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[TimHackford]

Hey, thanks for all your help so far in regards to my gain structure questions you guys really helped me understand my desk and digital gain structure a whole lot more! I'm really a newbie to live sound but slowly finding my way, I can grasp compression and gates etc and can eq certain things quite well but into the more technical things and I get lost quite quickly!

I run the live sound for my function band with the desk on stage with me

The PA I have is 2x RCF 732a tops and 2x RCF 905as subs

I run the system in mono From the Left out into the subwoofer into the top and from the Right out into the subwoofer into the top. Hope that makes sense

I would like to try running aux fed subs with my o1v96 v2 mixer, I know its possible but all the reading i've done online only tells me how I would set it up with one sub and I would like to achieve this with two subs. So could someone please tell me the signal path what leads need to plug into what, any special cables I need etc to achieve this?

I would like to run it via Aux 7 assigned to OMNI 3 on the desk..i believe there is a way of setting up a crossover on the desk too is that right? The Subwoofer has a crossover built in at 80hz but find even with the HPF set at around 100-150hz there is something still tickling the sub and if I use a low mid cut then that interacts with the HPF and cancels what it should be doing, I think running Aux fed subs will eliminate this completely and my mind will be so much happier.

Hope I have given enough information, any help will be really appreciated and I am grateful for your help so far.

Thanks Tim

[Ivan Beaver]

You just hook your console to one sub and run and XLR cable to the second sub.

Simple as that

[TJ (Tom) Cornish]

Tim,
There's no crossover function on the 01v96.  You can change the upper and lower bands of the EQ on your aux outputs to be a low-pass filter and a high-pass filter respectively, which may do some of what you want, but it's not a real crossover.

As Ivan said, chaining multiple active subs together is as simple as using XLR cables between them.  A basic setup would be: 

- Left out of the 01v96 to the left 732
- Right out of the 01v96 to the right 732
- Aux 7 routed to an OMNI out to the left sub, then a cable to the right sub.

In my opinion, aux subs are more trouble than they're worth for most folks - at least until they have a lot more experience.  What frequently happens is people disconnect a significant part of their system - the subs - and turn them into an effect.  This is fine if your mains actually go down to 50Hz or so and you actually want the subs to be more of an effect, but for a typical speakers on sticks system where the mains struggle much below 80Hz or so (or even if they can go lower, the crossover is usually set around here), you end up having to make funny decisions about what actually goes in the subs to not be missing a significant amount of low-end.

Aux subs made more sense back in the day when most desks had a fixed high-pass filter.  Nowadays - including on your 01v96 - you can roll that filter up to what makes sense for the particular input.  The slope may be gentle enough that some signal still makes it to the subs, but you have to weigh that tradeoff against the consequences of a non-unified system and having to set sub gain separately on each channel.

Go ahead and experiment, but don't assume aux subs are a panacea. 

[Douglas R. Allen]

Hey, thanks for all your help so far in regards to my gain structure questions you guys really helped me understand my desk and digital gain structure a whole lot more! I'm really a newbie to live sound but slowly finding my way, I can grasp compression and gates etc and can eq certain things quite well but into the more technical things and I get lost quite quickly!

I run the live sound for my function band with the desk on stage with me

The PA I have is 2x RCF 732a tops and 2x RCF 905as subs

I run the system in mono From the Left out into the subwoofer into the top and from the Right out into the subwoofer into the top. Hope that makes sense

I would like to try running aux fed subs with my o1v96 v2 mixer, I know its possible but all the reading i've done online only tells me how I would set it up with one sub and I would like to achieve this with two subs. So could someone please tell me the signal path what leads need to plug into what, any special cables I need etc to achieve this?

I would like to run it via Aux 7 assigned to OMNI 3 on the desk..i believe there is a way of setting up a crossover on the desk too is that right? The Subwoofer has a crossover built in at 80hz but find even with the HPF set at around 100-150hz there is something still tickling the sub and if I use a low mid cut then that interacts with the HPF and cancels what it should be doing, I think running Aux fed subs will eliminate this completely and my mind will be so much happier.

Hope I have given enough information, any help will be really appreciated and I am grateful for your help so far.

Thanks Tim

.   

Be sure to set the Aux to post fade.  I modeled with Smaart a 100 hz high cut and low cut with 2 filters and got excellent results.  The low cut is.  Type I eq, hpf set to 212hz.  Low/mid eq set to 112hz with a q of 1.1 and a boost of 8 dB's. This gives a 6 db down point of 100hz , 24 db down point of 50hz. Compared to a dbx crossover trace they are very close.  I have a photo somewhere.      Something to mention.  The low cut filters on the V are a measured 12db per octave cut.  If you put a 100 hz low cut on each vocal then assign these to a group that has a 100hz cut put in its master section eq you'll have a 24 db cut the resembles a l/r filter.  (Or whatever freq you need) Of course you'll have to unassigned the vocals from the stereo l/r, assign these to a group, then assign this group to the l/r out. Pair 2 groups for stereo if needed.  This may be easier or not.  Aux fed sub's would of course keep what ever you need out of the sub's.  I use aux sub's with my o1v96 as my normal setup.

