Aux fed subs

[badhabit]

This is a subject that I do not recall being discussed here, at least in the time I've been poking around here. I got turned onto this on another forum by a nice gentleman. I have yet to try this idea out, however, it appears to be the answer to my muddy sub sound. I am confident many of you pros already know all about this and that some use it in their FOH set-ups. It was recommended that if I could not afford to lose even one of my auxes, that since I was running mono FOH, I could hard pan left everything I did not want running to the subs, then run the left main out to one side of my DBX crossover. The send from that would go to power the mid/high FOH cabs. The right main send would go to the other channel of the DBX crossover and control only the sub/s. Then I could use the pan control on the mixer, along with the right main fader, to control the amount of sub and mid/high I wanted. This would be for certain instruments like the kick drum, a synth, bass guitar, and so on. This was stated as generally being superior to just using the high pass filters on the channels where I did not want sub/s. Are there any opinions on this technique? Pros and cons? How many incorporate this in their system? And my apologies if this has been discussed many times before or is just a plain stupid subject. Thanks.

[davidss1]

aux subs are great.

[abzurd]

It's used quite frequently and doing it via panning does work if you simply can't spare an aux. You're correct in that you'd hard pan the non-sub channels. In your example the sub channels you'd take towards the right. The amount you move towards the right will determine the sub level each channel gets and your right slider acts as like an aux send master level and will control your overall sub volume. I ran this way for a few years with my A&H mixwizard. It's a great way to get all your mixer has to offer when you aren't running stereo, which generally cause more issues than mono anyway and therefore it's perfectly fine, and usually preferable to run mono anyway.

 

There are no cons. It gives you much more control of the low end of your system and guarantees you'll not have bass rumble coming through your vocal, guitar, and most drum mics and into the subs because the path to the subs has been broken by using this method and not giving any juice to the subs for those channels.

 

I love it for dialing in the amount of low frequencies the room will tolerate. You know, the amount that's just shy of rattling glasses and vibrating ceiling tiles or making the room "swell". Low frequencies can mask high frequencies, but the opposite is not true. With that in mind it's always a delicate balancing act to not oversub a room and lose that definition and punch in the mix, yes the punch, which has a lot to do with the mains. Oversub your kick drum and you lose the click.

[badhabit]

It's used quite frequently and doing it via panning does work if you simply can't spare an aux. You're correct in that you'd hard pan the non-sub channels. In your example the sub channels you'd take towards the right. The amount you move towards the right will determine the sub level each channel gets and your right slider acts as like an aux send master level and will control your overall sub volume. I ran this way for a few years with my A&H mixwizard. It's a great way to get all your mixer has to offer when you aren't running stereo, which generally cause more issues than mono anyway and therefore it's perfectly fine, and usually preferable to run mono anyway. There are no cons. It gives you much more control of the low end of your system and guarantees you'll not have bass rumble coming through your vocal, guitar, and most drum mics and into the subs because the path to the subs has been broken by using this method and not giving any juice to the subs for those channels. I love it for dialing in the amount of low frequencies the room will tolerate. You know, the amount that's just shy of rattling glasses and vibrating ceiling tiles or making the room "swell". Low frequencies can mask high frequencies, but the opposite is not true. With that in mind it's always a delicate balancing act to not oversub a room and lose that definition and punch in the mix, yes the punch, which has a lot to do with the mains. Oversub your kick drum and you lose the click.

 

Thank you! At a recent gig, I noticed how much "crap" was going through our subs and muddying up the sound. Very disappointing it was. I understand about dialing in the right amount for the kick. It is a balancing act, and by no means am I an expert, not even close However, I am excited about the idea of getting the "crud" out of our low end and tightening it up.

[Rezrover]

 

However, I am excited about the idea of getting the "crud" out of our low end and tightening it up.

 

 

Does your mixer have HPF's you can engage on the individual channels?

[agedhorse]

When I provide sound for national acts, only about 15% even ask for aux fed subs and maybe 5% actually use it after listening to the system. Unless you are doing some really low-end heavy stuff and the gain of the sub band is much higher than flat, the benefit is pretty minimal and it's somewhat of a pain in the ass. You also need a seperate crossover path. I have had a higher number of acts request the system be set up "no aux fed subs" than those asking for it.

