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Strange Frequency

Bobby Bass

Bobby Bass

Nov 5, 2001
370
292
77
Green Acres, Burlington, North Carolina USA
#1
The other night I had a strange sound on Bass. It seems every Bb I hit on my bass triggered a roar that I just couldn't get rid of. I don't know if it was setting off a frequency in the PA system or what was going on. Any suggestions would be appreciated. I changed amp settings, moved the amp off the floor, turned it different directions, nothing helped. I wasn't miked & not direct into PA.
 
#3
Lots of things could have been done, but difficult to say without more info.

did the sound tech shut off the PA system and monitors completely? If yes, then there is no other explanation than stage/room acoustics, and you would need to adjust your bass rig - or move it to a different location (side fill off the stage) - to try to minimize the impact of this phenomena. Of course, you wouldn't be the only instrument in the room that would cause the acoustic excitement of just this one note (though the most likely), and even with no PA going, the band playing at full stage level would have been a mess if in fact it was an inherent room EQ problem.

I would look first to the drums, especially if they were being mic'd through the PA system (all drums) and especially if any drums were pumped through a drum monitor. This happens sometimes when the drums are "hard gated", and if the bass stage volume causes a drum head to ring, it will open the gate and keep it open as long as the note continues to sustain, due to the drum itself being tuned to (or near) the offending note. Muting the drums (in the monitors and FOH) would have revealed this if it were happening. A competent sound tech should have been able to navigate around this issue with some success, although it can be a dreadful situation for everyone when it happens. It may have also helped to minimize stage volume by running a DI feed to the FOH system, especially if stage acoustics were the culprit. You said you didn't do this, but IMHO it would have been worth a try.

JMHO...YMMV
 
#4
jimfist said:
Lots of things could have been done, but difficult to say without more info.

did the sound tech shut off the PA system and monitors completely? If yes, then there is no other explanation than stage/room acoustics, and you would need to adjust your bass rig - or move it to a different location (side fill off the stage) - to try to minimize the impact of this phenomena. Of course, you wouldn't be the only instrument in the room that would cause the acoustic excitement of just this one note (though the most likely), and even with no PA going, the band playing at full stage level would have been a mess if in fact it was an inherent room EQ problem.

I would look first to the drums, especially if they were being mic'd through the PA system (all drums) and especially if any drums were pumped through a drum monitor. This happens sometimes when the drums are "hard gated", and if the bass stage volume causes a drum head to ring, it will open the gate and keep it open as long as the note continues to sustain, due to the drum itself being tuned to (or near) the offending note. Muting the drums (in the monitors and FOH) would have revealed this if it were happening. A competent sound tech should have been able to navigate around this issue with some success, although it can be a dreadful situation for everyone when it happens. It may have also helped to minimize stage volume by running a DI feed to the FOH system, especially if stage acoustics were the culprit. You said you didn't do this, but IMHO it would have been worth a try.

JMHO...YMMV
Click to expand...
Only thing in PA & monitors was vocals. All Bb's on the neck was causing it. I got dirty looks for the singer all night. Played there before without any problems. I'm thinking it was being picked up in mikes almost like a low end feedback & rattling the drums. I go back there in July & try again.
 
#5
Have the band tune a quarter step flat or sharp to avoid the note. (not sure if I'm kidding about this.)

The PA should have had the offending frequency notched out of the main speakers and monitors, then. If it still persisted, then you can only address this by tuning your stage amp and trying different positions to locate it in an attempt to mitigate the problem. How loud are you on stage, how big is the room and audience? Do you have a parametric EQ at your disposal, so you could apply a deep notch filter cut to the frequency?
 
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#7
A room I play a lot has a resonance at G - I use a small rig, and experimented with where it was pointing- we a play in the same config all the time so I can't just swap places.. I found the best direction for it and cut some low mids from my amp. The went to my channel in the pa and dialed G down a lot. Same with the G on the acoustic Guitar. That helped a ton.
 
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#9
Funny. The room I used to do FOH in most often resonates art Bb - very, very badly. The band used to to a ton of songs in that key, and I'd grit my teeth and carve out entire frequencies. One day we had a sub band and everything, and I mean everything, they did was in Bb. Their instrumentation (violin, for starters) made it worse. During rehearsal I jokingly asked if they didn't want to by any chance take things up or down half a step, did they? They laughed and asked why, then said, "yeah, this might be kinda fun!" They did the entire set in B. Problem solved.

A year later, we stopped doing songs in Bb. I thanked the BL, and found out that the guys who installed the new array told him that was the resonant frequency of the room. I said I wished he had asked long before!
 
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#10
Some rooms are just weird that way. We once had a "practice garage" that would go bonkers when we hit an F#, no matter how loud or soft. The whole building would vibrate, doors and windows would shake, and everything went into total "feedback" mode. Have played some weird-shaped buildings where the lows would "load up" and sound like mud no matter what. Anyhoo, welcome to the world of crappy gigs and venues ;)
 
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