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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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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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What does the floor layout look like, can you provide a quick sketch? You say you will have two zones? How many speakers do you have total and per zone?

Like Rob said, I would use the QSC for both zones since it is a two channel amp. You can actually put quite a few speakers on each channel as these are 300w per channel.

1. I would use the JBLs and get rid of the rest if you have enough JBLs to cover both zones.
2. I would run all new wiring. Never trust an inherited 70v system wiring unless you are familiar with how it's wired, and by the sounds of it, it's a hot mess.
3. Don't expect much low end out of any of these. They are open back. You will need a back can to push them to their fullest potential.
4. Run the 75hz HPF on each channel. Again, they are open back. And even though they are 8", you lose quite a bit of low end from the transformer and the lack of a back can.
5. Wire everything in parallel. You can parallel it at the amp via barrier strip or daisy chain them at each speaker in a row. It's cheaper to daisy chain them since you would have to home run each speaker if you use a barrier strip.
6. Don't expect high fidelity out of these. If you're just using them for background music, then they will be fine.
7. Calculating the load and how to wire them will be dictated on how many you want per run. Once I have that number, I can calculate it pretty quickly.

Also like Rob suggested, I would only use the Denon for source selection. Running unbalanced will be perfectly OK, especially if the Denon is right next to the QSC.

Good luck.

Justin
 

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Nevermind, everything I am correcting now was based off of me reading the wrong model number on the QSC amp. Nothing to see here. Lol
 

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For background sound you can't beat 70 volt systems. Think like going do Disneyland. There is a speaker in the landscape every 10 ft in every direction across a 300 acre park. That would be a.7000 channel amplifier and miles of wire without 70v.

In your situation you would probably only need to use the 1.25 or 2.5 watt tap for plenty of volume in a bathroom. An amp that big (300watt) is complete overkill. A cheap 30 watt 70v amp could run 10 speakers on the 2.5w tap (25 watt load). Plus you can just parallel from speaker to speaker.

You can even get cheap 70v speakers with a volume knob on the grill of each speaker so you can fine tune the volume per area.

Sent from my SM-G950U using Tapatalk
 
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