Hi,
Just bought our New Qu7 for church, a first of switching to Digital Mixer from Analog seems to be having lots of issues with Feedback and howling from certain Microphones. Is there any Tutorial or Guide on how to setup Feebback assistant on certain input channels.
Thank you
Niks
Before you rely on the feedback assistant you need to be sure the gain structure is correct and the system is properly set up and eq’d taking care of the obvious ringing frequencies and over all system voicing.
It may be worth bringing in someone to go through the system, set it up and do some training on the mixer…..finding that right person can be tricky!
To be honest I’ve never used any feedback type of eliminator but I heard the after effects of them being over used and notching away way too many frequency bands.
I have a Qu-5, so this should apply. I use the mixer at our Church, which has an active reverb in our untreated Sanctuary. Add in a novice assistant sound engineer, this equals we have to rely on the feedback assistant for our FOH mix.
My use of the feedback assistant is still a work in progress, but we’re getting decent results, so no major complaints.
OK, now what I’ve done up to this point, common setup of mics to inputs, setting various aux mixes and so on. I took pains to identify which mics would be worse for feedback and paid more attention to those channels.
Test: LR selected and unmuted, try various combo of input fader vs LR Master fader output, trying to find feedback threshold and which input to output combo allows highest total output before feedback. Having found a preferred combo, go forward to FBA.
If you have bad feedback, you might need to edit amp gain as I did. I turned mine back and still get good output. Mine was a replacement install of Qu-5 mixer from another mixer, so all settings were up for edit.
First thing I think you may want to experiment with is at the beginning, the input gain. I do like the suggested per input PAFL to get output to show in the meter next to the screen. Per input channel, set gain to hit into the lightly lighting yellow which would be about analog -18 dB. I allow it slightly hotter than this, which means the first yellow is not quite solid on my loud speaking tests. Once you get the input gain where you’d like, go to next mic, repeating until all gains set as needed.
Now with LR selected, go to your Processing page, far left button under screen. Select the FBA/GEQ tab near the top left on the touchscreen to access the FBA control, flagged yellow in attached image. First click Detection On button, pink on the FBA, in attached image it’s flagged in red. Select your choice of fixed or live filters.
Attached image for reference, I’m editing the width of filter and cut to shape how much feedback affects audio. This is under the Adjust tab on lower left side of FBA, flagged as green in my image. Width and Cut flagged blue.
Click width and your lower right edit encoder with yellow light can control the edit for these. Ditto for cut.
I follow-up with broad mid cuts, and high and low shelves in LR PEQ because my room feedback is pretty bad otherwise. My FOH is just mainly sound reinforcement of spoken and vocals. Still waiting on room treatment to remedy better than just FBA, but this is where we’re at now, so like a good sound engineer, suck it up and deal with it.
Bonus: I start my Qu-5 then Go with a Scene that’s my preconfigured Start setup, then immediately go into LR select, access FBA and click Detection On. I believe I have built a FBA preset accessible in my library that I’ll load after start-up.
The first step to addressing feedback problems is to look at mic choice, (particularly frequency response and polar pattern in cheaper mics) then mic placement, and monitor and main PA placement. Only then should it be necessary look at gain structure. Using a “feedback eliminator” is the absolute last resort as you’re handing over the eq of your overall signal to a device that cannot distinguish feedback from an intentionally sustained note!
In my experience feedback problems are frequently due to cheap mics with over emphasized “presence peaks’. Cheap monitors with piezo horn tweeters and no crossover, and monitors poorly positioned to feed (either directly or via reflection) into vocal mics. S www.redtapemusic.net
My current big issue is the room is too “live”. I need 2 things 1 acoustic treatment, and 2 edit the angle my flown speakers are tilted downward.
Overly live rooms are most likely to impair clarity and lyric intelligibility rather than cause feedback. However some PA operators are tempted to increase SPL as a result, which of course compounds the problem.
The best way to reduce the level of reflected vs direct sound, and hence improve clarity in an over live room, is to get your main PA speakers as close to your audience as possible. Acoustic treatment will obviously also help. If budgets are tight then Rockwool based panels are very easy and cheap to build. S www.redtapemusic.net
I’m not one of those operators. I may be a Church volunteer, but I am still a pro at my job. And my speakers are 10 feet away from the front row, almost straight up. Because of my room design that is where they are.
I have my pastor involved, and until he approves upgrades, this is where I am.
I’ll agree rockwool self built panels is an option. We’ve yet to do it. I myself can’t physically do them as I’m disabled.
My RT-60 time creates a slapback so yes mine does affect feedback.
