My current home theatre setup uses a pair of Velodyne MiniVee 10″ sealed subwoofers.  So the first step is to take some measurements of the Velodynes as a performance baseline, that way I know I am getting an upgrade.

Took one of the two subs out of the system for testing.  Testing starts with a close mic frequency response test.  Method was pink noise, averaged 1000 times.  A lot of averaging was required to counter the sounds of cars passing out on the road.

Next I wanted to test the distortion at a couple of frequencies.  I picked 35 Hz and 67 Hz as two frequencies easily within the capabilities of the sub.  My current microphone pre-amp doesn’t have a low-enough gain setting for testing at large signal levels, so I had to carefully manage the signal level.  The first measurement is at a distance of 17″ with the microphone on the ground, making it a ground plane measurement.  The signal level is increased +6 dB, and the distance doubled to compensate.  Then repeated again.  The results:

• 35 Hz, 17″ –> 3.5% THD
• 35 Hz, 39.4″ –> 8.1% THD
• 35 Hz, 78.8″ –> 15% THD
• 67 Hz, 39.4″ –> 1.0% THD
• 67 Hz, 17″ –> 1.0% THD
• 67 Hz, 78.8″ –> 1.0% THD

The SPL guesstimate is 90-91 dB @ 2 meter ground plane for the 78.8″ test cases (equivalent to 90-91 dB at 1 meter in half-space).  Obviously very nice results at 67 Hz, the Velodyne isn’t sweating at all.  The 35 Hz is a challenge.