Volodyne Hgs System; The Problem Of Distortion - Velodyne ULD-15 Owner's Manual

one. it needs power to operate pro perly . If you wish to play you r system wit h the Ve lodyne off. the
ULO contro ll er must be bypassed externally, eit her by direct wiring or wit h the opt ional Crossoverl
Bypass accessory.
4. Subwoofer pops short ly after power on : Yo ur Velodyne has a built-in power-on delay that
starts when you engage the power sw itch. After five seconds it turns its elf on and a slight pop
may be heard. This is norma l operatio n.
S. Satell ite speakers pop when subwoofer is switc hed on : Your satellite spea kers may make a
slight noise as the ULD contro lle r' s internal hig h-pass crossover is powered up. To prevent this
problem , switch your Velodyne on before applying power to you r power amp .
For service please contact yo ur local Velody ne dealer. The following conditions a/ways require service by quali-
fied personnel:
1) If you wish to have the crossover point modified
2) If the power cord is damaged
3) If the unit does not appear to operate normal ly or e xh ibits a marked change in performance.
4) If the unit has been exposed to water
VELODYNE HGS SYSTEM
Velodyne's prime focus is in providing ultra low di stortion loud speaker systems that im press the dedicated
audiophile as well as the casual listener. Ve lodyne's patented High Ga in Servo (HGS) system insures that your
new ULD series subwoofer will reproduce the music yo u enjoy without the excessive nonlinear distortions that
plague conventional loudspeaker des igns.
The Problem of Distortion
Nonlinear distortion is defined as any form of distortion that moves energy from one portion of the audio
frequency spectrum to another. When a single tone is appl ied to a nonlinear system , the result is harmon ic
distortion , in which some of the energy leaves the system at integer multiples of the original input frequency.
When multiple tones are applied to the same system , intermodu lation tones are produced , usually as simple
combinations of the input frequencies, i.e ., sums and differences of integer mult iples of the applied tones. In
general, 3% nonlinear distortion is considered a reasonably small amou nt. This means that 3% of the total energy
leaving a loudspeaker is at frequencies other than the intended pure tone applied to the input. Our tests , however,
indicate that about 0.5% nonlinear distortion at normal listening levels must be achieved befo re the average
listener is truly affected by an improvement in bass response.
In the reproduction of deep bass notes, loudspeakers suffer from a "double-whammy" when it comes to non-
linear distortion. First, most loudspeakers have much more than even 3% THO (Total Harmonic Distortion) at low
frequencies. Even at 1 watt drive levels , many loudspeakers have 8 to 10% THO at 40 Hz. With the 50 watt drive
levels needed to produce realistic bass intensity. these distortion figu res rise to astonishing levels. Second, the
distortion products produced by a non linear woofer are much easier to hear than is the fundamental frequency.
Consider a speaker driven at 30 Hz with 5% 3rd harmonic distortion. If the 30 Hz tone is 90 dB SPL (Sound
Pressu re Level). equating to about 5 watts into a typical woofer, the 3rd harmonic , at 90 Hz , wo uld be down 26
dB, or at 64 dB SP L. However, humans are more than 10 times as sensit ive to sounds at 90 Hz than at 30 Hz.
The no nl inear distortion produced by a woofer must be weighted by the sensit ivity function of the human ear.
When this is do ne, it becomes clear that even a small pe rcentage of harmonic distortion is unacceptable in a bass
driver. It is also clear that high-order (3rd , 4th , 5th, etc.) harmonic distortio n products are more serious than are
2nd harmonic distortion products. These studies have led to the co nclusion that 0.5% is th e maximum tolerable
amount of no nlin ear distortion for a bass driver, and the less distortion the driver produces, the mo re capable it is
of accurately reproducing live so unds.
Since most woofers today have at least 10% THO whe n 0.5% is the maxim um tolerated, minor improvements
in woofer technology are essentially ineffective . ULD Series Subwoofers have about 90 times less nonlinearity
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