Velodyne Acoustics HGS-15 THX - Manual (Page 6)

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Product Features & Controls
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• 15" (12.7" piston diameter) or 18" (15.2" piston diameter) subwoofer with
tandem 3" voice coils and 220 oz. magnet
• Built-in 1250 watt (RMS) high efficiency class D amplifier
• Accelerometer based servo control system for extreme accuracy
• Adjustable (40 to 120Hz) low-pass crossover (defeatable)
• Selectable (80 or 100Hz) high-pass crossover outputs
• Balanced (XLR) inputs
• Line-level (RCA) inputs & outputs
• Speaker-level inputs & outputs with 5 way binding post connections
• Signal sensing auto turn on/off (defeatable)
• Variable volume control
• Selectable phase control (0˚ or 180˚)
• Selectable subsonic filter (15Hz or 35Hz)
• Frequency response of 18-120Hz (HGS-15 THX Ultra 2), 15-120Hz (HGS-18 THX
Ultra 2)
• Detachable power cord
• Magnetically shielded for video use
• Multiple staggered low-pass crossovers; 12dB/octave initial,
48dB/octave ultimate
• Gain compression circuit prevents over excursion & amp clipping
• Infrared remote control with power, volume & mute functions
• External remote connector for custom installation
• Power on & protection indicator LED
• Multi-layer resin laminate cone
• High-excursion rubber surround
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The Velodyne servo-control solution
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Your Velodyne HGS 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.
We determined that conventional motors are unacceptable when called upon to produce
the amount of linear motion we desired. This inadequacy led us to design an improved
motor structure by incorporating two coils, operating out of phase in a push-pull
configuration within two magnetic gaps & suspended by dual spiders for even greater
linearity. We designed this motor to produce over one inch (1-1/8" to be exact) of linear
motion, with a maximum mechanical limit of 2". Also, with this unique configuration, the
distortion products are reduced by a factor of two over conventional single coil structures
with dramatically improved cone control. This driver alone would result in less distortion
than any other non servo design. We also designed this motor to be magnetically shielded
from the start, to allow for convenient placement near the television monitors of home
theater systems.
The unique push-pull twin voice coil in these subwoofers is designed and built in-house on
a custom built NC coil winding machine. This unique machine winds this coil in a way like
none other. There are two coils, each with two layers, would on the same former. Two
layers are first wound inside the former and then two layers on the outside. This results in
increased heat dissipation over normal designs which simply pile added layers on top of
each other, burying several layers beneath the surface. We then utilized materials such as
Polyimide resin impregnated fiberglass, for the former. This material is capable of withstan-
ding the extremely high temperatures (320 degrees C) that can occur when driven by our
powerful amplifiers. This results in excellent long-term power handling capabilities.
These speakers also feature our new Multi-Layer Resin Laminate cone system. This new
cone starts with two-layers of reinforced pulp fiber, which are then heat pressed with a
binding resin to form an extremely rigid cone structure. This helps to reduce distortion by
decreasing cone flex and breakup. Attached to the edge of the cone is our newly designed
rubber surround, tailored for long life under the high excursions these units are capable
of.
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continued. . .