I finally got around to doing some measurements of the UMC-200 bass management.
My test setup is as follows:
Sound device: Tascam US-144MkII
"Use loopback as timing reference" REW setting used
Loopback from Tascam right-channel analog output to right-channel analog input
Tascam S/PDIF output to UMC-200 S/PDIF input 1 using S/PDIF left channel in software
Analog output of UMC-200 (either left channel or subwoofer out) to left-channel analog input of Tascam
UMC-200 configuration as follows:
S/PDIF input 1
Front speakers set to SMALL
Crossover frequency 100 Hz
High-pass slope 24 dB/oct
Subwoofer set to ON
Low-pass slope 24 dB/oct
All other speakers set to NONE
So the first thing I did was a measurement of the left channel output from 10 Hz to 1000 Hz. I did this for the maximum left-channel distance setting (minimum delay) of 32.8 feet. Measured again with a left-channel distance setting of 0 (maximum delay). I plotted the frequency response, which was as expected: 6 dB down at 100 Hz (Linkwitz-Riley 4th order, not shown). Then I plotted the group delay for these two settings. This is shown below, only down to the crossover frequency of 100 Hz, since the group delay gets noisy because of the rolloff of the high-pass filter below 100 Hz.
The group delay at 1 kHz and 32.8 foot distance setting is 3.2 msec. For the 0 foot distance setting, it is 32.3 msec This is a difference of 29.1 msec. To compute what it should be, the speed of sound at 20 deg C is 1126 ft/sec, or 0.888 msec/ft. Then 0.888 msec/ft * 32.8 feet = 29.1 msec. The measured difference in delay of 29.1 msec is right on the money and exactly as it should be.
Next, I measured the subwoofer out for the subwoofer distance settings of 0 and 32.8 feet. The results are shown below. I've restricted the maximum frequency, again to avoid noise due to reduced signal level from the rolloff of the low-pass section of the crossover.
Yes, both measurements are present in this graph. At first, I thought I had made an error, but I re-did the measurement and got the same results. The subwoofer distance setting does not change the delay of the sub at all. Not good.Edit: It looks like the sub channel measurements above were in error. See this post for more info. Please ignore the above sub measurements. The sub delay works correctly.Edited by andyc56 - 8/5/13 at 2:15pm