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Terminal Connector
The terminal connector combines the audio input, power
supply input, and subwoofer output connections into a
single seven-pin connector. The audio input uses two
pins for the differential input signal, and one for ground;
the subwoofer output and power supply input each use
two pins. A seven-pin plug accepts the wiring and can
be inserted into the terminal connector in the correct
orientation only.
Rear panel with pluggable terminal strip input
and fan connectors
The HM-1 Subwoofer
The low frequency response of an HM-1 can be extended
down to 42 Hz if used with the HM-1 Subwoofer or
placed next to a wall or ceiling (half-space loading). Each
HM-1 can power a subwoofer from the male 3-pin EN3
Sub output connector on the rear panel. However, de-
pending on the loading conditions, ample low frequency
energy may be obtained by driving a single subwoofer
from two HM-1s, resulting in a correctly-summed mono
signal. Cables for connecting one HM-1 to a subwoofer
and two HM-1s to a single subwoofer are shipped with
each HM-1.
The addition of one subwoofer increases the maximum
SPL of a single HM-1 by 4 dB (without sub: 116 dB SPL;
with sub: 120 dB SPL). The HM-1 Subwoofer has the
following specifications:
Transducer
10" low frequency cone driver
Enclosure/Finish
Medium Density Fiberboard (MDF) /
Oak Veneer (natural or black)
Weight
33 lb (11.0 kg)
Dimensions
Height: 17.5"; Width: 12.3"; Depth: 9.3
6
A 3-pin terminal block connector is used to apply the
amplifier signal from the HM-1 to the subwoofer.
Cooling and Fan Installation
The HM-1 depends on natural convection to cool the
heatsinks that absorb heat from the amplifiers and radiate
the heat into the surrounding air space. Natural convec-
tion requires free air in back of, and underneath the HM-
1 to allow air to flow up over the heatsinks. The HM-1
reaches an equilibrium temperature in approximately
15 minutes at a steady operating level.
In free air, at a typical room temperature of 25°C, the
HM-1 reaches an equilibrium temperature of
• 40°C in a quiescent state (no audio signal);
• 60°C at a moderate operating level (occasional
limiting);
• 75°C at the maximum operating level (continuous
limiting), or at a moderate level with a subwoofer.
If the temperature reaches 85°C, the thermal limiters
activate (see Protection and Limiting ) to prevent high
source levels from further increasing the temperature
and damaging the drivers and electronics. The thermal
limiters provide 30 dB of muting until the temperature
decreases to 75°C.
The HM-1 can be cooled by two fans, available as an
accessory kit. The fans should be used if:
• the HM-1 is enclosed in a soffit or ceiling mount
without adequate space for natural convection;
• the HM-1 is used in hot ambient temperatures or
direct sunlight;
• the user wishes to avoid accidental contact with
the heatsinks if the rear of the HM-1 is exposed.
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