Reverb bass through pa why?

fatsobasso · #1 08-07-2010, 01:10 PM

So i am getting some weird reverb like effect(low freq feedback)
Coming from the pa, only when the bass drum mic is turned on, it's a cheap bass drum mic, certain notes like b flats, just turns into a huge reverb like sound, bass note with no definition?

lunarpollen · #2 08-07-2010, 01:15 PM

Is the bass drum mike perhaps in front of a big hollow resonant thing like a bass drum? Or are you just using it to mike your cabinet?

fatsobasso · #3 08-07-2010, 01:17 PM

no mic on my bass, just bass direct into mixer and my amp, and the bass drum mic is just in front of the bass drum.

A440Hz · #4 08-07-2010, 01:52 PM

Resonance from the bass drum, perhaps? Is the drum damped at all (usually, a pillow is used)? The Bb just might be one of the resonant frequencies. BTW, just in case this is useful info, 60Hz is roughly equal to a Bb, so it's theoretically possible there's some sort of weird hum problem.

Also check the PA itself for feedback. Try to see if you can make it better or worse with EQ on the bass mic channel.

You might also just have some resonance with the mic itself. You said it was cheap. If you can borrow something like an AKG D112 or Shure Beta 52, see if the problem goes away. This might be the kind of problem that is solved by throwing money at it. Just don't tell the government that that works sometimes.

fingertap · #5 08-07-2010, 02:21 PM

Hollow, resonant stage floor, perhaps?

What happens when you stamp your foot hard between your rig and the offending drumb mike?

I had this problem on a flatbed truck stage. The floor itself rang out loudly whenever I got close to B. (C or B-flat) Solved the problem with a cabinet move and car floormats under the mikes.

All of the mikes were picking up the stage floor resonance but the bass mike was the worst. Set it on carpet or place it inside the drumb if possible.

~

fatsobasso · #6 08-07-2010, 03:38 PM

nah there was no stage, something with the 60 hz i think, but it sucks, and it is a crappy bass drum mic.

fatsobasso · #7 08-07-2010, 06:11 PM

I guess you can best describe in as a welling drone sound on certain notes like b flat.

projectMalamute · #8 08-07-2010, 06:51 PM

Quote:

Originally Posted by lunarpollen

Is the bass drum mike perhaps in front of a big hollow resonant thing like a bass drum?

.

derrico1 · #9 08-07-2010, 07:26 PM

Quote:

Originally Posted by fatsobasso

I guess you can best describe in as a welling drone sound on certain notes like b flat.

Posts 2, 4, & 8 get it, but I'm not sure if you've picked up. Sounds like your stage amp is producing sympathetic resonance in the kick drum (or possibly a floor tom) at certain frequencies.

fatsobasso · #10 08-08-2010, 07:09 AM

still happens with my amp volume off and just the direct line to pa, yeah i understand about the mic in front of kick.

derrico1 · #11 08-08-2010, 08:49 AM

Even with your stage amp off, the bass guitar/drum interaction can still happen via the stage monitors or FOH spill (esp. from the subs).

No way of knowing w/o being there to troubleshoot, but first step for me would still be to put a blanket or small pillow in the kick, lightly touching the beater head.

TimmyP · #12 08-08-2010, 11:50 PM

Most kicks are tuned too high and are under-damped (too ringy).

Tune the heads as low as they will go without the hardware rattling because its loose.

Dampen the heads so that when you tap them with your ear close to them, it sounds like you want the drum to sound through the PA.

If these don't fix it, insert a gate on the kick channel.

derrico1 · #13 08-09-2010, 06:02 AM

One last thing: because resonance problems can also happen with the floor tom(s), you might check if muting the kick drum channel immediately stops all the low-end ringing in the PA or just part of it. If floor toms are the culprit, taping or tuning the bottom heads will usually address the ringing.

fatsobasso · #14 08-09-2010, 11:27 AM

ty guys i will try some of the mentioned things.

jaywa · #15 08-09-2010, 01:55 PM

You may be able to notch the offending frequncy out with EQ and/or noise gates, but as with so many things sound-related, the electronic fix should be your last resort. Try the measures others have suggested first to address the resonance, and hopefully you can stop the problem at the source. Just be aware that some drummers don't take very kindly to having a lot of stuff taped to their drum heads or having their tuning adjusted.

derrico1 · #16 08-09-2010, 02:32 PM

If what you've been hearing turns out to be drum resonance, the root problem is likely stage volume and/or FOH spill.

In all but the most extreme cases, you can address the symptom by tweaking the drums.

The ultimate fix, though, is to lower SPLs on stage--at least at the drummer's position. This might be as simple as turning down a drummer's over-cranked monitor wedges, or it might involve getting the whole band to bring stage levels down.

If the problem is FOH spill onto the stage, good luck. If it's a place you play regularly, you might persuade the house engineer to rethink how the PA is laid out and run, but that requires a pretty delicate campaign.

KeithAlanK · #17 08-09-2010, 10:17 PM

It's plain old feedback.
Use a gate on the kick.
I use gates on ALL drums.