Damping material for infinite baffle?

I'm restoring a pair loudspeakers that use a sealed box for the bass driver, and an open baffle for the mid and trebble drivers. I've already changed all the drivers (with factory parts) and repaired the crossovers. But now I'm stuck. What is the theory behind using damping material inside the sealed box? Should it be placed against the inside of the speaker walls to try and absorb the rear wave? Of should it "fill" the cabinet? It is my understanding that the former is the way to do it, the idea being to "fool" the speaker into behaving like it is in a larger box than it actually is. And how much should you use? And what material and thickness works best? (I think that the design calls for fiberglass batting R-19)....I am planing to present these speakers to the designer as a gift, so I don't want to consult with him about the correct way to do it! Too bad I have no idea what I'm doing! Help!.....Robert.
Sounds like a cool and very thoughtful project. Kudos to you. The amount, type and placement of sound dampening material will affect the woofers performance and sound. Most applications call for layering the inside of the cabinet. This helps deaden cabinet resonance and helps "fool" the driver into thinking it's in a slightly bigger cabinet. Adding more material will make the cabinet appear even bigger internally. Manipulating the amount and type of material will affect the resonant frequency and Q of the system. Most folks will "play" with this to fine tune the individual drivers to the specific cabinet. One thing that you typically DON'T want to do is to pack the cabinet completely full. I have found best results when there is a air pocket directly behind the driver, even if the cabinet is on the small side. I'm assuming that these were an original pair and you're simply rebuilding them. I would try to stick with what he originally had, but not worry about it too much. I'm sure that he'll probably end up fine tuning them anyhow, whether you know it or not. Good luck and hope it has the surprise effect that your looking for. Sean >
Lamb's wool is very good for the acoustic stuffing. Kimber recommended it to me as better than poly or fiberglass, etc. I have a source in Ohio for a good price, but I don't have the info. with me (it's at home - I'm "working" he-he). But I can let you know - if interested, email me: bobb@spacecom.com. I believe your theory regarding enhanced enclosure-loading is correct. Shawn Casey (no longer at Kimber) told me to stuff pretty firmly BEHIND the cone; fill up the enclosure, but not cram it in there. Then listen, compared to the empty box. Stuff some more, or some less, & re-try it. You tune it by ear.
Thanks Sean and Bob. Yes, this project is important to me. The designer has been very kind to me, and I know he'd get a kick out of having one of his first production designs restored in this manner. And yes Sean, this is an origional pair, and I'm just rebuilding them. The material that was inside the cabinet looks to be fiberglass batting R-19, but it had almost completly disintegrated, so besides the material type, and the fact that it was one piece of batting, it's hard for me to tell what was really there. I'm sure the designer will tweak the system, but I'd like them to sound good when we first fire them up. Either way, I'll take what seems like wise advice from both of you, and try to fine tune the system by ear this weekend. Thanks again. Robert.