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CHAPTER 2
Regardless of the input module type, audio signals can be
daisy-chained using the loop output connector on the user
panel. A single source can drive multiple UPJ-1Ps with a
paralleled input loop, creating an unbuffered hard-wired
loop connection.
If driving multiple UPJ-1Ps in a system, make certain that
the source device can drive the total load impedance pre-
sented by the paralleled input circuit of the array. The audio
source must be capable of producing a minimum of 20 dB
volts (10 volts rms into 600 ohms) to produce the maximum
peak SPL over the operating bandwidth of the loudspeaker.
To avoid distortion from the source, make sure the source
equipment provides an adequate drive circuit design for the
total paralleled load impedance presented by the system.
The input impedance for a single loudspeaker is 10 kOhms.
If n represents the number of UPJ-1P loudspeakers in a
system, paralleling the inputs of n loudspeakers will pro-
duce a balanced input load of 10 kOhms divided by n.
NOTE:
Most source equipment is safe for
driving loads no smaller than 10 times the
source's output impedance.
For example, cascading an array of 10 units consisting of
UPJ-1Ps produces an input impedance of 1000 ohms (10
kOhms divided by 10). The source equipment should have
an output impedance of 100 ohms or less. This is also true
when connecting UPJ-1Ps in parallel (loop out) with other
self-powered Meyer Sound loudspeakers and subwoofers
TIP:
If noises such as hiss and popping are
produced by the loudspeaker, disconnect
the audio cable from the loudspeaker. If the noise
stops, then most likely the problem is not with the
loudspeaker. Check the audio cable, source, and
AC power for the source of the problem.
NOTE:
Ensure that all cabling carrying signal
to multiple UPJ-1Ps is wired correctly (Pin
1 to Pin 1, Pin 2 to Pin 2, and so on), to prevent the
polarity from being reversed. If one or more loud-
speakers in a system has reversed polarity, this can
cause severe degradation in frequency response
and coverage.
AMPLIFICATION AND LIMITING
The low- and high-frequency drivers in the UPJ-1P are
powered by a two-channel proprietary Meyer Sound
amplifier utilizing complementary MOSFET output stages.
The amplifier processes the audio through the use of elec-
tronic crossover, phase and frequency response correction
filters as well as driver protection circuitry. Each channel
6
has peak and rms limiters that prevent driver over-excur-
sion and regulate the temperature of the voice coil. Limiter
activity for the high and low channels is indicated by two
yellow limit LEDs on the rear panel (the high-frequency
limit LED is on top and the low-frequency limit LED is on
bottom).
The UPJ-1P performs within its acoustical specifications
and operates at a normal temperature if the limit LEDs
are on for no longer than two seconds, and off for at least
one second. If either LED remains on for longer than three
seconds, that channel incurs these consequences:
Increasing the input level will not increase the volume.
The system distorts due to clipping and nonlinear
driver operation.
Unequal limiting between the low and high frequency
drivers alters the frequency response.
Limiters protect the system under overload conditions and
exhibit smooth sonic characteristics, but we recommend
that you do not drive the UPJ-1P into continuous limiting.
NOTE:
Limit LEDs indicate when the safe
power level is exceeded. If a UPJ-1P system
begins to limit before reaching the required SPL,
consider adding more loudspeakers.
AMPLIFIER COOLING SYSTEM
The UPJ-1P amplifier employs a combination of natural
convection and forced air in its cooling system. The large
heatsink used in the amplifier allows natural convec-
tion cooling from air flowing over the fins. A low noise
fan forces air to the fins, keeping the temperature on the
amplifier low even when the loudspeakers are being used
at high ambient temperature, in tightly packed conditions
and/or at high continuous levels.
CAUTION:
To keep the heatsink from
!
getting too hot, ensure proper ventilation
around the loudspeaker, especially when using the
UPJ-1P in tightly packed conditions.
If the temperature of the heatsink reaches 75° C (167° F),
the fan switches to high speed and the On/Temp. LED on
the rear panel turns from green (On) to red (Temp.) The unit
continues to operate normally even if On/Temp LED is red.
When the heatsink temperature decreases to 65° C (149°
F), the On/Temp. LED changes from red to green
CAUTION:
The heatsink can reach temper-
!
atures up to 75° C (167° F) during normal
operation. Use extreme caution when approaching
the rear of the cabinet.
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