So, four 8-ohm speak-
ers wired this way will
yield an 8-ohm load.
The wiring diagram is
shown in (10).
Power rating
While it is usually not
an issue, most speak-
ers are rated for one
watt of power and
most decoders will
only put out a watt or
two. The total power
rating of an array of
speakers will be the
rating of the indi-
vidual speaker times
the number of speak-
ers in the array. For
example, three 1-watt
speakers in an array
will handle 3 watts.
So, now you can see
how speakers can
be matched to the
specifications of your
decoders. For a bit more in depth on speaker specifications,
check out this month’s Mr. DCC’s Workbench. There is a bunch
of data on my web site. I suggest you start at the speaker page
and work from there.
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One exception to this idea is the current version LokSound
decoders (or others) that actually like 4-ohm loads, so wire the
two 8-ohm speakers in parallel, as shown in (8). That’s why I
suggested you find out what your decoder likes and what it will
tolerate before you start.
Three speakers
Three 4-ohm speakers in series, as in (9), will yield 12 ohms
which will work just fine with almost all decoders designed for
8 ohms. I did this in a brass HO-scale Overland narrow hood
diesel and the results were amazing.
Four speakers
The four speakers shown in (4) were wired in a series-parallel
fashion. That is, two sets of two speakers are wired in series, as
shown in (7). Each series group has twice the impedance as the
original speakers. Then these groups are wired in parallel, mak-
ing the final impedance exactly what the speakers started with.
DCC Impulses Column - 7
9: Three speakers wired in series – the final impedance will
be three times the speaker rating – 4-ohm speakers yield a
12-ohm load.
9
10: Four speakers in a series-paral-
lel array – the final impedance will
be the same as the speaker imped-
ance – 8-ohm speakers will yield an
8-ohm load.
10
MRH-Jan 2014