Douglas R. Allen

[Bob Leonard]

Tim,
There's no crossover function on the 01v96.  You can change the upper and lower bands of the EQ on your aux outputs to be a low-pass filter and a high-pass filter respectively, which may do some of what you want, but it's not a real crossover.

As Ivan said, chaining multiple active subs together is as simple as using XLR cables between them.  A basic setup would be: 

- Left out of the 01v96 to the left 732
- Right out of the 01v96 to the right 732
- Aux 7 routed to an OMNI out to the left sub, then a cable to the right sub.

In my opinion, aux subs are more trouble than they're worth for most folks - at least until they have a lot more experience.  What frequently happens is people disconnect a significant part of their system - the subs - and turn them into an effect.  This is fine if your mains actually go down to 50Hz or so and you actually want the subs to be more of an effect, but for a typical speakers on sticks system where the mains struggle much below 80Hz or so (or even if they can go lower, the crossover is usually set around here), you end up having to make funny decisions about what actually goes in the subs to not be missing a significant amount of low-end.

Aux subs made more sense back in the day when most desks had a fixed high-pass filter.  Nowadays - including on your 01v96 - you can roll that filter up to what makes sense for the particular input.  The slope may be gentle enough that some signal still makes it to the subs, but you have to weigh that tradeoff against the consequences of a non-unified system and having to set sub gain separately on each channel.

Go ahead and experiment, but don't assume aux subs are a panacea. 

One of the best statements I've read concerning aux fed subs to date.

[TimHackford]

Thanks for all the replies guys really appreciate it, sorry I've not replied sooner ive been slammed with gigs!

Wish i saw all this sooner i'd of given it all a go at the weekend. Next gig is in a few days I will report back with how I get on! Surely if the levels set right and you have a decent eq on the channel is wont seem so much as an effect? Our bassist uses a multiband compressor built into his amp which keeps his sound extremely consistent on all strings, and the kick drum is what it is. I can only try and give these things a go if it doesnt work it doesnt work.

Douglas, thanks for that I will be giving that a go if I can get away WITHOUT aux feeding the subs then I will, the problem is I have found is that the HPF and LPF slopes on the o1v96 just arent steep enough I end up with instruments in the the subs even at 200hz...inputs peaking at around -12db so its not running hot either.

I will send the three vocals to a group and the two guitars to a group,
my biggest problem is the acoustic guitar...even with the bass completely rolled of the acoustic its still touching the subs with a HPF of 200hz, if i roll it off to 250hz it stops but then it rquires a mid cut of around 1k about 10db with a fairly generous Q which sorts the sound out but find it interacts with the HPF and cancels that out and im back to square one! So will sending the acoustic to a group cure this, Never really had a use to use the groups I thought they were for controlling just groups of instruments but we never needed to do that.

I dont touch the mixer while were playing its set and forget as long as the levels are peaking too high and the sound is right I leave it alone.

Thanks again guys
Tim

[Tim McCulloch]

Thanks for all the replies guys really appreciate it, sorry I've not replied sooner ive been slammed with gigs!

Wish i saw all this sooner i'd of given it all a go at the weekend. Next gig is in a few days I will report back with how I get on! Surely if the levels set right and you have a decent eq on the channel is wont seem so much as an effect? Our bassist uses a multiband compressor built into his amp which keeps his sound extremely consistent on all strings, and the kick drum is what it is. I can only try and give these things a go if it doesnt work it doesnt work.

Douglas, thanks for that I will be giving that a go if I can get away WITHOUT aux feeding the subs then I will, the problem is I have found is that the HPF and LPF slopes on the o1v96 just arent steep enough I end up with instruments in the the subs even at 200hz...inputs peaking at around -12db so its not running hot either.

I will send the three vocals to a group and the two guitars to a group,
my biggest problem is the acoustic guitar...even with the bass completely rolled of the acoustic its still touching the subs with a HPF of 200hz, if i roll it off to 250hz it stops but then it rquires a mid cut of around 1k about 10db with a fairly generous Q which sorts the sound out but find it interacts with the HPF and cancels that out and im back to square one! So will sending the acoustic to a group cure this, Never really had a use to use the groups I thought they were for controlling just groups of instruments but we never needed to do that.

I dont touch the mixer while were playing its set and forget as long as the levels are peaking too high and the sound is right I leave it alone.

Thanks again guys
Tim

See the bold text.  Yes, it IS too hot.  -18DBFS.

Don't freak about stuff "being in the subs".  It has some content there.  If it's audibly offensive to you you need to do more channel strip work or deal with the issue AT THE SOURCE.  Could be lots of things, but if it doesn't sound bad don't obsess over it.

Don't freak out over what frequency the HPF filter is set at... just raise the frequency until you either run out or it sounds right.  You may need to use both the EQ's LF band for the HPF and the low-mid band for additional sonic surgery.  There is nothing wrong with doing so.

