Since 1997
Brian Rovinsky, Owner
(Formerly, St. Cecilia Sound Gallery)
1290 S. Missouri St., Suite C • Clearwater, FL 33756-9183
(727) 446-2505
Email: info@sweethomeaudio.com
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Velodyne
F-1500R-B Powered Subwoofer
Velodyne Acoustics has been manufacturing subwoofers utilizing the servo-feedback principle for about 10 years now. Their ULD series, which is downward firing, remains popular, and with the addition of the F series which has variable low pass crossover filters and the amplifier built into the enclosure, as well as being forward firing, users have a wide selection to choose from. The servo-feedback type of mechanism employed by Velodyne consists of a 2.5 gram accelerometer which is attached to the voice coil of the speaker driver. When a signal is fed to the amplifier, which then is used to drive the speaker, the accelerometer senses the motion of the speaker cone, and this movement is converted to an electrical signal which is sent back to the built-in amplifier. The incoming signal from the main amplifier or preamplifier is then compared with the information supplied by the accelerometer. The difference, which consists mainly of harmonic distortion (even and odd order) produced by the speaker cone itself and effects on the cone by resonances inside the enclosure is electrically inverted and fed back to the speaker. Feedback occurs 3500 times per second, and the distorted movements of the cone are thus canceled out. This process works very well, and Velodyne has made a name for themselves, setting a standard in subwoofer design by which most others are compared.
How do the Velodyne subwoofers sound? We have compared a number of subwoofer designs, including servo- feedback, push-pull, as well as passive radiators. The servo- feedback subwoofers, in our experience, produce the purest low frequency sounds of all the designs. All musical instruments generate natural harmonics, mostly even order (second, fourth, sixth, etc.). It is the harmonics that are added by speakers that can render the sound unnatural (called harmonic distortion). Usually, a speaker will produce a strong second harmonic (e.g., 10%) and a less intense third harmonic (e.g., 5%), particularly at low frequencies and at high intensity. Most amplifiers have less than 0.5% Total Harmonic Distortion (THD), which is not audible. Therefore, it seems appropriate to design speakers with this level of performance. The Velodyne servo-feedback mechanism appears to reduce the harmonic distortion to about 1% at the frequencies covered by their units (18 - 100 Hz).
Price is just $475 (new it was $1,600).
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