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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Scott Holtzman on June 25, 2014, 09:49:49 PM
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Hi, long time reader. First post.
Quick background. I have been working around live sound as a secondary vocation for 30+ years in various capacities. HOW, theater and live music of many different styles.
My "day job" is an Electrical Engineer and I also have a background in physics. I enjoy speaker design, micing techniques and all facets of acoustics.
Recently I have been getting much more involved in live audio, as I plan on getting out of the engineering business in the next 5 years and concentrating on live audio, hoping to get on the road with the wife and a good crew and do small to medium size festival work.
On to the current situation. I hooked up with some local musicians/sound guys and have been working various gigs with their rigs and mine. Small clubs using Apogee/QSC KW series/Mackie 1600 series and most recently a Behringer X32. This year has been my first exposure to digital gear other than some Yamaha experience in a corporate setting. I have no issue with digital theory or the operation of digital mixers however it seems that I am developing bad workflows on the X32 and not keeping my head up.
Last week we were doing a gig for a packed house. The guitar player actually had to leave the stage as I failed to recognize a low frequency wave that had built up on the stage and developed into feedback. It was centered around 300hz. We don't use any monitor speakers I run 5 monitor mixes with in ear units. The feedback had to be from the subwoofers and back into a vocal or possibly drum mic. Bass and Electric Guitar are DI. Only vocal and drums have microphones.
I had the spectrum analyzer up at the time and the feedback recurred several times during the show. I was very tuned in on it and very on edge at this point. I handled the feedback by reducing master gain then bringing up instruments and rebalancing the vocals. I tried an aggressive low pass up to 200hz shelf and it sounded like crap so I had to abandon that idea. Then I tried applying a narrow 9db dip using the parametric centered at 200hz and about 120hz wide with a fairly steep roll off. This solution seemed to work during the second set the however in the last set of the night we once again had a very quickly building feedback event. My guess is some different samples from the electronic drums hit the resonant frequency and IM products and once again created a sort of bass trap on the stage. We have worked this room before but our usual KW181 subs were not available and I used some physically much larger Mackie dual 18" that have significantly deeper low end extension than the KW's.
After the gig the emotional flood gates opened with the band. Apparently they have had issues that I have had my head down in the mixed and making insufficient eye contact, perceive that I have missed solo's and don't have a good handle on the music. To top it all off the lead singers Sennheiser in ears were malfunctioning during the show and I was not told about it. It may have been an RF issue and I could have done a local spectrum sweep to see if I had known.
So now I am on edge being on notice that my performance has been less than satisfactory. I am not sure though I am fairly confident that I will be back for the next gig.
My question is, how can I in the two weeks I have to the next gig improve my workflow beyond additional practice on the X32 and start to rebuild the confidence of my band mates? I would like to be able to articulate my remediation plan to them however any time I discuss audio challenges I don't get much feedback. It seems to be a "that's what I am paid to do" thinking.
One additional point. While informing me of these issues they went to great lengths to add personal praise and how hard I work. Frankly while I appreciate the fact I am liked it really is not the issue, it's not an emotional event. It's business and art and my performance. I did not in any way take the criticism personally.
I want to make the band sound their best. Any comments would be greatly appreciated.
Thanks
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How do the band members, wearing in ears, have a clue about what it sounds like front of house? If they don't like the mix in their ears that is a problem you can fix, but I don't understand how they can judge a mix you can't hear...
Regardless, if your only open mics are vox and drums, and your vocal is high passed, and subs aux fed (my favorite method).... I would look to the drum mics. Some gating on the kick maybe?
As for workflow, line check, in ear mix, tweak FOH to taste. Adjust in ears if needed...
I have a pretty technical background. It was hard for me to stop looking at the console, trying to gain insight from what i saw on the meters, I would listen but try to equate what I heard to what I saw. I was a very tweaky person mixing lots of super small adjustments that I think it made me feel better but I don't think anyone could hear the difference, including me.
Anyway, I didn't and dont do much mixing, I did much more system config etc. One of the better engineers I work with helped make it a little more of an intellectual exercise for me. Thinking of the mix as a whole and how each musician and instruments fit into it. I had to learn to look up and listen and not look down.
