Radio Shack MPA-50 User Manual

10

Speakers

4. To determine the total impedance of

speakers connected in serial and
parallel combined, divide the imped-
ance of one pair of speakers by the
number of pairs.

For example, if you want to connect
four 8-ohm speakers in serial and
parallel combined, divide 16 (the
impedance of one pair of speakers)
by 2 (the number of speaker pairs)
for a total speaker impedance of 8
ohms.

5. Connect the negative (–) terminals

of all pairs of speakers to the ampli-
fier’s 

 terminal.

6. Connect the positive (+) terminals of

all pairs of speakers to the ampli-
fier’s terminal that matches the total
speaker impedance (

Ω

Ω

Ω

Ω

, in this

example).

For complex multiple-speaker arrange-
ments that require many speakers and
long runs of connecting wire, we recom-
mend you use a line transformer (not
supplied).

Note: When running lengths of wire
longer than 50 feet, use wire that is
heavier than 16 gauge.

There are several advantages to using
transformers.

• You can connect speakers with dif-

ferent impedances without causing
differences in output between the
speakers.

• You can add or remove a speaker

without having to recalculate the
entire system’s impedance.

• You can reduce signal loss when

you use speaker wire over 50 feet
long.

You need a separate transformer for
each speaker.

Line transformers have several connec-
tors called taps.

The primary taps (on one side of the
transformer) are the inputs and are rated
in watts. The secondary taps (on the op-
posite side of the transformer) are the
outputs and are rated in ohms.

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