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.
I'm assuming your measurement were at the listening position, if true, then your system measures quite well. The 4-6 dB spikes in the upper midrange could be sonically objectionable, but they could simply be measurement artifacts. Playing with toe-in might eliminate them. You might also consider one of the DSP room correction products from Perpetual Tech, TACT or Sigtech.
A piece of carpet in the hardwood floor will help to improve sound.....
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,
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.
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.
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?
Gregg, thanks. I'll move the speakers out another one to two feet and retest. The bass doesn't exactly roll off. At 63 Hz, it's +3dB and then it plummets to -6dB at 50, -7dB at 40 and -6dB at 32 rising to +2dB at 25 and -1dB at 20. That's strange, and noticeable. My other concern is the spike at 5k. It will take a few days to do the testing but I appreciate the suggestions.
I do not have any of your gear, but have done the same sort exercise many times in my room. If my advice is elementary, please forgive me. I have only been in the hobby for four years and feel my hearing is well trained.

I've been through this process with Kef 105/3's, Chapman T-7's, Merlin VSM-SE's, Spendor SP100's, and my current speaker, the Talon Khorus. It usually ends up taking me six months to a year to find a final spot for a new speaker.

1. There is a good mod for the analog RS meter that eliminates the error correction and increases sensitivity and frequency response. It costs about $12 in parts and works great. I wll try to find the link if you are interested.

2. A good starting speaker position can be achieved by using the Cardas Golden Ratio Method: (
If your room is rectangular, not L-shaped or square, his method will help you avoid camping on a resonant node.

3. To adjust the distance between the speakers, use tracks 1 and 2 (voice in and out of phase) on the XLO Test and Burn-In CD. This can fix problems where your side walls are dissimilar, like having wood on one side and sheetrock on the other.

4. This is what I finally ended up doing instead of guessing:: Walk the speakers toward the back wall one inch at a time. At each step play a song that has a walking bass line going down or up. This allows you to see if you hear all of the notes, or if there are dropouts. You can use the meter at each step, but your ears are a valuable measuring instrument too. Take notes at each step and take a few days at it. For example, in my room I found a pattern of bass nulls that repeated every 11 inches. There will be a spot better than the others, and the spot differs with different speakers. Putting the speakers on spikes will change the spot because you are raising the woofer.

5. Some speakers just won't behave in your room no matter where you put them. I've spent serious money on acoustic panels, bass traps, and skyline diffusers just to fix some of the problems. I still ended up with bass spikes and suckouts that affected the midrange and treble. This led me to step 5.

6. I bought a Tact RCS 2.0 room correction system two weeks ago. The unit fits your sytem's frequency response to one of 50 or so target curves, so the room mostly becomes a non-problem. In fact, you can pretty much put the speakers wherever you want and let the Tact handle it. This does not mean that the basic room acoustics can be ignored. I stil put damping at the first refkectin point and on the front wall, but frequency response problems are gone. You can also create your own curves if you want. I've spent more money on damping and absorbtion products than on the Tact.

7. As you can tell, I'm impressed. I suspect you might be able to buy reasonably-priced speakers and let the Tact deal with recessed mids, or tilted up treble, or thin bass. No, I am not selling anything, just feeling freed from moving some very heavy speakers aroung the room.


How much di dthe Tact cost?

I have spectral equipment and eidolons. Do you notice any difference in the sound that is not desirous by using the tact and having anothe rpiece of electronics fo rteh signal to run through?
Also what is your experience with acoustic treatments. I am loathe to shell out for big expensice tub etraps and I am wondering if there is another cheaper but good alternative.