Connecting Speakers

One word to remember before reading any further: Ohms! Ohms together with "+" and "-" is what we need to be aware of when connecting speakers. If you don't have your Ohms right, then you might end up with a burned up amplifier.

Every speaker has ohms. The term is Nominal Impedance and the unit is ohms. If you don't know the nominal impedance of your speaker, look for something called Re. Re is the resistance of the voice coil, and is close in value to the nominal impedance. Another thing to remember is SERIES and PARALLEL.

Series connection means we simply add each driver's impedance for a total impedance. This is described as

Rtot = R1 + R2+......

A parallel connection is a bit more tricky. the total impedance is described as


So, how does one connect in series or parallel? Well, I will try to explain by using examples and figures.

Example 1 - Series connection of two 4 ohms speakers. Let's say we have two subwoofers that have a nominal impedance of 4 ohms each. For a series connection, the total impedance would be 4 + 4 ohms = 8 ohms. The connection is done as shown in the figure below.
This connection would give a final impedance of 8 ohms.

Example 2 - Parallel connection of two 4 ohms speakers. For a parallel connection we would get a total of 2 ohms. Mathematically speaking it would be 1/Rtot = 1/4+1/4; 1/Rtot = 0.5 which means Rtot = 1/0.5=2. To connect said woofers in parallel:
This connection would give a final impedance of 2 ohms.

Example 3 - Series/Parallel connection of four 4 ohm speakers. Let's say we have four woofers that each has a nominal impedance of 4 ohms.
For a series connection, we would get 4+4+4+4=16 ohms. Since most amps can handle down to 4 ohms bridged, a series connection would be quite a waste of amplifier power. In theory, you would get 4 times the power going from 16 to 4 ohms. And since we learned before that parallel connections achieve lower impedance, let's see what happens if we try to hook the four speakers up in another way.

Two series of 8 ohms each that are parallel connected will yield a 4 ohm total impedance. Mathematically speaking:
1/Rtot = 1/8+1/8; 1/Rtot=0.125+0.125; Rtot=1/0.25 = 4 ohms

This connection would give a final impedance of 4 ohms.

by: Jonas Holmgren