Speaker Impedances - Speco PBM-15 Instruction Manual

25V and 70V CONSTANT LINE VOLTAGE CONNECTIONS
(refer to figure 4).
IMPORTANT NOTICE: When the 25V and 70V constant line voltages are used, a line matching
transformer must be used with each speaker. All transformers must be connected in parallel.
HOW TO CONNECT LINE MATCHING TRANSFORMERS IN PARALLEL
(25 VOLT LINE OR 70 VOLT LINE)
ALWAYS CONNECT LINE TRANSFORMERS IN PARALLEL
NEVER CONNECT LINE TRANSFORMERS IN SERIES
25V Transf. 70V Transf.
FIGURE 4

SPEAKER IMPEDANCES:

Speaker impedance taps for 4, 8 and 16 Ohm speakers are provided on a terminal strip on the rear
panel of the unit. Also, outputs for 25V and 70V constant line voltage are provided. To connect the
power output directly to a speaker or PA horn or a combination of speakers and/or PA horns which
have a resulting voice coil impedance of 4,8 or 16 Ohm, connect to the COM and the proper
impedance tap on the terminal strip. Be sure the speaker(s) or PA horn(s) is capable of handling a
reasonable power output from the amplifier or permanent damage to the speaker(s) or PA horn(s)
may result. Also, be careful not to overload the amplifier with too many speakers or PA horns. If it is
desired to use a number and variety of speakers, the speakers must be arranged in various series or
parallel arrays to provide proper impedance matching or the 25V or 70V constant line voltage must be
used. If you are not familiar with impedance matching consult a professional installer or technician for
advice. If the 25V or 70V constant line voltages are used, a line matching transformermust be used
with each speaker. Again do not overload or use incompatible speakers. Line transformer are the
preferred method for multi-speaker installation.
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