Help with passive setup at my church

It would help to know make/model of the sub. Reason? Because if the active sub has a built-in crossover this would make things MUCH easier.

As for the compressor, don’t worry about it. When there is live music and speech, you may want to use compression in a church to limit the dynamic of the signal. When you hook up a line signal from a DJ (who will play stuff that is all mastered anyway) this is not an issue. So advice 1: don’t connect the compressor.

Also the compressor is an outboard effect. I.e. you don’t put it in the signal line, but send stuff from the mixer through an aux insert to the compressor and back. You don’t compress the master signal.

Depending on the type of crossover, if used, it would normally be connected like this:
1) sub-out -> active sub
2) full-range -> amps -> passive speakers
Unfortunately this isn’t too simple on many crossover as it involves using the correct outputs AND setting everything correctly
It’s why I said that if the sub has (preferably stereo) inputs and high-pass outputs, it’s much better to use that.

Hooking up would then look like:
1) Master output DJ controller/sound card or laptop (not recommended) -> Mackie mixer line input (you can use mic channels that have a line input too, but I would advice using a line input channel, even if that doesn’t have trim/gain or EQ)
2) Mackie mixer master output -> Sub inputs (L/R) with XLR cables
3) Sub high pass output -> amps (L/R) with XLR
4) amps -> passive speaker with Speakon

Pretty hard to test at home unless you have the correct settings for the crossover. If you know it’s make/model perhaps I can say something more about it.

On a general note:

You need to somehow split the incoming signal from the mixer into a sub-woofer output (either mono or stereo) and a full-range minus sub-woofer range (typically above 75 to 100 Hz). For this you would use a crossover. There are many kinds of crossover and they all work differently. If the sub-woofer has a crossover, the high pass output will filter stuff under 75-125Hz and send that to the built-in amp and speaker and the rest will pass to the full range speakers.

Compressors are used to – duh – compress the incoming signal and send a compressed signal onward in the signal chain. What it effectively does is diminish the dynamic range of the signal. The dynamic range is the difference between the loudest and the quietest part of a signal. Let’s say the track has a natural/original DR of say 22 dB. You can compress the signal with a DR of say 5 dB. The quiet parts now sound loud as do the loud parts, with little difference. You lose a lot of the “emotion” of a track, but it’s standard policy for dance tracks. Not uncommon to have as little as 3dB dynamic range. Ridiculous, imho.

Compression originally comes from the recording studio, where it is used to bring certain elements to the front. Used in moderation it can make sure that even the quieter vocal parts can be heard over the guitar or piano. Or in a church it can make sure that the voice of the speaker can be clearly heard over the ambient sound of the room, even if the speaker goes from whisper to shout and back.

Most modern-day commercially available music is compressed between quite a bit and extremely compressed. Therefor putting a compressor on the signal from a DJ is a senseless exercise and should not be done.

Hope that helps some.

+1 for Vintage’s response – Don’t put the compressor on the master output (unless it was being used as a limiter and not a compressor in order to protect the speakers) – I would use it on any mics being used though as it will help the speakers to be heard better, as well as compensating for bad technique that comes from not being a pro…

Any questions, just ask.. The 2 responses above are rather long but they make good points.. If you are new to this, it’s better to ask than break anything 😉

<EDIT>

In response to some points that Caleb made…

1) DO NOT switch the output from the crossover to -10 rather than +4dB. This will give out a louder signal, yes, but it will also make it much harder to mix at the desk – as everything will now be effectively more sensitive – and probably will end up in the amp or sub being damaged due to a clipped input into the amp or the amp clipping due to being sent an overly hot signal. It is not necessary and will potentially wreck your kit.

2) Don’t bother with the compressor on the master output, unless it is being used as a limiter (and only a limiter).. Anything else will make the system sound worse.

3) Don’t connect the sub to the AUX OUT – for 2 reasons. 1) This still sends the full range signal to the mains, which sort of defeats half the point of having subs in the 1st place and will mean that the system will be really hard to balance. 2) Different levels being sent to the sub for each channel is not the correct way of doing things. Send a proper, complete master output to a properly tuned system and it will sound right.. Send everything through all the speakers. Besides, I suspect that in the church, the people who use the kit the majority of the time are not trained audio technicians. Keep it simple and the less you make all those strange coloured dials do, the better. They won’t be able to mess it up if you don’t let them..

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bob6397