Dolby Laboratories MPX500 User manual

Model MPX500
Microphone Multiplexer
Users' Manual

Users' Manual
For
Model MPX500
Microphone Multiplexer
Dolby Laboratories Incorporated
U.S.A. 100 Potrero Avenue, San Francisco, CA 94103
Tel: [phone]; Fax: [phone]
U.K. Wootton Bassett, Wiltshire SN4 8QJ
Tel: [phone]; Fax: [phone]
WARRANTY INFORMATION - USA: Warranty on the product covered by this manual is subject to the limitations and disclaimers set forth in
the warranty disclaimer originally shipped with the product and also printed on the back of the invoice.
Dolby and the double-D symbol are registered trademarks of Dolby Laboratories Licensing Corporation.
©1996 Dolby Laboratories Inc. ISSUE 2
S96/10837
Dolby Part No. 91438

MODEL MPX500
MICROPHONE MULTIPLEXER
Introduction
Intended for use with the Dolby CP500 Digital Cinema Processor, the Dolby
Model MPX500 Microphone Multiplexer ensures rapid and accurate theater
speaker equalization by enabling the simultaneous use of as many as four
microphones (supplied) placed throughout the auditorium.
The MPX500 rapidly switches between the four microphones and sends their
outputs to the CP500 over the special 31-meter (100-ft.) Dolby Cat. No. 582
input/output cable (supplied). Digital circuitry within the CP500 then averages the
mic outputs for display on its built-in real time analyzer and subsequent EQ
adjustments. This eliminates the time-consuming process of moving a single
microphone to different locations and manually averaging the results.
Four high-quality electret microphones are supplied with the MPX500 along with
6-meter (20-ft.) connecting cables that adapt the microphones' standard XLR
connectors to the “mini-XLR” style input connectors on the MPX500. The Cat.
No. 582 input/output cable for connecting the MPX500 to the CP500 contains two
individually shielded pairs, one for distribution of bi-directional RS-232 control
signals and the other for the multiplexed microphone signal.
A built-in microcontroller chip is programmed to control microphone selection,
switching rate between microphones, and the MPX500's LED display. There are no
user adjustments on the MPX500 itself.
Unit Set-Up
Position the MPX500 Multiplexer centrally in the listening area and connect the
four microphones to it using the four Cat. No. 581 adapter cables. Position the
microphones in the room so that they are substantially in the reverberant field
rather than receiving mostly direct energy from the speakers. A typical microphone

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placement is shown above. Take care not to place any of the microphones on the
central axes of the room, as standing waves and nodes at these positions can cause
measurement errors. The microphones should normally be mounted at the
listener's head height. However, if the seats have high backs, the microphones
should be raised up so that they are at least 23cm (9 inches) above the top of the
seat to avoid unwanted effects.
Connect the Cat. No. 582 input/output cable to the MPX500 Multiplexer and
secure the hold down screws so that the cable cannot work loose. Route the cable
to the location of the CP500 and connect it to the microphone connector on the
back panel of the CP500.
The procedure for theater alignment can be found in the CP500 Installation
Manual.
Components
Use the listed numbers for ordering replacement parts:
Cat. No. 580 Microphone Multiplexer Unit
Cat. No. 581 One Microphone with Adapter Cable (Part Nos. 51031 and 83294)
Part No. 51031 Microphone with 6' (2 meter) cable
Part No. 83294 Microphone-to-MPX500 Adapter Cable, 6 meter (20')
Cat. No. 582 MPX500-To-CP500 I/O Cable, 31 meter (100')

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Operation
Display Action
B-Chain Alignment
key
Allignment
key
Format
Selection
Menu
key
Menu
Selection
press:
System
Alignment
screen shows:
screen shows:
press:
press:
screen shows:
Mic Mux
key
B-Chain
Alignment
screen shows: press:
FORMATS Menu Cancel OK Exit
SK8
OK
To select one mic:
SK1 - SK4
To remove one mic:
SK1 - SK4 
SK5
To resume scan:
SK8
Begin by entering the microphone
multiplexer control screen on the
CP500:
Press the Menu key
Press ALIGNMENT (SK2)
(A system password may be required at this point)
Press the B-chain Alignment key (SK1)
Press the Mic Mux key (SK3)
Note: While performing equalization, this
multiplexer control screen may be entered directly by
pressing soft key 5 (SK5).
To scan through the microphones press
the Scan key (SK8).
The scan rate may be set by pressing the
Set scan rate key (SK6). Rotate the
front panel knob until the desired rate is
displayed then press OK. The number
displayed is the time spent connected to
each microphone.
Pressing any soft key SK1 through SK4
will halt scanning and enable the
corresponding microphone.
To remove a microphone from the scan
sequence, select the microphone by
pressing the corresponding softkey, then
press the Enable/Disable key (SK5).
Resume scanning by pressing the Scan
key (SK8)