Floral or memory foam best?

[mashaffer]

Which would be better at fooling mother nature WRT enclosure volume the floral open cell foam used for flower arrangements or the memory foam mattress pads? Put another way which would have the greater effect on total system Q?

mike

[gtforme00]

Try blowing into each material. You might get some odd looks for doing this! You ideally want a material that does not suffocate you, but provides reasonable restriction of air propagation. Pillow stuffing (known as dacron, polyester, and other names), stuffed appropriately might have more predictable results.

I have not tried the foams and am not an authority on the subject. I would be interested to know what you find! It would be interesting to measure the resonance frequency and Q of the enclosure with different materials.

I imagine that many air filter materials would also provide a similar function.

Regards,
David

[Timn8ter]

If I understand your question correctly, I don't think either material will give you the results you seek.
They willl exhibit different rates of frequency absorption but not change system Q. You want a material that changes mechanical energy into heat energy which requires the material actually be able to move. Polyester and/or fiberglass fibers have this quality. A stationary foam does not.

[moray james]

I have no hands on experience with memory foam and have no idea if it is open cell Fine pour open cell structure foam is what you want.
With fiberous material the fibers vibrate and rub together and the friction generates heat. So acoustical vibration is turned into heat and energy is dissipated. With open cell foam it is the friction of the air as it passes through the foam's cells which generate the heat and so damps. I replaced the long fiber wool in a set of ATC two way cabinets with Pearl Lite (heat expanded rock) used normally for plant soil. The difference was easily noticable with the Pearl Lite sounding much better. Bass was deeper and more controlled and there was a marked improvement in the midrange clairity along with enhanced detail. Everything sounded smoother more relaxed yet more dynamic at the same time.
You need to sift Pearl Lite to seperate the largest pieces (about the size of a rice crispy) from the small bits and the fine dust particles. Once sifted you can install it in a cabinet but you must insure that it only goes where you want it to and that it cannot get into any open back drivers. This is a fuss but it can be done and the material works very well and is much cleaner to work with than activated charcoal as KEF have used.

[Timn8ter]

I understand your point Moray but is using a material to change system Q in a subwoofer the same as using a material to damp high frequencies in a full range speaker?

[moray james]

different materials will have different absorption qualities but for the most part I think that what is of most concern is damping the driver near or at the resonant point of the box and driver combined. Higher frequency damping can be achieved with fiberous curtains and other such methods. I do think that Pearl Lite or activated charcoal come to about as perfect a method as there is given that they both are a PITA to use.

[Timn8ter]

I guess what I'm having difficulty with is not so much the type of material but how it is to be applied. The exception would be the Temperpedic foam which I think is too dense for this purpose but might work as a vibration damper.
I can't imagine trying to come up with the correct amount and application of florist foam or dealing with rocks. I suppose you could make a sort of pillow with Perlite though.

[mashaffer]

I am following your replies with interest. I was given to understand that the use of an open cell foam increased the apparent size of the enclosure so I am trying to get a handle on which versions (both of these are open cell foams I believe) would provide the greatest effect.

mike

[moray james]

http://www.kef.com/kefamerica/technology/pdfs/acewp.pdf

[Petriej]

A friend of mine works at a warehouse that moves all kinds of merchandise. He told me a crate fell and busted open so they couldn't use what was in it. He asked me if I wanted it and I said sure. Here's what's inside:

Hearos

So I have a couple thousand of these things. Can I put them in my subwoofer box?