Terrible squeal feedback through FRFR

[marmatkat]

Hi Folks. I played my second gig last night, and found my rig was producing a nasty squealing type of feedback on even moderate gain presets. The squeal was a microphone-type high frequency one that varied depending on the guitar's angle relative to my powered speaker. The presets were the same as my first gig, but the stage volume was higher and the venue was different. The upshot for the gig was that I had to forego the moderate gain presets, and it made my experience more stressful that necessary.

 

What I'd love to hear from you are ideas about: 1) what was causing the squeal, and 2) how I can eliminate it in the future. Following are the details. Thanks!

• Rig: P90 Hamer guitar, Helix LT, and a QSC K10 on a stand. The K10 settings were the same as before: XLR input from Helix, LF: EXT SUB, HF: FLAT, MIC/LINE IN A: LINE, GAIN A: +10dB (100%). The Helix output was around 11 or 12 o'clock (~50%).
• Stage setup: stage left to right (all with mics): Guitar 2, singer, Bass, me. Traditional amp backline, with the base of my K10 ~4' up.
• PA: Hotspot monitors close to each mic, mains in front of the band.
• Venue: Outdoor concrete deck, connected to a building, open on ~3 sides, with a wooden roof angled downward to the front.

Unfortunately the event had people out front during setup and teardown, so I didn't get to experiment much without irritating the audience. Also, I was nervous and wasn't at my best trying to debug. I played around with global EQ's high parametric setting, and its high cut, but without any luck (but it was my first try at the global EQ, so I didn't do a good job using it). I also tried raising and lowering the K10, angling it differently, and moving it around behind me.

 

My thoughts: I can think of two possible causes: The stage setup was bouncing high frequencies around, or/and the Hotspots were somehow feeding back. I didn't have the wherewithal to simply turn off all the monitors (time was tight, plus I'm embarrassed to say I wasn't thinking very straight).

 

What I'd try next time is tune in the global parametric EQ the way http://line6.com/support/user/1928801-digital-igloo/ suggests at http://line6.com/support/topic/18372-eq-setting-experiment/?p=136736 :

Everyone hears offending frequencies differently, but here's a fairly common trick:

• Add an EQ > Parametric block after the cab.
• Turn Page 2 > Knob 3 (High Gain) all the way up to +12.0dB. Things will sound horrible.
• Sweep Knob 1 (High Freq) up and down until things sound really horrible. You're now boosting the specific frequencies we're trying to remove.
• Press Knob 3 (Turn Gain) to return it to 0.0dB and then keep turning it lower until the offending frequencies begin to disappear.

Optional: Turn Knob 2 (High Q) down for a smoother cut; turn it up (to 5.0 ~ 8.0) for a more surgical notch that affects fewer adjacent frequencies.

I might download a spectrum analyzer for my phone to help pinpoint the nasty frequency.

 

I'm not ready to give up on the Helix - I really like it for the most part - but this shook me up. Thanks in advance!

[mdmayfield]

It's not too likely that this had to do with the Helix specifically - in my experience, this sounds like microphonic pickups in your guitar, in which case this would have happened with any guitar rig at the same volume and with a similar tone.

 

By microphonic I mean pickups that are not only picking up the strings' vibration magnetically (mostly lows and mids), but also airborne acoustic sound (including highs). That's what causes the annoying mic-like squeal instead of more musical guitar-ish feedback. Usually this is caused by loose coil windings in the pickup.

 

The increased stage volume compared to your first gig would explain why it happened only on the second gig. If you have a rehearsal place where you can turn up without annoying neighbors or having the police arrive, the problem should be pretty easy to reproduce.

[mikebruno]

Hey guys !

I have posted about the same problem exactly 2 weeks ago saying that j have bad squeals on solo patch.

Have had the P90 on that LP that night.

Do you have same problem with another gtr with regular humbuckers? You might not!

 

My thoughts was that I started to hate tweaters...

Cause you for get these feedbacks with regular Gtr cab..!

