Uncontrollable Boom!, a bad gig.

[Bassometer]

On the weekend I had a gig in a pub that holds about 125 people; the room was about 75% full. I was a bit late for sound check and got stuck setting up in the corner (which no doubt contributed to the boom).

All night long I fought with my tone, it was muffled and boomy. My gear consisted of a P-bass with round wounds and a 200 watt combo (Traynor SB112). I immediately turned the bass down to 9 o'clock, then I turned the midbass down to 10:00 but it still sounded boomy and undefined. I have never had this problem before in the room and I have played there half a dozen times before. My EQ points on my combo are 60hz, 200 hz, 800hz and 2.5khz. As mentioned above I cut the 60 and 200, the problem was if I cut too much it just pulled the whole bottom end out. The pub has a hard wood floors and wood walls.

Has anybody had this type of thing happen to them? Like I said, I have played that room before (with the same gear) and never had a problem. There just seemed to be a "soupy fog" of boom. Many of the locals noticed it and at one point they were yelling "turn up the bass" (a bass players dream haha) after I cut the low end.

Any thoughts?

 

[cheapbasslovin]

The boom, IME, happens in the 80-125hz range. With those EQ points it'd be tough to find that.

 

[Bassometer]

My guess is that the EQ points on the combo have a pretty wide Q.

 

[cheapbasslovin]

I stand corrected, it's easy to find that, hard to isolate it .

 

[Bassometer]

Maybe the problem occurred because I was set up in the corner - could it have that much of an affect? I know it is +3db for a wall and +6db for a corner but it just seemed way beyond that.

 

[Wasnex]

On the weekend I had a gig in a pub that holds about 125 people; the room was about 75% full. I was a bit late for sound check and got stuck setting up in the corner (which no doubt contributed to the boom).

All night long I fought with my tone, it was muffled and boomy. My gear consisted of a P-bass with round wounds and a 200 watt combo (Traynor SB112). I immediately turned the bass down to 9 o'clock, then I turned the midbass down to 10:00 but it still sounded boomy and undefined. I have never had this problem before in the room and I have played there half a dozen times before. My EQ points on my combo are 60hz, 200 hz, 800hz and 2.5khz. As mentioned above I cut the 60 and 200, the problem was if I cut too much it just pulled the whole bottom end out. The pub has a hard wood floors and wood walls.

Has anybody had this type of thing happen to them? Like I said, I have played that room before (with the same gear) and never had a problem. There just seemed to be a "soupy fog" of boom. Many of the locals noticed it and at one point they were yelling "turn up the bass" (a bass players dream haha) after I cut the low end.

Any thoughts?

If you play bass, boom will happen. You can cut your lows, boost mids, elevate your amp, move your amp, change where you stand, and sometimes nothing works. When this occurs, the best thing to do may be to simply turn down so the boom doesn't cover up the rest of the mix.

My advice: Once you realize the situation is hopeless, stop trying to fix the problem and just do the best you can to deliver the best possible show. Sometimes it can sound awful where you are standing and fine out in the audience, so put on your game face and act like everything is perfect. In other words rock out!

 

[Wasnex]

Maybe the problem occurred because I was set up in the corner - could it have that much of an affect? I know it is +3db for a wall and +6db for a corner but it just seemed way beyond that.

Corner loading has a huge effect, so yes placement of your amp is a significant factor. FYI, Eight-space loading produces +9dB boost rather than +6dB. How Does Boundaries Affect Loudspeakers?

 

[cheapbasslovin]

Yes, I suspect corner loading played a big role. Still, I think a properly targeted eq gets the job done.

 

[Pat C.]

Any thoughts?

Where in the room was a it boomy? Just by you or in the audience area? It's unusual for the bass to be boomy everywhere because bass will sum and cancel out at various points depending on frequency and room geometry. Sometimes it can be very boomy at your position but just fine out front. Sometimes it's the opposite where your spot is grooving and the rest of the room is washed away by the mud.

You said this is the first you've had this issue in this room. So it definitely sounds like your specific position on stage. If you were near another wall you added another boundary which can make a big difference.

If EQing doesn't help (and as mentioned the broad tone controls on most amps won't help this) try elevating the amp on a chair. This should help will the lows, but can cause some unwanted cancellation depending on the height the cab is set at.

Some background on the boundary effect. Note - this is my layman's understanding of these concepts, I'm not an acoustical engineer. A quick search found this thread on PSW with discussion.

Half space loading - cabinet on the floor with one nearby boundary (the floor itself) - is the typical default position of most bass cabs. Most gigs in not in the sky, nor in an anechoic chamber so whole space measurements are not as useful.

