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Horrid "room boom" at the practice place

C

Crater

Oct 12, 2011
2,520
2,152
Dallas, TX area
#1
I just joined a classic rock cover band, we're still in the formative stages but the BL has lots of experience playing in these types of bands. He's supplying the rehearsal room, it's at his place of business. The bass rig is supplied too - a Hartke 3500 amp into an Ampeg 2x10 cab. The cab is raised off the floor, but is against the wall and near a corner. The bass amp is also DI'd into the PA system, wholly unnecessary in my opinion as we don't play that loudly. (I play a G&L SB-2, by the way)

The practice room is about 10' x 25', and there's a terrible resonance right at low F#, 46.25 Hz according to the internet. I can't avoid this note, several of our songs are either in F# or have that as part of the chord progression. F# sounds about five times louder than any other note, of course there's a bit of resonance at F and G too.

So, I was thinking of buying a parametric EQ, inserting into the 3500's effects loop, and notching out the offending 46.25 Hz. I saw a used Rane PE-17 EQ on my local Guitar Center's website, but before I could purchase it, it was gone. :meh: Found another one on eBay but from a local 'asset disposal' company, and it too disappeared from eBay before the auction concluded! :( Apparently these Rane parametrics are out of production but valued by someone...DJs? sound engineers? Bass players who rehearse in long, skinny rooms?

I've looked at new parametrics but they either can't hit the 46Hz target frequency and/or they are mega-expensive studio EQs that cost more than an entire bass rig. If it was my practice room, I'd try some acoustic room treatment to tame the resonance, but it's not my room.


Looks like my options are:
1) buy a Rane PE EQ on eBay. (I hate mail order in general and eBay in particular)
2) get some other flakey, digital DSP parametric EQ/feedback eliminator, like Behringer
3) Bring my own bass rig (this won't really help, because I believe the problem is the ROOM, not the rig)
4) "fire him!"
 
#6
+1 to getting it out of the corner. Corners pronounce bass. There's an old HiFi trick to get more bass out of a bassless system on the cheap. Guess what it is?

...putting the sub in the corner of the room.
 
#7
Definitely get the cabinet out of the corner and away from the wall, if possible.

From Sound On Sound Magazine -

"Hard surfaces reflect sound at all frequencies, but the boundary effect (as it affects the listener's position in a room) becomes more pronounced at low frequencies, where the wavelengths of sound are correspondingly longer. When you move very close to a reflective surface, the low frequencies which bounce back are almost in phase with the direct sound you're hearing which, in effect, doubles the amount of bass you perceive. A boundary creates a 6dB lift at low frequencies, and this isn't limited to the back wall of a studio -- it's just where most people seem to notice it first.

If one wall can cause a 6dB bass rise, what sort of damage can two walls do? Position yourself in a corner, and you get in-phase reflections from two nearby walls, producing a 12dB increase in bass. If you now move your head down to floor level, you'll find that the floor joins in and adds another 6dB just for good measure."
 
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#10
Thanks for the tips... I usually lower my fader to ZERO on the PA mixer during practice. One of the first things I did when I got to the practice space in fact. The PA's sub is right next to the bass rig and with both of them going, the rumble is overwhelming. Guitar player/BL plays through a Fender tube amp, don't remember the exact model, but it's not a twin, I think a Vibrolux or something, probably 40 - 60 watts. His amp isn't mic'd. The drummer plays a Roland electronic kit.

Again, the practice room isn't mine, it's in the BL's place of business, so I don't think he'd let me put up acoustic treatment. I will see if I can move the bass rig away from the wall at the next practice. I don't think patching a parametric EQ into the amp's effects loop is "too complex", but it's just a hassle to buy one that will do the job.
 
#11
Crater said:
I don't think patching a parametric EQ into the amp's effects loop is "too complex", but it's just a hassle to buy one that will do the job.
Click to expand...

If you get to the point where you think you need to get some hardware to do the job, again, look into the Fdeck HPF3 for $100. Most parametrics will not have the low cut capability that this unit has. Its specifically designed to surgically deal with the very low end.

A parametric with bandpass filters cannot cut the lowest frequencies the same way this unit can.
 
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#14
ddnidd1 said:
If the BL will allow it, try dialing back the lows a bit on the open mics. They will pick up and send lows to the PA that aren't needed.
Click to expand...
That is a distinct possibility.

Also, your offensive frequency is far more likely to be on the 2nd harmonic than fundamental. Don't discount the guitar contribution at 90hz either.

You can pull away from the corner 1/4 wavelength of F2 quite easily. Do the maths, it's about 3ft.
 
#15
is everybody hearing this boom at that one note, or just you, stuffed in the corner with the bass rig and the sub?

+1 to moving out of the bass trap corner, and to losing the sub and most of the PA except for enough to monitor vocals, that's just silly.
 
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#16
I put my money on a phase issue between PA and instrument amps, it tyîcally occurs at lows frequencies where you really shouldn't find anything but the bass kick.
First unplug from the PA, if you want to invest money use a hi bass filter (SFX Thumpinator or alike) or get a bass trap.
 
#17
Crater said:
I usually lower my fader to ZERO on the PA mixer during practice.
Click to expand...

ZERO on a mixing desk is normally at its nominal level, that means you have signal passing by.

Try to practice at moderate levels and avoid corners for amps. Also, use the PA only for what´s needed, you don´t have to run everything trough it.

The frequency you have found, sounds to be a standing wave, you can use some bass traps to lower it or a parametric eq as you already stated.
 
#19
Hey, let's get back to your original idea - parametric EQ. In some rooms, moving your cab, elevating it, etc. just will not do enough to address the resonance. F# and G are very common room resonances. All the windows in my house shake and rattle with F#.

There are currently two Rane PE-15 parametric EQs for sale right here on TalkBass, and at a reasonable price. The PE-15 does about 90% of what a PE-17 does, and will be excellent for your needs. I have a PE-17 (along with the excellent DC-24 compressor) and it is very useful.

Buy one of these > http://www.talkbass.com/threads/rane-pe-15-parametric-eq.1100544/

And, by all means, get your bass out of the PA mix. Your bass cab and the PA speakers may have a phasing issue that actually reinforces the frequencies at F# that are the problem. Vocals will sound better through the PA without competing with bass frequencies as well.
 
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#20
Jazz Ad said:
I put my money on a phase issue between PA and instrument amps, it tyîcally occurs at lows frequencies where you really shouldn't find anything but the bass kick.
First unplug from the PA, if you want to invest money use a hi bass filter (SFX Thumpinator or alike) or get a bass trap.
Click to expand...
Phase issue? As in phase cancellation? In this instance I think that'd be the opposite of the problem.
 

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