly are needed is not such a bad thing. However, it does wonders as far as creating a kind of enclosure for your speaker. And sounds awesome. Posted Image

Firstly, take a sharpie to the door and mark all of the holes that you need to keep open. This included the door handle holes, but mostly where the door trim plugs go in. Anything that screws in need to still be able to, and will be sealed anyway once filled, so you don’t need to cover those.

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I’ve marked mine with little x symbols. You won’t see them once the door trim is on, so it’s okay. The next step is pretty easy in that you just go through and cover each of the holes, cutting a larger piece than you need and sticking it over the hole. Then go through and tap on the bare areas and work out which ones are hollow sounding and whack some dynamat on there. Just cutting up small strips seems to do the trick.

The only problem areas is where the door lock rods come through. You DON’T want the Dynamat to stick to these rods and make it impossible to open/close/lock your door. So, this is how I got around it and still had as much sealing as I could.

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Above is the hole with the rod sticking out of it. I’m going to make a kind of flap to seal it as much as possible.

Firstly, cut a strip that goes just past where the rod goes into the door.

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Next we want to have the rest covered from the outside, but we don’t want the dynamat to stick to the rod. Work out where the rod moves and cut a second piece of Dynamat to be pressed against the back of the first, thereby creating a smooth area for the rod to move along.

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Then stick that pad onto the serivce hole and try to close up the sticky ends as much as possible while leaving a free channel for the rod to move along.

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Here’s a side shot…

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And then here’s the finished product.

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And finally, mount the speaker and you’re all done. If you want MORE overkill, you can cover the door 100%, but the key thing is the service holes on this side.

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#2 Chris.

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Posted 23 February 2011 - 09:05 AM

looks good.

#3 Banned.ScrewYouTeam.inc

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Posted 23 February 2011 - 09:18 AM

I do believe people would normally want to cover the service holes in thin MDF, painted to make it somewhat water proof, rather than just stick the sound deadener over the holes.

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#4 SleeperSaab

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Posted 23 February 2011 - 11:28 AM

Hi Im James, on 23 February 2011 - 09:18 AM, said:

I do believe people would normally want to cover the service holes in thin MDF, painted to make it somewhat water proof, rather than just stick the sound deadener over the holes.

Interesting. I see that there might be value to that, but how much, I wonder. That dynamat sticks pretty well and is about the same thickness as thin mdf.

How much of a difference would it make, do you think? Has anyone here compared the two?

#5 peaandham

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Posted 23 February 2011 - 04:38 PM

Hi Im James is correct, how ever if you don't feel like doing alot just covering the largest bottom one and the one on the right of it should suffice, then just dynamat over the top smaller ones.

Otherwise if you want to do a flawless job, MDF it all.

SleeperSaab, on 23 February 2011 - 11:28 AM, said:

How much of a difference would it make, do you think? Has anyone here compared the two?

Pretty big difference, i went from using Dynamat over my service holes, to covering the up in MDF that was painted with deadner and then dynamatted over and i was astounded by how much of a difference it actually made.

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#6 SleeperSaab

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Posted 23 February 2011 - 05:27 PM

Okay, I'm intrigued.

How thick mdf are we talking? And how do you keep it on there?

Once the mdf is in, do you dynamat over the top?

Edited by SleeperSaab, 23 February 2011 - 05:27 PM.


#7 Banned.ScrewYouTeam.inc

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Posted 23 February 2011 - 10:43 PM

SleeperSaab, on 23 February 2011 - 05:27 PM, said:

Okay, I'm intrigued.

How thick mdf are we talking? And how do you keep it on there?

Once the mdf is in, do you dynamat over the top?

3mm should be sufficient.

I gaffer taped the MDF over the service holes in my doors, but didn't sound deaden the doors at all :silly:

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#8 peaandham

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Posted 24 February 2011 - 05:57 PM

3mm MDF is fine. I cut a piece slightly to big for the hole, made sure the trim would go back on and then used Sikaflex to hold it in place.

The best way though, is to cover the hole in Duct tape, place the MDF onto the duct tape and then duct tape over that piece, this makes it easy to remove if needed.

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#9 aerosport

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Posted 27 February 2011 - 01:08 AM

I used 6mm mdf. I'm now just currently looking for some of those diffuser pads.
Here's how I went about doing my doors if it helps anyone.

