Fun With Foam: SDA Driver Basket Insulation

skrol

Dynamat caustic fumes? That is something I hadn't thought of. Is this a known issue?

inspiredsports

I just did some quick googling and can't find an online msds for Dynamat Extreme so I immediately emailed Dynamat's main technical support group for a link or pdf. I will post a link as soon as they get back to me.

I did find msds sheets for some other competing products that are claimed to be absolutely safe and non-toxic. There is a fine point / distinction here. I think Dynamat EXTREME is safe, where older asphalt based versions may be problematic.

. . . more to come.

F1nut

There are no caustic fumes from Dynamat. Whomever said that is full of it. I have a large box of it here, just opened it, took a big whiff, nothing.....absolutely no smell, odor, etc.

inspiredsports

6'&glassy wrote: »

. . . caustic fumes from dynamat type (glues and tars) products could lead to deterioration of speaker parts if used in abundance.

####################################################
Club Polk Members are fortunate that the BEST RECOMMENDATION here
has been to use Dynamat "EXTREME" which is clearly BUTYL and aluminum.

Note that some old Dynamat products DID contain Asphalt, but not "EXTREME"
#####################################################

First, it may not even be an issue as interior speaker cabinets probably remain in a safe temperature range, but here goes:

I've done research & about a dozen brands/trade names/products have sold through the years as sound deadeners, most in BOTH asphalt (bad) and butyl (good) formulations.

Asphalt starts melting at 180 degrees F and asphalt fumes are toxic and can damage metals. Asphalt IS IARC (International Agency for Research on Cancer) listed.

Butyl is stable to at least 300 degrees F and probably to 500 degrees F, Butyl IS NOT IARC listed.

The test to determine formulation of your sound deadening material is to soak a sample in Mineral Spirits for 1 hour, remove and place sticky side on white paper. Black = Butyl, Brown = Asphalt.

########### SOURCES ##########

--- http://www.diymobileaudio.com/forum/product-selection-comparisons/45413-home-depot-dynamat-real-time.html - Posts #25, 55, 109 & 125 cut through hours of BS.
--- I have not been provided an MSDS by Dynamic Control, Inc. (Dynamat) or asnswered as to what brand butyl they use, but Exxon is a dominant producer and I located theirs at - http://www.rtvanderbilt.com/documents/MSDS/US/G00020.pdf

########## Various Sound Deadening Products ##########
B-Quiet
B-Quiet Extreme
B-Quiet Ultimate
Cascade V-Max
Cofair
Damplifier
Deamplifier Pro
Dynamat
Dynamat Extreme
eDead V1
eDead V1SE
FatMat
Peel & Seal
Protectowrap
Second Skin
Scorche Accumat AMT060
RAAMmat
RAAMmat RXT
RAAMmat BXT
#############################

motorstereo

[Asphalt starts melting at 180 degrees F and asphalt fumes are toxic and can damage metals. Asphalt IS IARC (International Agency for Research on Cancer) listed.

Great; just great now you tell me. 25 years in the asphalt industry and breathing in more of that **** than anyone has a right to. I wouldn't waste my time "deadening" baskets with the stuff. How a basket can "ring" while being securely mounted to a solid wood surface is beyond me. Kinda goes against the laws of physics.

NJPOLKER

motorstereo wrote: »

[Asphalt starts melting at 180 degrees F and asphalt fumes are toxic and can damage metals. Asphalt IS IARC (International Agency for Research on Cancer) listed.

Great; just great now you tell me. 25 years in the asphalt industry and breathing in more of that **** than anyone has a right to. I wouldn't waste my time "deadening" baskets with the stuff. How a basket can "ring" while being securely mounted to a solid wood surface is beyond me. Kinda goes against the laws of physics.

WRONG
But thats OK
It does not ring like a telephone by the way.
Drew

zingo

Ring ring... Your speaker basket is calling...

DarqueKnight

motorstereo wrote: »

How a basket can "ring" while being securely mounted to a solid wood surface is beyond me. Kinda goes against the laws of physics.

???

That might be true if the entire basket was mounted to the baffle. Consider that only a small part of the basket, the rim, is secured to the baffle. The largest part of the basket is hanging in open air and is actively impinged upon by the sound waves bouncing around the cabinet's interior.;)

motorstereo

DarqueKnight wrote: »

???

