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I work for the IT department in an office, we moved into a new building that has ceiling speakers but its a mess above the drop ceiling. Some are wired in parallel, some are branching off in series...they all need to be rewired. Then I realized we have multiple model speakers, and the transformer on them has me over my head...I thought I was just going to run them all off a mono amp but this is apparently a 70V commercial audio system.

Which one of these is the better model speaker to use for music? We will only be connecting some of the office so I have extras I can swap around with to use the better speakers. So far I have found these three:
-CDK INT'L CX-801 (20W @ 8ohm)
-JBL CSS8008 (15W @ 8ohm)
-Lowell 8C10W (15W @ 8ohm)

I have two amps to use for two zones, they left us with a PA grade QSC ISA300T which has outputs for 70V and 100V. Then we have the receiver from the old office that I want to run just 3-4 ceiling speakers off in the bathrooms....I assume I will have to bypass the impedance transformers on the speakers to use them with the consumer grade receiver?

What I do not understand is how to wire the impedance transformers because they are slightly different. The Lowell transformers have a common then 1/4W, 1/2W, 1W, 2W and 4W. The CX-801 has 1.25W, 2.5W, 5W, 7.5W and also wires for 0ohm, 4ohm and 8ohm. Then the JBLs have a set for 25V, 70V and 100V. I guess the JBLs are the most universal and maybe the other two only support 1 of the 3 voltage types?

I am going to get a count on all the speakers and how many I want to use. Any help in the meantime would be greatly appreciated!







 

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Slowpoke
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1,359 Posts
I'd use the QSC with the 70v outputs for power. You can use all the speakers together. Just match the wattage as closely as possible across speakers, total up the wattage, and stay under the amp's RMS power rating. Some will be louder than others (think efficiency). Daisy chain them (parallel).

You can bypass the transformers and use lo Z, but you'll need to calculate and stay within impedance limits - which might mean some series-parallel wiring. Personally I'd use the transformers though. It's far simpler.

Save the tuner for signal maybe? It won't give you balanced outputs, but still useful for control. You can also use it for another zone, but it doesn't work with a 70V system. You'll need to exercise a bit more care in calculating loads.
 
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