Sound deadening doors for Hybrid Audio Technologies Clarus 61-2

[GammaRadiation 10+ year member]

You don't accomplish anything by putting a layer of closed cell foam behind the speaker.

No, but doing the whole outer door skin plus rolling some up and throwing it in the bottom of the door does. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

My motto is deaden, deaden some more, and then cover hard surfaces with soft foam.

 

[KyleBechtold 5,000+ posts]

No, but doing the whole outer door skin plus rolling some up and throwing it in the bottom of the door does. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
My motto is deaden, deaden some more, and then cover hard surfaces with soft foam.

the thing is what frequencies will that affect.. and its not the midbass.. is your higher frequencies.. Like stated above making an enclosure would REALLY be the best bet.. I have looked into doing this.. Bose.. while not appreciated on here does a small ported enclosure and has 3" speakers sounding better than most 6" speakers that people install on here due to lack of attention to detail in the install..

 

[GammaRadiation 10+ year member]

I would never port my midbass unless it were a true midbass (60-240Hz) for fear of group delay and what it would do to the upper harmonics of the tune. IB/Sealed all the way as my personal preference. One of the main complaints about bose systems is that the midbass is sloppy and boomy. To the untrained ear that is dramatic and strong. Hence, bose popularity among the untrained ears. Not to go off on a rant, but since you mentioned it, Bose customer's audiophilia training stops at what the dance floor of the hottest club in the area sounds like.

//content.invisioncic.com/y282845/emoticons/highhorse.gif.6bbb570c3f53dc0dcce8a2b8ad05cf11.gif

 

[Rudy 10+ year member]

Isn't that the conventional wisdom though? Can it do more harm than good?

This is a case where conventional wisdom has no base in reality/. As KyleBechtold pointed out, the best you could hope to accomplish in the space available is some influence on frequencies at the upper threshold of the audible range. That's if closed cell foam was a godd absorber - which it isn't.

I'm not being critical, I used to accept this idea too, but here's how it became conventional wisdom despite being completely wrong. Persona fter person opens their doors, puts vibration damper on the pouter skins followed by a layer of CCF. Put it all back together and there is an improvement. Conclusion: both the vibration damper and CCF are critical components. Nobody has opened their doors, applied vibration damper, put the doors back together, listened, pulled the doors apart, added the layer of CCF, put them back together and noticed an additional improvement.

 

[keep_hope_alive Premium Member]

i have about 100SF of CCF in my garage. maybe i should do some testing with it. maybe in a test enclosure? or snag a door from a junk yard for cheap? if i do that, then i could experiment with various amounts of deadener/fill and RTA each. hmmm...

i am more interested in trying a variety of door fill materials. but only after deadener coverage area tests. i see the tests as follows

1. as-is factory door

2. holes closed/sealed (removable), no deadener

3. 25%, 50%, 75%, 100%, 200% coverage with/without holes closed. - tests would be RTA and ASTM resonanace testing

the tough part would be deciding what deadener to use, then justifying spending ~$200 on deadener for a test.

I did find those ASA papers on car door testing - but my license for them does not extend to public sharing. //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[keep_hope_alive Premium Member]

closed cell foam absorption coefficients (note that the test conditions are important to know in order to make sense of the data). for our interest, the test would need to have the CCF against a rigid wall/surface without an air cavity.

http://www.matelys.com/publications/CP07.pdf

note that if you had the foam extend across structual supports so you had an air cavity - you would improve the absorption coefficients and create a "broad-band" membrane absorber. this would be worth trying.

it is well documented that CCF is not a good absorber. i only use it to prevent rattles. not inside the door, but on the door surface so the door panel is against it.

 

[GammaRadiation 10+ year member]

This is a case where conventional wisdom has no base in reality/. As KyleBechtold pointed out, the best you could hope to accomplish in the space available is some influence on frequencies at the upper threshold of the audible range. That's if closed cell foam was a godd absorber - which it isn't.
I'm not being critical, I used to accept this idea too, but here's how it became conventional wisdom despite being completely wrong. Persona fter person opens their doors, puts vibration damper on the pouter skins followed by a layer of CCF. Put it all back together and there is an improvement. Conclusion: both the vibration damper and CCF are critical components. Nobody has opened their doors, applied vibration damper, put the doors back together, listened, pulled the doors apart, added the layer of CCF, put them back together and noticed an additional improvement.

Cool story, bro. But I started out with 1 layer of butyl based (second skin damplifier) inner and outer door skins (with treated plywood backing over large holes) and back wall. Improvement but what the hell, I got a good price on RAAMatt and was doing my friend's entire vehicle anyway. Second layer. Minor imaprovement. Third layer on the outer door skin and first layer on the roof. Meh improvement on SQ, minor drop in wind noise. Oh and it made my doors slam like a Mercedes. Closed cell foam and Second Skin's speaker diffuser. Rolled up "bass traps" in the bottom of the doors. Noticeable improvement on the smoothness of the notes and a minor improvement on volume.