Not sure this is helpful.... These are my thoughts, post a couple of adult beverages. Perhaps I will edit in the morning.
Sent from my iPhone using Tapatalk
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One of the hardest things about working digital is the "listen, don't look" thing. It used to be you just twisted knobs till it sounded right... and we never really looked at the labels on those knobs in the dark. With digital, if you don't look down next thing you know your sweeping who knows what. On the X32 there is no way around the looking down minus a laptop. However, there are handles for other things. Live in sends on fader mode when it comes to routing effects. Use the user defined keys, they really help you get around quick just by touch. Put big labels on things. The more muscle memory you get, the better.
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How do the band members, wearing in ears, have a clue about what it sounds like front of house? If they don't like the mix in their ears that is a problem you can fix, but I don't understand how they can judge a mix you can't hear...
Regardless, if your only open mics are vox and drums, and your vocal is high passed, and subs aux fed (my favorite method).... I would look to the drum mics. Some gating on the kick maybe?
As for workflow, line check, in ear mix, tweak FOH to taste. Adjust in ears if needed...
I have a pretty technical background. It was hard for me to stop looking at the console, trying to gain insight from what i saw on the meters, I would listen but try to equate what I heard to what I saw. I was a very tweaky person mixing lots of super small adjustments that I think it made me feel better but I don't think anyone could hear the difference, including me.
Anyway, I didn't and dont do much mixing, I did much more system config etc. One of the better engineers I work with helped make it a little more of an intellectual exercise for me. Thinking of the mix as a whole and how each musician and instruments fit into it. I had to learn to look up and listen and not look down.
Not sure this is helpful.... These are my thoughts, post a couple of adult beverages. Perhaps I will edit in the morning.
Sent from my iPhone using Tapatalk
No it's good stuff, great reminders. You are right I do look for data, in the VU's the RTA etc. Something I can quantify to what I am hearing.
The monitor mixes are not a problem, we have tweaked them to perfection in practice and the members run the app on their i-devices on stage so they can tweak their ears.
Honestly, as to how they heard it, frankly I think it almost blew them off the stage. The stage is in an alcove at the front of the room with a glass window behind it. It was somewhat subtle at front of house, with all the other issues I had in the first three songs I missed it for synth samples. We were rushed and could not setup until 9PM because of a previous party. Had to make do with short line check.
In addition to the technical insights I am also looking for some feedback on how to get the confidence back of my band mates.
Tall order for a first topic!
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150hz and down can do some really weird things. In our venue we stack all of our subs on one side of the stage, otherwise a bass trap gets formed onstage and the sub disappears from the house. Its really bizarre. If your at a kit centerstage it makes it feel like your inside the kick drum.
As far as the confidence thing goes... sounds like you had a rough night all around. Without getting to hear the house during a sound check you can only do what you can do. Idealy you should be able to move around the house a bit during the show but it sounds like this a rather involved show so that is not possible. If you did the best you could with your ears in the position you were in then you did what you could. Some people will drop reference mics around a venue and watch them all night on SMAART. Not my idea of a fun night, but to each their own. Start the next gig with a good soudcheck. Walk the room. Blah blah blah. After you get the room sounding good sit on your hands until it doesn't. In the mean time... Don't take your eyes off the stage. Make it look like your twiddling things. Nod occasionally. Bands like it when you nod...
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In addition to the technical insights I am also looking for some feedback on how to get the confidence back of my band mates.
A few off the top of my head: keep your eyes on the stage and watch the band cue each other; know and study the music and anticipate what is coming; demonstrate to them your eagerness to make them sound as good as they can with your actions; be a champion for the band's needs at the venues in which you play; anticipate and solve problems their sound problems, even the ones they don't yet know they have; practice your craft and learn your tools so you can use them seamlessly.
You obviously care about it, that goes a long way for many...
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As a quick guess off the top of my head, I'd look into the compressor settings on the kick drum, if you are using one. Sometimes too much makeup gain can introduce a low feedback loop. I'm not familiar with the X32. Could you have assigned a GEQ to the kick? With an iPad could you have gotten closer and try to notch it out?
When I'm doing sound for a band, we will do a sound check. Then during the second song, I'll wander up beside the stage or close enough to see if everything is good, or if anyone needs anything more in their monitor, or any other issues.
