Timely thread for me. I had this exact experience last night. We played an outdoor venue that isn’t really problematic with feedback but I still like to ring out the frequencies most likely to feed back, especially on the monitors. Setup time ended up being rushed and I didn’t have a chance to use the FBA to find and notch out the potentially problematic frequencies.
I did manage a quick soundcheck and everything sounded fine…until we started playing. Halfway through the first song the crowd started complaining that they couldn’t hear the lead singer. I’m the guitar player and mix from stage so I did the best I could to turn the other instruments down and bump the lead vox up a bit. Worked OK, then after another song or two, crowd complaining again. I almost maxed the fader on the lead vox and the crowd said they could hear it again.
My turn to sing a song… crowd said they couldn’t hear me. I sang louder but all that did was create feedback. Had to finish the set this way.
After we finished that set I started going through all the mixer settings and discovered that at some point I had left the FBA enabled with no filters initially set and Hold disabled on all output channels and what they ended up doing was completely, and I mean completely scooping out everything from about 100hz to about 3kHz. By the end of the first set I had the vocal faders almost maxed and the master out at about +5db. No wonder I was getting high pitched feedback. I had the levels cranked and the only frequencies that weren’t cut were the higher ones.
Anyway, lesson learned. I disabled FBA on all the channels, brought the levels back down to normal, and everything was smooth sailing after that.
Major lesson learned. Always check the FBA before starting.
That said, I do find it very useful when I use it correctly. We are a loud band with a singer that has a soft voice so feedback is a problem at a lot of indoor venues. When used as intended, to ring out a room, it works great. I will typically set between 8 and 12 fixed filters then set it to Live.
But yes, if used incorrectly, it can destroy a mix. In my case it was 100% user error.
One of the reasons I bought this particular mixer is because it has the FBA built in. It has allowed me to retire my trusty dBx AFS2 I had been using for this purpose with another mixer. I don’t think I would have bought this mixer if it didn’t have this feature.
Yep, @Guitarman, that’s how it was on the second gig I used the CQ18T for. People kept asking me to turn it up because they couldn’t hear the singer from the back of the room. (It was a piano, guitar, and singer). Since I was new to the CQ, I didn’t know what was going on. I’m pretty sure, though, that I had not hit HOLD on the FBA.
Since then, I’ve used the CQ18T for many performances for an a cappella chorus with quartets. The quartets sing all the way up at the front of the stage with two pencil condenser mics in an X-Y configuration to pickup the whole width of the quartet. Often, those mics are either level with the FOH speakers or even in front of them. Without notching out the feedback frequencies in that situation, you can’t get those mics up loud enough to effectively reinforce the quartet singing into them.
This is where I find a feedback eliminator so useful. I used to use a QSC TouchMix8 and its feedback eliminator worked great. But you could only use it pre-show because you had to explicitly turn it on to start finding the feedback frequencies (it would automatically slowly increase the main outs fader to induce the feedback), but after that, it wouldn’t listen for feedback anymore. That’s really the only way I think this is useful. Instead of ringing out the system with a 31-band GEQ, which forces you to pull down a whole lot of frequencies around those that are giving feedback, the FBA allows you to just notch out those frequencies. But you have to turn it off (put it on HOLD) once you’ve notched them out so that it doesn’t keep pulling down and widening the notches throughout the performance.
That said, it’s easy to not realize that the FBA is not on hold, especially when you’re frantically getting everything setup with hardly any time because the venue didn’t let you in early enough. It would be great if the programmers of this algorithm gave us an update in a future firmware version that has some safeguards to not allow the notches to go too low or to have their Q set too wide—that is, keep them as just narrow notches, since that’s the whole purpose and advantage of a feedback eliminator over a GEQ.
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FML! I did it again. Outdoor gig so no real need for the FBA. I thought I reset all of them and then disabled them but apparently I did not. Halfway through the first song I realized something was very wrong. As soon as the song ended I want straight to the FBAs and found that all of them had Hold off and they were set to Fixed. They scooped out pretty much everything.
My first instinct is to blame user error …again… but could something strange be going on here? I have another gig Sunday so I’ll pay even more close attention to the FBA and see what happens.
Good luck with the gig. Please share an update on how it went!
Well, the FBA part of it worked great once I got my head out of my hind end. This time I pulled another good one.
Yesterday during soundcheck I was EQing the kick drum and when I would turn it up I would get a ton of feedback between 70hz and 75hz. I had to apply a pretty drastic cut using the kick drum channel’s parametric EQ. Even with the cuts I wasn’t able to turn it up to where I wanted it. I was pulling out my one remaining hair trying to figure out WTF was going on.
Eventually I realized that I pulled another genius move.
The way I dial in the FBA is I apply a heavy compressor to the output I’m using the FBA on. This has the effect of causing feedback pretty quickly while also preventing runaway feedback. It lets me dial in the FBA pretty quickly and without annoying the patrons too much.
What happened was when I powered on the mixer, the first thing I did was to apply this compressor to the main and monitor outputs to get ready to dial in the FBA. But like an idiot, before I dialed in the FBA I decided to work on the EQ for the kick drum. Stupid me forgot to disable the heavy compressor on the FOH outs so naturally, turning up the kick just a little would cause that massive feedback.
Once I disabled the compressor everything worked fine.
So basically, everything that hasn’t worked fine so far has been user error on my end. This is my first fully digital mixer so I guess I need more time to get used to all the menus and screens since it’s not easy to see a full birds-eye view like I could with an analog layout.
I hadn’t needed to use FBA until last weeks gig, there was a house mixer (X-Air 18) and I always bring the CQ20B because we use in-ears anyway, so I hooked up the mains to 2 channels on the X-Air and got a ton of low end feedback, I don’t think I could have done anything on the CQ side, as I applied a very agressive high pass filter and was still getting feedback, I didn’t learn how to use FBA until yesterday. I suspect the in-house mixer had a very pronounced low end boost somewhere in the chain, judging from the sound of recorded music, it’s a small rectangular cramped room and the “stage” is at the end of it.
Still, it got me studying FBA and now I think I will do the following:
1.- Connect everything, check gains on every channel, leave ONLY the vocal mics open.
2.- FBA ON and set to FIXED, disengage the HOLD function and slowly raise the mains volume until I get feedback, if there’s any.
3.- Let FBA do its thing, then engage the HOLD function, adjust to taste.
I have little experience with feedback because we monitor using in-ears, and all instruments go direct to FOH, no amps onstage. The only other time I’ve had feedback problems usually had to do with a mic having more gain than needed.
Is this approach reasonable?