That might be true if the entire basket was mounted to the baffle. Consider that only a small part of the basket, the rim, is secured to the baffle. The largest part of the basket is hanging in open air and is actively impinged upon by the sound waves bouncing around the cabinet's interior.;)

Do you think the soundwaves inside the box have enough energy to make the speaker frame "ring"? I don't think it's possible but I've been wrong before.

Face

Remove a PR and flick the spokes or bottom of the basket with your finger, you'll hear what we mean by ringing.

zingo wrote: »

Ring ring... Your speaker basket is calling...

LOL Jake.

george daniel

did'nt Sal put a cat inside his SDA's?:rolleyes:

DarqueKnight

motorstereo wrote: »

Do you think the soundwaves inside the box have enough energy to make the speaker frame "ring"?

Obviously I do, or I would not have gone to the trouble to dampen my speaker baskets, nor would I have been advised to do so by a Polk engineer.

Here are some further thoughts for your consideration:

1. Do you think the sound waves coming from the front of a speaker can cause windows to rattle and furniture to vibrate? Have you ever heard such a phenomenon?

2. The acoustic waveform coming from the back of a speaker driver is equal and opposite to the waveform coming from the front of the driver. If the waveform coming from the front can rattle things ten feet or more from the driver, why wouldn't an equivalent waveform coming from the back of the driver rattle things a few inches from it?

3. Are you aware that manufacturers of quality loudspeakers expend considerable effort to dampen cabinet vibrations because such vibrations audibly color the sound coming from the front of the drivers? Are you aware that those cabinet vibrations are caused by sound waves inside the cabinet? If sound waves inside the cabinet can cause thick pieces of MDF to vibrate (ring), why wouldn't the same sound waves have enough energy to cause the relatively thin metal in the driver basket to vibrate (ring)?

motorstereo wrote: »

I don't think it's possible but I've been wrong before.

As have we all.

ShinAce

If you want to know about vibrations, look at a guitar or a violin. Using the same strings tuned to the same frequency, they still don't sound the same. The difference is in the 'vibrational modes' of the instrument body and cavity.

Holographic interferometry can be used to visually show it.

Worst of all, once you manage to 'sink' the speaker basket enough that the ringing is softer and shorter, the speaker cone is still ringing like crazy. There's not much you can do about the vibrational modes of speakers, which explains why there are so many different materials used for speaker cones.

The point here, like DK just pointed out, is that the speaker gives off energy from both sides of the cone. The sound that is stuck in the box needs to dissipate in some manner. One way is for it to bounce off a wall and then punch through the speaker cone(not good). Another is for it to make the box ring and the ringing turns to heat eventually(not good). Another is for the speaker parts to ring and heat up(not good). Another way is to sink this energy into some material not used for the sound in any way(good). Examples include stuffing the box with mineral wool, lining the inside of the box with concrete, or attempting to dampen the speaker by adding weight to the basket or even a better gasket between the driver and box.

/rant

motorstereo

Thanks for your good explanation and advice Raife. What the heck have I got to lose? I'm on my winter layoff and looking for a winter project. I guess you'd have to say I was afraid of mucking up an already great sounding speaker. I'll give it a shot as it looks like something that I'm capable of doing correctly.

Face

What I notice some other manufactures do, they add bracing that comes within .5" of the driver/magnet assembly, and use dum dum to couple the driver to the cabinet.

motorstereo

Face wrote: »

What I notice some other manufactures do, they add bracing that comes within .5" of the driver/magnet assembly, and use dum dum to couple the driver to the cabinet.

Informative posts such as these are the main reason I spend so little time here. If I wasn't on my winter lay off and bored silly;

Face

motorstereo wrote: »

Informative posts such as these are the main reason I spend so little time here. If I wasn't on my winter lay off and bored silly;

FYI: dum dum is a automotive term for a putty type material used for sealing, etc... Think of a large blob of Mortite.

motorstereo

My bad Face; I was thinking the dum dum lollipop since there's youngsters about on these holidays. Never heard of the stuff you mentioned. Good idea though

F1nut

Dum dee dum.....

