Radio Shack MPA-50 - Manual (Page 6)

6 Speakers
ˆ
Speakers
SPEAKER PHASING
Phasing is the direction the speaker
cone moves with reference to the polari-
ty of the connection wires. Proper phas-
ing is important when you use more than
one speaker in the same room or area.
Out-of-phase speakers can lose up to
one-half of their potential volume, and
can have a significantly decreased bass
effect.
Speakers are in phase if all the speaker
cones move in the same direction when
an equal signal is applied. Phasing is
correct if you observe the correct polari-
ty (+ to + and – to –) when connecting
the speakers.
Most speaker terminals are color-coded
or have a mark that indicates the termi-
nal’s polarity. Usually, terminals with
positive polarity are red or have a plus
symbol (+), and terminals with negative
polarity are black or have a minus sym-
bol (–). If the speaker terminals are un-
marked, follow these steps to determine
their polarity.
1. Remove about 1 inch of insulation
from both ends of a short piece of
wire (available at your local
RadioShack store). Then twist the
exposed wire to secure all its
strands.
2. Connect one end of the wire to one
of the speaker terminals.
3. Touch the positive end of a 1.5-volt
flashlight battery to the speaker ter-
minal that does not have the wire
attached to it.
4. Touch the negative end of the bat-
tery with the lose end of the wire
attached to the other speaker termi-
nal. Note the direction of the cone
movement — inward or outward.
5. If the speaker cone moves outward,
the speaker terminal where you
touched the positive end of the bat-
tery is positive. Mark that terminal
with a + and mark the other terminal
with a –.
If the speaker cone moves inward,
the speaker terminal with the wire
attached that touched the negative
end of the battery is positive. Mark
that terminal with a + and mark the
other terminal with a –.
6. Remove the wire.
Repeat Steps 2–6 for each speaker with
unmarked terminals you plan to connect
to the amplifier.
DETERMINING TOTAL
SPEAKER IMPEDANCE
Caution: A total speaker impedance
that is higher than 16 ohms (
Ω
) or lower
than 4 ohms can damage your amplifier
or speakers. Be sure to make the proper
connections.
Before you connect speakers to the am-
plifier, you must determine the total
speaker impedance. In determining the
total speaker impedance, you must first
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