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[Nathan Riddle]

Personally, I find myself not in the aux-fed sub camp.

I've read the material, understand how it works, I should probably try it out for kicks.

But I came from a church where they setup the subs on aux and varied the sub level depending on what 'felt' correct. To me, aux fed subs needs to be deployed correctly for it to not be 'weird'. I like my sound to be pure, the system is linear. The system at that church wasn't deployed strategically and gains structure was really off. So I never knew where zero was and we were running with EQ in the channel and sub and mains and it was all convoluted and confusing. Never knew what to do, increase the aux master for more subs, or the channel send, or ch EQ, etc...

Tim MC has pointed out to me that aux fed subs can be used for effect, and if a BE wants it done then who cares how I want it deployed. I agree. Especially with good engineers & festivals & high profile acts.

The church world is slightly different and I find it generally easier to teach a volunteer to turn the channel up and take the HPF to 150+Hz than doing that plus remembering to add the sub send for channels that need it would be confusing for a new guy/gal who shows up to 'push faders'... YMMV

I think, now that I know how to deploy aux subs properly, I could make use of the benefits, but I am always leery of using resources of a system when it isn't necessary.

For your situation, try it. Can't hurt. You'll learn something and that's always good.

[Luke Geis]

It is definitely a technique that is not for everyone or even every situation. If it has to be quick and the number of open mics is low, the benefits may not really shine. Subs on aux is tough for some to grasp as well. The thinking that it will sound weird or isn't right from an objective point of view makes the transition harder. The thing is that if you send everything to the subs and set the balance of the subs the way you normally do, it would be exactly as if you went from the mixer into the subs and then into the speaker from the subs pass through.

It is hard for people to grasp that there are no rules when it comes to subs on an aux. You can do whatever you want with them. You want more oomph from the kick but are happy with the click/attack, easy peasy, simply send more kick into the sub aux send. Want less thump and bump, turn it down in the subs. There should be no need to worry about what unity or nominal is. Turn it up or down till it sounds right. You can do this for every single channel, vocals and all. You are in essence treating the subs as a totally separate mix. Think of the mains as that, your main mix. The subs are now used to fill out what the mains don't do. Obviously things like kick, bass and keys will need to have at least some level in the subs.

One thing that I found when doing this is that I needed less overall EQ to get a clean and impactful mix. Now I wasn't neutering the low end on the vocals to keep them from being too boomy. I no longer had to add a 50hz EQ hump to get the thump I wanted, I could simply add more to the subs. The big help with the subs is that now that so little information is going to the subs, I had a little bit more headroom in them.

Here is a video I made outlining why you would want to use subs on aux: https://www.youtube.com/watch?v=ycJfDYpkpMk

[Jean-Pierre Coetzee]

Honestly in my opinion if you have a properly installed system with enough headroom it makes no difference. The concept of Aux fed subs just doesn't sit right with me, I won't mind subs on its own channel but it should be linked directly with the main channel volume(as in it should have the same volume).

If you set your crossover correctly then mess with the sub volume then your crossover frequency shifts, it could go up or down depending on many things. You can use a sub going from the mono channel and simply not route stuff to it and that should theoretically be fine.

I want simplicity, if I need to add a bump at 50-80 Hz(I find most lab level subs can't reproduce 50 Hz at any reasonable volume anyway) then there isn't enough rig for the gig to start with. Likewise if the vocals sound boomy in the mains then the crossover frequency is probably way too high anyway. You have a HPF use it, if that doesn't solve your problem then there is a massive problem elsewhere.

[Mike Caldwell]

95% of the time if I'm doing bluegrass and the system has subs the subs are aux fed everything else depends on the situation, bands and system configuration.

[Joe Pieternella]

If you set your crossover correctly then mess with the sub volume then your crossover frequency shifts, it could go up or down depending on many things.

X32 and probably lots of other boards allow for the "c" bus to have it's level be dependant on the LR faders.

I haven't tried this one but assigning a DCA to LR and whatever out you're using for subs. Or alternatively using a subgroup/DCA as mains assigned to another DCA together with your sub-send.

