Here are what I perceive to be the pros of aux fed subs.
Granular Control Over Sub Content. With aux fed subs, the engineer has complete, discreet control over what ends up in the subs. The only way something gets there is to be turned up in the aux.
In a typical worship band situation, that is probably going to mean the kick, floor tom, bass, and synth. And tracks if you have them. That’s pretty much it. And you can control how much of each channel goes there. So if you want a lot of kick but just a touch of synth in your subs, you can do that. It makes for a very clean sub feed.
Separate Sub Processing. Because the subs are on an aux, you can do some additional “group” processing on it. For example, you could put a compressor on the sub aux and add a little dynamic control. This may or may not be a good idea, but it could be done.
You could also add a plug in like Lo Air to synthesize some additional low end content. Again, this may or may not be a good idea. But you could do it.
Variable Sub Level Control. This is the big one everyone seems to go after; the ability to push the subs up or down with a single fader. As we all know modern music is “all about dat bass” and everyone loves their bass. Except for those who don’t. And when it becomes so overwhelming that the audience can’t hear the vocals.
But hey, with aux fed subs, you can turn the subs down just as easily! The fader goes both ways. Aux fed subs make it easy to tweak the level of the subs on a per song, or even per chorus basis.
Those are some of the pros. However, as I’m writing this out, I’m thinking of rebuttals to each. So in the spirit of the most excellent and helpful presidential candidate debates [that was sarcasm], here are the rebuttal answers to each.
Granular Control. You can do this in a full range fed system by using a high pass. If your high pass filter is set above the level of the sub cross over, very little if anything will end up in the subs. And pretty much everything besides the kick, floor tom, bass and synth should have a high pass on it. And tracks if you use them. So there’s that.
Separate Sub Processing. You could just as easily do this on a group that feeds the main output. Though I’m still working on justification…
Variable Sub Level Control. This is really a mix issue. If you want more kick in the mix, turn up the kick. If you want more bass, turn up the bass. If you want more floor tom, well, you get the idea.
So, while it may be alluring at first to have this amazing, discreet control over the subs, it’s not the only way to do it. Moreover, it creates some problems that are hard to overcome down the road. And we’ll tackle those next time. And I’ve probably tipped my hand as to which way I currently lean, huh?