new build: need advice on damping

[chazdrumzalot]

I'm about to build a pair of Dual chamber reflex cabinets this weekend for my W5-1611s. I have three different damping materials to choose from: a pound of acousta-stuf, a sheet of acoustic foam (both from madisound), and some old sheets of carpet padding. I'm wondering if one layer of carpet padding followed by one layer of foam will be overkill for this situation, and will ultimately just take away volume. Also, my understanding is that the carpet padding will reduce wall vibrations rather than kill any standing waves or reflections; is this really critical in a smallish speaker with a vertical and horizontal brace? But regardless of which dampers I use, should i plan on damping every wall? I've seen some designs where the baffle or a side wall is left free of damping materials but I don't understand why. I'm building with 3/4 BB ply.

[steviedon]

I've actually had the best luck with cotton/wool quilting felt, or fiberglass ceiling tile insulation, which happens to be the cheapest solution besides recycled material. You shouldn't need to damp any cabinet resonances with a well built and braced BB cab......only damp the backwave/internal reflections. I generally line all internal panels, but stay 2" away from the driver on the baffle and likewise for the port(s). I would leave one panel removable, or perhaps make a detachable back part of your design......then you can play with lining after the drivers have settled in.

[chazdrumzalot]

Yeah, I'm leaving the back panel free so I suppose I'll just have to experiment. But to clarify, are you suggesting to omit the carpet padding and just line the walls with either the foam or acousta-stuf?

[zman01]

Chaz,

What I have read in the forums and interpret from Steviedon's post is that bass reflex type of cabinets need their internal walls to be lined with wool-felt or fiber glass material for best results. One particular item I have read DaveD and Chrisb mention numerous times is the Ultratouch Recycled Denim material. Please check on the thickness part too - as far as I can remember I have seen thickness from 1/2- 1 inch for most enclosures.

-Zia

[steviedon]

Originally Posted by chazdrumzalot

Yeah, I'm leaving the back panel free so I suppose I'll just have to experiment. But to clarify, are you suggesting to omit the carpet padding and just line the walls with either the foam or acousta-stuf?

Yes, scratch the carpet padding. As for layering damping materials......it is possible to go overboard and effectively change the tuning with too much material. Foam may be a good solution if is is open cell. Acousta-stuf would be very hard to attach to internal walls and I imagine not very effective at killing the backwave/reflections. Try to strike a balance between effective and minimal.