17
70V/100V Power Amplifier Considerations
a) Sizing – Add up the total wattage of all the taps you are connecting to the 70V/100V line. It
is an accepted rule-of-thumb to add 20% to this figure to make sure that the amplifier does not
get over-taxed. For example, if you are connecting six (6) speakers tapped at 15 watts, the
amplifier should be rated at 108 watts or higher.
b) Low Frequency Capability – Many 70V/100V power amplifiers on the market today are
from the era when business music systems extending only down to 100 Hz were widely
accepted. These less expensive amplifiers are not capable of driving today’s high fidelity
systems that require sound below 100 Hz. Unless you plan on high-passing the system at
100 Hz, it is VERY IMPORTANT to use a power amplifier capable of full output down to and
below the lowest frequency going INTO the amp, which is often around 50 Hz. An amplifier
with low-frequency capability is absolutely crucial whenever the system includes a subwoofer,
and is very important for today’s high fidelity business music systems.
Connection of Low-Impedance Speaker Systems
Parallel Hookup of Low Impedance Speakers (Control 24C or 26C)
(mono shown — duplicate for stereo)
Parallel Hookup of Low Impedance Full-Range Speakers with C19CS Subwoofer
(mono shown — duplicate for stereo)
Bi-Amplified Hookup of Full-Range (or High-Passed) Speakers with C19CS Subwoofer
(mono shown — duplicate for stereo)
+
–
+
–
+
–
+
–
To
Add’l
Spkrs
One Amplifier Channel
Direct Output
+
–
+
–
+
–
+
–
+
–
One Amplifier Channel
Direct Output
To
Add’l
Spkrs
+
–
+
–
+
–
+
–
+
–
+
–
+
–
One Amplifier Channel
One Amplifier Channel
Direct Output
Direct Output
ACTIVE
CROSSOVER
High-Pass or
Full-Range
Low-Pass
To
Add’l
Spkrs
To
Add’l
Spkrs
Subwoofer
Subwoofer
Subwoofer