Velodyne Acoustics HGS-15X THX - Manual (Page 14)

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Important!!!
Do not use both LINE LEVEL and SPEAKER LEVEL connections simultaneously!
Volume control
This control allows you to balance the output from the subwoofer to the main
speakers/amplifier in your system. This control should be set to achieve similar
output level from both the main speakers and subwoofer when listening to music.
The remote may then be used for minute/temporary adjustments, such as increasing
the volume for home theater usage.
Low-pass crossover - 40 to 120Hz
All inputs sum the left and right channels together, with the resulting signal passing
through an adjustable low-pass crossover before being amplified. The crossover
control allows you to adjust the upper limit of the subwoofer's frequency response
from 40 to 120Hz. The subwoofer's response will begin rolling off above the
frequency you set this control to. You should set the crossover frequency to obtain
a smooth and seamless transition from the subwoofer to the main speakers in your
system. If your main speakers are smaller units with limited low frequency output,
you may wish to choose a higher frequency (such as 100-120Hz) than you would
with larger speakers which have greater low frequency output. With larger speakers,
you might start with this control set lower, such as 80Hz.
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is harmonic distortion. In which some of the energy leaves the system at multiples
of the original frequency. When multiple tones are applied, intermodulation tones
are produced, usually as simple combinations of the input frequencies. Generally,
3% distortion is considered a reasonable amount for speakers. This means that 3%
of the total energy leaving the speaker is at frequencies other than the intended input
signal.
Most subwoofers on the market today however, produce much more than 3%
distortion at common listening levels. Many models we have tested produce greater
than 20% distortion @ 20Hz when driven to 100dB. This is a typical output level
obtained in many systems, particularly home theater systems. Even at 1 watt, many
conventional units produce several percent distortion. Secondly, the odd order,
higher harmonics are much more offensive to the human ear than the closer 2nd
harmonic.
An interesting result of this reduced distortion is that some of the bass, when played
over an extremely accurate subwoofer system, seems to actually be missing. The
truth, however, is that the "missing" bass was never there to begin with! Distortion
products of conventional woofers actually add to the bass spectrum making it
appear louder than recorded. This is due to the additional and unwanted harmonics
(distortion) of the fundamental signal. While conventional subwoofers offer little
to combat distortion products, we at Velodyne have developed another way. . .
continued. . .
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Installation
Your new Velodyne servo subwoofer provides for a number of installation
options. Read all the installation information below in order to determine
which installation option is best for your system. Remember to perform
all installation procedures with system power turned off!!!
Inputs
Your new subwoofer is equipped with speaker-level, line-level and balanced (XLR)
inputs. Use the LINE LEVEL jacks when connecting your subwoofer to a pre-amp,
signal processor, line-level crossover, or receiver with pre-amp level outputs. The
SPEAKER LEVEL jacks connect directly to the speaker outputs of any amplifier,
integrated amplifier or receiver. Your amplifier section will notice no additional
loading effects when you use these inputs due to their very high impedance.
Distortion in Loudspeakers
Nonlinear distortion is a problem which plagues all speakers. This particular type
of distortion is a common problem in subwoofers, which must move large amounts
of air to produce adequate levels of deep bass. 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 applied to a nonlinear system, the result
The Velodyne Servo-Control Solution
Your Velodyne HGSX subwoofer produces sound in the same manner as conventional
loudspeakers: a cone-shaped piston is forced to move by means of a linear motor.
However, this is about the only conventional part of the subwoofer.