Delayed in-fill speakers from QU 16

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    Profile photo of WaihekeSoundie

    Hi all,
    I do realise that this question has been asked before but I did not see a definitive answer as to whether it is possible on the QU 16.

    For larger events I would like to run some additional speakers as in-fills for the crowd up-field of the main PA. Ideally I need to delay these infill speakers so that the audience hears them and the main PA at the same time.
    I see that there is no delay on the ALT OUT but I can assign a mix to the ALT-OUT and the mixes can be delayed. But how can assign the output of LR post fader to, say Mix 10 (LR). Can I do this? Or would I have to replicate and maintain the entire main mix’s channel settings in my chosen Mix’s channel inputs?

    The only other way I can see of doing this is to physically patch back in– so, for eg send the main LR mix post-fade to the ALT-OUT and then physically patch that ALT-OUT back into ST1 or ST2 and pull up that ST1 or 2 in my chosen stereo mix (say Mix 9/10) and then send a delayed output of that mix though it’s mix outputs.

    I figure this would work but is there a better way on a QU 16 (without resorting to external hardware)? It is losing me 2 input channels and a stereo mix bus to do it this way.

    Thanks as always.

    Profile photo of dpdan

    I suggest using a stereo mix like perhaps (9-10).
    Push the blue MIX button for 9-10.
    Use the “Pre Fade” button on the left side of the console and hold it down while simultaneously clicking the green SEL (select) button on each channel to make the green SEL light not lit. This will make all the channels “Post Fade”.
    Then set each and every one of the faders in mix 9-10 to unity gain or 0 db.

    MIX 9-10 will now follow your main L/R mix, and you will also have the option to set the delay for MIX 9-10.
    You will also want to make sure that the effects return faders are turned up in your delay mix 9-10.

    If you want to, you could now assign the L/R and MIX 9/10 MIX outputs to a DCA,
    then the DCA would be your master for all mains and delays. This way you won’t have to guess at keeping the balance between them consistent. If you want to alter the mains, you would go to the “Custom Layer” to change the level.

    Profile photo of WaihekeSoundie

    @dpdan– Many thanks, that is soo helpful!!

    If I wanted to create a centre fill speaker I would follow the same process clearly.. but can I sum one of my stereo mixes to mono? I say this because generally I want to use mixes 1..4 for wedges but I don’t generally use the stereo mixes so they are free..

    Profile photo of WaihekeSoundie

    Ah yes, the pan setting is mix specific so I can pan left or centre when sending to my centre fill.. I would prob hard pan left as it is easy to see that’s what you have done.

    Re the “alt driven sub” mix– do you put this in a DCA with the LR main mix so when you bring the LR down you also bring down the subs?

    Profile photo of Andreas

    Mixes do have their own pans, just keep them centered and you should get two identical mono signals from a stereo mix.

    Profile photo of WaihekeSoundie

    So regarding the crossovers for the AUX driven sub mix:
    You use one crossover that takes the LR mix but just sends to the tops and another crossover that takes the sub mix and only sends to the subs. I assume the slope and crossover points on both these crossovers must be identical…
    And becuase they are both being driven from the same DCA their relative gains wont be shifting with main mix adjuctiments (which I gather is important because otherwise the crossover point or phase shifts or something?)
    I think that is fairly clear and I understand why you would do this.

    How would you set up delay speakers up field with Aux fed subs on a QU 16? I can see that it is easy to just send them the LR mix without the sub component but that does not sound ideal…

    Thanks anyone… @dpdan

    Profile photo of DavidCo

    Andreas: this unfortunately won’t work in the case of stereo to stereo crosspoints, ie ST channel to a stereo mix. He would have to use a mono aux if that is required.


    Profile photo of knga

    To easily set all faders to POST fade on mix 9-10, select that mix, than go to Routing, and press All post. It is quicker and you also see what you are doing. With pressing ‘pre-fade’ I often confuse when it’s pre or post (if Sel button is lit or not). So I prefer going to routing and setting it there – I didn’t know that for quite a long time, so just my recommendation for you:)

    Profile photo of dpdan

    I assume your delayed up field speakers are stereo as well as the front mains.
    I used a separate stereo crossover for my bi-amped main speakers and a separate crossover for the subs.

    In your case, and just like mine, you could use a stereo mix for subs and just use one side of it.

