Room Treatments redux

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Gordon Gray

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HI all,

Just wanted to share an experience I had last weekend.

I have a variety of acoustic panels in my room that I've effectively tuned by ear.

Very bad, I know, but that's how I address the issue. I'm old school and trust my ears.

I re-installed one ATS bass panel (24" X 36" X 4") on the back wall centered between my speakers because I felt (after hours of previous experimentation) I still had a mid-bass room resonance issue.

After three days of listening, I'm confident that the re-install was a very positive move.

More blah, etc.

So the question is, except for JonFo and others that use a far more rigorous technique, have you ever re-adjusted the panel treatments even though you thought you had the "ideal" placement and commensurate benefits?

GG
 
Yes, I'm currently going through and re-doing all my panels from 2" to 4" thickness and have noticed a huge improvement in mid-bass and bass in general. 2" panels don't seem to really do anything at all when it comes to stuff under 500hz or so.
 
Yes, I'm currently going through and re-doing all my panels from 2" to 4" thickness and have noticed a huge improvement in mid-bass and bass in general. 2" panels don't seem to really do anything at all when it comes to stuff under 500hz or so.
4" + 4" air gap behind the panel is your best bet for broadband absorption.
 
I have 3 four inch thick bass panels in the rear of the room and 3 two inch thick panels behind an open rack. I prefer reflective front corners behind the ML"S. Still a bit of a hump at 60 Hz.
Does the trick here....
 
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Gordon, the air gap will help with lower frequency absorption. 4" + 4" is more or less standard advice to all.

Best tool to assess this is Whealey's, excel-based calculator, found here. Simply plug in thickness, air gap and absorption coefficient to get a comparison between gap and no gap.

OC703 = 23,600 rayls/m
OC705 = 30,000 rayls/m
though you'll find variable values for these.
 
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Gordon, any updated pictures coming soon? Perhaps we should send over that intrepid photographer, Rich, to take pictures. :)
 
Bernard,

Hope to post within a week or so.

Only change is the MBL speakers.

Gordon
 
Has anyone played around with room Accoustics directly behind the panels? My vistas are about 6 feet off the back wall.

Recently I started playing around with it. I tried blank cork board but that killed all rhythm and darkened the sound, IMO too much.

I added egg cartons to the board and the life has come back.

The sound is quite interesting...the background is quite quiet now. Clarity is separation and especially sound stage was much more focused.

The sound doesn't seem as dynamic however...and there is still some reserved trebel but honestly I'd rather be on the warm side.

So, has anyone tried their accoustic panels behind the speakers?
 
So, has anyone tried their accoustic panels behind the speakers?

Yes and I believe 'generally speaking' the closer to the wall...absortion, the further away...'diffusion'. In your case. 6' (excellent BTW) , nothing more than diffusion....if that.
 
Did some more testing and found that removing my sidewall treatments really opened up the speakers. Before removing them they had a bit of a constrained sound and after removal the soundstage has become wider and more lifelike.

Has anyone else had similar results? I know this is very room dependent but I found it interesting... Still messing around with proper backwave treatment, currently using 4" absorbers behind each speaker but wanted to also test something like a BAD panel behind them.
 
Given ML's dipole radiation pattern, side wall treatments are probably less critical than with box speakers. However, as you mentioned, this could be very room dependant, so the only way to find out is to experiment. In my room, I've installed staggered shelves on my only side wall, with (high WAF) photos and knick-knacks to act as diffusors (minimal absorption). I've found that actually worked better than absorption at those (theoretical) first-reflection points. YMMV.
 
As an aside, Gordon, I went round to Jerry's to hear his 116Fs a couple of weeks back. I'm no fan of Krell amps, but an old KAV250s driving his 116Fs was the best I heard them perform - ever - and by a margin. A real case of synergy - and I've heard the 116Fs with quite a variety of amps now.

TBH the 116Fs now rate as better than I thought them capable of i.e. damned fine. We got some great results with a passive preamp and the Chinese pre I've posted about. Very enjoyable session.
 

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