Speaker Connection In Series And Parallel

The diagram above shows two speakers connected in series. Assume that the positive lead from the power source connects to the left speaker's positive terminal, and that the lead connecting over to the speaker on the right also goes to that speaker's positive terminal. The right speaker's remaining terminal is negative and is connected to the negative terminal of the power amplifier. Because there is one path for current that passes through two impedances, the impedances add. Were these 8O speakers, the resulting total impedance would be 16O. As the higher impedance will reduce current flow for a given voltage, this represents a lighter load to the amplifier than the single speaker.

In the second example, the speakers are wired together in parallel; there are two paths for current to flow. If the speakers are the same impedance, then each will flow the same amount of current, for twice the total amount that the single speaker would otherwise flow (for a given voltage). Therefore, if each speaker is 8O, the overall circuit impedance is 4O. It should stand to reason that a single 4O speaker would flow the same amount of current.

Audio amplifiers are designed to drive a specific speaker load, usually 6O to 8O for most modern home audio receivers. The percent Total Harmonic Distortion is generally lower in an amplifier driving an 8O load, even if designed to drive a 4O speaker load. Most home audio speakers produced today are rated at 8O impedance.

As you can see in the wiring examples above, how multiple speakers are connected to an amplifier channel has a great affect on the performance of the amplifier. If not rated for a 4O load, an amplifier connected to such a load can over heat and shut down, or possibly even be damaged. Also, an amplifier will not provide its best sonic quality driving an impedance load heavier than it is rated for.