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Crossover

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Crossover

Postby moik » Sun Feb 24, 2019 4:26 am

This has always confused me.

We have powered subs and powered FOH. Should I match the crossver on the sub AND foh speakers?
The reason I ask is;
Say I set the crossover on the sub to 120hz I would imagine that the foh will only receive any frequency OVER 120hz? If this is the case do I really need to use the ‘sub’ or similar setting on the foh?
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Re: Crossover

Postby Sam Spoons » Sun Feb 24, 2019 10:34 am

If you have a crossover in the sub that has an "HPF" or "To Tops" output you should leave the tops set to full range (i.e. no "with sub" setting).

A crossover works by attenuating the frequencies above and below the crossover point but still passes them at a decreasing level as you get further from the crossover point (which will be given at the point where the two filters are attenuating by 3dB). You need the slope of the filters to be matched for it to work correctly and if you have different makes of tops and subs that may not be the case if you try to use separate HPF/LPF in each. You definitely don't want two HPFs working which is what you would have if you switched the 'sub' setting on on the top as well as using the "HPF output from the sub.

HTH
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Re: Crossover

Postby moik » Sun Feb 24, 2019 12:06 pm

Thanks so much Sam. You have confirmed what I always suspected.

And yes, I’ve been doing it wrong.
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Re: Crossover

Postby Sam Spoons » Sun Feb 24, 2019 1:04 pm

You're welcome. The modern method seems to be to have a LPF in the sub and a HPF in the top but, unless they are matched in slope and crossover frequency the result will be less than optimum. Old subs seem to have a complete crossover built in so can work pretty well with any tops and that's how I run my EV sBA750 sub with QSC K12 tops set to full range (with the 'with sub' switch set to off).
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