Strange feedback from vocal mics on floor tom

AxisDrummer

Senior Member
Never had this one happen before but with all the experience here at DW, I'm sure it's happened somewhere to someone.

Just changed out all my drum heads on my toms (Clear Emp over Clear Amb). I don't want to brag because I'm not a great natural tuner, so I had to bleed and sweat to get this. But I think I have all my toms sounding better than ever (ditched the Pinstripe batters for Emps).

Toms and all drums are un-mic'd at practice. Kick gets mic'd for shows at small bars. Every time I hit my 14x12 Floor last night, a really loooong 10 second low-pitched feedback came from the vocal mic on the same side. Sounded kind of creepy but cool, like a ghostly "WOOOOOO". Our vocal mics are the standard SM58 and the culprit is about 6 feet away from said floor tom. I also have a 16x14 Floor and no feedback came from that one.

Now this was for practice in a finished carpeted basement. Hopefully this won't happen live, but I'll find out next Friday.

I don't want to change MY tuning...it sounds great! But if I had to re-tune, I'm assuming I need to do it with the batter. This didn't happen with the Pinstripes because it was more of a dead THUD than some nice singing resonance which I have now.

Help?
 

Stroman

Platinum Member
I think you'll find that type of feedback is very room and location specific. If it does happen live and your sound person can't get rid of it via EQ or mic location, you may have to retune, I suppose.

You have a monitor? Or is the feedback happening because the mic is picking up the mains?
 

AxisDrummer

Senior Member
I think you'll find that type of feedback is very room and location specific. If it does happen live and your sound person can't get rid of it via EQ or mic location, you may have to retune, I suppose.

You have a monitor? Or is the feedback happening because the mic is picking up the mains?
I'm leaning towards and hoping this won't happen live in a much larger venue than my basement.

I don't use a drum monitor for practice. We use 2 floor monitors in the typical fashion in back of the vocal mic line and that's it. The only thing coming through the monitors for practice is vocals.....and now a floor tom!
 

ShadoWReX

Member
Can you put a gate across the 58 channel? Had a similar problem with an SVT Bass Cabinet (BIG & LOUD BASS!!!) causing an acoustic guitar (which was DI'd into the board) to produce a weird feed-back, similar to what you mentioned. The board had a gate on every channel and after putting it across the acoustic guitar channel -resolved the problem. External Gates are relatively cheap -I picked up a 4 channel gate for under $100 a few years back on EBay.
Another option -altho expensive, is a feed-back suppression unit. We used one a couple of times with amazing response. The last option would be to mess with the EQ -thereby changing the sound.
IDDRummer is right! Rooms make a BIG difference and this might be (here comes a pun) a mute point... when playing at your venue!!
Good Luck!!
 

TColumbia37

Silver Member
I would guess that it has something to do with a combination of the room, and your tuning. Some rooms have different frequency response from others, so you can expect unusual sounds in different places. I often have to change the EQ on my guitar rig, depending on the room I'm playing in. If you don't want to retune, maybe put a little dampening on that head, or get some sound foam for the room? That should help to absorb some of that extra low end resonance, which I assume is what you're hearing.

EDIT: Bo makes good points. Try that before anything else, so you don't end up spending extra time and money when there's a good chance you won't need to.
 
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Bo Eder

Platinum Member
You don't need any extra gear. Usually the culprit when you get feedback is going to be low frequencies. You hit the floor tom, and the frequencies hit the vocal mic, and with the mic EQ'd the way it is, it's most likely boosting too many low frequencies. Low frequencies travel outwards like when you throw a rock into a pond, so those frequencies stand a good chance of getting back to the microphone as well, this is what causes the feedback loop.

Whenever I mix a band, sometimes I know beforehand what needs to get cut, so I usually shave off the low end on most of the microphones to begin with, and this usually gives me a feedback-free evening right there. Try that.

If you'd like to test my theory you can do this (I usually do this with floor monitors, but if you don't have those, the theory still should apply):

When you power-up your system, put all your EQ's in the flat position, turn all the mic gains down, put the master EQ at zero, and run your master output to zero. Then, leaving your mics where they are, turn up the gain on each until you hear a little bit of ring in the system. When you hear the ring, at the mic channel, pull you low frequency eq knob down until the ring goes away. Do this for every channel that has a mic. Then when you're done, bring up each mic to zero, and you won't have anything feeding back.

Usually when I do this I'd have a notch-eq where I can select the offending frequency even better, but this'll do in a pinch.

In general if you want a nice clean sound out of your system, pull your low EQ down some and boost the hi EQ just a touch. Alot of people do the opposite, or have too much low-end in the system and it just sounds like mud to the audience. You definitely don't need to boost your low end because the speaker cabinets themselves are boosting the low end that's there, and that can cause even more feedback. Good luck!
 

Aeolian

Platinum Member
Yep, the professional soundman has it. About the only things that should have any low frequency in them are the kick and the bass. Occasionally keyboards if it's important to the arrangements. Most entry mixers have a LF filter button. That either rolls off between 80-100Hz. This should be engaged on just about everything. That big booming FM DJ voice while doing individual mic checks just turns to mud when everything is going.

If you have a more sophisticated system, you may be able to change where the LF roll off point is and/or use the LF EQ to notch out a frequency that is resonating. But for the most part, it's just punch the 100 buttons, and turn down the bass a bit.

Gates are handy where you have a loud drum monitor stack that is causing an undamped kick to resonate, or where the room is really boomy and just a bit of short thump from the kick sounds like a wide open 26" in the room.
 
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