Just a couple thoughts.
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Last week we were doing a gig for a packed house. The guitar player actually had to leave the stage as I failed to recognize a low frequency wave that had built up on the stage and developed into feedback. It was centered around 300hz. We don't use any monitor speakers I run 5 monitor mixes with in ear units.
Maybe I'm missing something, but if the band is IEM, and feedback forced the guitar player to leave the stage, it would have to be pretty darn loud for them to hear it first, and I'd guess you probably should have heard it from your mix post before they did. Was it going into the IEM mix or was it stage only??
From your post, it sounds like you are over-analyzing things, getting bogged down in the details - based on the info about spectrum analyzer use, notched frequencies, and a "narrow 9db dip using the parametric centered at 200hz and about 120hz wide with a fairly steep roll off", etc. You have the technical down. :)
Maybe that's where the "eyes down" perception is coming from. You are mixing a band playing "live".. stuff happens.. and techies often tend to rely on the tools rather than their ears (not that tools aren't useful). It took me a long time to learn the difference and to trust what I was hearing in the room, even if that didn't jive with the displayed data.
If you know the source is around 300Hz (or lower) and you only have drums/vocals mic'ed, then it's a good bet you're looking at the kick.. That's where I'd start... you mentioned electronic drums.. are those additional kit or primary? If primary.. why would they be mic'ed?
And, unless your band is getting info from their "friends out front" on the mix, there's absolutely no way they can tell what's in FOH (someone already mentioned that) when using IEM's and be critical of you missing solo's... if they can't hear those.. that's a separate IEM mix issue.
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You could also quickly mute each suspect channel, and see which one gets rid of the low feedback.
Hmmmm not the kick, oh look it's the acoustic sitting on the stand that's not muted. (It happens).
That kind of thing.
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They heard feedback from their IEMs before you did? that's crazy. Honestly, you should try to make things feedback (a little bit, doesn't have to be loud) during a setup/check so you know where the limits are.
Also put the dang RTA away. I had when I go somewhere and see people using smaart during a live show and while I love smaart it is for tuning and setting up the system no for use during a performance - USE YOUR EARS ONLY!
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They heard feedback from their IEMs before you did? that's crazy. Honestly, you should try to make things feedback (a little bit, doesn't have to be loud) during a setup/check so you know where the limits are.
Also put the dang RTA away. I had when I go somewhere and see people using smaart during a live show and while I love smaart it is for tuning and setting up the system no for use during a performance - USE YOUR EARS ONLY!
I second that, it seems the magic fixes are too heavily emphasized. they can get you in the ballpark but can't hit that home run swing.
By the way all these posts about setting it flat, a "flat" setting on mains sounds just that, flat.
You still have to have an ear to tune and mix,some people develop that over time, some do not. Just because you can hook it up/install it does not mean you can mix.
Trust your ears, use" magic" sparingly, accept forgiveness from the band, push on,.
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.....while I love smaart it is for tuning and setting up the system no for use during a performance - USE YOUR EARS ONLY!
You obviously know it all. Now those of us who use real time spectrum analysis as a part of our show-time tool kit can put that stuff away and follow your lead, oh omniscient one.
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I would first like to say "Welcome to live sound".
You're getting really good replies here. Take note of what Nils and Rob posted. Move around the room while the band is playing. If my band complains about something they here on stage, then I get up there and listen while they're playing.
Can you control the X32 remotely with an iPad? I use a DL1608 / iPad mixer, so I can go wherever I need to and make the necessary changes.
If the feedback is low-mid or lower, it is acceptable to make the system feedback purposely, then dial out that offending frequency. Also agree that using gates can help.
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1)I have no issue with digital theory or the operation of digital mixers however it seems that I am developing bad workflows on the X32 and not keeping my head up.
2) I failed to recognize a low frequency wave that had built up on the stage and developed into feedback. It was centered around 300hz. We don't use any monitor speakers I run 5 monitor mixes with in ear units. The feedback had to be from the subwoofers and back into a vocal or possibly drum mic. Bass and Electric Guitar are DI. Only vocal and drums have microphones.
