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[Paul Rennick]

Hello all, my name is Paul and I'm a first time poster here, but long-time forum user elsewhere.
As you know everyone and their brother seems to have their own best practice so I'm checking my suspicions here.
I can provide more detail if required but I'll try to keep this as "coles notes" as possible to start the discussion.

We run a portable church setup with a small Behringer X32 console, Ultranet (in-ear) monitor stations, 2 self-powered EV Mains, and Matching self-powered EV subs underneath that we run in stereo.  Very typical small-church setup.  The mains and subs are jumpered on the same 2 main feeds from the board (L, and R) with their respective internal Crossovers active.   

I commonly run sound but happened to have a Sunday off the board, but was playing bass-guitar instead. I had a gentleman show up that Sunday that was not a regular to run the board. He proceeded to re-route the FOH so that he was running the same stereo mains to the 2 EV uppers, and a separate 3rd main to one sub at House Left, and then jumpered the L and R subs together.  So he's essentially running stereo mains, and mono subs.  His claim was that he wanted the subs on their own controllable channel.  That way he could route bass guitar and kick through the sub-channel ONLY on a separate feed that was controllable. He claimed that this way he could clean up the vocal presence in the upper mains because the mains didn't have to reproduce everything in the house mix.

He name dropped a big church in the area and said that's how the larger churches do it. 

Now I will admit that I've been doing this for 25-years or so, and have a diploma as a recording engineer, BUT have never ran FOH in a large venue before.  So I'm trying to keep an open mind and think outside my box, but I'm seeing a couple holes in his thought process and it's just not sitting right with me. 

So before I start to tangent on the multitude of reasons that this practice just seems to complicate life for VERY little gain, can someone chime in that has real industry experience on multiple different large venue systems? 
Is this a typical industry best practice?   

[Scott Holtzman]

Hello all, my name is Paul and I'm a first time poster here, but long-time forum user elsewhere.
As you know everyone and their brother seems to have their own best practice so I'm checking my suspicions here.
I can provide more detail if required but I'll try to keep this as "coles notes" as possible to start the discussion.

We run a portable church setup with a small Behringer X32 console, Ultranet (in-ear) monitor stations, 2 self-powered EV Mains, and Matching self-powered EV subs underneath that we run in stereo.  Very typical small-church setup.  The mains and subs are jumpered on the same 2 main feeds from the board (L, and R) with their respective internal Crossovers active.   

I commonly run sound but happened to have a Sunday off the board, but was playing bass-guitar instead. I had a gentleman show up that Sunday that was not a regular to run the board. He proceeded to re-route the FOH so that he was running the same stereo mains to the 2 EV uppers, and a separate 3rd main to one sub at House Left, and then jumpered the L and R subs together.  So he's essentially running stereo mains, and mono subs.  His claim was that he wanted the subs on their own controllable channel.  That way he could route bass guitar and kick through the sub-channel ONLY on a separate feed that was controllable. He claimed that this way he could clean up the vocal presence in the upper mains because the mains didn't have to reproduce everything in the house mix.

He name dropped a big church in the area and said that's how the larger churches do it. 

Now I will admit that I've been doing this for 25-years or so, and have a diploma as a recording engineer, BUT have never ran FOH in a large venue before.  So I'm trying to keep an open mind and think outside my box, but I'm seeing a couple holes in his thought process and it's just not sitting right with me. 

So before I start to tangent on the multitude of reasons that this practice just seems to complicate life for VERY little gain, can someone chime in that has real industry experience on multiple different large venue systems? 
Is this a typical industry best practice?

Look up "aux fed subs" and you will find many discussions.

He is correct, it's common practice, not just in large venues.  The C channel on the x32 is perfect for this application.

[Paul Rennick]

He could have wanted to set his own filters in the board for those respective channels, thus choosing his own crossover frequency between his uppers and lowers but as far as I can tell you can't disable the internal crossover in the self-powered subs anyways.

[Jeremy Young]

Welcome to the PSW forums Paul.  What you're describing is typically called "aux-fed subwoofers".  There are pros and cons to it, but it is a common routing technique (one more tool for the toolbox). 

The internet is full of informative reading if you have the right search terms, so now that you do, I wish you some happy learning!  I did a quick search for the term "aux-fed" on these very forums and came up with 12-pages of threads.

[Luke Geis]

His technique is known as subs on an aux and is probably the most commonly used method done by Pro's the world around. It does have some inherent con's, but the pros outweigh them considerably.

