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Old 11th May 2012, 10:34 AM   #1
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Default Active Tops & Active Sub Advice

Hi Gang

I wanted to check the following setup should work ok please?

Mixer with 2 XLR balanced outputs going to 2 x active tops on the right and 2 x active tops on the left.

The 2 tops on the left are connected to each other via a balanced Output on the speaker going into the balanced input of the other speaker. Same on the right.

In order to connect the subwoofer can I just take a balanced output from any one of the tops to feed the active sub?

Any advice would be grand!

I just want make sure nothing will blow anything else basically.

Cheers.
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Old 11th May 2012, 01:53 PM   #2
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There is no reason this shouldn't work just fine – loZ from the mixer outs feeding multiple hiZs for the amps. If the outputs are buffered (unlikely, it's easier just to parallel them up, and it means that if the first amp in the chain loses power you don't lose all the others) even better. Obviously, you could get slightly more level if you filtered the ultra lows out of the top cabs, but is this worth the extra complexity involved, or the supplementary wiring? Unless, of course the subs have highpass outputs, in which case you wire to the subs first, then daisychain the highs off the output of the subs, and for small gigs just use the tops.

Some subs mix the two sides of the stereo, too; useful if your low end material is not well balanced between left and right. (not a problem in the days of vinyl, but now we can have a bass synth in autopan, or similar monstrosity, and lows will fade in and out…).

But it won't damage anything.
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Old 14th May 2012, 10:41 AM   #3
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Thanks for your reply - very helpful and it worked a treat so thanks.

The only issue I do have now is a ground loop hum on 1 of the tops.... Can you buy isolator's with an XLR connection? I have the phono one's but it's XLR to XLR to connect the speakers.

Also - can you buy any adaptors for mains leads to prevent ground loop issues?

Thanks again for your advice!
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Old 14th May 2012, 10:53 AM   #4
AndrewT is offline AndrewT  Scotland
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XLR connected balanced feeds should not have a hum issue.

Check all your PIN1s
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regards Andrew T.
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Old 14th May 2012, 06:05 PM   #5
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If the subs and the tops are plugged into the same power, there shouldn't be any problem. Of course, "shouldn't be" and "won't be" are not always identical in the real world, and it's better that the console be on the same phase, preferably the same circuit as the power amps (= active speakers), but this isn't always easy to arrange. Lighting guys can generate some horrendous interference at times. However, we're talking balanced, and the ground loops are feeding into (surprise) ground, which is not essential in the signal transfer. So build yourself some XLR tubes with no pin one continuity, or a resistive coupling – I find 47Ω a good compromise between floating and current flow, or build a little box with ground lift switches on it, and leave your amplifiers safe, and your cables screened, without vast currents developing voltages across the screens (of course, a well balanced input can reject volts of common mode inaudibly; but not all power amps have inputs of that standard).

Transformers probably work slightly better – I have a couple of line isolators in my odds box – but a decent line level transformer with frequency response and power handling, is expensive, bulky and heavy.
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