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

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Product Features and Controls
• 15" (12.7" 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 and 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
• 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 and amp clipping
• External remote connector for custom installation
• Power on
• Multi-layer resin laminate cone
• High-excursion rubber surround
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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.
As in our other servo products, we then incorporated closed-loop
accelerometer based servo-control of the loudspeaker. At the heart of this
control system is a low mass accelerometer rigidly attached to the voice
coil. The accelerometer continuously monitors cone motions, providing us
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continued. . .
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
and 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, allow for
convenient placement near the television monitors of home theater systems.