 

If you are doing something with a lot of heavy low end, it may be beneficial. If you don't have high pass filters on each channel, get the right tool for the job and get a board with HPF's. Aux fed subs are a poor substitute for the right tool.

[Shaster]

 

This is a subject that I do not recall being discussed here, at least in the time I've been poking around here. This would be for certain instruments like the kick drum, a synth, bass guitar, and so on. This was stated as generally being superior to just using the high pass filters on the channels where I did not want sub/s. Are there any opinions on this technique? Pros and cons? .

 

 

Actually this thread is pretty common, I can almost remember my exact post from last time.... but not to worry. at my age it's good to exercise the old memory cells.

 

I only seem to need aux fed subs when the PA I'm stuck with doesn't have a proper crossover or viable HPF. Then I find it helpful to only put kick and bass... through the subs.

 

If I have functioning HPF and a working crossover I personally have better luck not using an aux for subs YMMV.

 

I have tried aux feds on my current system both using an aux and panning. I prefer using the HPF and just crossing over as per the "optimum" crossover point. That works best for my needs.

 

I will say that aux fed or not I would engage your HPF on the appropriate channels anyway. With vocals and such, you don't normally want that stuff in your tops or subs.

[badhabit]

Yes, my board does have HPF on each channel. They are not adjustable, set at one point, 100hz. Is that optimum? I do have a DBX 223 stereo crossover and have set the crossover point at 100 hz in the past. I thought I would use one channel for the mids/highs and the other for the subs if I tried going with aux fed subs. I don't know if my mixer's HPFs are as good at this or not. I mean, I believe everyone that if they work well, that would be much easier. I'm just not sure about this particular mixer's capabilities. Do HPFs generally work the same on moderate cost mixers? Mine is a now discontinued Soundcraft MPM20/2. I do appreciate everyone's input and can see that using the HPFs would be much easier. Thanks again.

[badhabit]

One of the reasons I was intrigued by this way of running the subs, was this article by Don Boomer, who said:

 

 

Aux Fed Subs has been the practice of many regional and national sound providers for years now. This technique can provide you with a way to tame the low end mud from your system, give you back some punch and control the clarity of your system. The idea is to eliminate sending

[6Imzadi]

Agedhorse's system is probably a super good, well thought out and implemented system. He has more than enough rig for the gig, so to speak. So, the guys who use it don't necessarily need AFS. Not all of us have that luxury all the time. I, for example, have one room where I do not have enough rig. I have to bring it up to the red line. If I didn't run AFS, I would need to run it lower to avoid blowing my subs. The extra "garbage" in the sub chain would damage the drivers in my subs. It has done so in the past.

 

Also, I have discovered that the mixer is an important weapon in the elimination of that junk. If your stuck with 100HPF, then you are a good candidate for AFS. A variable HPF is really helpful. Not everyone can afford to buy a new mixer, but you have what you need to run AFS.

 

Try it out and tell US what YOU think about it.

[Unalaska]

I'm in the no aux-fed-sub camp. I've got one rig that is mono biamp using the Left main out as sub and the Right as mid/high. Amp is 1 P5000 using a crossover in each of the 2 channels: Ch1 90hz LPF, Ch2 100hz HPF. It doesn't make any difference to pan stuff one way or the other, sonically it's the same. On my bigger systems it eats an aux up or I need a dedicated mono output frm the board and it ain't happening. Amp racks are wired stereo triamp (optional stereo biamp, stereo tri/mono sub, stereo biamp, mono sub, mono biamp via DRPA presets). I don't feel that spending the extra $ on a crossover will really improve the sound. And NO ONE has ever asked for aux-fed either. After hearing the system still no one has asked.

[soulvillemusic]

Isn't it true that the average sub won't reproduce all the frequencies of a bass guitar and therefore some of the bass frequencies need to come through the mains? I may be wrong in this assumption but if not then wouldn't routing the bass through the subs mean the PA isn't reproducing all the bass guitar?

