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Appendix B: Technical Info
Do The Math: Ohms, Loads,
and Such
An ohm is a unit of resistance — the more ohms,
the more resistance (or, more accurately in this case,
impedance). The more the resistance, the less the power.
If you’re dealing with just one speaker (or cabinet)
per output, the load in ohms is usually printed on it
somewhere. That’s your load, usually 8 ohms or 4 ohms.
If you’re driving an assortment of speakers, things
can get complicated. There are two basic ways of
linking multiple loads (or speakers in this case): series
and parallel.
Since series connections are not normally used in
PA applications, we’ll concentrate on the parallel
connection. Parallel means that the positive amp
output connects to the positive terminals of all the
speakers, and the negative amp output connects
to the negative terminals of all the speakers. If one
speaker fails in a parallel confi guration, the others will
still work.
Calculating parallel loads is easy, as long as each
speaker has the same value — just divide the value by the
number of speakers. For instance, four 8-ohm speakers,
connected in parallel, will equal 2 ohms (8/4 = 2). If the
loads are not all the same, the formula gets a little more
complicated, but nothing that you can’t do with a
simple calculator.
ZT =
1
1
Z1
+
1
Z2
+
1
Z3
+ . . .
Using this formula, an 8-ohm speaker and a 4-ohm
speaker, connected in parallel, will equal 2.7 ohms.
Remember that the Juice amplifi ers require 2 ohms or
greater per channel in Stereo or Mono mode, and 4
ohms or greater in Bridge mode.
Summary of Contents for Juice J-1400
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