 

[GammaRadiation 10+ year member]

i have about 100SF of CCF in my garage. maybe i should do some testing with it. maybe in a test enclosure? or snag a door from a junk yard for cheap? if i do that, then i could experiment with various amounts of deadener/fill and RTA each. hmmm...
i am more interested in trying a variety of door fill materials. but only after deadener coverage area tests. i see the tests as follows

1. as-is factory door

2. holes closed/sealed (removable), no deadener

3. 25%, 50%, 75%, 100%, 200% coverage with/without holes closed. - tests would be RTA and ASTM resonanace testing

the tough part would be deciding what deadener to use, then justifying spending ~$200 on deadener for a test.

I did find those ASA papers on car door testing - but my license for them does not extend to public sharing. //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

I've done some sealed woofer 20-200Hz poly stuffing vs no stuffing experiments in MDF, Pine Plywood, and OSB sealed boxes. By far the best performer was MDF + Stuffing as far as transfer function magnitude goes. Poly stuffing always provided a smoother response and most often a minor volume increase. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I used a cheap-o walmart 8" woofer in 0.75cuft gross sealed boxes of identical dimensions and a 75w RMS JBL amplifier running at ~8v. Term lab meter @ 1m from the cone in a 12x14x10 room. Plywood floor over 1" padding between the woofer and the meter.

 

[06goat 10+ year member]

Cool story, bro. But I started out with 1 layer of butyl based (second skin damplifier) inner and outer door skins (with treated plywood backing over large holes) and back wall. Improvement but what the hell, I got a good price on RAAMatt and was doing my friend's entire vehicle anyway. Second layer. Minor imaprovement. Third layer on the outer door skin and first layer on the roof. Meh improvement on SQ, minor drop in wind noise. Oh and it made my doors slam like a Mercedes. Closed cell foam and Second Skin's speaker diffuser. Rolled up "bass traps" in the bottom of the doors. Noticeable improvement on the smoothness of the notes and a minor improvement on volume.

Im not sure Rudy is the one to be taken lightly when it comes to sound deadening in a vehicle.

And how long have these "Rolled up bass traps"

 

[kmoto]

Thank you everyone for your input. I learned a little something from everyone who posted. Just some observations I made... One way, you set the boundaries at the outer shell of the vehicle with multiple layers of deadener and try to deaden everything between you and the outside shell . Another way, create a boundary with mass loaded vinyl at the plane of your speakers, floor and ceiling of your car then use small amounts of deadener to lower resonance of large panels behind the plane of your speakers. Different cars, different equipment, different ears...I guess it comes down to what your expectations are for the sound in your vehicle. Upper middle of the pack SQ on a reasonable budget is my plan.

This is a quote of Mr.Buwalda taken from the Clarus manual " A word of warning though: there is a fine line between too little and too much acoustic treatment; just as some vehicles can benefit from some selectively applied treatments, there is a point where the vehicle can begin to approach “semi-anechoic” conditions, and lose its liveliness, which is not ideal. Reflections are all around us, and are a part of our day-to-day lives. It is our opinion that some lateral reflection is a good thing; it helps to establish stage boundaries, and gives the recoded playback and more visceral and “believable” sound. "

 

[keep_hope_alive Premium Member]

I've done some sealed woofer 20-200Hz poly stuffing vs no stuffing experiments in MDF, Pine Plywood, and OSB sealed boxes. By far the best performer was MDF + Stuffing as far as transfer function magnitude goes. Poly stuffing always provided a smoother response and most often a minor volume increase. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
I used a cheap-o walmart 8" woofer in 0.75cuft gross sealed boxes of identical dimensions and a 75w RMS JBL amplifier running at ~8v. Term lab meter @ 1m from the cone in a 12x14x10 room. Plywood floor over 1" padding between the woofer and the meter.

i typically use a more organic stuffing over straight poly - usually something with some cotton content. you just can't get that stuff wet. i typically raid old couch cushons and pillows (be sure they aren't ***** soaked first!!!). I got a ton of stuffing when i threw out my old futon matress.

i think the stuffing testing in the Loudspeaker Design Cookbook is a good reference as well.

we almost got to build our own anechoic chamber and reverberant chamber for testing acoustic treatments at work - then the economy shelved that project. //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[Rudy 10+ year member]

Cool story, bro. But I started out with 1 layer of butyl based (second skin damplifier) inner and outer door skins (with treated plywood backing over large holes) and back wall. Improvement but what the hell, I got a good price on RAAMatt and was doing my friend's entire vehicle anyway. Second layer. Minor imaprovement. Third layer on the outer door skin and first layer on the roof. Meh improvement on SQ, minor drop in wind noise. Oh and it made my doors slam like a Mercedes. Closed cell foam and Second Skin's speaker diffuser. Rolled up "bass traps" in the bottom of the doors. Noticeable improvement on the smoothness of the notes and a minor improvement on volume.

