Electro-Voice Precision Series Quick Start Manual

Description

The M-153 module is a loudspeaker system-specific signal
processor accessory designed for use with the Electro-Voice
QRx-153/75 loudspeaker when powered with the Electro-
Voice Modular Precision Series P1202 amplifier.The EV
QRx153/75 requires biamping and other signal processing to
achieve its high level of performance and the M-153 delivers
the required signal.
The M-153 module provides optimal, yet cost-effective signal
processing consisting of a crossover function with user-selec-
table high-pass filtering, infrasonic filtering and level ba-
lancing between the LF and HF sections.
The QRx153 must be biamped at 500 Hz and the M-153
module provides a 24-dB-per-octave crossover at that fre-
quency. The crossover circuit utilizes a Linkwitz-Riley filter
that keeps the LF and HF sections in polarity with each other
at the crossover point and has a steep roll-off to prevent
out-of-band signals from degrading the system's performan-
ce.

Installation and Operation

The M-153 is straightforward to install. First, remove the
screws holding the blank cover panel on the left as you face
the front of the P1202 amplifier. Then slide the module into
the slot A, making sure that it mates securely with the
connector inside the amplifier. Use the same screws that held
the blank panel to hold the M-153 in the chassis.
The M-153 module automatically routes the appropriate si-
gnal to both channels in the amplifier and it is important to
remember that the P1202 can only be used with one M-153
module, not more.
Upon insertion into the P1202, channel A powers the LF
section and channel B powers the HF section. The HF chan-
nel's gain is automatically attenuated by ~6 dB to sonically
balance the two sections of the speaker perfectly. If additional
level balancing is required, it is possible to do it using the
power amplifier's rear-mounted gain controls.
On the front of the M-153 are two switches: the blue micro-
switch on the right side of the module engages a high-pass
filter at either 45 Hz or 90 Hz. When the QRx153 is going to
be used as a full-range speaker, the switch should be set to the
45 Hz position (switch in the out position); when the QRx153
is being used in combination with a sub, such as the QRx218S,
the switch should be set to the 90 Hz position (switch in the
in position). It is easy to verify which frequency mode the
switch is in by the status LED next to the switch.
Architects and engineers
specifications
M-153
Precision Series
Amplifier Module
The 45 Hz switch position also engages a 12 dB infrasonic
filter to prevent low-frequency overload.
The M-153 module also has a 31-position precision-calibrated
gain control. It is possible to precisely match system levels
using this control.
On the inside of the M-153 is EV's Voice Coil Protection
(VCP) circuit, which simulates the thermal condition of the
connected speaker. If the circuit detects a dangerous voltage
level that might cause the connected speaker to be damaged,
it lowers the signal from the amplifier to a safe level. There
is a red LED on the front of the M-153 module, that activates
when this circuit is in protection mode.
It is also possible to defeat the VCP circuitry. On the right rear
side of the circuit board, there is a jumper switch that can be
reversed to turn the VCP circuit off. It is recommended to
keep this circuit active to prevent driver damage because the
Precision Series amplifiers are capable of producing peak
output that far exceeds the rated output.
For ease in system setup and use, there is a green signal present
LED which illuminates when a signal of at least -35 dBu
reaches the amplifier's input.
The combination of the M-153 module, P1202 amplifier and
the QRx153 speaker system creates a wide bandwidth, low
distortion and highly intelligible sound system.