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  3. 989972365

Room Acoustics Problem?

By Audiogon standards, I have a mid-level system with Brystons (BP-25, 7B-STs), Thiel CS6's and the Perpetual Technology DACs (posted not too long ago on Virtual Systems). I'm annoyed by a saturated sounding mid-range and was exploring some options with the help of fellow Agoners on other posts. Then, I ran into Sean's March 3 post on how to run a more accurate frequency distribution reading with the Radio Shack SPL meter and the Stereophile CD. Here goes: At an 80db base, 20-25 Hz is OK, 32-50 drops off to -6db, 3db spike at 63, 80-315 OK, 3db drop at 400, 500-4000 OK, 4-6 db spike at 5000 & 6300, 10000 OK, 12500 and over drops off like crazy (3 moving to 10 db). OK is defined as plus or minus 2db. Does this sound like a room acoustics problem? Big room, lots of cushy furniture, hard wood floor. Is there something else I should be looking at? Help! Thanks in advance.
ozfly
edle
235 posts
 
A piece of carpet in the hardwood floor will help to improve sound.....
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joeabrams
132 posts
 
While I agree with the previous two folks, I also think that the combination of Bryston and Thiel can sound bright and forward under some conditions. If this system does sound "bright" to you, DO NOT toe the speakers in unless they are wider apart than their distance from your listening seat -- keep then parallel to each other. Also, this system can be VERY cable-sensitive. What speaker cable are you using?

Best of luck,
Joe
nilthepill
842 posts
 
OZfly, I assume that you already have corrected for the ERROR added by the measuring device. If not here are the corrections. ADD the error value to measured value and review the results to see where the problem is.
Freq error
20 6.2
25 4.4
31.5 3
40 2
50 1.3
63 0.8
80 0.5
100 0.3
125 0.2
160 0.1
200 0
250 0
315 0
400 0
500 0
630 0
800 0
1000 0
1250 0
1600 0.1
2000 0.2
2500 0.3
3150 0.5
4000 0.8
5000 1.3
6300 2
8000 3
10000 4.4
12500 6.2
16000 8.5
20000 11.2

Of course this may make your upper mid-range, low treble problem worse. In that case room acaustics would not cause big boost unless you have highly reflective surface-mirror, cabinet glass or big picture frame between you and speakers. If not, thiels are known to on brightet side in low treble range. Joe suggestion in combination with near field listening, verified by trial and error re-measurements should do the trick or try different IC between Pre amp and amp.
ozfly OP
887 posts
 
Thanks all. I did measure at listening position and did adjust the readings to correct for instrument design. Speakers are fairly parallel to one another and I do have an oriental on the floor. But, I used a slightly different adjustment than Nilthepill recommends (with those adjustments, things look better -- there is still a big dip in the 32-50 Hz range and a 2-4 db spike at the 5k - 6.3k range but the 20k is only down by 5db -- everything else is in the 2db range with a couple of 3db issues). I am using the Stealth Premier speaker cable but agree that an alternative might be good. The low end dips and upper mid spikes still drive me nuts when I'm listening so please keep the suggestions coming. Thanks.
gregg_c
36 posts
 
I have the CS6's as well but have found that the bass in my setup rolls off more or less nicely into the mid-20hz range. I am driving them with a Krell FPB-300. I have found that using different amps can cause changes in the frequency response especially in the deep bass. My speakers are also a little over 4 feet from the rear wall. I found that I got the smoothest overall response where they are now, not closer or further out from the rear wall. It sounds to me that you are getting a room interaction problem to get the spike in the 20hz region after they start rolling off in the 32-50hz region. How close are they to the rear wall?
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