CHAPTER 2

When driving multiple loudspeakers in an array, make certain that the source device can drive the total load impedance presented 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) in order 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 array. The input impedance for a single loudspeaker is 10 kOhms: if n represents the number of M2D/M2D- Sub loudspeakers in an array, paralleling the inputs of n loudspeakers will produce 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 M2D and/or M2D-Sub loudspeakers 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 M2D/ M2D-Subs in parallel (loop out) with other self-powered Meyer Sound loudspeakers.

CAUTION: Shorting an input connector pin to the case can form a ground loop and

cause hum.

TIP: If abnormal 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.

M2D INTERCONNECTIONS

For the low and low-mid frequencies, the M2D utilizes two 4-ohm, 10-inch cone drivers featuring lightweight neodymium magnet structures.

A complex passive network connected between the amplifier and the drivers is used to ensure smooth response in the critical midrange. At the lowest frequencies, the two high-power, back-vented cone drivers combine to reproduce coherent low frequencies. In the mid frequencies, the passive network feeds only

one of the two drivers while correcting the phase shift at low frequencies for proper addition with the other driver. This technique eliminates interference between the high- frequency and low-frequency drivers that would otherwise occur near the crossover frequency, and maintains optimal polar and frequency response characteristics.

To reproduce high frequencies, the M2D employs Meyer Sound's patented REM ribbon emulation manifold to couple a constant-directivity horn to a compression driver with a 1.5-inch exit (4-inch diaphragm). REM controls the output of the driver and introduces it to the horn throat within a three-inch path length, dramatically minimizing distortion. This unique horn design produces a coherent wave front that is characteristic of, but much more powerful than, a large ribbon driver.

CAUTION: All Meyer Sound loudspeakers are shipped with the drivers in correct

alignment. However, if a driver needs to be replaced, make sure the replacement is reinstalled with the correct polarity. Incorrect driver polarity impairs the system performance and may damage the drivers.

M2D AMPLIFICATION

All three drivers in the M2D are powered by a two-channel proprietary Meyer Sound UX-M2D amplifier utilizing complementary MOSFET output stages (class AB/bridged) capable of delivering 700 watts total. The amplifier employs electronic crossover, phase, and frequency response correction filters – as well as protection circuitry

–to process the audio signal. All the specific functions for the M2D are determined by the control card installed inside the amplifier; one channel of the amplifier drives the low and low-mid section of the M2D through the passive network while the other channel drives the high frequency section.

M2D LIMITING

Each channel of the amplifier has limiters that prevent driver over-excursion 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 the top and the low-frequency limit LED is the bottom, as shown in Figure 2.4).

10