Quarter space - cab on floor up against a wall - will give up to 6db gain in the lows (frequency dependent and usually less in real world application) compared to half space. Even if it's closer to the 3db you mentioned, it is still significant.

Eighth space - a corner position with two walls and floor - can theoretically add an additional 6db. Again, probably less, but definitely enough to cause a ruckus.

 

[Gravedigger Dav]

What about the stage? is there empty space under the floor? for that you will need acoustic decoupling.

 

[Wasnex]

Yes, I suspect corner loading played a big role. Still, I think a properly targeted eq gets the job done.

My point is: Learn and use all the tricks, but don't take it too seriously when the sound sucks especially when the problem is beyond your or anyone else's control.

EQ can definitely help, but if the problem is the formation of a broadband diffuse field, you have to cut the entire low frequency band and there really is no practical solution that provides, what I would consider, satisfying results.

The proper fix is to use acoustic design and treatment to correct the acoustic problems, rather than address the symptoms with EQ. Unfortunately acoustic design and treatment requires lots of time and money.

Plenty of venues have truly horrible acoustics, and if you can't deal with it, you probably should not be a professional musician because you will probably be frustrated by the sound more often than not.

In this case, the OP has learned it is not a good idea to set up the bass in the corner of a specific venue. Perhaps it would be a good idea to talk this over informally with the band to see if they noticed, and if other musicians have had a similar problem when they were in the corner. Hopefully the problem is bass specific and some corporate memory can be formed, so the bass doesn't get stuck in the corner of this venue again.

IMHO, don't rule out the corner in other venues. Sometimes you can get a big fat bass sound that will totally blow your mind.

 

[Bassometer]

Wow - this is excellent advice and I will add it to my "tool box". Just to add, no the stage is not hollow (there is no riser, it is floor level) and as far as where the boom is (that is a good point), I assumed it was everywhere (until I read this). It probably was not boomy in some spots. Good stuff thanks

 

[Wasnex]

@Pat C. I think this is a decent page explaining boundary effect Speaker Placement 101: Is Speaker-Boundary Interference Killing Your Bass?

Basically you get cancellation where the distance between the driver and the boundary is 1/4 wavelength. I usually like elevating my cabs at least 18" for some cancellation in the low mids.

See attached frequency wavelength chart.

 

[LeonD]

I've had the boom happen. Especially if playing on a raised, hollow platform like in churches. Two things completely solved the problem for me.

One is using an Auralex Gramma riser. This decouples my speaker from the stage. The second thing is using a high pass filter. This removes the very low, mostly inaudible frequencies.

Depending on the specific situation, one of the items above may be more relavant. It's so easy to do both though, I don't even try figuring out which one to use, I just use both.

 

[Pat C.]

Yeah, the 1/4 wavelength boundary cancellation is a cool thing to note, but frustrating too because a bass produces all the frequencies. It's a bit easier dealing with just a kick drum which usually has a peak at its fundamental. Best practice is probably to move the cabinet further from the offending boundary to lower the frequency of cancellation if possible. Seven feet is about 40hz, that'd be the minimum distanced to avoid cancellation from the E fundamental on up. At least nine feet for a low B fundamental.

I first came across this info a long while back in a tech note from Peavey. I searched it out, here's the .pdf for anyone who's interested.

http://assets.peavey.com/pv/support/soundsystems/new_boundary_cancellation.pdf

@Pat C. I think this is a decent page explaining boundary effect Speaker Placement 101: Is Speaker-Boundary Interference Killing Your Bass?

Basically you get cancellation where the distance between the driver and the boundary is 1/4 wavelength. I usually like elevating my cabs at least 18" for some cancellation in the low mids.

See attached frequency wavelength chart.

 

[onamission]

Elevating is the first step in boom reduction.

 

[Downunderwonder]

The acoustic guitar can boom the same frequency in the room.

Maybe someone took the 100hz filter off the guitar or a tomtom.

 

[Plutonium244]

A high pass filter is nice to have in the bag.

 

[faulknersj]

Hard to tell without being there...but based on the crowds reaction, I’ll bet you tried to dial it in to sound good where you were standing onstage at the expense of it sounding good out front (where the corner boom wasn’t present).

When in doubt...set the EQ flat imo

 

[Inky13]

We do 4 or 5 jobs a year at this bar that’s encircled with corrugated tin walls. Super hard to dial in a good sound.
I’m not a big fan of tweeters, but I turn them on and cut the lows. Turn the volume of everything down and go with it.
Play the job, drink free beer, get paid and go home.