As for the acoustic I think the issue is at the guitar.  Mic?  Pickup?  Any EQ on either the guitar or the pickup DI/box (like a Baggs or Fishman)?  You could be trying to undo something the player has done, or the mic is in the wrong place or the the pickup was installed incorrectly, or it's just the construction of the instrument.  It's the way you describe it that makes me think the issue is not with channel strip EQ....  Another possibility is that you have a really big "haystack" of sub response - very common and often seen as desirable for some sounds or genres - and that increased sub level makes the acoustic GTR LF stand out more than it might otherwise.

[Luke Geis]

I used to get frustrated with full range left right systems for this very reason. You could engage the HP filter and use the low EQ knob and still never seem to get enough cut out of the subs and sound natural with an analog desk. Moving into the digital age has certainly left that excuse moot, but I am not a fan of using exorbitant amounts of EQ for any reason. I go by the moto " get it right at the source ". This is of course challenging when the source is not always yours to control. The HP filter of most digital desks are good at getting the low end out when you roll them up to 200hz or higher, but it makes things sound a bit unnatural to me still.

The Aux fed sub while not a perfect solution, is one that certainly improves the odds for live sound. I find it lowers the amount of work I have to do in order to make things sound natural and because there is so much less information going to the subs it increases headroom to use for the kick and bass guitar. One of the larger arguments against the Aux fed sub is that there is a hole where information seems it should be coming from. The keys, vocals, guitar and other instruments seem to loose low end content that makes it seem like there is a missing piece of information. Well there is........ Especially if you cross the subs and tops over pretty high. To me a high crossover is anything above 100hz. That is honestly a lot of information for the subs to be reproducing and it can leave the tops sounding thin, especially if you use steep filters. I will typically cross the tops over somewhere between 80hz and 100hz depending on how they sound. Larger 15" speakers tend to stay pretty warm sounding even when rolled off pretty high, where as 12" speakers fair a little better when crossed over closer to 80hz. It is the subs that present the largest part of the problem. If the tops sound fairly good there is no reason why the subs can't be tied in to match up. Having the subs crossed over at 80hz and below helps a lot in this case. Below about 80hz people can't really determine the source of that information. So if the subs are crossed over around 80hz or lower, they are truly only filling out the lower octave of information that most people can't locate anyway. If you have the subs crossed over at 120hz ( as is typical for mid tier MI grade powered subs ) there is a significant amount of information that can be located and if fed via an aux, can leave the tops sounding weak.

A properly tuned pa with aux fed subs should be indistinguishable from that of a conventional full range deployment. I go at it like this:

1. Tune the tops to sound good naturally for vocals and other instruments. This usually entails higher crossover points. For instance I have my SRX835P's crossed over at 120hz. This makes them sound natural and not too thin.

2. Tune the subs to fit acoustically to the tops. Depending on where your tops are crossed over, the acoustical crossover point could be significantly lower than 80hz? I believe my subs are crossed over at around 70hz for the system used with the SRX835P's. That seems like a large hole, but acoustically it is not.

The final thing to keep in mind is that there is no rule that says you can't put everything in the aux fed subs............. Just about everyone I hear complain about how aux fed subs don't sound right also only put a couple of instruments into the subs. So your saying you don't like the sound of not having the vocals in the subs? So why don't you add them to the subs? The guitar sound too thin..... So add them into the subs and help fill it out. Easy fix right? I find it easier to keep the system separated in such a way that I can add what I want and where. I probably over complicate things though?

How about this:

1. My entire drum mix goes to a sub mix that has all of it's own processing. The kick is doubled and one goes direct to sub only and is not in the drum sub mix, while the other goes through the sub group. The kick in the sub group mix is EQ'd for the high end part of the kick sound. The sub kick portion of course for the low end. Each has their own compression settings and are controlled via a DCA.

2. My entire vocal section goes to a sub group as well. All the post processing is done there and then a DCA controls them. The sub group for the vocals is used to tune out the common issues like 250hz build up or feedback reduction. The channel EQ is used to make that vocalist sound pretty. There is also group compression and limiting being used in the vocal group.

3. The instruments I simply buss to a DCA. I will, if need be, tie the bass guitar and kick together with sidechain compression and or gating, but in live sound that is not often needed since the stage level will nullify most of that work. I find that I can get most of my dynamic control taken care of with the channel compression.

4. The mains and aux fed sub go through their own processing. The mains mix has compression and limiting employed as do the subs. There is a fine balance that must be maintained and it is the most typical thing I will adjust from song to song. This is mostly done as magic sauce for gluing the mix together and lowering the crest factor. If I do it right, the mix will lock in and sound more processed like commercial media and the lower crest factor that is achieved helps keep the level in a zone while also not eating headroom. I can regularly acquire a -10db crest factor for my live mixes which doesn't sound overly compressed and helps greatly when the music passages taper down. The dynamics of the mix as whole still exist, but are placed into a zone more or less. This has less to do with the aux fed subs of course, but you have to tie the two halves together somehow to keep balance.

[ProSoundWeb Community]