Velodyne DD-18 Measurements and Analysis
Graph 1: System amplitude response, 1m, On-axis @ 2.828 Vac , Preset 4 Engaged. Measurement environment: Outdoors, nearest reflecting surface: 30m (~100’) No smoothing applied.
In Graph 1 we see the DD-18, measured outdoors, pole-mounted, driver firing upwards, approximately 30m (~100’) above the ground. The system’s measured amplitude response goes far in explaining the sub’s exceptional subjective characteristics. The smooth mid-band performance, artifact-free low & high frequency roll off, are all factors contributing to the systems 5-star performance. (The hashy appearance of the response plot in ~<12 Hz was due to a low flying airplane that happened by while the sweep was underway and should be ignored).
Graph 2: Max dB spl curves, 2m, on-axis, scaled to 1m. Green curve: Servo @ 1, Red Curve: Servo @ 8. Measurement environment: Anechoic.
Graph 2 shows the DD-18’s max. dB spl response plots, with two curves provided to present the systems response with Servo gain at 8 and at 1.Increased distortion components add in to the mix increasing dB spl output slightly at Servo setting 1. The degree to which increased distortion will increase the overall amplitude magnitude is frequency dependent. Note also the upward shift of the LF knee when compared to that seen in Graph 1. This results from the processors functioning correctly and keeping the driver’s excursion within software-defined, safe limits.
Graph 2b: Normalized THD&N curves; Servo settings 8 & 1
I also ran 2 quick THD&N sweeps, one at Servo setting 1 and again at 8, both at the same drive level used in generating the curves seen in Graph 2. Dividing one curve by the other for easy comparison, the results are seen in Graph 2b. Not unexpectedly, an increase of a few dB below about 65 Hz is seen in the THD&N levels at Servo setting 1 when compared with Servo setting 8. (Had both THD&N curves been identical, normalizing one to the other would have produced a flat line spanning the graph at 0 dB).
Graphs 3 – 8 are a walk through the various digital processing features built in to the DD-18; tested/measured not only to see if they work (don’t laugh – I’ve bumped into subs where some of the processors didn’t function correctly) but how and how well they work.
The subsonic filter (Graphs 3 & 4), Contour EQ (Graph 5)(acts as an extra, limited-function EQ), low pass crossover (Graphs 6 & 7), and PEQ in combination with the supplied mic (Graph 8, along with Figures, 12, 13, and 14) are all essential features that help the end user integrate the sub with their existing system while at the same time maximizing the performance of the sub within that system, further helping to maximize the performance of the entire system. With the comprehensive array of processor/control features and the Velodyne everything-is-important design approach where it comes to the cabinet, driver, servos, & power amp, you have in one neat package all the ingredients for a world-class sub. Just get it. You can always turn it down later if it’s too loud.
Graph 3: Subsonic filter slope, 6, 12, 18, and 24 dB/Octave. Filter frequency: 15 Hz. Measurement environment: Nearfield, scaled to 1m.
Graph 4: Subsonic filter frequency, 15 to 35 Hz in 5 Hz increments. Slope set to 24 dB/Octave Measurement environment: Nearfield, scaled to 1m.
Graph 5: Contour EQ: +6 dB to -12 dB in 3 dB increments. Contour frequency: 120 Hz
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