3) I handled the feedback by reducing master gain then bringing up instruments and rebalancing the vocals. I tried an aggressive low pass up to 200hz shelf and it sounded like crap so I had to abandon that idea. Then I tried applying a narrow 9db dip using the parametric centered at 200hz and about 120hz wide with a fairly steep roll off. This solution seemed to work during the second set the however in the last set of the night we once again had a very quickly building feedback event.
4)My guess is some different samples from the electronic drums hit the resonant frequency and IM products and once again created a sort of bass trap on the stage. We have worked this room before but our usual KW181 subs were not available and I used some physically much larger Mackie dual 18" that have significantly deeper low end extension than the KW's.
5)My question is, how can I in the two weeks I have to the next gig improve my workflow beyond additional practice on the X32 and start to rebuild the confidence of my band mates?
Scott,
1) Only look at the board when you are actually making adjustments, and learn to push faders without having to look at them.
2) 300 Hz is not low frequency, and should not be reproduced by "subs".
The balance between subs and tops should be set before the show starts, and typically should be around 100 Hz.
You should get a pair of isolation headphones (I like the GK Ultraphones) so you can listen to the individual channels (and headphone mixes) to determine where the origin of the feedback is, and correct it there, not globally.
3) Reducing master gain, then bringing up instruments again is not a net change regarding gain before feedback, and if you have compressors set post fader, can result in even more feedback, as gain has been increased, while the compressors limit output level. If the feedback was centered at 300 Hz, cutting at 200 is the wrong choice. Loads of compression (more than 6 dB on peaks) may sound good in the in ears, but can easily result in feedback that is hard for you to hear, masked by other louder sounds.
4) Bass traps are not created by samples, they are properties of rooms. As well as keeping eye contact with the band at all times, you need to walk around and check out the room and stage to hear what it sounds like in various spots. Had you done that, the problem would have been apparent.
5) Set up the system in the largest room (or outdoors) and get the top and bottom processing set correctly and equalized. If you don't have a system processor, get one. After getting the system properly equalized, set up the vocal mics and start experimenting- other than a HP around 80 Hz, and a low mid cut to deal with the proximity effect, they should sound natural when you speak through them. Experiment with the compressors- you can "ring out" the system without blowing anything up when the compressors are set at a high ratio with lots of gain reduction, probably what was going on at the last gig.
Once you have identified and corrected the problems, tell your band mates what you have done.
Art
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They heard feedback from their IEMs before you did? that's crazy. Honestly, you should try to make things feedback (a little bit, doesn't have to be loud) during a setup/check so you know where the limits are.
Also put the dang RTA away. I had when I go somewhere and see people using smaart during a live show and while I love smaart it is for tuning and setting up the system no for use during a performance - USE YOUR EARS ONLY!
The RTA is built into the board, I can look at any input, buss DCA group etc. It is very easy to see feedback on it.
Anyway, maybe I am not being clear. Nobody heard feedback in the IEM. What I think happened is a troublesome frequency was initiated by the electronic drum pad. That frequency was "trapped" by the shape of the stage and in my current working theory of sufficient amplitude to be picked up by the kick mike. The gate opened and the compressor "sucked up" for lack of a better word the feedback and created it's own feedback fed by the compressor.
Due to my distance from the stage, the amount of crowd. The position of the subs I believe the bass feedback was of sufficient amplitude on stage to be felt and heard before being noticeable at FOH. By all means my ear should have caught it. I also believe I had my head down trying to get the mix set as we did not have time for a sound check, line check or to ring out the room. We were not allowed to setup until after a party and by then the venue was packed.
For those asking about moving around. I use the iPad app for the X-32 and try and move around the house as much as possible.
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Steve -- Thanks for the welcome. I participate in other forums and no how "same old questions" from newbs can get the seasoned vets down. I was truly in a know over this for the past few days and thought it would be a great opportunity to join the community. I might also possibly have something useful to share.
Art - Great feedback, let me address your points.
1 - Agree, and working to improve this and have as good a memory for the x-32 as I did for the analog boards
2 - You are right, the crossover is actually at 90hz. I believe that the slope of the crossover is 3db per octave so if the offending frequency was 300hz that would only be 6db down off the back of the crossover. I absolutely need ears. I have been thinking about getting another IEM pack so I can use the solo from the iPad and listen anywhere in the room. Compressors are pre-fader as are the gates.