It saves a lot of energy because you delegate the specific tasks to the part of the system that is most efficient at the job. It does and can very much clean up the overall sound of the mix. And lastly, it allows you to tune the subs separately from the mains adding yet another layer of control.

The downsides are as you would expect from a monitoring and playback frame of mind. In live sound, it is generally ideal to reduce the number of sources that any 1 sound comes from and subs on an aux is one way to help in that regard. We are not in the studio and we are not building an audiophile type system. The predominant goal is control and conservation of energy ( headroom ).

To go one step further than subs on an aux with a mono send would be to do subs on an aux fed by a stereo bus and deployed as stereo. Then you can tune what is fed into each sub differently and further improve upon destructive interference.

Conceptually you have to think outside of the box with live sound anyway. The physics, challenges, and issues of using multiple speakers is one that is constantly trying to be worked out. This is why strange end fire sub arrays, cardioid arrays, and other such oddball sub deployments are used. The goal is to fix a problem and improve the outcome. Going with the standard tops over subs approach is essentially the old world way of doing it. Most of the time it works just fine, but there is always a better way.

[Paul Rennick]

Thanks all, so I did the "Aux fed subs" search and read through 6 pages of pro-con argument and understand most everything.  As stated before we are  a church running a portable setup so we have a few volunteers running the system. Most of this would confuse them so i can't say that I would be pushing for this change across the organization but i'm probably going to try this myself.  I find it hard to justify this change across the whole organization while half the volunteers don't know how to use any of the existing dynamics controls.  I've also looked through their parametric EQ settings and most look like a bitcoin run.  24db spikes everywhere. -facepalm

I completely understand now about keeping sub-harmonic vocal stuff out of the subs and not trusting HPF's alone, but I really thought between the HPF on the vocal channel's themselves, plus the internal crossover within the sub, that it would be enough. 
Firstly, my beef was that I thought he was strictly trying to keep low frequencies out of the main, but now I see that that could have been true, but more so it's to keep vocal's out of the subs. 
Secondly when I mix (being a bass player), I really want to hear the crack and attack of the bass strings, and the beater of the kick drum.  Nothing insane or excessive, but it completes the tone of their respective instruments.  I felt by routing these signals to a sub ONLY that was crossed over around 80Hz or whatever the internal is preset at, you would lose this attack. 
     
Maybe I can experiment with using the Mono send for the subs.  That way:
1. I still have main fader control over both.
2. I can assign bass guitar/kick to both.
3. I can assign vocal to the stereo bus only.

That seems like a logical compromise. 

[Jeremy Young]

Hi Paul, sounds like you've got the idea, but to be clear, in an aux-fed sub arrangement you would still be sending the "kick" or "bass" channels to the L/R Mains as well as the Subwoofer aux, so you would not lose the attack that you're worried you'll lose.

Highpass filters (on channels and in system crossovers) are slopes.  There is still energy below the crossover or HPF, and with enough channels contributing this low-end energy even at a low level, it's still energy that the system is trying to recreate.  The larger/louder the system, the more energy there will be down low being reproduced - more than you may realize until you give it a try.  Subwoofers being largely omnidirectional, that extra energy goes back on stage, comes back into those mics, and just further adds to the problem. 

I suggest trying it out yourself and keeping it as a trick up your sleeve, but as you mentioned it may not be the best approach in the hands of the under-trained.  The more experience you gain and comfortable you get, the more tricks you can confidently try to bring your skills to the next level.  Have fun!

[William Schnake]

So before I start to tangent on the multitude of reasons that this practice just seems to complicate life for VERY little gain, can someone chime in that has real industry experience on multiple different large venue systems? 
Is this a typical industry best practice?

Paul, my company does large shows 12,000 plus and small shows 75 - 100 people.  We have been using the 'aux fed sub' method since 2001.  It keeps all of the vocals out of the subs and generally cleans up the mix.  We generally add sub only to kick, bass and keys.

Bill

[Caleb Dueck]

We generally add sub only to kick, bass and keys.

This is very similar to my generic training instructions for aux subs - kick, bass, and pre-recorded music (includes audio from video) is routed to not only the mains but also the subwoofers.  Sometimes keyboard but not often in my limited experience. 

The primary benefit - hard cut most input sources from getting to the subs.   Minor benefit - separate processing and master level of subwoofer send. 

Aux subwoofer send level doesn't replace sub-100Hz EQ. 

Sent from my VS980 4G using Tapatalk

[Geert Friedhof]

Aux fed is one solution, another one is matrix sent subs, and use the HPF on selected channels.

[ProSoundWeb Community]