John30_30

I think this is an excellent tweak for vintage Polks in a room with non-carpet flooring; i.e. tile, wood, etc.
I found the sonority of my RTA11T's to be just way too overpowering :eek: when I moved them into the living room, which has wood flooring I'd put down 10 years ago.
Since I was going to be pulling drivers anyway, I went ahead with replacing the gaskets with mortite around the drivers and passives, already having some of it laying around handy. But that was a take-it-or-leave-it thing.

However, the foam insulation on the back of the drivers was necessary and really did mute the reverb by the drivers without otherwise diminishing them.

However, having done both passives in one tower and neither in the other, it sounded to me like the one with both passives taped off now had the bass excessively muted, or at least more than I wanted. Even with the regular gaskets, the bass has always seemed very punchy and healthy from these speakers....in a carpeted room, though.
The one with no tape on the passives at all still seemed too piercing in the middle registers, so I taped the basket of just the upper passive, (which I believe is set a full 5th above the lower one, which is yet more cool Polk engineering) which got me alot closer to what I wanted. Pulled half that tape off, and by Jove, I think we've got it!:D:D

Ideally, I'd think carpet is almost a necessity for proper acoustic muting, or even alot of wall fabric, drapes would be helpful with hard flooring, but this tweak easily alleviates radical remodeling to still be able get a full register of good sound.

Thanks, D.K.!

motorstereo

Ok against my better judgement I decided to give the foam tape a shot. My crossovers are presently out being rebuilt. While I'm waiting for them now would be the time to do this tweak. Taped up the passive radiators with frost king 7/16's rubber seal and all went quite well. Put the passives back on the shelf as I'm leaving them out till the crossovers are back. You can imagine my dismay to find half of the foam tape unstuck from the units the following day. No problem; must be some sort of build up on them. Clean the spokes with super clean and brake clean and this still doesn't fix the problem. The 2 drivers that I did are holding up fine though. Those who have done this may want to check their speakers to see if the glue is still holding their strips in place. I also thought I might have a bad batch of foam and went to Lowes as opposed to Home Depot for my 2nd roll. No change in the stickum. When I first applied the foam strips they stuck quite nicely and I thought all was well. Thankfully I didn't reinstall any units right afterward or I wouldn't have known about the glue not holding. I hope I'm an isolated case but I wouldn't bet on it.

inspiredsports

Dynamat Extreme is the best, albeit more permanent, solution. Trust us, you'll like it

Surface prep for the foam tape might be necessary, although I'm not personally sure of what to advise because I wouldn't want something to hit and melt part of the speaker or glues used to hold the various speaker parts together. I'm thinking something highly evaporative like alcohol, but wouldn't want more than a drop to touch anything but the outside of the spoke metal.

I'm not sure I read carefully enough, but at least the spokes of the 6.5" drivers need to be covered to insure no internal ringing can occur.

Next time I unseal my cabinets I am also going to judiciously place small amounts of Dynamat Extreme on the sides of my caps

motorstereo

Just checked my drivers and one of them has had the foam tape come unrolled from around the edge. The small pieces on the spokes are still intact. I'm thinking tomorrow every single bit of this foam is coming off as I don't trust it now. I'd rather have a problem with non-existant ringing rather than have a piece of foam get wedged between the cone and the frame. That could ruin a driver. If superclean or brakeclean won't clean the spokes enough for the foam to stick then I'll have to pass. I'll have to research that "dynamat extreme" and see what that has to offer. I must admit the passive radiator does ring somewhat when it's out of it's home but I'm still thinking it cannot ring when it's secured. At any rate the possibility of the foam taking out one my drivers isn't worth it to me.

F1nut

Agh! There's nothing to research, it works.

http://www.etronics.com/p-8929-dynamat-xtreme-door-kit-10435.aspx

DarqueKnight

motorstereo wrote: »

Just checked my drivers and one of them has had the foam tape come unrolled from around the edge. The small pieces on the spokes are still intact.

I had some concern about the foam popping off, especially the curved pieces. I did the Mortite tweak five days after applying the foam and nothing had popped off then. When I was pulling one of the drivers out of my SRS's prior to applying Mortite, I did scrape off one of the little foam blocks on one spoke.

This evening I took one of the passive radiator out of one 1.2TL and and the tape was still in place over two months after application. Shining a flashlight up into the cabinet didn't reveal any tape coming loose from any of the drivers.

If I had seen any loose tape, I would have scheduled some time to pull it all off and replace it with Dynamat Xtreme. BTW, when I was applying the tape, I pressed down really hard with the fingers from both hands.

