Damping

[IslandHydro]

So, are there any guidelines on how much damping material to put in an enclosure? I've been toiling over tightening up the bass on my current build, and one of the techniques I employed was to put way more dampening in the enclosure than I normally would. Now, after doing a couple other things that have made good headway toward tightening, I am wondering if perhaps they are over damped. Not really sure how to sort this one out, thoughts appreciated.

[JonMarsh]

Do you have any kind of measurement equipment? Have you modeled the low frequency portion of your build (what is your build?) using something like Unibox, which can simulate options in damping? Is it a sealed box or ported? (sealed you put more an more damping into it, while measuring the Fb frequency peak, until the peak starts going back up, then back up to the last value).

Ported you should only line the walls- if you don't like the bass, change the parameters of the reflex design (port/system tuning). I'd suggest modeling it first and consider where you have your speaker in the room- this affects the low end a lot because of boundary reinforcement. Ideally, boundary distances (to floor, side wall, rear wall) should be at golden mean ratios to distribute the resonance so it doesn't build up in one frequency range. that, or flush mount so that you're working in infinite baffle half space mode- but then the system has to be design for that, with no baffle step compensation.

[IslandHydro]

Do you have any kind of measurement equipment? Have you modeled the low frequency portion of your build (what is your build?) using something like Unibox, which can simulate options in damping? Is it a sealed box or ported? (sealed you put more an more damping into it, while measuring the Fb frequency peak, until the peak starts going back up, then back up to the last value).

Ported you should only line the walls- if you don't like the bass, change the parameters of the reflex design (port/system tuning). I'd suggest modeling it first and consider where you have your speaker in the room- this affects the low end a lot because of boundary reinforcement. Ideally, boundary distances (to floor, side wall, rear wall) should be at golden mean ratios to distribute the resonance so it doesn't build up in one frequency range. that, or flush mount so that you're working in infinite baffle half space mode- but then the system has to be design for that, with no baffle step compensation.

Thanks for the response John, lots of questions, here's some answers:

The room is a major issue, as it's a walk-out basement with carpet over poured concrete floors, and drywall over cement walls (2/3 up, standard framed for the top 1/3). So room modes are an obvious issue. I've done some work on that, including a superchunk behind the couch. This is a 5.1 home theater system, but the fidelity of the mains / subs (2.1) are a primary concern as I also use it for music listening.

I've been using WinISD for box design. I'm using REW and Dayton DATs for measurements. The build is as follows:

2x Dayton RSS390HF-4 subs, built into bottom ends of builtin bookcases. Box sizes somewhat governed by the bookcase shapes, but not too bad from a design perspective. Both run sub 20hz F3's.

L/R Mains are as follows (each speaker):
2x Dayton RS225-4 woofers
2x Scanspeak 15M/4624G Discovery midranges
2x Morel MDT29-4 Textile dome tweeters (1.1")
1x Fountek NeoCd1.0 Ribbon Tweeter

XO between the subs and mains is via the preamp (Outlaw Audio 975) with a 2x4 minidsp on the sub outs for room corrections. All XO's on the mains are via MiniDSP 4x10 (active XO's with room correction capabilities).

Initially the bottom of the mains were ported, but in my quest to tighten up the bass, I recently reconfigured the enclosures as sealed (resulting in a drop in box volumes). This helped tighten up the bass considerably, at the expense of F3 on the mains (compensated by raising the sub/main XO frequency). Lots more details available if your interested.

Cheers,
Doug

[JonMarsh]

Are you getting close to where you want to be? How about an inexpensive rig for measurement, such as that PE thing that uses a CD for test signals? Can always help to identify where the problem really is, and to what degree you can address it by setup- since you have the mini-DSP with room correction, I'm assuming you do have measurements. What does it look like, and what's the room layout and seating position, as well as speaker positions?