Controling Low Freq Feedback

Started by Dotneck, September 01, 2010, 06:49:10 AM

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After all these years of playing guitar I am just now starting to amplify a flat top. I'm getting more opportunities to play with a group at church functions...so I bought a used iMix from Hogtop and had it installed in my rosewood Gibson J-185 a couple weeks ago.

Been having fun trying the new sound. Of course, I made the mistake of picking up the guitar on a Saturday and playing an event on Sunday before being completely familiar with the new rig. Ended up feeding back and couldn't figure out where it was coming from on the fly. Rolled over the to the UST side and was okay...at first I thought I was just dealing with the boomy nature of a rosewood jumbo.

Now I realize the feedback comes from playing the B on the fifth string. Which is used pretty often in the G, E, Em chords etc....

How do you tame this feedback? Will a different guitar react differently?

Larrivee 00-70 
Gibson Advanced Jumbo  - J-185 - J200 Jr.
 National Resophonics  M1 Tricone
 Eastman MD-904 - DGM-1

If you have isolated the problem to a particular note you are half way there. Some gentle EQ notching at that frequency should eliminate the problem.
Ron


As Ron says, that's what the notch thingy is for. Find it, notch it and dial it out.

Quote from: ducktrapper on September 01, 2010, 09:09:28 AM
As Ron says, that's what the notch thingy is for. Find it, notch it and dial it out.

yes, I understand that. I don't have a notch thingy. First time we played I was plugged directly into a mixer that a two band EQ (high and low). My amp has a sweepable mid control...and I can make the feedback better....but I can't get rid of it. I don't think the sweepable mid is narrow enough to qualify as a notch filter....

So I guess, as I think as I write, this leads to outboard EQ? I'm familiar with rack mounted EQs...I hope I don't have to get into building a rack of gear to play anacoustic guitar!
Larrivee 00-70 
Gibson Advanced Jumbo  - J-185 - J200 Jr.
 National Resophonics  M1 Tricone
 Eastman MD-904 - DGM-1

I think that 5 and 7 band eq pedals are still available.Smaller and cheaper then a rackmount.
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Quote from: Dotneck on September 01, 2010, 09:48:15 AM
yes, I understand that. I don't have a notch thingy. First time we played I was plugged directly into a mixer that a two band EQ (high and low). My amp has a sweepable mid control...and I can make the feedback better....but I can't get rid of it. I don't think the sweepable mid is narrow enough to qualify as a notch filter....

So I guess, as I think as I write, this leads to outboard EQ? I'm familiar with rack mounted EQs...I hope I don't have to get into building a rack of gear to play anacoustic guitar!

My mistake, I was thinking you had the built in electronics. In that case, with a passive system, I use my Boss GE-7 which does an even better job. In most cases, midrange can be dialed out almost completely.   

So, you have a dual pickup system AST/UST, playing thru an amp and then on to the house PA, yes?
Are you on a stage, possibly a raised wooden floored construction which is hollow below?
If so, then try isolating the amplifier from the floor using something that will dampen out the low frequencies to prevent them being transmitted into the stage floor by the amp. ie, acoustically decouple it from the floor.
I have had this prob a couple of times. Previously i have dialed it out using the eq on the amp, but that leaves you with a tone lacking in bass. Last week, i was on a particularly 'lively' stage, and we had the idea of raising the amp off the floor using the sound engineers cable case. I could feel the reduction in vibration thru the stage immediately and it cured the prob. I was even able to dial in about 2-3 db extra at 70Hz to give more punch as the evening progressed with out any feedback.
mel

Place the amp behind and to the left of you off the floor (chairs do well), then if you still have the problem roll off some of the mid range, or, get a lutehole /feedback buster. I have a simple K&K with their XLR preamp and hardly ever have to touch it, if I do it's for G# and barely takes a touch on the mids and bass to kill it. On my full PA I have a cheapo Behringer 2496 feedback destroyer that handles the whole hall pretty darn well.
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