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10
Speakers and Speaker Wiring
The MCP35A control panel of the SI and PI products is designed to use 25-volt distributed speakers.These speakers have
line-matching transformers with various power level taps. 8-ohm speakers or speakers without line-matching transformers
cannot be used with the SI and PI products.
Distributed speakers can be tapped at various power levels and this is determined by which wire from the speaker’s trans-
former is used for connection.The user must determine which power tap gives acceptable volume in a given location.
However, it is best to tap the speakers at the lowest acceptable power tap in order to ensure that enough speakers can be
connected to the system without overloading the system amplifier.
The chart below shows the wire colors and power taps for the T725 transformers used in all Bogen distributed speakers.
For SI35A and PI35A applications, use the
25V column for speaker connections
Caution: Do not attempt to connect a 25V speaker directly to the MCP35A, using GND as one of the connecting points.
This could seriously damage the MCP35A because the unit uses a balanced output when connected to the speakers lines.
The MCP35A control panel of the PI and SI contains an internal amplifier with 35W power handling capability.Therefore,
the combined power of all the system speakers cannot exceed 35W. To determine the required power that the system
amplifier must handle, add up all the power taps selected for all the speakers in the system.This is the total system power
requirement. If the total of the speaker power taps is too high for the system to handle, it may be necessary to tap the
speakers at the next lowest setting in order to keep from overloading the amplifier. In many instances, the required speak-
er tap setting will be either 1/4 or 1/2 watt (you should also factor in 20% additional power loss through wires, transform-
ers, etc. as a safety margin). The MCP35A’s 35-watt amplifier should provide sufficient power for most applications.
If the system’s power requirements are greater than 35 watts and cannot be lowered, it may be necessary to use an exter-
nal booster amp.The booster amp replaces the internal amplifier of the MCP35A. Booster amp connections are described
later in this manual.
Time Tones
A tone signal sounds through all speakers when the clock terminal is grounded through a closure from a master clock.
Reference call out #6 on page 5.
T 7 2 5
Leads 25V 70V
Black COM COM
Brown 4
Red 2
Orange 1
Yellow 1/2 4
Green 1/4 2
Blue 1/8 1
Violet 1/2
Grey 1/4
White 1/8