Meyer Sound Self-Powered Loudspeaker HM-1 - Manual (Page 6)

6
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
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.