I don’t understand how a slapback echo can produce true feedback ?
You don’t say what your RT60 time is for the room as a whole, but it sounds like it includes a discreet repeat, presumably from the back wall?
If there’s any delay in the system you will certainly get regenerated repeats but not the true “howl round” that is generally regarded as “feedback” in PA terms?
A “Feedback eliminator” will obviously not be able to do anything to address excessive reverb or slapback echoes as these are time domain issues.
Using a very small delay in the main PA was, many years ago, used as a way to increase the threshold of feedback, as it means the mic and PA are no longer in phase at most frequencies.
Incidentally, have you tried switching the polarity of any mics that seems particularly prone to feeding back ?
OK maybe it might not be a true slapback delay, however my audio from the speakers bounces off the back wall of the Sanctuary, then again bounces off the front wall and into the waiting mic to, yep amplify and do it over. Feedback loop. How’s that?
And only one actual FX out of the Qu-5 is routed to LR FOH. FX rack 6 with the 4 band dynamic EQ is inserted to LR 2 Bus. My intent here to cut dynamically 4 distinct frequency bands. With or without that FX, FBA is helping for now.
Our Sanctuary dimensions about 15’ tall cathedral ceiling, 30’ wide, 60’ long. And an RT-60 room reverb if 3.88 seconds. I am not amplifying it a lot, just a small amount.
Regardless, there’s my situation. And for now, we’re running FBA. It’s very much a band-aid, and I know it, but we’ll get by for a bit longer.
Nobody needs to worry, a poorly mixed album isn’t about to be sold from us. We’re not in the entertainment biz. We’re just here to worship God, and try to get those that can’t just well, do so a bit better.
Thank you and good evening all. Hopefully happy mixing to each.
PS all mics regardless of polarity will feedback, some worse than others based on channel gain then fader position. It doesn’t take a lot of amplification/sound reinforcement to get it to have certain hotter frequencies feedback.
“OK maybe it might not be a true slapback delay, however my audio from the speakers bounces off the back wall of the Sanctuary, then again bounces off the front wall and into the waiting mic to, yep amplify and do it over. Feedback loop. How’s that?”
From your measurements that’s a distance of at least 120 feet., giving a delay of over 100ms before the sound returns to the microphone. 100ms is definitely “slap back echo” territory!
The amount of delay created by that audio path means it’s almost certainly not the source of any “howlround” feedback problem. It will be causing intelligibility problems, but probably not the “howlround” feedback FBA deals with.
In very reverberant spaces that cannot easily be treated , like the large churches I install PAs in in the UK, the most effective solution is to install multiple small speakers along the church very close to the listeners ears, and use this to distribute sound evenly around the space, rather than just two sources at the front of the church. S www.redtapemusic.net
Yep understood about the side speaker aspect. However, here I must deal with the looks factor that won’t pass, and then again cost for speakers and amps. Then the cabling that’s not in place. It’ll be easier to wait on acoustic treatment in my case.
Money no object? I’d find a lot to do over and swap better hardware. But this is my dealt hand, I’ve gotta play what I’ve got.
Had I lots of savings, I’d even buy this myself and redo my entire system, anchored by a new SQ5+, but yep again the money, it’s not here.
I think the point is that due to the physics involved with audio waves and the way their amplitude decreases as they spread out within a space, it is extremely rare for a PA system to feedback due to the reflections in the main audience area. The volume of the audio coming out of the PA speaker is many magnitudes louder than the volume of any audio being reflected back towards the stage. This means that your feedback is more than likely being caused by audio coming directly out of the speaker, not the indirect reflections caused by the room. Adding acoustic treatment cannot/will not reduce the chances of feedback due to any audio coming directly out of the PA speaker because that audio wave will never interact with an acoustic panel before reaching the mic.
Now that is a very generalized statement. If your PA is reflecting off a hard surface that is very close to the speaker, it is possible that a reflection is causing feedback. But I can guarantee your feedback is not being cause by audio reflecting off the back wall 40-60’ away (which means the audio is traveling 80-120’ before it gets back to the stage).
This is why RedTapeMusic is correct when they said
Acoustic treatment can/will help the intelligibility of a room, but it is unlikely going to affect the potential for feedback. Especially if that treatment is going on the main sanctuary walls. Treating the stage walls could help if you are using wedge monitors that are located very close to the wall and pointed directly at the stage walls when there is also a mic close by. But the potential for feedback could also be greatly reduced simply by repositioning either the monitor speaker and/or the microphone in those situations, as well as “ringing out” the monitor send properly.
