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 Question 556

 How do you calculate total speaker impedance? For example, 4 speakers wired in series or parallel. Is there a formula? — PV, Atlanta, GA
You can calculate the impedance of a collection of speakers the same way you would calculate the resistance of a collection of resistors. Each time two speakers are connected in series, so that the electric current must pass through one and then the other to get to its destination, their impedances add. Thus two 4-ohm speakers in series are equivalent to one 8-ohm speaker (4 ohm + 4 ohm = 8 ohm). Each time two speakers are connected in parallel, so that the electric current can pass through one or the other to get to its destination, the reciprocals of their impedances add to give the reciprocal of their overall impedance. Thus two 4-ohm speakers in parallel are equivalent to one 2-ohm speaker (1/4 ohm + 1/4 ohm = 1/2 ohm). Once you have figured out the impedance of a pair of speakers, you can treat it as though it were one speaker and proceed to figure out the impedance of a larger group of speakers. For example, four 4-ohm speakers in series have an overall impedance of 16 ohms and four 4-ohm speakers in parallel have an overall impedance of 1 ohm.