I went and 100% my outer skin and I read somewhere that wrapping your "lock rods" in elec tape lowers their resonating frequency or something like that. So I figured it wouldn't hurt it. (also notice how I mounted the crossovers :P)
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note: Before I taped up the holes I used cardboard to make up templates of each hole. (rear door pic sorry, I didnt even end up doing the rear inner skin)
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Using the cardboard templates I then cut out the 6mm mdf pieces, coated them in spray on deadener and taped them accordingly to the door holes (which had been previously taped over)
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Then I went and sound deadened over everything.
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In regards to avoiding the rods sticking to the deadener, I used small conduit (split tubing) to cover where the rods would have been touching the deadener.
After refitting the door trim I noticed some of the deadener sticking out of the edges. This was fixed with a stanley knife :)

Edited by aerosport, 27 February 2011 - 01:11 AM.

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#10 peaandham

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Posted 02 March 2011 - 01:03 PM

Its good to see some new guys getting into deadening doors, the proper way.

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#11 Dylby1

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Posted 03 April 2012 - 01:27 PM

this and the other sound deadening tutorial i've read ( http://www.mobileele...g_your_vehicle/ ) will be invaluable when i do my car in the coming months.

Thanks heaps to the writers of these, i would've just ended up whacking it on "that'll do" style.

Edited by Dylby1, 03 April 2012 - 01:28 PM.

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#12 ~Samuel~

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Posted 03 April 2012 - 07:40 PM

peaandham, on 23 February 2011 - 04:38 PM, said:

Otherwise if you want to do a flawless job, MDF it all.

if you want a flawless job putting MDF in your doors is retarded. Try some acrylic or even some thin alloy cut with tin snips.

Well done to the OP on a good tutorial, looks like you did a great job on those doors :good:

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#13 peaandham

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Posted 03 April 2012 - 08:15 PM

~Samuel~, on 03 April 2012 - 07:40 PM, said:

if you want a flawless job putting MDF in your doors is retarded. Try some acrylic or even some thin alloy cut with tin snips.

Flawless was probably the wrong word to use at the time.

MDF works well but Sam you are correct, I personally wouldn't look at using alloy but acrylic would do a great job. Probably could save more if you buy the acrylic from a wholesaler as opposed to coating the timber in primer and top coat to ensure it doesn't degrade over time.

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#14 IamtheSteg

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Posted 07 April 2012 - 05:39 PM

Ok I'll bite :D

Why Acrylic over MDF? And what sort of thickness acrylic? (The missus has some 8mm chopping boards im currently eyeing off ;) )

Also once you have established the service hole plug of your choice does anyone see an upshot to screwing these in place with short metal techs as opposed to relying on gaffer/duct tape (neither adhesive inspires me with confidence wrt longevity...)

Also - i just went out to the garage to measure up the chopping board thickness and found some 6mm mdf panels waiting to be jigsawed - so are there any reasons i shouldn't be using it (covered in spray on sound deadener first of course!)

FWIW I am planning on at least 50% Dynamat coverage and Dynaxorb tiles behind each midbass driver (I've used acoustic foam tiles b4 and was happy that they made a +ve contribution but the Dynaxorb seems much less inviting for water to hang around in long term...)

Also - Sam, if i may ask - why alloy? Would Aluminium do the trick (can chop up some of the GLW's baking trays i guess :D :D :D but that will obviously be thinner/less dense than 6mm MDF of similar acrylic...

Edited by DailyDriver, 07 April 2012 - 05:41 PM.


#15 jamiebosco

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Posted 09 April 2012 - 11:22 AM

DailyDriver, on 07 April 2012 - 05:39 PM, said:

Ok I'll bite :D

Why Acrylic over MDF? And what sort of thickness acrylic? (The missus has some 8mm chopping boards im currently eyeing off ;) )

Also once you have established the service hole plug of your choice does anyone see an upshot to screwing these in place with short metal techs as opposed to relying on gaffer/duct tape (neither adhesive inspires me with confidence wrt longevity...)

Also - i just went out to the garage to measure up the chopping board thickness and found some 6mm mdf panels waiting to be jigsawed - so are there any reasons i shouldn't be using it (covered in spray on sound deadener first of course!)

FWIW I am planning on at least 50% Dynamat coverage and Dynaxorb tiles behind each midbass driver (I've used acoustic foam tiles b4 and was happy that they made a +ve contribution but the Dynaxorb seems much less inviting for water to hang around in long term...)

Also - Sam, if i may ask - why alloy? Would Aluminium do the trick (can chop up some of the GLW's baking trays i guess :D :D :D but that will obviously be thinner/less dense than 6mm MDF of similar acrylic...

I'll have a stab in the dark...

Because car doors are not water-proof,and MDF will absorb moisture and turn to mush?





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