[rvroberts]

Unpotted single coil pickups are susceptible to microphonic feedback.  That's what that sounds like.  Even unpotted humbuckers do it - I had exactly that problem with Fender Shawbuckers (even with a traditional amp - Vox AC15 and high-ish gain).  So you have a batch of things you can do - first you need to know if the feedback is coming from your rig. If you are also in all the monitors, that might be contribution.

But this is why we all got our pickups wax potted in the old days and now everyone is going.....it's not like the old days and not potting the pickups - so you could get your pickups wax potted. Imperceptible loss of "airiness".  Obviously high frequencies don't help, so I did get significant improvement by cutting global EQ in the high end - which turns out to be good for guitar sounds in general anyhow - 5K and above cut drastically.  But I had to actually change pickups to get good solid reliable performance - so much for true vintage pickups!

Speaker placement can help too - but it sounds like you have tried that.  I use my boxes as monitors facing me - but I'm not going to claim that will solve your problem.

Like someone else said, try some modern humbuckers - if that fixes it - get your pups wax potted.

[CraigGT]

When we've had weirdness like that it has always come down to induction loop hearing aid systems but considering that yours was an outdoor show that's probably not the cause. It confuses the hell out of our guitarist though!

 

Craig

[marmatkat]

Thanks very much for the replies. My comments:

 

An update: I set up my rig on my back deck outside yesterday, and was not able to reproduce the feedback at the same volume, etc. as the gig. Also, I talked to our sound guy (our other guitarist) who remembers turning off the hotspot monitors to do the test, which had no impact - I still got the feedback.

 

Pickups: I bought the guitar used, and the seller said that the pickups are Lollers, which are supposed to be potted. However, I have not taken the pickups out to verify any of this. As far as trying humbuckers, I'd be surprised if that didn't fix the problem, but I don't have two guitars. Plus, I like the sound of mine - unless I'm getting this horrible feedback regularly in the future.

 

I guess I next steps will be to: try it in the practice space, which has a concrete floor, as does our next gig in three weeks. In the meantime, I'll download the spectrum analyzer, get used to it, and play with the parametric equalizer.

[shanecgriffo]

i'd say, start saving! it's always good to have a back up guitar for a gig 😉

[yoMuzicMan]

Not sure if this is your issue, but I was on a very small stage once where I had to stand right next to one of the main speakers.  I was probably only 3 feet away, but I was behind it.  As soon as I stood next to the main speaker, the loud mic type feedback was there.  If I moved away a couple more feet, it was gone completely. 

[marmatkat]

That's interesting. I was also on a small stage, within touching distance of one of the PA cabinets, which is about shoulder height. I was half blocked from the audience by it, and my powered speaker was always pointed toward that PA speaker's back.

 

I didn't think to change places with the bass player next to me. (Whose bass was resonating loud as hell.)

 

Thanks foe sharing!

 

Not sure if this is your issue, but I was on a very small stage once where I had to stand right next to one of the main speakers.  I was probably only 3 feet away, but I was behind it.  As soon as I stood next to the main speaker, the loud mic type feedback was there.  If I moved away a couple more feet, it was gone completely.

 

[CraigGT]

Not sure if this is your issue, but I was on a very small stage once where I had to stand right next to one of the main speakers. I was probably only 3 feet away, but I was behind it. As soon as I stood next to the main speaker, the loud mic type feedback was there. If I moved away a couple more feet, it was gone completely.

With my science head on, that could be your pickups inductively coupling with the PA speaker magnets.

 

Craig

[marmatkat]

Thanks, Craig. That's one thing I did not try - moving away from the PA speaker. Good to know for next time it happens.

 

 

With my science head on, that could be your pickups inductively coupling with the PA speaker magnets.

Craig

[marmatkat]

Had a gig on Saturday, with no feedback. I had my K10 about 10' behind me, and the PA cab about the same distance as before, but there was a metal shed wall between it and me. (Our stage was just inside the door of a large garage/barn, with the PA out front!) I'll just keep playing and see if it happens again.