3 - I agree completely see my previous post
4 - I understand this, my theory is that the electronic drum produced a waveform of sufficient amplitude and duration to trigger the trap effect and ultimately the feedback product.
5 - Already done. I have the previous generation (not the ipad controlled) Driverack. However it is still in the box. Experience has shown me that sometimes that's the best place for outboard gear when you are just getting your workflows down on a new desk. I also was trying to get out of lugging around extra gear however I just got the S-16 digital snake so I could put it in that equipment case.
Thanks again.
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1)Nobody heard feedback in the IEM. What I think happened is a troublesome frequency was initiated by the electronic drum pad. That frequency was "trapped" by the shape of the stage and in my current working theory of sufficient amplitude to be picked up by the kick mike. The gate opened and the compressor "sucked up" for lack of a better word the feedback and created it's own feedback fed by the compressor.
2)I use the iPad app for the X-32 and try and move around the house as much as possible.
1) If anyone had the kick drum up in their mix, they heard the feedback in their IEM. The use of compressor on a kick drum is asking for feedback, and will increase the tendency of an inconsistent kick drummer becoming even worse. Use no compression, and set the gate so the drummer has to kick reasonably hard to open it, and he will. If any other instrument or sample is loud enough to open the kick gate, things are seriously wrong either with the drum tuning, drummer, mic position, EQ, gate settings, or a combination thereof.
2) Excellent, but obviously "as much as possible" needs to be more ;^).
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They heard feedback from their IEMs before you did? that's crazy. Honestly, you should try to make things feedback (a little bit, doesn't have to be loud) during a setup/check so you know where the limits are.
Also put the dang RTA away. I had when I go somewhere and see people using smaart during a live show and while I love smaart it is for tuning and setting up the system no for use during a performance - USE YOUR EARS ONLY!
Load of crap... The spectrograph in SMAART is amazingly useful during a show to display your cue bus. When i am separated from the band by 150 feet and 500 people and I am trying to mix monitors from FOH, being able to see the response in a single channel or monitor channel is an amazing tool. Typically I can spot hot frequencies before they can be heard as feedback and fix things before anyone even knows there is a problem. The more complex the system, the more useful this tool becomes.
i see no reason to give up perfectly appropriate tools.
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2 - You are right, the crossover is actually at 90hz. I believe that the slope of the crossover is 3db per octave so if the offending frequency was 300hz that would only be 6db down off the back of the crossover. I absolutely need ears. I have been thinking about getting another IEM pack so I can use the solo from the iPad and listen anywhere in the room. Compressors are pre-fader as are the gates.
Scott,
Isolation phones are a lot easier to put on and off than sticking in IEM, though having them plugged in to a portable pack would be cool.
There is no such thing as a 3 dB per octave electronic crossover (a single pole is 6 dB), but if there was and it was set at 90 Hz, it's output would be -3 dB at 90 Hz, -6 dB at 180 Hz, and -9 dB at 360 Hz.
What "crossover" were you using?
Art
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Scott,
Isolation phones are a lot easier to put on and off than sticking in IEM, though having them plugged in to a portable pack would be cool.
There is no such thing as a 3 dB per octave electronic crossover (a single pole is 6 dB), but if there was and it was set at 90 Hz, it's output would be -3 dB at 90 Hz, -6 dB at 180 Hz, and -9 dB at 360 Hz.
What "crossover" were you using?
Art
We were using EV ZLX-15P that has a built in crossover. I just looked no specs on it in the manual. I assume it's a 3rd order Butterworth, that's a bunch of assuming. What concerns me is my fundamental assumption that this crossover was 3db per octave which I now see is wrong.
Something I thought I knew and would have argued to the death, major sigh
Please feel free to tell me that I am all wet on my bass trap theory, that is also a damn good point on the kick gate. Although from what these guys described this bass wave on stage was visceral and building very fast. I have a call into the drummer, who is a buddy to see if he heard in his ears. He is the only person that takes any kick in their monitor mix.
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Once the sound is loud enough they will hear it from bleeding into other mics. I find the longer feedback goes the harder it is to trace the source.
