-
Welcome to ASR. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
Taking and Interpreting Measurements with REW (FREE eBook)
- Thread starter Keith_W
- Start date
tw99
Addicted to Fun and Learning
@Keith_W I've just read through the shorter eBook - very useful indeed. One question I have is about the SPS measurement that you recommend doing even if using MMM.
I originally measured my speakers individually using MMM and created filters directly from that MMM output - in this context, how would I use the SPS measurement ?
I originally measured my speakers individually using MMM and created filters directly from that MMM output - in this context, how would I use the SPS measurement ?
OP
Keith_W
Master Contributor
- Thread Starter
- #63
The MMM does not capture any timing information. If you want to make any timing corrections, e.g. time align a subwoofer, make phase corrections, etc. you will need a SPS. Also, no timing information also means no decay measurements - can't examine impulse or step response, waterfall, spectrogram, RT60, etc.
If you want to make DSP corrections, the correct way is to take some kind of spatially averaged measurement - either an MMM or multiple sweeps and average them - and use that to correct the frequency response. Which is what you did. But correction of the freq response is only half the story.
A comment about the Schroeder frequency: The formula given by Copilot is also given by Floyd Toole in Sound Reproduction. In the 4th Edition it’s in Sec. 5.1. He also writes: «The multiplier constant changed from the original 4000 to 2000 in the 1996 paper, emphasizing that this is not a precision calculation». My conclusion is to be careful with the Schroeder frequency, and be careful with Copilot, ChatGPT, etc.
