Damping.

[johnnyrichards]

So is there a consensus on damping rear waves? PE has their convoluted foam on sale right now, how would that compare to typical mattress topper? How about their peel-n-stick damping sheets?

To be clear, I am not inquiring about damping impedance spikes, but the rear waves of the drivers.

Gonna put in a order soon, just wondering if the PE products are worth the price, or not.

[Face]

Re: Damping.

If you're referring to their "egg crate material", I wouldn't bother. IMO, it's almost useless for a woofer enclosure.

[djkest]

Re: Damping.

If you're referring to their "egg crate material", I wouldn't bother. IMO, it's almost useless for a woofer enclosure.

What about 1/2" Sonic Barrier?

[901Fixer]

Re: Damping.

I don't wanna thread-jack but since this topic has been brought up and I find conflicting information all the time, what frequencies can be damped and at what point does it not work? I'm referring to conflicting opinions I've seen about woofer and sub-woofer enclosures. I see builds where someone will specify a quantity and type of damping material and then I see where someone will post that the long wavelengths are not effected by damping. There does seem to be a consensus on higher frequencies being controlled with the proper material but down to where?

If there is an existing post that will provide some clarity on this please post it.

[CUtiger]

Re: Damping.

Johnny glad you brought this topic up as my cabinets are starting to come together and I began debating this topic last night. After about four hours of searching this forum I'm not sure there is a consensus.

I think it will largely depend on what frequencies you are most interested in damping and what logistics you are willing to deal with when applying the material. FG(pink stuff and rigid ceiling tiles)/roxul/the denim insulation seem to offer the best performance to price ratio especially for lower frequencies but at least in my mind would seem to be more difficult to apply in a smallish enclosure.

Some other alternatives I saw last night were using pieces of thick carpet, which would be nice and cheap if you could convince a carpet installer to give you some leftover trimmings. Anothe option I was thinking about that I haven't seen used was using a couple layers of thick industrial felt. I would think it would perform better than the peel and stick sheets and isn't that expensive.

http://www.thefeltstore.com/Portal.a...N=C748CC8FF299

[sdl2112]

Re: Damping.

There's some info. here.

http://www.troelsgravesen.dk/cabinet-damping.htm

[djkest]

Re: Damping.

Direct quote from Zaph Audio:

For damping vented enclosures, I use Whispermat, Sonic Barrier or 1/2" carpet padding doubled up. Whispermat is the best value. Sonic Barrier is expensive but occasionally handy since it comes with adhesive and is sold in small (but expensive) quantities. Carpet padding is surprisingly effective and cheap but it varies in performance. I never use egg crate foam because it just plain does not perform well. For sealed, I feel that "Acousti-Stuff" is the best performing, but standard craft store dacron pillow fiber will do oK for about 1/3 the cost.

[Face]

Re: Damping.

What about 1/2" Sonic Barrier?

I either use Sonic Barrier, Black Hole, or No Rez depending on which is on sale. FYI, BH and NR are a step from from Sonic Barrier, but are a PITA to trim without using a table saw or very large scissors/snips.

[Bart Oetken]

Re: Damping.

Johnny I think the mattress topper from wallyworld is the best bet here. For the price of $15 or so you can get a queen size 1/2" or 1" mattress topping. Its really easy and with some adhessive you cant go wrong. I love the fact that it has the wavy lines in the foam. Instead of just a flat peace of foam. The 1 1/2 egg crated foam is to much THICKNESS from pe. I found if you do three walls it sounds really too flat in my personal taste. But Ive had good luck with the mattres topper.

Im like you I like the pe damping, but for the quanity wallmart is cheaper in this department. I couldnt find myself paying $50 plus for damping. You might check out ceiling tile. I tried it in a 8" dvc dayton bass reflex enclosure with a prescion port. and lined half the enclosure with ceiling tile. And, it didnt sound bad at all. Its nice to work with. kind of messy when you file the egdes down. I think it adds a good damping barrier. I go to my hardware store and buy broking peices of 2' x 4' ceiling tile for half the price of a new one. They cant sell broken peices for full price. So thats where use diy guys get a break. And a 2x4 piece can cover alot in a big enclosure.

But that sticky foam with the peel back paper does look nice.

[dthomas]

Re: Damping.

So is there a consensus on damping rear waves? PE has their convoluted foam on sale right now, how would that compare to typical mattress topper? How about their peel-n-stick damping sheets?

To be clear, I am not inquiring about damping impedance spikes, but the rear waves of the drivers.

