Ringing Out The Room – Channel or Overall PEQ?

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This topic contains 170 replies, has 21 voices, and was last updated by Profile photo of zzzzzzris zzzzzzris 5 years, 5 months ago.

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  • #47014
    Profile photo of coffee_king
    coffee_king
    Participant

    Hi All
    Still trying to get my head around dealing with feedback on the QU16.
    So Ive been doing a lot of research and ringing out the room is a solution of sorts, but do I knotch out the channel PEQ per mic or the overall master PEQ?

    Thanks in advance.

    #47015
    Profile photo of Dick Rees
    Dick Rees
    Participant

    Where is the feedback coming from? What’s causing it?

    When you can answer these questions then you can use the various tools available in the Qu to deal with the situation.

    #47016
    Profile photo of cornelius78
    cornelius78
    Participant

    There are pros and cons to both methods, it it depends on your application and gear as to which will suit better. In general I’d recommend using the LR output’s peq to deal with room resonances and feedback (then use the geq if you have to,) and save the channel eq for fixing/enhancing the sound on individual channels. Of course there are some acoustic problems that a peq just can’t solve, so ringing out the room should only be done after things like getting the correct speaker placement, mic choice and mic placement etc.

    #47017
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    If it’s a given mic from a given source (a monitor maybe) then I’d tweak the monitor – otoh I’d probably tweak a channel before the FOH mix, unless it was a general room issue that was being picked up from a number of mics.

    Not always easy to tell though…

    #47023
    Profile photo of coffee_king
    coffee_king
    Participant

    it’s a given mic from a given source (a monitor maybe) then I’d tweak the monitor – otoh I’d probably tweak a channel before the FOH mix, unless it was a general room issue that was being picked up from a number of mics.

    Makes sense cheers I’ll follow that rule.

    BTW We dont use wedge monitors we use IEMs.

    Ta.

    #47026
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    IEMs make the world a better place 😉

    #47028
    Profile photo of cornelius78
    cornelius78
    Participant

    It’s unlikely IEMs would be the cause of your feedback, although if you have poor gain structure you could be getting digital clipping somewhere in the signal chain, which would sound bad.

    If it is actual feedback though my money would be on mic/speaker placement (specifically their pickup/coverage patterns,) and their associated eq, room resonances, using too much make-up gain on various compressors so when those compressors engage you exceed your gbf limit (especially if a lot of them engage all at once,) or you’ve accidentally created a feedback loop somewhere, eg sent an fx return back to its send, or you’ve tried to get creative with psuedo subgroups and have accidentally double bussed something etc.

    #47029
    Profile photo of Andreas
    Andreas
    Moderator

    From what I read between the lines I’m not sure if checking for room resonances should be the first to look at.
    With IEMs and proper mic and speaker placement you normally should not have big issues with feedback.
    As already asked: Are there any gates/compressors in you vocal channels? Turn them off, at least for testing.
    When your singers are not singing loud enough, turn down their IEM level…
    I’ll add another question: How does your feedback sound? Is it a sort of low end oooooommmmmm? That’s a room resonance, should be easily dealt with one PEQ notch in LR (or fill in some audience).
    Is it a higher pitch feedback, ensure you’re FOH speakers are not feeding your mikes. A different placement would be the correct solution. Maybe you could post a draft of your stage layout (including FOH speakers).

    There are so many possibilities, you really need to learn to isolate your problems one by one. Then, when its properly identified, you can judge how to deal with it.

    #47044
    Profile photo of deeps
    deeps
    Participant

    When i set up I always get FOH done then monitors
    We use samson d412 powered as monitors

    If we get feed back i tweak the channel and if still drop the monitor
    I dont believe in adjusting FOH PEQ to sort feed back

    But with in Ear you cant get feed back unless your mic gain is too high
    The IEM cant be too loud as the singers would complain
    Very strange

    Maybe try playing with the gate if feed back is coming when channel not in use

    and Subscribed

    #47052
    Profile photo of Dick Rees
    Dick Rees
    Participant

    NO GATES!!!!!!!

    The gates are what is giving him fits right now.

    GATES ARE NOT MEANT FOR FEEDBACK CONTROL, COMPLICATE THE PROBLEM AND MAKE IT WORSE!!!

    #47059
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    I tend to put very low gates in, they all open when the band starts, but they are nice when there is nothing going on. Not a feedback defence, just a hiss and bother defence between songs/sets.

    Without wedges you will be getting the feedback from FOH, so I’d look critically at speaker placement, because that makes a huge difference.

