Meyer Sound M3D Manual Do Utilizador

 

Meyer Sound Laboratories Inc

M3D™ Line Array

•

7

Each front 4 ohm, 18-inch, low-frequency driver is 

powered by one channel of the HP-4/M3D-Sub amplifier; 

also, each rear 8 ohm, 15-inch low-frequency driver is 

the drivers are connected to the amplifier in the 

M3D-Sub.

Conventional limiters assume that the impedance of a 

speaker remains constant and set the limiting threshold 

by measuring voltage only. This method is inaccurate, 

because the speaker’s impedance changes in response to 

the frequency content of the source material and thermal 

variations in the speaker’s voice coil and magnet. 

Conventional limiters begin limiting prematurely, which 

under utilizes system headroom and deprives the 

speaker of its full dynamic range.

The TruPower Limiting (TPL) system accounts for varying 

speaker impedance by measuring current, in addition to 

voltage, to compute the actual power dissipation in the 

voice coil. TPL improves performance before and during 

limiting by allowing each driver to produce its maximum 

SPL across its entire frequency range. TPL extends the 

lifetime of the drivers by controlling the temperature of 

the voice coil. In addition, TPL eliminates power 

compression when the system is operated at high levels 

for extended periods.

The true power is monitored for each of the four 

amplifier channels. When the safe continuous power level 

is exceeded, the TPL limiter controlling that amplifier 

channel engages. TPL activity is indicated by the LEDs on 

the user panel. 

The M3D and M3D Sub perform within their acoustical 

specifications and operate at a normal temperature if the 

limit LEDs are lit 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 is hard limiting 

with 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.

The left-and-right front low-frequency drivers are 

driven by separate amplifier channels but are routed to 

one limiter; the LO TPL F LED on the user panel indicates 

TPL activity for the front drivers. The two rear low-

frequency drivers are driven by one amplifier channel; 

the LO TPL R LED indicates TPL activity for the rear low-

frequency drivers. The two high-frequency drivers are 

driven by one amplifier channel; the HI Limit LED, shown 

high-frequency drivers.

The limiters cease operation when the power level in the 

channel returns to normal and do not affect the signal 

when the LED is inactive.

Figure 13.  

Red 

Black

 

Red 

Black

 

Right Front MS-418 N 

Left Front MS-418 N 

Right Rear MS-815 

Left Rear MS-815 

- 

+ 

+ 

- 

- 

+ 

+ 

- 

Red 

Black

 

Red 

Black

 

- 

+ 

- 

+ 

Fans 

User Panel 

Upper Control Card (Front) 

24.033.042.32 

Lower Control Card (Rear) 

24.033.042.31 

Figure 14.