I tune/balance/run the system with the Subs' master send set to unity and dependent on the LR master. All channel sends to unity.
Now all I need to do is select whether ie not to send a channel to that bus; one press of a button just as easy as phantom power on/off.
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[Jeremy Young]

Adjusting the level of the subwoofer send will affect your system crossover, and is not typically recommended.  Sending a "unity" - or whatever you want to call it - level on the kick channel to the mains and sub send (whether aux or matrix) means that the relative balance between subs and tops stays linear.  I'm a firm believer that if you need more 50hz in your kick, you should add that in the channel EQ.  It can be as simple as a post-fader aux-send where that channel aux send is set to zero (unity if you want to call it that) so that as you change the channel level in the mix, the contribution to the subwoofer send moves with it.

There was a time when not every board was digital, channel HPF's were not variable, and depending on the board predetermined HPF slope and frequency you could put a lot of low end energy into the system with a bunch of open vocal mics on, even with the HPF switch engaged.  Might be shocking, but it doesn't even feel that long ago.

For those who have never tried it but are frowning on it, how about this - give it a shot!  It's not for every system or application, but it does give you additional control over the mix compared to a L/R bus only.  When using active subs/tops with built-in crossovers it's quite easy.  If you're using the crossover built into one of those boxes on the feed-thru to the other, it won't work.  Using an external crossover, you'll need to make sure it has enough inputs to handle your routing scheme (so 2inputs minimum if you run mono, 3 minimum if you run stereo tops). 


If your rig uses an unusually high crossover frequency between mains and subs, you may find aux-subs leaving you with a thin sounding mix.  In that case, that's probably not the right system for that technique, or perhaps you need a mid-box in between that is part of your L/R bus and leave the ultra-low-end on the aux sub bus.  Then again, boosting the low-shelf on a channel that's routed only to the mains can still help bring back some of that warmth in my experience.

I personally use aux-fed subwoofers more often than not, because in combat audio you usually have more than enough challenges to deal with on the fly without dealing with excessive low-end buildup.  I like tools that put more control at my fingertips during the event.  I find my channels are either in the subs, or not in the subs, not somewhere in-between.  The first time I tried it with a venue/rig/artist I was really familiar with, I immediately noticed the difference in subwoofer headroom and mix clarity.  That said, I am the sole operator of my systems, so I am the only one who needs to know/understand the routing.

[Luke Geis]

Let's get some of the misconceptions nailed down.

1. The system as a whole is tuned as if it were all ONE system. The subs level, crossover and all are set and that balance should be maintained.

2. Most all digital mixers can link the " C " / " Mono " channel to the L/R. Although you shouldn't really have to mess with that too often anyway.

Some of the tricks I employ to best utilize subs on aux:

1. For the kick, without the kick in the subs, make the kick sound the way you want in the main L/R mix and then add to the subs as needed until the low-end content is to the level you desire.

2. Pretty much the same for everything else. Get it sounding right in the mains, then add the needed amount to the subs.

3. I treat the subs as a totally separate mix. If I only need a little bit of bass guitar or keys, I will only add as much as is needed. Kick is the same. Sometimes you need to send above unity and sometimes you don't.

4. Being certain that the subs send is POST fader is key. Subs on aux do not work well with a Pre fader pick point.

[Paul Rennick]

Thanks for chiming in everyone.  I'd like to A/B this. Next time I'm on, I will run it L/R as per usual and I'm going to walk the floor, listening to the subs directly for vocal content, and then back to the mix position to give it a full listen.  Then the next time after that I'm going to try it out.  I really want to give it a true A/B comparison.

Thanks again.

[Brian Jojade]

I really want to give it a true A/B comparison.

Chances are, what you'll end up finding is if things are set up correctly, the difference is going to be pretty subtle.  If you have a good HPF on the channels you don't want going to the subs, combined with the crossover in the subs, there will be very little subject matter there to start with.  You can hear what this is by turning OFF the mains and listen to the subs alone.

By using Aux fed subs, that's the junk you can get rid of.  It's just one of those tricks that can be used to make things a tiny bit better.  If it's making a drastic difference in your sound, then something else is way off to start with.

[ProSoundWeb Community]