[abzurd]

 

Isn't it true that the average sub won't reproduce all the frequencies of a bass guitar and therefore some of the bass frequencies need to come through the mains? I may be wrong in this assumption but if not then wouldn't routing the bass through the subs mean the PA isn't reproducing all the bass guitar?

 

 

You aren't routing the bass (the instrument) through JUST the subs. You're splitting the signal to be able to mix in the amount of sub you want for each instrument. All instruments should always be in the mains, but only a few should be in the subs too (typically - Bass, kick, keys, floor tom).

[abzurd]

 

When I provide sound for national acts, only about 15% even ask for aux fed subs and maybe 5% actually use it after listening to the system. Unless you are doing some really low-end heavy stuff and the gain of the sub band is much higher than flat, the benefit is pretty minimal and it's somewhat of a pain in the ass. You also need a seperate crossover path. I have had a higher number of acts request the system be set up "no aux fed subs" than those asking for it. If you are doing something with a lot of heavy low end, it may be beneficial. If you don't have high pass filters on each channel, get the right tool for the job and get a board with HPF's. Aux fed subs are a poor substitute for the right tool.

 

 

 

I don't agree that aux fed subs are a poor substitute for lack of HPF. First off, they are pretty much same thing, it's just that the HPF is a rack mount in the form of a crossover. Yes, it generally has a steeper slope, but for most applications in the kind of rigs we're talking about here, that's a good thing.

 

IMO, aux fed makes for a much easier dial in of the mix and is far more forgiving. Although I don't see why there would be disdain for the practice, career pros can mix in their sleep and really know what they're doing. I'm no career pro engineer, but have to be competent in many skill sets. I have to show up to an unknown venue and, with the help of 4 other members, have 2 hours or less to set up PA and lights, pretty up the stage, hide cases, line check, sound check, troubleshoot if needed, and change clothes. Then I pretty much emcee and run the entire event because nobody seems to be in charge once their in their fancy clothes. After being there for 4-5 hours we'll do a 3-4 hr performance where I'll front the band while mixing.

 

Aux fed subs allow me to dial in the mix very quickly to the room. I realize a good bit of the benefit could be mimicked by EQ, but aux feeding is more visual and quicker (for me anyway) and guarantees what's in the mix and what's not. Another point is that a typical channel strip HPF DOES NOT take the rumble out of vocal mics.

 

So hey, maybe my mixing skills suck, but when I run aux feed there is more punch and clarity to the mix. If my skills suck though, and I actually care, have been hanging out here for 10 yrs learning and applying the knowledge every weekend, imagine how poor the skills are of the typical mix from stage group OR the typical small time sound company operator. While the skill of the musicians varies, 9 of 10 local bands I've seen just sound awful all the way around. Heck, I's guess around 1/2 the national acts I've seen have had sound I'd deem unacceptable, with probably 10% unlistenable (not that aux fed subs would make a difference just saying there are some pretty {censored}ty "pros" out there too).

[abzurd]

HERE is a great article about the subject. It talks about the main con being that of system alignment. The overall theme is some like aux-fed some don't. I do because it gives me the best results and does so quickly compared to not. I say, for those that haven't tried it and have the means, give it a shot. You'll find out soon enough if it's for you or not.

 

Oh, I also found a boatload of riders that request or require aux feeding the subs. I'm kind of surprised the rider would be as technical as to dictate one or the other since A) it's controversial and 2) if you have an FOH engineer that doesn't like doing it then they are probably not going to be as good at it, or more likely they're just going to say they're doing it, but not. ..... who's going to check?

[soulvillemusic]

You aren't routing the bass (the instrument) through JUST the subs. You're splitting the signal to be able to mix in the amount of sub you want for each instrument. All instruments should always be in the mains, but only a few should be in the subs too (typically - Bass, kick, keys, floor tom).