Sent from my DROID RAZR HD using Tapatalk
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We were using EV ZLX-15P that has a built in crossover. I just looked no specs on it in the manual. I assume it's a 3rd order Butterworth, that's a bunch of assuming. What concerns me is my fundamental assumption that this crossover was 3db per octave which I now see is wrong.
Something I thought I knew and would have argued to the death, major sigh
Please feel free to tell me that I am all wet on my bass trap theory, that is also a damn good point on the kick gate. Although from what these guys described this bass wave on stage was visceral and building very fast.
Scott,
Yeah, when a drum head starts to resonate from a feedback loop, the amplified output from a double 18" can get visceral very fast.
At any rate, the crossover contained in the top cabinet simply crosses between it's woofer and tweeter, on the EV ZLX-15P that is somewhere around 1500 Hz, so it (or it's slope) has no bearing whatsoever on your kick drum's acoustical/electrical feedback, which was caused by too much gain, then masked by the room response and compression making you unaware of it.
BTW, a "3rd order Butterworth" electrical crossover (nominally 18 dB per octave) can result in anything from around 12 to 36 dB per octave acoustical crossover. You are going to have to learn a lot before you will be able to properly set up your DriveRack unless there happens to be some pre-sets already in place for the tops and subs you plan to use.
Unless you had set the EV ZLX-15P to "speech" mode, it has response down to 55 Hz, so would be overlapping with the sub. You don't even mention whether the sub was crossed over, though even crossed over properly, too much gain (whether from either sub or top or both) would still result in the same problem you experienced.
Also, the overlap output of the sub and mains is most likely not in phase (the DSP used in the ZLX-15P and it's tuning frequency would reult in a different phase response than the 2 x 18"), which can "steer" the response of the LF in directions other than forward, you may have been sitting in a cancellation zone caused by the speaker's interaction or room modes.
Anyway, you are learning- brings me back to the first time I experienced a similar problem (only on a floor tom) back in 1977, some things like room acoustics, drum resonances, and physics never change.
Have fun!
Art
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I'll chime in here as someone relatively new with the electronic analysis tools.
I agree the tools like SMAART and others are great tools for the live engineer. That said, my experience is the various tools are quite addicting visually. Of course, that is my problem. As the night settles down and as I tire, my attention to the band can waver - being replaced by my attention to "all the pretty colors". Yes, I'm making lite of this a bit, but I know me.
I know I need to make a conscious effort to limit the time of my gaze/analysis of the electronic aids, and concentrate on the band's performance. Even when I'm frantically trying to solve a problem, or fire the band up in front of an audience cold (no line check, no sound check, no ringing of the system), no matter how frantic, I have to look for queues/problems from the band. I find one simple trick to help a bit : put the monitor high enough in your field of view such that it is just below your view of the performance and practice using your peripheral vision for both the screen and the band.
In a nutshell I'm saying it is easy to get heads down in the computer work - you have to be aware that is a problem, and work at it.
As far as that low feedback, I have a problem with that at times - I find it hard to pick out of the mix, seems to "hover around the ankles" (I know it doesn't but that is how it seems). I find it the hardest for me to locate and attack.
frank
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Good stuff Art, couple of things.
I know that the Butterworth is an analog filter design however I thought that DSP's tried to simulate the characteristics of the complex LCR networks. For example an older Peavey digital crossover has a 3rd order Butterworth or a Linkwitz Riley curve selection.
With regard to the ZLX's they indeed do have a crossover for the subs, in the menu you can select three crossover points of 80, 100 or 120 and lastly it has a mode for the EV ELX-118 sub.
I also agree that there was some cancellation, certainly attributable to phase discrepancies in the crossover overlap zone between the subs and the tops. Additionally, the band likes the standard sub on either side of the stage deal so I never get any stacking gain or the phase coherence of locating the subs together. Also the KW112 and KW181 we usually use seem to cover more sins than these older Mackie dual 18's with the EV's on top. The Mackies were also modded with a thermostatic fan kit across the entire heat sink, all the heat sinks were stripped and high quality compound used and the factory tin solder was sucked off and reflowed with silver solder. The critical caps were replaced with higher quality components. The have served well. Looking to replace them, that's another thread.
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Good stuff Art, couple of things.
