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Author Topic: Aux fed subs  (Read 7307 times)

Russ Buck

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Aux fed subs
« on: March 21, 2011, 07:50:25 pm »

I am wondering opinions on feeding subs through a aux send, reasons why and if for a church sound system this is a good approach.  The biggest benefit I can see is controlling what you don't want to go through the subs.  but I just wonder if this is leaving to much for operator error, and added cost of dsp or cross over, since I would need one for mains and one for subs.
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g'bye, Dick Rees

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Re: Aux fed subs
« Reply #1 on: March 21, 2011, 08:00:18 pm »

I am wondering opinions on feeding subs through a aux send, reasons why and if for a church sound system this is a good approach.  The biggest benefit I can see is controlling what you don't want to go through the subs.


Yup.
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 but I just wonder if this is leaving to much for operator error,

Nope.  If properly set up there is no more room for operator error than other approaches such as engaging a filter or rolling off the lows on selected channels......and it's more effective.

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and added cost of dsp or cross over, since I would need one for mains and one for subs.

Do you have a cross-over now?  If so, use one channel for the tops and one channel for the subs.  There are many more reasons (for me) to run your system in mono anyhow so if you have a cross-over now you already have what you need.  All you have to do is re-configure the system.  At most you'll just need to add a couple of cables. 
« Last Edit: March 28, 2011, 04:36:39 pm by dick rees »
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Mike Spitzer

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Re: Aux fed subs
« Reply #2 on: March 21, 2011, 09:33:09 pm »

I'll second what Dick said. What's your current setup (board, cx, etc.)?

The way we're set up is running L/R to one amp and out to the speakers in stereo. The center channel is fed to another amp that splits to two subs. Some boards, like the A&H GLs have an option to feed a particular aux to the C or M fader, which is nice, and makes it that much easier.

We run stereo for various reasons, but, like Dick said, there's nothing wrong with mono and often that's actually the best way to go. Just depends on what you're doing.

-mS
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Brad Weber

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Re: Aux fed subs
« Reply #3 on: March 21, 2011, 10:24:27 pm »

I am wondering opinions on feeding subs through a aux send, reasons why and if for a church sound system this is a good approach.  The biggest benefit I can see is controlling what you don't want to go through the subs.
That is the primary benefit and for many churches it can be a good benefit.  Of course what you have on stage, what you run through the system, the type of music played, the system design and components and soi on can all affect the potential benefit.
 
but I just wonder if this is leaving to much for operator error, and added cost of dsp or cross over, since I would need one for mains and one for subs.
Whether there is any added cost depends on the crossover or DSP, there are a number of processor devices that will handle left, right and subwoofer inputs and support the appropriate processing.  Aux fed subs is a bit more complex to operate than a 'traditional' mains and sub arrangement but whether it is too much for the operators depends on your operators and their training.  As Dick noted, in many cases once it is properly set up you don't really have to do anything different, it's not really that much different than an ancillary (lobby, overflow, Cry Room, etc.) audio feed.  But it does take getting set up properly, may have to be adjusted if anything changes and can be messed with.
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David Hoover

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Re: Aux fed subs
« Reply #4 on: March 28, 2011, 03:40:55 pm »

I am wondering opinions on feeding subs through a aux send, reasons why and if for a church sound system this is a good approach.  The biggest benefit I can see is controlling what you don't want to go through the subs.  but I just wonder if this is leaving to much for operator error, and added cost of dsp or cross over, since I would need one for mains and one for subs.

I've tried this both ways on like three different systems.  I think it depends on the room and the operator's preference.  It does not require any additional DSP/crossovers/eq.  The same DSP/crossovers/eq can be used in either set up.  For me, I'd rather start on a flat system and use some EQ to achieve my mix.  If I had to choose one or the other, I'd rather not use the aux subs.  However, there is a third option that I like the most.  I use a stereo feed for my mains and a mono feed for the subs.  On most channels, I'll send them to stereo and mono buses so that I get a natural flat sound that goes to subs and mains, then, I EQ for my mix.  However, for vocals (as an example), I can turn off the mono bus to take them out of the subs completely.  So then, on this setup, it's either subs or no subs for each channel.  I think this gives the most natural sound.  At the end, this gives the option of compressing the subs and mains together, or tweaking each individually to get that sound I am looking for to pull the band together.  Practically, I also like having the stereo and mono faders right next to one another because they can be quickly tweaked if necessary.  This is on a digital board though, so the EQ is parametric and I can change whatever I need to.

In a room with aux subs - if you plan on running subs super loud, then it might be good to run aux subs.  In our young adult ministry room, it's almost like the more subs, the better.  In that case, it seems to work out to crank kick and bass aux to go to subs and acoustic guitars and etc. you can leave in the subs only a little or not at all.  It also helps on an analogue board because it gives you that one extra EQ option that makes your mix just a little bit better. 

There's some suggestions, but don't forget that a properly crossed over, EQ'ed, and tuned system will make the biggest difference before any of that.  I would say try both since all you have to do is move a plug to an aux.  Test them both and mix with both a few times to see what you like.  You can develop your own opinion.

On my personal system, I run a little Yamaha O1V mixer and I run speaks and subs all off the stereo bus.  It sounds best to me that way and it's easier.  I just high pass vocals or pull bass out on sources if need be...that mixer does not have compression or output EQ on the aux sends either, so that's why the stereo bus is best.  I mix in stereo, so the left subs right mains isn't practical for me.

