# READERS’ LETTERS: Understanding series and parallel speaker connections

A member writes:

Damping Factor(DF) is equal to the impedance of the load divided by the out put impedance of the amp. For example if an amp has an output impedance of say0.1 ohms and the speaker is 8 ohms the DF is 80. If you have 2 8 ohm speakers in series the total impedance is now 16 ohms and dividing by 0.1 gives a DF of 160, a higher DF. So damping goes up in series. Basically as impedance goes up DF goes up and vice versa.

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A member writes:

1 ~ Have called PS Audio, &, McIntosh: Both recommend hooking up ONLY ONE speaker to an amplifier. While, when hooking up speakers in series, the individual resistances / impedances are additive, the McIntosh man said that this creates more current draw, perhaps too much! {Although I’ve done this a number of times, with powerful amps, didn’t have a problem}.
2 ~ In parallel: This DECREASES the resistance into the load, that the amplifier, `sees.’ As recalled, the formula is: Resulting Resistance = Resistance {of the speakers} multiplied, this divided by the SUM of the speaker impedances. Example, two 8 ohm speakers, 8 X 8 = 64, this divided by the sum, 8 + 8 = 16, the result is: 4 ohms. Be careful with this, actual speaker impedance is not linear, may dip, for example, as the frequency decreases. Suppose that you have music with a lot of bass? Some amp designs can drive low speaker impedances, down to 2 ohms, even less, and, some, can not! You don’t want to short out your amp! Be careful! Carefully check the specifications of the amp, & call the manufacturer. Some amps are designed to turn off if there is too much current draw, &, some aren’t, have been destroyed!

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Another member writes ...

Current draw is the opposite of resistance. Voltage doesn’t change so lower resistance results in more current since lower resistance is an easier load. Series hookup results min higher resistance and therefore lower current draw. By the way all this assumes a solid state amp. You must have misunderstood the McIntosh advisor.