APPENDIX: MULTIPLE SPEAKER LOADS IN PARALLEL

Multiple Lo-Z Loads in Parallel:

If each speaker load is connected across the same signal source (the output of the amplifier), then the loads are in parallel with one another. If one of the speakers fails in a parallel-connected system branch, the remaining speakers will continue to operate. If all speaker loads are the same impedance, the total imped- ance of a parallel-connected system branch is the impedance of one speaker load divided by the number of loads in the branch (example: three 8-ohm loads in parallel: 8/3=2.667 or roughly 2.7 ohms, too low to use on the CX168).

It is not recommended to connect speakers of different imped- ances in parallel because power will be divided unequally between them. If you are experienced with mixing and matching speaker loads of varying impedances, no damage to the amplifier will result as long as the total impedance is within 4 to 16 ohms per channel, dependant upon operating mode.

Most PA-type speaker cabinets are provided with two or more input jacks that are wired in parallel. If one cabinet is connected to the amplifier, the load impedance is equal to the one cabinet’s specified impedance. If you attach another similar cabinet to the remaining jack of the first cabinet, the two cabinets are now in parallel with each other and the impedance will be half of the one-cabinet value. Consult your speaker’s documentation for connection details as there are many connection methods in use.

Below are examples of parallel connections of 4, 8 and 16 ohm speakers. 2 and 4 ohm parallel loads are not usable because the parallel impedance of 4 ohm loads will always be 2 ohms or less; this is too low an impedance for the CX168 amplifier.

27

Page 27
Image 27
QSC Audio CX168 user manual Appendix Multiple Speaker Loads in Parallel, Multiple Lo-Z Loads in Parallel