 

Got it. I was visualizing it wrong. Personally I don't want to lose an aux but I had never considered the L/R main output method. Seems simple enough and since I don't run anything in stereo I think I'll give that try. I think the article you posted was informative because I hadn't thought of the concept that even though we may use HPF on the vocal mics, the sum of all of those mics will still build up some low frequency signal (at least that's how I understood it). I plan on giving this method of aux fed subs a try at the next gig.

 

Good thread. I've seen plently about aux fed subs but don't think I'd ever read about the "poor man's" L/R method. Yet another good piece of advice gotten off the forum.

[dennis a]

 

It talks about the main con being that of system alignment.

 

 

When a sub is dialed in to "taste", it not only changes the alignment but changes the acoustic crossover point between the sub and the low mid...as you increase the level of the sub, you also raise the xo frequency. To get around this, set the "sub aux" at unity, do your gain structure in such a way that you have adequate sub action with aux at unity, then if you are so inclined align the sub to the low mid. On the channels that you want to route through the subs, dial the corresponding aux to unity ONLY...do NOT dial to taste. If dialing to unity isn't working for you, you need to rethink your gain structure. This procedure will maintain alignment and xo frequency.

 

Dennis

[stangconv]

Holy I'm confused... So would you still use a crossover?

 

Here is how our rig is setup now

 

Mixwiz main outs to

Dual 15 band EQ

Behringer DCX2496

Which then sends the low end to 2 LS1004's and tops to 2 21004 dual 15"s

 

We don't usually use aux 5 and 6 on the mixer so would you just send the aux outs straight to the amp?

 

Aux 1-4 are monitor mixes through 31 band eqs.

 

Is there a better way to set this up?

[karlw]

When I toured as FOH, I used aux-fed subs routinely. Mainly, it was easy to set up and I thought it sounded great. My rig was Meyer MSL-3, UPA and USW subs. Only the bass and kick went through the subs. The act was a big band (jazz).

[agedhorse]

You need a seperate crossover path to retain the 100Hz LPF on the sub feed.

 

That means that if you have a stereo crossover you must either go to mono or add a second identical crossover (for maintaining filter alignment) to get another path. You need at least 3 crossover inputs for stereo tops and mono subs.

[stangconv]

So just leace it as is?

 

Have you worked with the LS1004's aged? Any tips on how to get them setup ideally? Crossove point?

 

Just want some starting points on new subs

[Rezrover]

 

We don't usually use aux 5 and 6 on the mixer so would you just send the aux outs straight to the amp?

 

 

If I have this in my head right, you turn on your kick & bass in Aux 6, set the switch to Aux 6 for that slider, take the mono out into a crossover, crossover to amp, amp to speakers.

 

I looked at AUX Fed subs and said {censored} it; my rig works great the normal way.

[Craig Vecchione]

 

If I have this in my head right, you turn on your kick & bass in Aux 6, set the switch to Aux 6 for that slider, take the mono out into a crossover, crossover to amp, amp to speakers. I looked at AUX Fed subs and said {censored} it; my rig works great the normal way.

 

 

If this is a newer Mixwizard, you need to also engage the Aux 6 assign to mono switch to redirect from the aux output to the mono main output. If it's one of the older models, there is no mono output, so you obviously use the Aux 6 output and have to ride the knob along with the main faders for mix adjustments.

[abzurd]

I recently moved to stereo mains and mono subs so the break music sounds better (We do a lot of weddings where there is DJ stuff). I use the built in crossover on my powered subs and take the mono out of the mixer (Presonus StudioLive), then take the mains L&R to an Ashly stereo crossover.

[dboomer]

Thank you! At a recent gig, I noticed how much "crap" was going through our subs and muddying up the sound. Very disappointing it was. I understand about dialing in the right amount for the kick. It is a balancing act, and by no means am I an expert, not even close However, I am excited about the idea of getting the "crud" out of our low end and tightening it up.

 

So there is an easy way to understand just what going to aux subs can do your your system. Next gig just make a recording from the sub send of your crossover and listen back to all the stuff that ends up in your subs. The main benefit of aux subs is the reduction to almost zero of anything from a vocal mic reaching the subs.

 

http://peavey.com/support/technotes/concepts/AUX_SUBs.pdf