I know that the Butterworth is an analog filter design however I thought that DSP's tried to simulate the characteristics of the complex LCR networks. For example an older Peavey digital crossover has a 3rd order Butterworth or a Linkwitz Riley curve selection.
With regard to the ZLX's they indeed do have a crossover for the subs, in the menu you can select three crossover points of 80, 100 or 120 and lastly it has a mode for the EV ELX-118 sub.
I also agree that there was some cancellation, certainly attributable to phase discrepancies in the crossover overlap zone between the subs and the tops. Additionally, the band likes the standard sub on either side of the stage deal so I never get any stacking gain or the phase coherence of locating the subs together.
BW, LR and other crossovers that originally used capacitors and coils (each additional cap or coil is an "order" of 6 dB per octave) can all be emulated in the digital domain.
I missed that the ZLX's have a crossover for the subs (the spec sheet doesn't mention it, the manual does) but it is probably 24 dB per octave (the manual doesn't say), so any cancellation or build up would be limited to around 1/3 octave centered around whichever crossover frequency you chose, so you not hearing the feedback probably was due to the limiter and room modes.
There are advantages and disadvantages of either center or L/R subs. In some rooms, putting both subs on one side or the other may be the best compromise. Generally, I prefer mains above subs so the crossover alignment always remains the same.
If you are having trouble keeping the kick drum from feeding back, locating the subs closer (as in downstage center) to them would not be advisable ;).
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If I may I would like to offer a couple of ideas here. First of all depending on the volume of the system you should have the front line mics behind the rear of the drivers in you FOH cabinets, this is one thing I have learned from doing high volume gigs.
The second thing would be to have a look at an external source for the resonating frequency, I have had this happen to me on more than one occasion and found that the inhouse lighting bars were resonating and creating a feedback loop.......gaffing up the ends of the pipes fixed the problem.
If the subs/top cabs are touching or located on the stage and the stage is hollow timber sealed (carpeted or not) on all sides this can also create a problem with resonance, relocating the cabinets will fix this problem.
Aside from that I would be looking at the tom mics and more than likely it will be the floor tom creating the resonance, If there is a compressor on the kick/snare as someone else has mentioned then this can create a problem if it is set to hard, when the compressor lets go there will be a surge of gain that could be the source.
My advice is to pull back the channels that you may suspect as being the offenders one by one till you find the source.
I can see that you have great technical knowledge and I am not trying to be negative here but practical experience in a live situation is paramount, if you do not have the experience it can lead to problems such as you experienced. I acknowledge that everyone has to start somewhere and experience is gained by practical application, I commend you for coming into a forum like this and asking for advise as you will learn much faster from the experience I have seen so far in here.
As you do more shows you will start to recognise these problems and find it much easier apply a solution. Try and train your ears to focus on one instrument/vocal at a time, once you master this you can efficiently block everything else out and just hear that one channel you want to hear, this is also a very valuable tool for trouble shooting :)
PS: I also use Smaart during the show and find it to be invaluable in some cases
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Mike - Those are all great suggestions, and also would have been by "go to's" in addition to channel mutes.
The discussion was originally not so much technical as to how I missed the feedback from my position and failed to react to it. If I had heard the feedback I am sure I could have solved it. If my head wasn't buried in the mixer I would have seen the look from the stage and ran up with the iPad and solved it.
No matter what the crowd situation is and how rushed things go down I have to efficiently multi-task and move around the room.
I appreciate all the input.
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From experience I understand what you are saying and yes if you are not concentrating on what is happening out front it is quite easy to not hear what is going on on stage, The suggestion a few posts up to have a set of noise cancelling headphones is also a great idea as you can usually hear a the offending frequency when you select the channel causing the problems.
Walking the room is a must as it can sound very different around the room from where you are situated. It can sound perfect in the centre and then you move to the right and the sound will change, then you move to the left and hear another inadequacy and by knowing what is not right on both side but sounds good in the centre you can then balance the sides to achieve the same result as you move from left to right.
Live mixing can be quite overwhelming at first as there are just so many variables to consider but as with anything practice makes perfect ;)
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as with anything practice makes perfect ;)
Done plenty of live mixing but the club venue knob twister for hire is a whole different animal. It's hard to hone your craft when the guitar player is ready to beat you over the head with his tele :-)
This year has been an education at a corporate or HOW gig I have never had to go find a stoned CEO.