    My recommendation to use a DCA is so that the level of subs to mains would stay consistent.
    So, you would have L/R mains,
    stereo delayed up field speakers,
    and subs from one channel of a stereo mix. you don’t have to have a mono mix for subs, but what I belive knga was suggesting is that you do NOT run your subs in stereo, they should always be mono.

    you could now assign the following to a DCA:
    L/R mains, delayed up field, and subs

    Profile photo of [XAP]Bob

    Be really nice to be able to slave a mix fader from LR

    Profile photo of WaihekeSoundie

    I am not quite getting the mono vs stereo subs point. Could you expand please.

    I think that you are saying I should use one of my 4 mono mixes for the AUX send to the sub’s crossover. My natural inclination is to send a stereo to my stereo crossover but if I have to run in mono then only take the the Left out from it which means the crossover sums to mono for me.

    But I think you are saying that I should I send a single mono (from a mono Mix) into the left of my crossover and then take the Left out from my crossover– not sure that my DBX Drive rack PA is expecting only a single input..

    Any advice would be appreciated..thx

    Profile photo of dpdan

    So, you are using a DBX Drive Rack PA.
    It only has two inputs, so you would use it in stereo,
    the left and right main outputs from the QU would connect to the two inputs.

    Your DBX Drive Rack PA’s outputs would connect to the appropriate amplifers for your speakers.
    The Drive Rack PA can run three-way stereo, or two-way stereo.

    If your speakers are Bi-amped (two-way) then you will need four channels of amplification for stereo sound. Typically, two stereo power amps would be needed, one for lows (left/right) and one for highs (left/right).

    The suggestion to use a separate MIX output from the QU for subs is so that you can control exactly what is fed to the subwoofers. This eliminates things like the popping B’s and P’s and esses from vocal mics from sounding like a bomb.

    It is difficult and nearly impossible to make suggestions about all this technical stuff without knowing what speakers and amps you are using. We now know that you are using a DBX Drive Rack PA, which leads me to believe that your speakers are at least biamped. Please fill us in with more info about your setup.

    So, if your speakers are not powered, (passive) then it is reasonable for me to assume that you are using the DBX Drive Rack PA for those speakers, along with some outboard amplifiers mounted in some kind of amp rack. If that is the case, you will need another crossover for the subs, a DBX Drive Rack (or any one of many other choices) will suffice. Now, since you prefer to reserve your four mono mixes for monitors, (and that’s fine) you will use just one of the output channels of a stereo MIX output, like 7 of the 7-8 pair, assuming it is not yet used. The second crossover (whatever that is) will most likely be a stereo crossover, but we only need to use one of the channels of it, for the subs, since they are mono. The output of that crossover will feed another amplifier to power your subs.

    Now, if your subs are powered, (active) you will NOT need to get another crossover because powered subs already have a crossover built in.

    Too much to go over here until you can provide a list of gear that you are using…. then, we can help get your system running at it’s best.

    Profile photo of WaihekeSoundie

    @dpdan– many thanks for your advice.
    I have
    1* QU 16
    2* RCF HD 32a 12″ active powered speakers as my main tops
    2* RCF 522a 12″ active powered speakers as back ups but also as delay fills if I need them
    2* RCF 312a 12″ active powered speakers centre fills if I need them
    1* JBL PRX 618S XLF powered 18″ sub
    Some stage monitors
    DBX Driverack PX (PX not PA)
    Rane RPM 26Z which I have programmed as a 2 way crossover (it is a backup for me mostly though I can drive it with AES which reduces / frees up 2 longer mic cables)

    Those are the main bits and pieces.
    My tops are rated about 130db and my sub the same. My tops will outrun my sub at full output but the set up is pretty loud so I don’t generally need to run it at full output for smaller venues (150 people) and for larger gigs / outside I get in extra subs.
    For medium gigs I had been thinking about dropping the crossover a bit — my thinking being that might make the main FOH tops take a bit more bass load off the subs to even things up a bit but I’m not sure about that and maybe Aux fed sub might mean I don’t need to…

    I’ve been doing sound for about 10 yrs now – I do sound for about 7 local bands – they range from 3 piece up to a 9 piece and most of my gigs will have 2 or 3 of these bands in succession festival style with a DJ or two thrown in. I’m getting a few slightly larger gigs now hence my question about fills. Potentially I would be aiming for FOH mains, centre fills, delayed side fills and an AUX fed (powered) subs.

    Many thanks dpdan / everyone! So much to learn eh.

