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Old 5th August 2019, 04:44 PM   #101
Brian Steele is offline Brian Steele  Grenada
diyAudio Member
Join Date: Nov 2007
Originally Posted by Brian Steele View Post
The only thing that sticks out at me is perhaps the sweep length (unfortunately I didn't record it, but I believe that I used 512K long test signals - REW suggests using 1M long test signals as shorter ones apparently result in less accurate harmonic information in the resulting distortion graph).
I don't have the Enigma on-hand to repeat the distortion tests on it. However, I do have on-hand a 4th order BP subwoofer that I built many years ago (see The Subwoofer DIY Page v1.1 - El Uglito for more details. Note however that it now uses different drivers, so FR and distortion measurements done back then don't apply), so I did some distortion testing on that subwoofer to see if the signal length made a difference. The results suggests that the signal length makes little difference at bass frequencies, at least when set to 512K or 1M. If anything, distortion measurements using a 512K signal seem to be a little higher than distortion measurements using a 1M signal.

Note: cursor set to 34.9 Hz, mic about 3" from the subwoofer's vent (to minimize impact of the room on the measured response).

Test signals:
1. 10-20K, 512K
2. 10-20K, 1M
3. 10-2K, 512K
4. 10-2K, 1M

1. Measured FR using test signals indicated above. Basically identical at bass frequencies.
2. Distortion measurement using 1st test signal
3. Distortion measurement using 2nd test signal
4. Distortion measurement using 3rd test signal
5. Distortion measurement using 4th test signal
Attached Images
File Type: png 20190805-el uglito.png (50.7 KB, 34 views)
File Type: png 20190805-el uglito (10-20K 512K).png (54.9 KB, 33 views)
File Type: png 20190805-el uglito (10-20K 1M).png (55.3 KB, 34 views)
File Type: png 20190805-el uglito (10-2K 512K).png (50.9 KB, 33 views)
File Type: png 20190805-el uglito (10-2K 1M).png (50.6 KB, 32 views)
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