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Feedback Issues-please help

I'm hoping someone can help me or point me in the right direction here. I play in an acoustic duo with the following setup:
Yamaha 2x400 watt powered mixer
2 fender wedge monitors(individual volume controls)
2 mics(not very good ones, they came with the system)
2-15 inch passive spekers. we play a taylor guitar(expression system) and a martin with both a bridge pickup and an internal mic. these are run through the PA.
I'm experiencing a lot of problems with feedback from, I bel;ieve, both the martin guitar and the monitors with relation to mics. I dont really know too much about setting my powered mixer for optmal sound. We play in small clubs with tiny stages and cant really move our speakers(FOH) far away from us. I read somewhere that the monitors should always be placed in front of the mics(which I have never done)and that the output levels for individual channels should be just below peak(o level). And then Eq applied. I always seem to get feedback if too much volume(over 30 percent say) is used on both Main and Monitor. Any ideas?


moonbaby Mon, 11/20/2006 - 08:04
To really get a handle on feedback, it is imperative that you use the best vocal mics you can afford. This means that you should be using a good, solid Shure SM58 for vocals (yes, there are others, but at $100-a-pop, these are the cheapest decent mics for live sound on the market). Then you have to learn the proper placement of these mics in relationship to the monitor wedges and the house speakers.
For starters, in terms of placement, start off with the monitors. Set up your mics with the layout you use for staging a show. Each person's monitor should be pointed at the "back end" of the 58, like a flashlight poiting up at the performer's face..OK ? This is because the "null" spot (the least senstive spot on the mic) is at the rear of it's "ball". DO NOT "fly" the monitors !! I have seen many coffeehouses put stage monitors up in the air over the stage to reserve floor space...NO! ALWAYS fire the sound UP at the performer's heads ! Now there are some mics ("hypercardioid") that are less sensitive at the sides of the mic, not the rear. When that's the case, you would "fire" the sound at the .....SIDE of the mic, like it would be a flashlight aimed at the performers' ears...Dig?
OK, so you need to get decent vocal mics, not some POC they throw in to make it a "value". Cheap Chinese-made junk mics SUCK for sound and are notoriously bad for feedback. BTW, the Shure SM58 is a "cardioid" mic ("null" at the rear of the ball), their Beta Series is "hypercardioid" ("null spot " at the sides).
You also must learn to use the graphic EQ properly so as not to aggravate the feedback issues. For starters, set the sliders at the "O" point (no cutting or boosting). Pull the lowest band down (that is the region where the only sound is rumble and noise). As you raise the masters on the system, you can CAREFULLY and slowly "ring out" the offending bands on the EQ. This is an art in itself, but not rocket science. You need to learn how to relate the pitch of the feedback to the bands on your EQ. Then you start to lower the volume on the band closest to the feedback "node". The closer the mic to the speaker, the higher the pitch of the feedback (usually). Do NOT boost ANY of the bands on the EQ, and also be sure that you are not cranking up the channel EQs, as well ("zero" those out, no cut or boost). And finally I've seen bands that place their house system behind them (!) because they are used to hearing all of the system during rehearsals. NO! Use a bit of common sense here. You want to keep as much sound from entering the "hot spots" of the mics as possible. This means putting the house speakers in FRONT of the band...I realize that's elementary, but I've seen all sorts of dopey rigs and, well, ya never know...