    Profile photo of WaihekeSoundie

    So above is my gear and a bit of context about the gigs I do and my experience.

    I get what has been said about how to set up the fills and using the DCAs to ensure that the levels of the mains and fills remain consistent. Thank you for that.

    I get how to physically connect up the mono sub out and see that I can engage the internal crossover in my active sub so don’t need another crossover.

    I am not quite sure how I configure my SUB out mix though.
    This is what I think I should do:
    — The SUB Out mix and LR Main mix need to be controlled by the same DCA-so that both masters go up and down at the same time; (If I have fills I put the SUB Out mix in that same DCA)
    — Instruments only to go to the sub are assigned to the SUB Out mix and their levels are up in that mix but they are NOT assigned to (levels are down in) the LR Main mix. These instruments need to be PRE (LR main) fader in the SUB Out mix
    — Instruments that are in both mixes (like keys and continuity music) should be POST-fader (and at unity) in the SUB out mix
    Is this correct?

    What I’m not clear about is how I set my delay fills if I go this approach?
    Obviously I can just run my delays as a postfader mix from LR Main as I would if I had not split the bass out to the mono sub feed.. but that is going to mean my up field speakers have no kick, say. Is this what people do?

    Profile photo of dpdan

    Nice equipment you have!
    Thank you for the detailed list.

    Personally, I see no need whatsoever for the DBX processor/s in your system.
    Your top speakers have a switch that should be in the “FLAT” position. This means that your top speakers are going to try to reproduce frequencies that you already have handled by your subs. Unfortunately, the switch does not have a ‘Low Cut” position, so it is very important for you to roll off all the frequencies in the graphic EQ of the QU for your main L/R mix below let’s say 70-80 Hz. So, at least the first five EQ faders should be all the way down, this is ideal when you are augmenting them with subwoofers. This is not as good as having a sharper cutoff like the DBX processor can provide, but it is perfectly sufficient, unless you want to carry that DBX around and make those additional patching.

    For my small jobs, I use QSC K12 speakers for tops and K10 speakers for monitors, they all have the switch flipped (except drum monitor) to the “with sub” position, this relieves the top speaker from wasting it’s power on low frequencies that it can not do very well anyway, thus increasing the tops’ headroom.

    Here is how I personally approach sub woofers. I am 60 years of age and come from a time when there was no such thing as subwoofers. It was imperative back in the day that any “professional” loudspeaker, Altec Lansing, JBL, Electro-Voice should be able to faithfully reproduce frequencies down to at least 50-60 Hz. Engineers that designed these speakers fully understood the fact that typically, the bigger the woofer the more “air” it could move, provided of course it was housed in a very efficient bass cabinet made for it. Once subwoofers became all the rage in live pro sound, there was now no longer the need for our “quote” HUGE Full Range speakers. We could get very good sound with much smaller speakers mounted on purpose built tri-pod speaker stands or floan in the air on a truss system, but these smaller speakers desparately relied on subwoofers below them to handle frequencies that they simply COULD NOT produce faithfully. It wasn’t too long before it became common for our subwoofers to be sent audio from a separate output on the console. This allowed the engineer to route only sounds with significant bass response to them, so, things like vocals, acoustic guitars, brass that do not have useful frequencies in the sub region would not be routed to the subs, why would we? No need to clutter up the sound in our subs with these sounds.

    “Instruments only to go to the sub are assigned to the SUB Out mix and their levels are up in that mix but they are NOT assigned to (levels are down in) the LR Main mix.”

    NO, in the sub mix, you turn up whatever channels that have significant bass response,
    but you still want that in your main L/R mix. A bass guitar and kick drum for instance would sound terrible with just subs.
    Both kick and bass guitar have full range frequency response.

    “These instruments need to be PRE (LR main) fader in the SUB Out mix”

    NO. all channels in the sub mix should be POST fader, so that when you raise the bass guitar in the L/R mix it is automatically raised the same amount in the subs.

    “Instruments that are in both mixes (like keys and continuity music) should be POST-fader (and at unity) in the SUB out mix
    Is this correct?”


    “What I’m not clear about is how I set my delay fills if I go this approach?
    Obviously I can just run my delays as a postfader mix from LR Main as I would if I had not split the bass out to the mono sub feed.. but that is going to mean my up field speakers have no kick, say. Is this what people do?”

    NO, in my opinion, your delayed speakers should have everything in them just like the mains.

    We’re gettin there 🙂

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