Why does my speaker's rated impedance not match an ohm meter reading?
All speakers will have a “rated nominal impedance”. Impedance is resistance to AC electrical signal flow which the power amplifier must deliver. The lower the impedance, the greater the current that the power amplifier must provide. Measuring speaker cabinets using an ohm meter will not give accurate results because ohm meters read DC resistance, not AC impedance. AC impedance will always be greater than the DC resistance, a typical 16 ohm speaker will measure approximately 12 ohms, an 8 ohm speaker will usually measure between 5 and 7 ohms and a 4 ohm speaker will usually measure between 2.5 and 3.5 ohms.