Gonna put in a order soon, just wondering if the PE products are worth the price, or not.

At what frequencies is your driver being used. Below 400Hz the best bet is to make your cabinet as stiff as possible as damping materials other than those that add mass won't help a lot. Above 400Hz a lot of different materials are going to be beneficial.

I have always found that very well braced cabinets and polyfil are usually sufficient. It also helps tremendously to make braces non symmetrical. As random as surfaces can be on the interior will only help to break down waves. I like to strategically place polyfil inside the cabinet taking advantage of the bracing to help hold it in place. Personally I don't think open cell foam has any practical advantage over polyfil. But if you can get it cheap enough it works just fine.

Fiberglass is great stuff but if your cabinet is ported probably not a great idea unless you go to the trouble of wrapping it in batting etc....

A lot of the high priced foam stuff is just that high priced foam. My experience is anecdotal but I have tried some of them and did not find they added any benefit over a cheap bag of polyfil pillow stuffing.

I usually add about 1lb/ft3 but don't really bother to weight it just eyeball it. In the end the most likely affect of no stuffing will be cabinet resonating or noise escaping the port. The first is best attacked with cabinet bracing first the latter is fairly easy to control with basic stuffing.

[Deward Hastings]

Re: Damping.

As you've probably gathered from my previous posts I'm firmly in the "absorb the backwave" camp . . . the thinking being that any reflected sound that exits either through the port or back through the driver cone should be regarded as distortion (although, granted, some people prefer the "warmth" or "fullness" of that distortion over clarity). So I don't even think of it as "damping" . . . it's purely a question of "absorption" . . . and for that nothing beats the "rigid" panels of fiberglass or rockwool (although I'm finding a lot to like with batts of "blue denim" insulation too). They all work better than polyfill or foam . . . and generally a lot better for a lot less money.

There can be problems with this approach if you are trying to use box or pipe resonance for enhanced (boombox) bass . . . but it takes a lot of stuffing to fully absorb those low frequencys anyway. The critical frequencies are where box dimensions are between a quarter and a couple wavelengths . . . below it doesn't matter, above and it's easy with most anything (or you're into the range of the fully-enclosed tweeter).

If what you are "damping" is panel resonances then even minimal "bracing" (strips of wood glued on the panels) works better than any of the stick-on mats (although they work fine for quieting sheet metal in cars).

[XtremeRevolution]

Re: Damping.

For absorbing rear waves...

I've used both loose and rolled polyfill before in a few small cabinets. Hated it. Ended up going with acoustic foam and it made a massive difference. I use 1.5" thick acoustic foam in my Statement Monitors and it does a good job. I have zero complaints, but its also not a particularly sensitive speaker to back waves given the design.

I've used loose fiberglass insulation. It does an "ok" job. Probably not the best for vented speakers, but its not fun to work with or cut up on your own.

I then bought one of these:

http://www.atsacoustics.com/item--Sc...ool--1106.html

So far, this has been the best performing option I've used, and its not particularly expensive when you consider that you're getting a gigantic box of it.

[billfitzmaurice]

Re: Damping.

So is there a consensus on damping rear waves? PE has their convoluted foam on sale right now, how would that compare to typical mattress topper?

Urethane foam is urethane foam. So long as the thickness and density are the same so will be the results.

nothing beats the "rigid" panels of fiberglass

Inch for inch, yes. But it's not the easiest material to work with, and you can get just as good a result with other materials, you just need to use more of it.

[dthomas]

Re: Damping.

I agree with Bill on this.

Plus if you are worried about what hits the rear of the cone on most 7" or smaller midwoofers the most destructive stuff comes off the frame, spider and motor structure so stuffing the cabinet has minimal effect on this.

I have had very good results with good old pillow stuffing and batting. Easy to glue in. And nothing replaces the effect of a rigid, heavy cabinet.

[XtremeRevolution]

Re: Damping.

I agree with Bill on this.

Plus if you are worried about what hits the rear of the cone on most 7" or smaller midwoofers the most destructive stuff comes off the frame, spider and motor structure so stuffing the cabinet has minimal effect on this.

I respectfully disagree. The difference between using stuffing or lining the walls with absorption material and not using any at all is very significant if not severe. If back waves have nothing to be absorbed by, they will find their way back into the rear of the cone as distortion and it is not just noticeable, it's uncomfortable to listen to. The frequencies affected will depend on the coefficient of absorption of material used. I've found that problems begin to set in with frequencies under 700hz. This can actually be demonstrated with a simple test.