>>servo-controlled ?<<
Velodyne pioneered the concept of using an accelerometer attached to the voice coil of a speaker to measure its movement, compare that movement to the input signal, and correct for any discrepancy between the two in real time. A servo-controlled subwoofer.
It allows Velodyne to build subwoofers that produce less than 1% harmonic distortion. Subwoofers that don't use servo-control rarely get below 10%. Even very highly regarded high-end, super expensive subs.
Wendy Carlos said, many years ago, that Velodyne subs were the only thing to have because of this servo business, and that she used two of them in her recording studio as part of the playback system. (The studio had Faraday shielding all the way around, top and bottom, so there was no ambient radio or electromagnetic noise in her equipment. You could turn every volume control in the room up to maximum, without an input signal, and you would hear nothing.)
She also said it would be great to apply the same kind of servo control across the entire audio spectrum, but that it wouldn't be possible due to the limits of computational power.
It occurs to me that computational power has increased quite a bit since Carlos said that. By now, a speaker that uses separate servo-controllers for each driver should be possible. Let's get some VC funding and build us some super-accurate speakers, Dude! |