It’s great info, and I’m not disputing it.
We do have 2 monitors on stands at the piano and organ, but the Monitor Mix is never unmuted because the players don’t actually want them, after initially requesting them.
It’s likely just a mad sound engineer theory that if I treat the room, and halving the room reverb RT-60 to 1.8 or so, feedback would be less likely.
So OK, I’ll just focus on acoustic treatment to make it sound better/intelligible. I may tune the LR 2 Bus parametric EQ a bit more to lower the hotter frequencies and diminish feedback potential. I’ve done it before with other mixers in my system in the past. FBA is still helpful for now, bandaid or otherwise.
I’m still going to treat the room and edit the speaker fly tilt. The speakers unfortunately ended up with very little downward tilt, so they do throw the audio at the back wall.
I didn’t have a dB reading, but we’re not pushing our system at all. My Crown XLi 1500 amp is dialed back.
I am the mad scientist after all.
Just to clarify, I’m not suggesting that acoustic treatment isn’t a good thing. You absolutely should try to treat the room in an effort to reduce the RT times and doing so will definitely improve the “intelligibility” of the PA system.
It’s a long shot, but it is possible that when your PA sounds clearer/cleaner, you will end up making mixing changes that do end up helping to reduce the chances of feedback. In that sense adding treatment might indirectly help reduce the chances of feedback. I say indirectly because you could achieve the same reduction in feedback occurrences by applying the same mix changes today without the treatment. It might just sound better with the treatment.
What I am trying to prevent is an expectation that adding treatment to the room is automatically going to reduce your chances of feedback. That generally won’t happen and if you “sold” the purpose of the treatment as such, people will likely be disappointed in the results after treatment.
Maybe I’m not saying it well enough, but I think we’re on the same page Brian.
I’ll blame my medical condition for not allowing me to articulate at my best.
Happy Thursday. While y’all are out about today, stop to get a nice big coffee.
Thankyou Brian-1, you explained that much more concisely than I did!
This is a bit of a wildcard suggestion, but I have been asked to help with two churches that were struggling with feedback and on both occasions they were live streaming services alongside the in church PA.
Both systems had omni mics installed amongst the congregation to ensure their singing was audible in the stream. In both churches these mics had inadvertently been added to the PA mix, and would, of course, provoke feedback as soon as the main PA faders were raised. It’s a long shot, but worth checking if you have such mics in the system? S www.redtapemusic.net
FWIW all my mics are cardioid, except my pulpit mic. That one is multi-pattern.
Pulpit Lewitt LCT 441 FLEX on cardioid
Yamaha baby Grand piano mic Lewitt LCT 440 Pure
2 Shure BLX PG58 handheld wireless dynamic cardioid
2 Shure BLX SM58 handheld wireless dynamic cardioid
1 Audio Technica older 3000 series wireless lavaliere cardioid
1 Sennheiser wireless handheld condenser XSW
2-e865
2 Audio Technica hanging choir cardioid condenser as room mics for Livestream Aux Mix only
Output: Sanctuary Peavey SSE12s just in front of pulpit flying about 12’ up, centered then both angled somewhat LR and slight downward tilt
Amplifier Crown XLi 1500 2 channel gain knobs on about the 10 o’clock position
I’d like to mic the piano with magnetic mount gooseneck set, replace all the Shure BLX with more Sennheiser like that e865.
If I were hunting for the most likely source of feedback, my first check would be to make sure the Audio Technica hanging condensers were not finding their way into any of the speakers in the church, both PA and monitors. As you mention the Shure PG58 capsule is an “entry level” capsule, so not the highest quality. You also have a lot of wireless mics, so I’m guessing mic positioning can be very variable? That must make avoiding feedback a bit of a challenge. I would certainly also be aiming to mute any mic that was not in active use in the service.
Do you know which source is the most prone to feeding back? Is it one of the Lewitt large condenser mics (the pulpit or grand piano mic)? Given how close the PA is to the pulpit, a large diaphragm condenser mic wouldn’t be my first choice and it is certainly more prone to feedback than other microphones might be.
Also, given that your PA is so close and right above the pulpit, I would be worried that angeling the speakers farther down would exasperate the feedback problem, not reduce it. Although the specs on those speakers say they only have a 40 degree vertical coverage, so perhaps there is some wiggle room there. But you need to be mindful of that limited vertical coverage area as you make adjustments to ensure the maximum number of people are covered by the speaker.
I’d love swapping out those entry level Shure’s. Made certain, the hanging mics are never turned up in the sanctuary LR 2 Bus.