Nobody is suggesting that you can't build an inefficient barrier using multiple layers of vibration damper - just that it doesn't make any sense to do it that way.

Rolled up "bass traps" in the bottom of the doors

I'd need to see measurements that showed improvement to believe that was anything more than misunderstanding the purpose of bass traps in a listening room, similar to the: they use foam on the walls of recording studios so I'll put (closed cell) foam on the outer skin of my car door conventional wisdom question I was responding to.

Oh and it made my doors slam like a Mercedes.

The difference in the closing sound over a single layer and multiple layers of vibration damper is downward resonant frequency shift from the added mass. Nice feature but really nothing to do with the doors' potential as a speaker mounting sytem. It's completely impractical to try to lower a vehicle panel's resonant frequency below the audible range because of the absurd amount of mass required. Since there's some offsetting panel stiffening with vibration damper it's even harder to accomplish.

Noticeable improvement on the smoothness of the notes and a minor improvement on volume.

These are the kind of completely subjective descriptions that make it possible to sell "audiophiles" speaker wire trestles and special magic markers to enhance CD fidelity. The funny thing about claims like these is that they not only don't demonstrate any change they don't even provide enough information to to tell if the claimed change is good or bad.

You may like my "school story" but everything I've said is consistent with the relevant physics and easy to demonstrate. You refuted it with the equivalent of wine tasting cliches.

 

[Flex68 10+ year member]

when i add absorption to my doors, i will use PVC sheets (available in rolls at any home improvement store, typically for covering your windows in winter). i will sandwich fiberglass batt insulation inside and seal the edges using a tape made for securing the PVC, and secure (probably with silicone) it to the outer door skin along the length of the door in rows (probably three rows since i have two rows of structural tubes). it will be a very cost effective method of adding a substantial amount of absorption - probably $30 per door.

I am subscribed, and loving this! (Thanks to the OP and all contributors: its like I am an addict being fed free drugs!)

Regarding the above comment, would you then cover this with the same sound dampener that you'd place on the innermost door skin? Or would there be no practical need, at that point, for deadening/dampening the outer door any further?

[Practicality is subjective, I know, but looking at that KILLER Scion install, all I could think is, "Ah, that is the way an install is supposed to be done...so do I have any right to try to do my own build with only a $1500 budget?!?" I was thinking that perhaps I could manage $200 in sound dampening material--- since that is practical for me for my build--- but I couldn't manage even a quarter of what you guys did on the Scion...regardless of whether or not it is justifiable, or an important part of an "ideal" install.]

 

[Rudy 10+ year member]

when i add absorption to my doors, i will use PVC sheets (available in rolls at any home improvement store, typically for covering your windows in winter). i will sandwich fiberglass batt insulation inside and seal the edges using a tape made for securing the PVC, and secure (probably with silicone) it to the outer door skin along the length of the door in rows (probably three rows since i have two rows of structural tubes). it will be a very cost effective method of adding a substantial amount of absorption - probably $30 per door.

That's an interesting idea with enough potential benefit to be worth trying and measuring. Sealing the surface of the absorbent material (perfectly) will eliminate the moisture problem. It might be better to seal the material in "bags" that completely wrap it and then just bond the bag to the outer skin. Sealing the edges of plastic sheeting to the doors is going to be tricky and doesn't get you any advantage that I can see. This way the only possible point of failure would be the bag material itself. If it doesn't deteriorate with time, the only thing it can do is fall off - no big deal.

In any case, this idea completely gets around the reasons CCF doesn't absorb sound. It's also better than the idea of waterproof open celled foam since that is making it close to CCF.

You still have the thickness/frequency problem. Even 2" isn't going to get you much below 2 kHz the first time through. It's going to get you lower for some of the reflected sound. Not sure how much problem energy we're still dealing with at that point though.

All of this complication should make it clear that if you're willing to go to extremes for speaker performance an enclosure, preferably not in a door, is the way to go.

 

[GammaRadiation 10+ year member]

Im not sure Rudy is the one to be taken lightly when it comes to sound deadening in a vehicle.
And how long have these "Rolled up bass traps"
I dont know who he is, and I dont really care. He shouldn't make blanket statements.

Been in there 4 years and haven't molded or degraded. It is neoprene based CCF that was supposed to have been treated with some anti mold/mildew chemical. Similar to the stuff Second Skin sold at the time but I got it from an upholstery shop.