Speaker Connections
A note about amplifiers:
You should always use the recommended load for
your amplifier. However, if you must use a load other than the
recommended load, here is a short guide.
Solid-state Amps: Most solid-state
amplifiers would rather look at an open circuit (no speaker at all)
than a load. Therefore, you can usually use a load that is higher than
the recommended load. Do not use a lower impedance load, as this could
cause serious damage to your SS amp.
Tube Amps: On the other hand, most tube
amplifiers need a load to avoid transformer or tube socket damage. If a
mismatch can not be avoided on a tube amp, it is better to go towards a
lower impedance rather than too high of a speaker impedance. This may
stress the tubes some, but, tubes are cheaper than transformers.
Series Connections:
As the graphic shows, you connect the positive wire to
speaker A's positive terminal, connect a wire from speaker A's negative
terminal to speaker B's positive wire, and then connect the negative
wire to the negative terminal of speaker B. You could continue this
string for as many speakers that you have available, however, it may
not be very practical.
The impedances add in a series connection.
If speaker A equals 8ohms and speaker B equals 8ohms, the total load is
A plus B, or 16ohms. If you string three 8 ohm speakers in series the
net impedance will be (3X8) 24 ohms.
You can use speakers with unlike impedances and as
before, you simply add to get the total load. When you use unlike
speaker impedances in a series connection, the larger impedance will
have to dissipate more watts than the smaller impedance, and if the
sensitivity ratings are the same, the speaker with the larger impedance
will also be louder. This is not a problem if you assure that each
speaker is properly rated and you don't mind that one is louder than
the other.
Example:
Speaker A and B are each rated at 25 watts.
Speaker A=8ohms and speaker B=4ohms. A total of 50 watts is delivered
to the circuit. In this example the 8ohms speaker will be asked to
dissipate about 33 watts, while the 4ohm speaker will need to dissipate
only 16 watts or so. As you can see, this could be a real problem for
speaker A. The roles are reversed in a parallel circuit.
Parallel Connections:
Speakers are wired in parallel by hooking the positive
terminals to positive terminals and negative terminals to negative
terminals.
If all of the speakers have a common impedance, you
can simply divide the common impedance by the total number of speakers
to get the net impedance.
Examples:
Two 8 ohm speakers wired in parallel will have a net impedance of (8
divided by 2) 4 ohms.
If you have three speakers, each at 8ohms, divide 8 by three to get a
total impedance of 2.66ohms.
If the speakers do not have a common impedance, you
can use formula 1 for two speakers or formula 2 for more than two
speakers.
Un-like Impedances Formula 1:
Speaker A=8ohms and Speaker B=4ohms.
(8*4)/(8+4)=2.66ohms.
Un-like Impedances Formula 2:
Speaker A=8 ohms, Speaker B=4 ohms, Speaker
C=16 ohms.
We'll solve the bottom part of the equation first.
1divided by 8= .125, 1 divided by 4= .25, 1 divided by 16= .0625
.125 + .25 + .0625= .4375
Now the top part of the equation.
1 divided by .4375= 2.2857 ohms.
You must be sure that each speaker is rated for the demand that it will
be expected to dissipate.
Example:
We'll use the same example as before, but this
time the speakers are wired in parallel. Speaker A and B are each rated
at 25 watts. Speaker A=8ohms and speaker B=4ohms. A total of 50 watts
is delivered to the circuit. The 8ohms speaker will be asked to
dissipate about 16 watts, while the 4ohm speaker will need to dissipate
only 33 watts or so. In this case speaker B is being ask to dissipate
more watts than it is rated to do. Also, speaker B will sound louder
than speaker A, assuming the sensitivity ratings are the same for both
speakers (and assuming that speaker B is not yet blown [grin]). Note,
this is backwards from the series connection.
Series/Parallel Connections:
Series/Parallel connections are a combination of the
two previous mentioned connections. The most common examples in guitar
amp cabinets involve four speakers. These are usually connected in one
of two ways and these are illustrated in the next graphic.
Consider the S/P 1 connections. Again we'll
assume that each speaker's impedance is 8ohms. Speaker A is connected
in parallel to speaker B and together they make up a network equal to
4ohms. Speakers C and D are also connected together in parallel and
also make a network equal to 4 ohms. Now, the two networks are
connected in series to give us an 8ohm output.
Now consider the example labeled S/P2. Assume that
each speaker is 8ohms. Speakers A and B are wired in series to make up
a network that equals 16ohms. Likewise, speakers C and D make up a
series network equal to 16ohms. Now network A/B is connected in
parallel to network C/D. The result is a net impedance of 8ohms out.
Commom Questions:
Q:How can I hook up four 16 ohm speakers to equal 8 ohms?
A:You can't!
Q:How can I hook up four 8 ohm speakers to equal 16 ohms?
A:You can't!
Q:How can I hook up four 8 ohm speakers to equal 4 ohms?
A:You can't!