Hartke HyDrive HD Serie Manuel Du Propriétaire page 5

About Impedance
Basically, impedance is the amount of current that will flow through a speaker at
a certain voltage. It is measured in Ohms (Ω). The actual impedance of a speaker is
not constant across all frequencies. So, for convenience we use the term "nominal
impedance", which refers to the impedance that a speaker presents to an amplifier at
a reference frequency.
A speaker typically has an impedance rating of 4Ω, 8Ω, or 16Ω. Generally, the lower
the impedance of a speaker, the more power will be developed by the connected
amplifier. For example, a 4Ω speaker will extract more power from your amplifier
than an 8Ω speaker. If you connect a speaker with an impedance lower than the
amplifier's output rating, the amplifier can overheat and damage the power output
section. It is important to learn how to connect multiple speaker cabinets safely
without damaging the speakers or the amplifier in this way.
Here is a simple rule of impedance: When two speakers with the same impedance are
wired in parallel, the total system impedance is cut in half, and when two speakers
with the same impedance are wired in series, the total impedance is the sum of the
speakers individual impedance.
Hartke HyDrive HD speaker cabinet input jacks are parallel connections. The formula
to calculate the total impedance of a parallel speaker system is:
(R is the rated impedance of a speaker cabinet)
If all speakers have the same impedance, the total impedance will be equal to the
impedance of a single speaker divided by the total number of speakers. For example,
if you have two 4Ω speakers connected in parallel, the total impedance is 4 divided
by 2, or 2Ω. You should be careful when connecting speakers in parallel to an
amplifier. The impedance can quickly fall below safe levels. This is especially true
when connecting speakers in parallel to a bridged amplifier.
Typical Parallel Speaker Impedance Calculations:
HyDrive HD Series Cabinets
1/Rt = 1/R1 + 1/R2 + 1/R3 + ... 1/Rn
16Ω + 16Ω = 8Ω
8Ω + 8Ω = 4Ω
4Ω + 4Ω = 2Ω
4Ω + 8Ω = 2.7Ω
8Ω + 16Ω + 16Ω = 4Ω
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