M2D-Sub Amplification; M2D-Sub Limiting - Meyer Sound M SERIES Operating Instructions Manual

CHAPTER 2

M2D-SUB AMPLIFICATION

The M2D-Sub loudspeaker is powered by the Meyer
Sound HP-2/M2D-Sub amplifier, a high-power two-
channel amplifier. The amplifier utilizes complementary
MOSFET output stages (class AB/H) capable of delivering
2250 watts total. All the specific functions for the M2D-
Sub loudspeaker such as crossover points, frequency and
phase response, and driver protection are determined by
the control card installed inside the amplifier.

M2D-SUB LIMITING

The M2D-Sub loudspeaker uses Meyer Sound's advanced
TruPower limiting system.
Conventional limiters assume a constant loudspeaker
impedance and therefore set the limiting threshold
by measuring voltage only. However, this method is
inaccurate, because the driver's impedance changes in
response to the frequency content of the source material
and thermal variations in the driver's voice coil and
magnet. Consequently, conventional limiters begin limiting
prematurely, which under-utilizes system headroom and
lessens the driver's dynamic range.
In contrast, TruPower limiting accounts for varying driver
impedance by measuring current, in addition to voltage,
to compute the actual power dissipation in the voice coil.
TruPower limiting improves performance before and during
limiting by allowing each driver to produce maximum SPL
across its entire frequency range. In addition, TruPower
limiting eliminates power compression when the system
is operated at high levels for extended periods, and also
extends the driver life cycle by controlling voice coil
temperatures.
The actual power is monitored for each of the two
amplifier channels. When the safe continuous power
level is exceeded in any channel, the TruPower limiter
controlling both amplifier channels engages. Limiting
activity is indicated by the Sub Limit LED on the user
panel (Figure 2.5).
Figure 2.5. The M2D-Sub's LED indicators
The M2D-Sub loudspeaker performs within its acoustical
specifications and operates at a normal temperature if the
Sub Limit LED is lit for no longer than two seconds, and
12
then go off for at least one second. If the LED remains
on for longer than three seconds, this indicates that the
amplifier is incurring hard limiting that can result in the
following negative consequences:
 Increasing the input level will not increase the volume.
 The system distorts due to clipping and nonlinear
driver operation.
 The lifespan of the drivers is reduced because they are
subjected to excessive heat
Each low-frequency driver is driven by a separate amplifier
channel but is routed to one limiter; the Sub Limit LED on
the user panel indicates TruPower limiting activity for the
drivers. The Sub Limit LED indicates when the safe power
level is exceeded (Figure 2.5).
CAUTION: While the limiters protect
the system under overload conditions
and exhibit smooth sonic characteristics; we
recommend that you do not drive the M2D-Sub
loudspeaker into continuous limiting. If an entire
system of M2D-Sub loudspeakers begins to limit
before reaching the required sound pressure
level, you should consider adding more M2D-Sub
loudspeakers to the system.
M2D-Sub Excursion Clamp
The drivers in the M2D-Sub are protected by an excursion
clamping circuit that provides instantaneous braking
for the drivers without the pumping effects commonly
produced by compressor/limiters.
The circuit uses sophisticated filters to minimize the
distortion normally caused by clamping and clipping. As
the M2D-Sub's input signal is increased past the clamping
WARNINGS:
point at each frequency, the output signal remains at a
THIS PRODUCT MUST BE GROUNDED
fixed level for that frequency, protecting the drivers and
This surface may reach high tempuratures white in use.
To ensure proper operation, allow at least 6 inches
minimizing negative sonic effects. The Exc.Clamp LED,
clearance from this surface and adequate ventilation.
To reduce the risk of electric shock do not remove cover.
shown in Figure 2.5, illuminates when the maximum
No operator or serviceable parts inside.
Refer servicing to qualified personnel.
allowed peak voltage at each frequency is reached.
To reduce the risk of fire or electric shock
do not expose this appliance to rain or moisture.
This circuit works for all frequencies, not just very low
ATENCI"N:
ACCESO INTERNO SOLO
frequencies where the drivers are more vulnerable to
AUTHORIZADO A PERSONAL T...CNICO CALIFICO
overexcursion.
ACHTUNG:
GEH�USE NICHT OFFENE WARTUNG
UND REPARATUR NUR DURCH ELEKTROF�CHKRAFTE
The limiters cease operation when the power level in the
ATTENTION:
ENTRETIENET REPARATIONS
INTERNES NE SONT AUTORISEES QU'AU
channel returns to normal. Limiters have no effect on the
PERSONNEL TECHNIQUE QUALIFI...
signal when the LED is inactive
U.K. WARNING:
THIS APPARATUS MUST BE EARTHED.
NO OPERATOR SERVICEABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED PERSONNEL.
Auto-Voltage Select
95-125V ~ 208-235V~
50-60Hz 50-60Hz
1400W RMS MAX 1400W RMS MAX
Operational Voltage Range:
Turn on 85V~ Turn off 134V~
Turn on 165V~ Turn off 264V~
Meyer Sound, Berkeley, CA USA