Speaker Damping Material

[Cliff45]

Hey Retro-

Hey, I totally get what you are saying there in your last post. From what I thought I knew about speaker acoustics, bass response is lost in a speaker enclosure by two things: either poor design geometry producing standing wave interference inside the enclosure itself, or "diaphragmatic absorption" which is produced by the actual flexing of the enclosure material itself. Don't think I got a fancy term like "diaphragmatic" all by myself, it's used in the classic tome by F. Alton Everest "The Master Handbook of Acoustics". I am sure everyone here knows this info anyway, I am just saying all this to sort of "think out loud" if you will, I'm certainly not trying to "instruct" anyone at all I assure you! Maybe I just totally missed the request you were actually making in your post, sorry if that's the case!

A dense material (like "egg crate" foam) that takes up a lot of air volume inside the enclosure would have the effect of reducing the internal volume of the enclosure and therefore dropping the Q of it, which kills the bass response as well. If it's foam an inch thick, you can just subtract one inch from the speaker box inner dimensions for every surface you put it on. I assumed since the Owens Corning material is both fairly thin (you can get it in 1" thickness), as well as not very dense it would not affect the tuning of the enclosure very much at all. The specs give it a rating of only 0.10 in absorption below 125Hz, that being just 10%. And there's certainly no demand to totally cover the entire surface area inside the box either, correct? Still, I see you said you were NOT using fiberglass, and that's exactly what the stuff I suggested is made out of inside its core. Sorry I missed that in your post! Mr. Weems suggests some kind of material called "Acousta-Stuf" in his book, saying it was a crimped type of long tri-lobal fibers. This material is known to be quite superior to ordinary Dacron "pillow fill", from what I have read.

I have no data on the actual cabinet construction you're currently using, since none was given anywhere. But, if you're simply trying to damp the cabinet resonances, then the already suggested DYNAMAT is the absolute best way to do that. I remember the subject of cabinet filler was covered very well in David B. Weems classic "Great Sound Stereo Speaker Manual" on page 50 of the 1990 1st edition....

I guess I am feeling pretty old now, looking at all these books I bought way back when they were ALL 1st and 2nd edition printings! At least mostly are on solid-state circuitry and not all tube, though. That would REALLY make me feel old! BTW - Is it as cold in NY as it is in Michigan right now? We're at about 8 degrees F right now, THAT temp would certainly damp some speakers, wouldn't it?

[VictoriaGuy]

In my AN 2.8 enclosures, I just replaced the 1" yellow fiberglass board with 3" of pink fiberglass insulation (upper 1/3 of enclosure) - the bass 'seems' a bit better (ie louder,lower) now.

Nice thing about larger drivers (10" in this case) is that you can work through the speaker cutout- this job only took about 25 min start to finish.
Cheers
John

[chriselm]

I am currently building this
http://www.troelsgravesen.dk/JA8008_DTQWT_cabs.htm

What do you think about this material?
http://www.monacor.de/typo3/index.ph...pr=EN&typ=full

Would it kill the low frequencies?

[loninappleton]

For the environmentally friendly and conscious, there was discussion of bamboo fiber fill a while back. It comes in a bag like polyester fiber fill for pillows and sold in big box fabric stores for craft projects..

Other current recommendations for those who don't want to mess with fiberglass or worry about closed vs open foam products like egg crate is the hard to find 3/4 felt used as carpet underlayment.

I see the advantage of the felt as being able to be stapled in to keep it where you put it.

Mcmaster Carr also sells a product like this called F-13 grey wool felt.

www.mcmaster.com

I am hoping to find some locally though.

[Retrosonic]

The Speaker project is now finished, and they came out great.

Per the manufacturer, I damped the upper top 1/3 of the cab.
I used the No Rez product, and it was amazing. I'll never use anything else. Made the speakers really sing. Well worth the 70$ for two large sheets.