While there are times
when you want to inten-
tionally wire speakers out
of phase, they are few
and far between in model
railroading. So, I’m going
to discuss how to have
the speakers be in phase –
meaning that all the cones
go in the same direction
at the same time, effec-
tively doubling the size of
the speaker.
If you have any ques-
tions, try an experiment.
Hook two speakers up in
phase and listen. Reverse
the leads to one speaker
(making them out of
phase) and listen. You will
probably hear a reduc-
tion in the low frequency (bass) reproduction and a loss of
directionality of the midrange and high frequency sound. The
sound will frequently appear to be in a large ball surrounding
the locomotive, as compared to a point source between the
speakers.
Over the years, I’ve only had one installation where I intention-
ally wired the speakers out of phase and it was for two switch-
ers separated by a flat car with a speaker in each loco. The “ball
DCC Impulses Column - 5
Impedance
You now know what impedance your decoder wants to see and
what range it will tolerate. You also know how many speak-
ers you want to use in your installation. For the purposes of
this column, I’m going to assume that you are using a decoder
that is designed for an 8-ohm load and will tolerate any load
between 4 and 16 ohms. So my goal is to provide as close to 8
ohms as possible and not to go outside the 4 to 16 ohm range.
See Mr. DCC’s Workbench at the end of this column for more
insight into speaker specifications.
There are two ways to wire two electronic elements: series and
parallel. How you wire multiple speakers will determine what
the total impedance seen by the decoder will be.
Series wiring is where all of the electrons go into one unit and
come out and go through the second unit. When you wire
two identical speakers in series, the impedance doubles: two
8-ohm speakers in series will be a total of 16 ohms. With three
identical speakers in series, the impedance triples: three 4-ohm
speakers in series will yield 12 ohms.
Parallel wiring is where the electrons split and part of them go
through each unit and they join up together afterwards. Wir-
ing identical speakers in parallel will halve the impedance: two
8-ohm speakers in parallel will provide a load of 4 ohms.
Polarity
If you are only wiring one speaker to a decoder, the polarity
markings on the decoder or speaker are meaningless. Just hook
them up and go.
6: A speaker with a polarity
mark (red dot in the drawing).
The speaker probably will come
with one. If not, you may add
your own.
6
MRH-Jan 2014
