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.
MRH-Jan 2014
