Originally Posted by HTPCat
Sorry, should have explained. I trust audyssey (I am using the pro kit), but in my case my trims are maxed at -12dB on my LCR due to my very efficient JTR T12 speakers. My surrounds are Def Tech ProMonitor 1000s and are set by audyssey at SR 0 & SL -1.5. I am using the internal amps in my Denon AVR4311 and can't use attenuators so I am doing as others suggested in trying to lower the trims by adjusting the MV @ 0 to 80dB and using -5 MV as my reference. I attempted to make these adjustments using my rat shack spl meter and the AVR test tones, but was told that the test tones were pre-audyssey, thus my rather crude attempt at using REW to accomplish this task - I admit I am a complete nubee at REW ( I have just finished reading your guide and setting it all up) and am fairly new at any measuring and Room correction applications.
FWIW - I assumed that audyssey is attempting to set all my speakers to 75dB at 0 MV and so I added 5dB to the SR & SL and measured from MLP using the settings noted in my previous post for the REW generator and got 77~78dB (not sure why it isn't 80dB) so I then adjusted the trims on the rest of my speakers to match the 78dB level.
OK, I remember your unusual situation, sorry. Things would be simple if you had an external SPL meter, like the Radio Shack one. You don't have an SPL meter?
Trouble with using the UMIK-1 is you need to make sure it is calibrated. Supposedly, the calibration file that comes with the mic should have a "sensitivity factor", which REW uses to auto-calibrate the mic. The sensitivity factor is stored at the beginning of the calibration file, as per this example:
The problem is that I don't see this sensitivity factor in the calibration files from Cross Spectrum Labs. Without the sensitivity factor, your mic isn't calibrated. If the mic isn't calibrated, you can't run the test as you described. To calibrate the mic, you need an external reference, i.e. a SPL meter. Then, if you had an external SPL meter, you wouldn't need to do the test using REW. Vicious circle, isn't it?
Recommendation: invest in an inexpensive SPL meter (you really need one). Or, better yet, if you have the budget, invest in an external power amp, which would allow you to use line-level attenuators, which would be the elegant, reliable solution to the problem of super-efficient speakers. An external amp like the Emotiva is quite reasonably priced, and would be a nice edition to your system.
Edit: BTW, PDXRealtor provided this post on how to add the mic's sensitivity factor to the CSL calibration files, if you want to give it a try. I tried to do that, but even with this sensitivity factor, I found that the UMIK-1 levels were still not accurate. That is why I always calibrate my mic using an external SPL.
Edited by AustinJerry - 12/20/13 at 8:41pm