For someone who has never damped their drivers, I would recommend using the foam first because it is cheap and easy to remove if the result is imperceptible or undesirable. One day, in the far future when I'm more caught up on other projects, I'll probably replace the foam with Dynamat Xtreme. Since posting this report I have used DX on another project and really like it. I think the adhesive on DX can stick to water.

motorstereo

Thanks guys; I'm pulling off what hasn't fallen off already today and trying out the dynamat. It's really not that expensive when you compare it to some of the other tweaks. The foam would be a very expensive tweak should a loose piece take out a driver.
Glad to hear the dynamat has better holding power. I had my passive's spokes done exactly as you showed in your pics darqueknight. Took my time and pressed them into place as I should. Overnight at least 3 or 4 spokes had fallen off so I decided to remove them all and try something different. One 3/4 strip on either side of the rounded piece in the middle. Same problem. Wiped the spokes down with superclean thinking there might be a problem there. No difference.
I'm just glad that I didn't reinstall everything right away and ruin something. I'll give my local car audio shop a look see today and see if they have any "dynamat" in stock.

DarqueKnight

DarqueKnight wrote: »

One day, in the far future when I'm more caught up on other projects, I'll probably replace the foam with Dynamat Xtreme.

Earlier this week I replaced all the foam damping material with Dynamat Xtreme. After 15 months, the foam strips were still firmly adhered to the metal baskets and I had to scrape them off with a plastic putty knife.

The Dynamat Xtreme provided much better damping than the foam. I compared three drivers, one with Dynamat Xtreme, one with foam and one with no damping material.


The basket of the Dynamat Xtreme treated driver was by far the most quiet.

Sound level measurements were taken of each driver while it was held by the magnet assembly with the thumb and middle finger of one hand. The edge of the rim of the driver was lightly tapped with the handle of a screwdriver with the other hand. A Radio Shack analog sound level meter was placed three inches from the driver's edge opposite the tapped edge. The meter was set to C weighting with slow response.

Bare driver: Average 90 dB-C (rang like a bell).

Foam treated driver: Average 82 dB-C (dull "thunk" sound).

Dynamat Xtreme treated driver: Average 74 dB-C (quieter dull "thunk" sound).

Removing the foam and installing Dynamat Xtreme took 1.5 hours for each speaker.

Listening Evaluation

The foam in the right speaker was replaced with Dynamat Xtreme and compared to the foam treated left speaker. My preamp was set to mono and the balance control was shifted left to right. I did not hear any difference from the midrange up. There was a very noticeable improvement in bass tactility and in micro and macro bass growl details. There was also a small improvement in bass speed.

Foam vs. Dynamat Xtreme

If you look around, you can still find the original formula Dynamat. Dynamat Xtreme is easier to work with and has better adhesion properties than the original Dynamat. However, Dynamat Xtreme is difficult to remove and represents a semi-permanent vibration damping solution. Some people might not like the sound of damped driver baskets. Considering that possibility, using the easier to remove foam as a trial option might be better. Also, one forum member reported poor adhesion of the foam to his driver baskets, therefore foam might not be a viable option in some situations and environments.

MillerLiteScott

I bet your fingers are sore.

DarqueKnight

Not at all.

I took F1nut's advice and always use very, very sharp scissors to cut the Dynamat. That way, it is no more difficult than cutting paper. The foam scraped off real easy with the plastic putty knife. I used a power screwdriver to remove and replace the 44,684 driver and passive radiator screws.

Note 1 to those planning to do this tweak: If you use a power screwdriver, don't tighten all the way down when replacing the screws because you run the risk of stripping the wood threads. I only go 3/4 the way down and hand tighten the rest of the way.

Note 2 to those planning to do this tweak: If you use very sharp scissors to cut the Dynamat, you can move through the sheet so fast that the sharp metal foil edges brush against your fingers and cut them...so watch it. You could also use a cutting board and razor blade, but I find scissors to be faster.

hearingimpared

Nice write up Ray. When I did my baskets, and yes I had sore cramped up fingers and hands, I used an Exacto knife and a metal ruled straight edge to cut the pieces all at once for the midwoofers then peeled each piece off and applied. I repeated this for the passive radiators as you already know require bigger pieces.