Test Bench: Velodyne SC-10 Subwoofers & SC-1250 Amplifier
Frequency response (at 0.5 meter with crossover disabled and Jazz EQ, amplifier set to SC-10 mode) 28 to 185 Hz ±2.0 dB
Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room, two SC-10 subwoofers stacked) Amplifier set to SC-10 mode: 20 Hz at 86 dB SPL 104.8 dB average SPL from 25 to 62 Hz 113.1 dB maximum SPL at 62 Hz Amplifier set to Generic mode (no limiting): 20 Hz at 88.8 dB SPL 106.5 dB average SPL from 25 to 62 Hz 114.6 dB maximum SPL at 62 Hz
I measured the frequency response of the SC-10/SC-1250 subwoofer/amplifier system 0.5 meter from the subwoofers with the microphone placed on the floor and the SC-10s placed in the optimal corner of a large listening room. This technique includes the true acoustic summation of all radiating devices or openings without resorting to estimates of total radiating area and splicing of response curves, which often tend to overstate the true low-frequency capability.
The SC-10/SC-1250 system has unusually extended upper-frequency response, enabling it to mate with a great variety of small main speakers possessing limited bass output. Furthermore, the amplifier crossover settings were usually within 2 to 9 Hz of the actual acoustical cutoffs, and measured level from setting to setting was never more than 3 dB different, making the controls more accurate than is typical.
The amplifier's Jazz EQ setting provided the smoothest frequency response. The Movie setting simply increased volume by 4 dB over the entire operating range. Rock increased volume by 4 dB between 40 and 120 Hz, while the Games setting cut output below 35 Hz by 6.5 dB but added 6.5 dB between 40 Hz and 100 Hz.
The automatic Equalization function worked reasonably well for a single subwoofer or a pair mounted close to each other. When using a pair of SC-10s, one atop the other, response with the Jazz EQ setting was arguably slightly smoother than that obtained with the auto-EQ.
Per Velodyne's suggestion, I also tested frequency response with the SC-10s placed at the left and right stereo locations of my front satellite speakers. With this positioning, the auto-EQ function simply reduced overall levels by 4 dB without providing any significant response correction.
I measured the system's bass limits with two SC-10s placed one atop the other in the optimal corner of a 7,500-cubic-foot room and set to maximum bandwidth. The measurement microphone was 2 meters away. (This microphone placement has no measurable modal effects and no room gain below 16 Hz.) In a smaller room users can expect 2 to 3 Hz deeper extension and as much as 3 dB greater sound-pressure level (SPL).
The system played quite loud (107 dB) above 40 Hz and had good extension but, overall SPL capability still fell off at 12 dB per octave below 62 Hz. Setting the amplifier to its Generic mode, which disables compression and limiting circuitry intended to protect the SC-10 driver, had only a modest effect on output, resulting in about 1.7 dB additional SPL on average from 25 Hz to 62 Hz (but no more than 3 dB at any given frequency) while staying within our standard 10% distortion limit.