Speaker And Wiring Impedance - AudioControl ARCHITECT P250 EQ Installation Manual

Speaker Wiring and Impedance
Speaker impedance often is and should
be straight forward. Speakers, like other
resistors, if wired in parallel "show" lower
values than the individual components.
Here are two examples for calculating
speakers wired in parallel:
Calculating Impedance
For three 8 Ohm speakers wired in
parallel (pluses connected to pluses)
the impedance is 1/8 + 1/8 + 1/8 = 3/8
Then take the inverse or 8/3 = 2.66 Ω
For two 8 Ohm speakers wired in
parallel (pluses connected to pluses)
the impedance is 1/8 + 1/8 = 2/8
Then take the inverse or 8/2 = 4 Ω
Often the real world is more complicated
than theory, and for speakers this is the
case. An 8 Ohm speaker is not 8 Ohms at
all frequencies. Plus passive crossover net-
works add their own changing conditions.
Speaker Wire Resistance:
Wire Gauge versus Run Length
Wire Gauge
24 GA
22 GA
20 GA
18 GA
16 GA
14 GA
12 GA
Run Length
25' 50'
1.3Ω 2.6Ω
0.8Ω 1.6Ω
0.5Ω 1.0Ω
0.3Ω 0.6Ω
0.2Ω 0.4Ω
0.1Ω 0.25Ω
0.08Ω 0.16Ω

Speaker and Wiring Impedance

Be aware of speakers that have significant
dips from "nominal" values in portions
of their frequency range, and speakers
that are rated at unusual impedances, for
example 3.5 Ohms. The Architect model is
tolerant of lower impedance loads, how-
ever, all good designs use some margin of
error.
Your choice of speaker wire gauge and the
length of the runs, also affects the speaker
impedance load presented to the amplifi-
ers. As you can see in this table, even fairly
short speaker runs can have significant
resistance if you use a smaller wire gauge.
This can be a benefit if you are paralleling
lots of speakers. The wire itself acts as
an impedance limiter, since the amplifier
cannot see a speaker load lower than the
resistance of the wire. The downside of
this wire resistance is that you waste some
part of the total power available to the
speakers.
100' 250'
5.1Ω 12.8Ω
3.24Ω 8.1Ω
2.0Ω 5.0Ω
1.28Ω 3.2Ω
0.8Ω 2.0Ω
0.5Ω 1.26Ω
0.32Ω 0.8Ω
500'
25.7Ω
16.0Ω
10.1Ω
6.4Ω
4.0Ω
2.5Ω
1.6Ω
ARCHITECT
™
Model P250 EQ
Installation Manual
15