I hope this helps!!!
« Last Edit: March 28, 2011, 03:42:40 pm by David Hoover »
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Mac Kerr

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Re: Aux fed subs
« Reply #5 on: March 28, 2011, 05:36:15 pm »

I've tried this both ways on like three different systems.  I think it depends on the room and the operator's preference.  It does not require any additional DSP/crossovers/eq.  The same DSP/crossovers/eq can be used in either set up.  For me, I'd rather start on a flat system and use some EQ to achieve my mix.  If I had to choose one or the other, I'd rather not use the aux subs.  However, there is a third option that I like the most.  I use a stereo feed for my mains and a mono feed for the subs.  On most channels, I'll send them to stereo and mono buses so that I get a natural flat sound that goes to subs and mains, then, I EQ for my mix.  However, for vocals (as an example), I can turn off the mono bus to take them out of the subs completely.  So then, on this setup, it's either subs or no subs for each channel.  I think this gives the most natural sound

How is this different from aux fed subs? How do you use the same DSP/crossover? This method presupposes you have a separate mono bus, and other than the fact that using an aux gives you the option of variable level, using the mono bus does the same thing in a slightly more limited way.

Mac
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Jim Ogann

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Re: Aux fed subs
« Reply #6 on: March 29, 2011, 02:05:56 pm »

I am wondering opinions on feeding subs through a aux send, reasons why and if for a church sound system this is a good approach.  The biggest benefit I can see is controlling what you don't want to go through the subs.  but I just wonder if this is leaving to much for operator error, and added cost of dsp or cross over, since I would need one for mains and one for subs.
We have used it on our analog boards for years and loved it. Our new digital board doesn't support it well so we dropped it but the digital board's EQ is so good we get the same control. You should use a crossover anyhow since it will also give you a high-pass filter -  - which protects your sub.
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Brad Weber

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Re: Aux fed subs
« Reply #7 on: March 30, 2011, 08:08:10 am »

We have used it on our analog boards for years and loved it. Our new digital board doesn't support it well so we dropped it but the digital board's EQ is so good we get the same control. You should use a crossover anyhow since it will also give you a high-pass filter -  - which protects your sub.
Maybe there is something else being addressed as EQ will not provide the same effect as aux fed subs and I off hand don't know of any digital boards that would not potentially support it.  But yes, a high pass filter for the subs is always a good idea.
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David Hoover

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Re: Aux fed subs
« Reply #8 on: March 31, 2011, 12:08:48 pm »



How is this different from aux fed subs? How do you use the same DSP/crossover? This method presupposes you have a separate mono bus, and other than the fact that using an aux gives you the option of variable level, using the mono bus does the same thing in a slightly more limited way.

Mac

Example of a normal setup: Subs are low passed at 80Hz.  Mains are high passed at 80Hz.  The whole system should provide a pretty flat response if the subs and speakers are at the same levels.  There should be a zero level to where you know the signal is pretty balanced between subs and mains.

Normally, in our setups, the subs are one mono feed, and the mains are two mono feeds (L and R to make stereo).  So, to run the subs in combination with the speakers at all times, one could combine the left and right to mono for subs.  This can be done through a matrix, through a signal processor, through an amp, or whichever you choose.  We choose to run the mono sub feed to the console.  So, we always have left, right, and sub feeds.  So then, if that makes sense, all one has to do in order to go from full range to aux sub is to simply pull the mono sub feed from wherever it was plugged in and plug it into an open aux send that one has.  It's that easy if one has the feed at the board.  If it's a digital console like I have, then all I did was un-assign the aux output and assign the mono output to subs. 

Does this make sense to you?

I guess it is slightly more limited, but in the room I mix in, the sound is more natural when everything is going to subs and I just EQ it for preference.  My mains are spread really far apart and the subs are placed in the middle, so a little overlap in the signals gives a much better sound when standing close to the subs or close to the speakers.  I lightened up the X-Over slope as well to help with that problem for the people that are in the far sections.
« Last Edit: March 31, 2011, 12:15:43 pm by David Hoover »
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Brad Weber

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Re: Aux fed subs
« Reply #9 on: March 31, 2011, 12:56:06 pm »

I think the point was that the way probably the majority of people use a crossover or basic speaker processor would be with an input per channel, e.g. left and right in with left high, right high and either left and right low or a sum mono low out.  Any approach using a dedicated subwoofer feed would require a dedicated third input for the subwoofer signal and dedicated routing and processing of the subwoofer signal.  So for some people that may very well entail additional or different signal processing.
 
FWIW, high passing the mains at 80Hz and low passing the subs at 80Hz does not mean the resulting crossover is at 80Hz nor that it is flat.  The type and slope of the filters can affect that but probably more overlooked is that what really matters is not the filter frequency but rather the resulting acoustic crossover, in other words how the actual sound from the speakers interacts.  For one thing, having the same low and high frequency band signal levels out of the crossover does not inherently mean that the assocaited low and high band sound pressure levels are the same.  Or turn up the subwoofer levels and it is not just the subwoofer level increasing, it is also the resulting crossover frequency increasing.  It is not understanding some of these isues that I believe often causes less than optimal results with aux fed or any dedicated bus fed subwoofers.
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Re: Aux fed subs
« Reply #9 on: March 31, 2011, 12:56:06 pm »


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