Hartke TX600 Manuel Du Propriétaire page 8

Choosing the Correct Speaker Cabinets
When choosing a speaker cabinet to use with your Hartke TX600, there are many
specifications to consider (impedance, power handling, frequency response, etc). While
most specs are pretty straight forward, there is often questions 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 typical speaker has an impedance rating of 4Ω, 8Ω, or 16Ω. Generally, the lower
the impedance of a speaker, the more power will be developed by a given amplifier. For
example, a 4Ω speaker will extract more power from your amplifier than an 8 ohm speaker.
If you connect a speaker with an impedance lower than the rating of the amplifier's
output, 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.
Typically, amplifier speaker output jacks and speaker cabinet input jacks are parallel
connections, and will follow the rules described in this section. When speakers are
connected in parallel, the impedance is reduced. The formula to calculate the total
impedance of your speaker system is:
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 must 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.
The amplifier can deliver 600 watts of power to a minimum 4Ω speaker load. When
choosing speakers, make sure that they can match or exceed the output power of the
amplifier, or you can damage the speakers.
8
1/R = 1/R
t 1
Where "R" is the impedance of a speaker cabinet.
16Ω
8Ω
8Ω
8Ω
16Ω
4Ω
4Ω
+ 1/R + 1/R + ... 1/R
2 3
Typical Impedance Calculations
+ 16Ω =
+ 16Ω = 5.3Ω
+ 8Ω =
+ 16Ω +
+ 16Ω +
+ 8Ω = 2.7Ω
+ 4Ω =
.
n
8Ω
4Ω
16Ω = 4Ω
16Ω + 16Ω = 4Ω
2Ω