    #47080
    Profile photo of DoctorG
    DoctorG
    Participant

    This is a complex issue because so many factors must be considered and so many variables are involved. It requires a basic knowledge of the sound characteristics of the mics, instruments, and speakers involved as well as room acoustics and a feel for sound frequencies. One also needs to know the capabilities of the mixer and its associated outboard units in order to know how best to attack the problem. For example, do you have a measurement mic, and can you view an RTA graph for the main, monitors, and channels? What GEQs are available – only outputs or also for channels? With an RTA, it is generally easy to see at what frequency the feedback is occurring, and a GEQ can be used to reduce the offending frequencies. Here are some suggestions (I’m assuming you know the factors that you need to consider with each of these.): Use directional mics as much as possible. For vocal mics, roll off (shelf) lows and highs as much as possible. Condenser mics particularly need such EQ. Don’t ignore proximity effect. Some roll-off of mid bass may be needed to correct for this. For live bands, the biggest feedback problem is the monitors. Be sure the monitors are positioned as far as possible from the mics in use and that the directional characteristics of mics and speakers have been given due consideration. Also roll out as much highs and lows as the musicians will tolerate. Keep monitor volume as low as the musicians will tolerate. Ideally, use In-ear monitors. After the levels have been established for main and monitor speakers, use an RTA and GEQ to smooth the frequency response of the room. Do this for monitors and mains separately, if possible. Be sure to pull down any frequencies that tend to project above the center line of the RTA curve. Use as narrow a Q as possible when setting the GEQ. Next, open each mic and use the RTA to remove as many feedback frequencies as possible, using a GEQ if available, or the PEQ for that channel. Start with as narrow a Q as possible, but widen the Q if several frequencies close together are involved. Don’t remove more signal than is necessary so as not to discolor the sound. Try to avoid any boosting of particular frequencies. Try to get the slider or trim as high as possible with the nomal setting of group and main sliders, but do not set the trim so high that clipping occurs. Leave some headroom there. Do this for each mic, in the places where they will be used. Next, open each combination of mics that will be used at the same time and determine if additional cuts need to be made to either EQ or level. Different vocalists tend to trigger different feedback frequencies, so you may need to re-EQ mics for different vocalists. This obviously is somewhat simplistic, but it should give you the idea of what needs to be done to minimize feedback.

    #47081
    Profile photo of Dick Rees
    Dick Rees
    Participant

    DocG…

    Paragraphs please, sir.

    #47091
    Profile photo of Dick Rees
    Dick Rees
    Participant

    DoctorG

    “Participant
    This is a complex issue because so many factors must be considered and so many variables are involved. It requires a basic knowledge of the sound characteristics of the mics, instruments, and speakers involved as well as room acoustics and a feel for sound frequencies. One also needs to know the capabilities of the mixer and its associated outboard units in order to know how best to attack the problem. For example, do you have a measurement mic, and can you view an RTA graph for the main, monitors, and channels? What GEQs are available – only outputs or also for channels? With an RTA, it is generally easy to see at what frequency the feedback is occurring, and a GEQ can be used to reduce the offending frequencies.

    The GEQ may be used, but the better tool is PEQ. And any EQ should come only after assuring proper speaker placement.

    ” Here are some suggestions (I’m assuming you know the factors that you need to consider with each of these.): Use directional mics as much as possible. For vocal mics, roll off (shelf) lows and highs as much as possible. Condenser mics particularly need such EQ.

    This is pretty much urban myth and is simply not true. A microphones propensity to feed back is governed by pattern and placement, not by the type of transduction.

    “Don’t ignore proximity effect. Some roll-off of mid bass may be needed to correct for this. For live bands, the biggest feedback problem is the monitors. Be sure the monitors are positioned as far as possible from the mics in use and that the directional characteristics of mics and speakers have been given due consideration. Also roll out as much highs and lows as the musicians will tolerate.”

    You can delete the “asa far as possible” part. The sentence following is correct, but a simpler statement would be to place the monitors in the nulls of the microphones: 180 degrees for cardioid mics and 130 degrees for hyper-cardioids.

    Additionally, EQ’ing things according to a formula (always do this) is not right. Properly setup and placed monitors should not require a lot of EQ. Local reflections are the common variables and as such must be dealt with on a case by case basis. Cowboy hats can be the worst offenders…

    ” Keep monitor volume as low as the musicians will tolerate. Ideally, use In-ear monitors.”

    IEM’s? maybe so, maybe not…

    ” After the levels have been established for main and monitor speakers, use an RTA and GEQ to smooth the frequency response of the room. Do this for monitors and mains separately, if possible. Be sure to pull down any frequencies that tend to project above the center line of the RTA curve. Use as narrow a Q as possible when setting the GEQ.”

    This is not how to do it, sort of backwards…and GEQ does not have variable Q on the Qu desks. The only thing I have with variable Q GEQ are my Sabine GraphiQ’s.

    ” Next, open each mic and use the RTA to remove as many feedback frequencies as possible, using a GEQ if available, or the PEQ for that channel. Start with as narrow a Q as possible, but widen the Q if several frequencies close together are involved. Don’t remove more signal than is necessary so as not to discolor the sound. Try to avoid any boosting of particular frequencies. Try to get the slider or trim as high as possible with the nomal setting of group and main sliders, but do not set the trim so high that clipping occurs. Leave some headroom there. Do this for each mic, in the places where they will be used. Next, open each combination of mics that will be used at the same time and determine if additional cuts need to be made to either EQ or level.”

    Again, this is sort of OK, but the statement is rather rigid and many clarifications need to be made to to situational variables.

    ” Different vocalists tend to trigger different feedback frequencies, so you may need to re-EQ mics for different vocalists. ”

    Not true. Feedback is dependent on the critical distances within the signal path and manifests at different frequencies. The vocalist has literally nothing to do with it in the world of physics.

    “This obviously is somewhat simplistic, but it should give you the idea of what needs to be done to minimize feedback.”

    Some of it is simplistic, some of it is over-thinking and much of it is simply mistaken.

    #47094
    Profile photo of Andreas
    Andreas
    Moderator

    Cowboy hats can be the worst offenders…

    Even eye glasses may be a problem. Had this once with a guitarist doing background singing as well. Everytime he looked down to his guitar a “nice” feedback came up, redirecting the wedge sound directly into his condenser mic (no gates, no big EQ, no compressors).
    Took a while to isolate that problem, since it seemed to only happen when I looked elsewhere and he immediately raised his head to check what’s going on. Moving the wedge slightly cured it 100%.

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