Ask the band eating pizza on stage to try and not get grease all over the microphones
Clean vomit out of a monitor
Have my wife look after a musicians G/F puking outside
I have to be forgetting something.
I love it though, the energy and immediacy of the feedback from the crowd. It keeps me young.
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on what is happening out front it is quite easy to not hear what is going on on stage, The suggestion a few posts up to have a set of noise cancelling headphones is also a great idea as you can usually hear a the offending frequency when you select the channel causing the problems.
Not noise canceling but good isolation.
Many years ago a friend tried a pair of Bose noise canceling headphones to monitor a record mix. The recording was a disaster because of the coloration the cans introduced.
Sent from my iPad using Tapatalk HD
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Low-freq feedback onstage (especially if it is coming from the FOH subs) can be difficult to catch from a challenging FOH position. As a performer I have had several experiences with a severe "wrap-around" from a FOH rig where the "whooom" onstage was already deafening before the the FOH guy caught it. In one instance the guy was oblivious to all of our waving and gesturing, until the lead vocalist finally hollered over the mic about it.
It is far more important that you maintain eye contact with the musicians rather than the console. Just a simple fact.
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Low-freq feedback onstage (especially if it is coming from the FOH subs) can be difficult to catch from a challenging FOH position. As a performer I have had several experiences with a severe "wrap-around" from a FOH rig where the "whooom" onstage was already deafening before the the FOH guy caught it. In one instance the guy was oblivious to all of our waving and gesturing, until the lead vocalist finally hollered over the mic about it.
It is far more important that you maintain eye contact with the musicians rather than the console. Just a simple fact.
Sometimes, it's the room. I played a large, national chain, well-known (recently closed) "Country" venue in Dallas a number of times over the 18 months it was open. Line array FOH, EIGHT dual 18 subs under the concrete stage, Midas Pro2-TP console, 1000w stage mons + dual 18 Drum sub, and wood facia stage walls.
Sounded freakin' AWESOME out front, but the low end bass "boom/rumble" resonating around the stage from the combined subs was absolutely horrible. We were not IEM back then (different band) so used the stage monitors. Great mix on those too, but it didn't matter WHERE I stood on the stage (I was wireless) that rumble was still there. It became confusing when playing the Low B (5-string bass) because it was hard to tell what I was actually hearing...
Yes, the FOH guy (Stoney Larue's former FOH) came up, listened, tweaked, adjusted and finally gave up saying it was room dynamics. Happened every night we played there... I just had to deal with it...
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Someone else has already mentioned Aux feed subs. Are you aware of what that means and what it can do for you? In a nutshell keep everything out of the subs that doesn’t have any sub content, like the vocal mics. This will help a lot with low-end feedback problems. This will probably require you to use the DSP to crossover things.
On a digital console you have a lot of flexibility, learn all about it but set it so you can ignore all of the complexity and concentrate on mixing.
It is easy to miss cues from stage. I caught the tail end of the horn players the other night trying to indicate a change they wanted in the monitors. Outdoor show. This was after a bunch of songs so I though everything was fine and then all of a sudden with no other changes on stage they chose to indicate a need for a change in the middle of a song. And this band took forever to start the next song so why wasn’t there time to ask for the change then. There was even a sound crewmember next to the stage that they could have asked. But they waited till he left because he thought everything was fine at that point. End of rant.
One monitor suggestion don’t always give them what they ask for usually you need to give them what they should be asking for. The horn players wanted more of themselves in the monitor. I punched their mix up on my headphones and realized that what it sounded like they needed was a little bit more of them selves but a lot less of the vocals. So I brought the vocals down in their mix and brought the horns up a little bit, and they were happy. If you just keep bringing everything up as they ask it can get too loud, sometimes you need to subtractive mix. But I think you said everyone was on IEMs, so just file this part away for the future.
Another trick, I like to tune the system for linearity (what goes in is what comes out) then insert an EQ on the vocal sub group and tweak that for the best gain before feed back. If you EQ the whole system with a vocal mic so you can get the most out of it you usually butcher the sound for the rest of the instruments. I have explained this in more detail in other posts on here.
I hope this helps someone.