Room resonance and louder note?

Chrisk-K · #1 01-05-2011, 08:30 PM

When I play my basses at my home, the A note on the E string is much louder than other notes, especially when I use a neck pickup on my Js or a P pickup. I've tried different amps and cabs and the result is the same. Interestingly, the open A note doesn't show the same symptom.

Is this caused by "room resonance"? That is, does my house material somehow increase the amplitude of the A note? Is there a cure?

billfitzmaurice · #2 01-05-2011, 08:35 PM

Move the amp closer to or further away from the wall, that may help.

BurningSkies · #3 01-05-2011, 08:41 PM

I play regularly at a place where the room SHAKES within a couple note range. The stage they had was sort of a diagonal in a corner, then they moved to to an opposite corner. Same problem I ALWAYS set up on the the side of the stage that's farthest away from where two walls meet, and in this case it works beautifully.

I had a sit-in drummer a for this gig a while back and he pretty much demanded I put my rig right to his left (hi hat) so I smiled and 'rang his bell all night long as the place shook and dust fell from the ceiling.

All of this is to say that you may not be able to fix everything but try getting away from a corner and if you can, move out from a wall a bit. If in doubt, roll your lows. If you have a parametric or a graphic try to isolate the frequency of the room and pull it out til its bearable.

SnappyFerret · #4 01-05-2011, 08:44 PM

Concert halls have sound-absorbing materials put around in strategic locations. You could put up some drapes to help absorb some of the sound. Or if you have a hardwood floor, you could put a throw rug or big piece of carpet on the floor. Moving around stuff (furniture) that could interfere with certain sound wave frequencies resonating too much might help too.

SpectorDetector · #5 01-05-2011, 08:47 PM

A resonance would usually take away energy not increase it (I'm sure someone here will tell me I'm wrong..), so like the first reply said, play with moving your amp around a bit in relation to the the wall behind it. Closer should make more of a mid-bass hump and farther away SHOULD smooth it out a bit more. Sometimes it's not a realistic scenario to pull your amp out 6 ft into the room though!

Foz · #6 01-06-2011, 12:10 AM

Quote:

A resonance would usually take away energy not increase it

No - a modal resonance creates areas of positive and negative pressure where the resonance frequency is louder/reverberates longer - and also creates locations where there is a balance [a node] where there is neither positive or negative pressure and in these locations the frequency's amplitude and reverberation time is diminished. Moving the sound source can alter the extent a particular mode is excited - placing the sound source in a tri-corner [wall+wall+floor for example] excites all of the room's modes.

Absorbing modes is non-trivial - requires an absorber able to work low in the band.

http://forum.studiotips.com/viewtopic.php?f=8&t=535

mongo2 · #7 01-06-2011, 04:17 AM

I find that if I reposition myself or the cabinet there are different frequences that are louder or softer.

craig.p · #8 01-06-2011, 04:44 AM

Quote:

Originally Posted by Chrisk-K

When I play my basses at my home, the A note on the E string is much louder than other notes, especially when I use a neck pickup on my Js or a P pickup. I've tried different amps and cabs and the result is the same. Interestingly, the open A note doesn't show the same symptom.

Is this caused by "room resonance"? That is, does my house material somehow increase the amplitude of the A note? Is there a cure?

This is not a room-resonance problem. It's a bass-setup problem. Your pickups are too close to the strings. Never mind the standard "rules" for pickup spacing -- they are less than worthless, and I say this with over 35 years of playing bass and doing setups under my belt. Get your pickups MUCH further away from the strings; grab a Phillips and screw them right down. On the P bass, angle the E/A pickup DOWN under the E string so the E string string-to-pickup distance is the same as or greater than the A string string-to-pickup distance. (The E/A pickup should have a noticeable tilt to it.)

On some pickups (Ric bridge, for example), it's possible to drop the pickup so low that the strings are no longer in the pickup's magnetic field. You'll know when it happens: the string will sound not just weak but also "distant," with a loss of dynamics, if that makes any sense. You'll have to experiment and find a "sweet spot." But try to err on the side of too far away rather than too close.

After you drop your pickups, you'll have to run your amp's gain a little higher. (Of course.)

You can also put a compressor in the signal chain. Or use a limiter if you want to preserve string attack.

There's also the possibility that the string sets you're using have an E string that's hotter than it should be, relative to the remaining three.

billfitzmaurice · #9 01-06-2011, 06:39 AM

Quote:

Originally Posted by mongo2

I find that if I reposition myself or the cabinet there are different frequences that are louder or softer.

That's the result of boundary reflections. Explained here:

http://www.padrick.net/LiveSound/CancellationMode.htm

Quote:

Your pickups are too close to the strings.

Possibly. String height could also be involved, as could be the nut height. If there's a major difference between a fretted A on the E string versus an open A look at the relative height of the strings with respect to the pickups and the fingerboard when fretting the E string at the 5th fret. The difference should be minimal.

SpectorDetector · #10 01-06-2011, 07:27 AM

Quote:

Originally Posted by Foz

No - a modal resonance creates areas of positive and negative pressure where the resonance frequency is louder/reverberates longer - and also creates locations where there is a balance [a node] where there is neither positive or negative pressure and in these locations the frequency's amplitude and reverberation time is diminished. Moving the sound source can alter the extent a particular mode is excited - placing the sound source in a tri-corner [wall+wall+floor for example] excites all of the room's modes.

Absorbing modes is non-trivial - requires an absorber able to work low in the band.

http://forum.studiotips.com/viewtopic.php?f=8&t=535

I was thinking a mechanical resonance, not a room node. How do bass traps work? I always got how diffusers and panels worked on the higher frequencies, but never bass traps. For instance, how would you make one? Thanks!

billfitzmaurice · #11 01-06-2011, 08:27 AM

Quote:

Originally Posted by SpectorDetector

I was thinking a mechanical resonance, not a room node. How do bass traps work? I always got how diffusers and panels worked on the higher frequencies, but never bass traps. For instance, how would you make one? Thanks!

Bass traps work the same way as any absorbtion devices, they just have to be thicker. They're actually mis-named, as anything capable of absorbing the 14 foot and longer wavelengths of 80Hz and lower frequencies would have to be literally feet thick. They actually work in the midbass, roughly 100 to 200 Hz.

plangentmusic · #12 01-06-2011, 08:31 AM

"A"'s and Bb's in some room just BOOM. It's a sympathetic vibration. I find it can be open or fretted by obviously the fretted note on the E string is the fattest and most prevalent.

Not much you can do. Lower the low mids (100hz)a bit and deal with it.

guroove · #13 01-06-2011, 08:37 AM

I would think that if it were the room resonance causing it, then the open A would have the same amplifying symptom as the A on the E string, since they have the same fundamental frequency.

Robby Hoinsky · #14 01-06-2011, 08:52 AM

Not to belabor the dead horse here, but that room is not your problem, your bass is. The room problem is a problem too, as any regular sized, untreated room is going to have its own modal characteristics that will make certain frequencies excessive in some spots and practically non-existent in others.

Robby

Groove Doctor · #15 01-06-2011, 09:03 AM

I notice you have several basses - does the same thing happen to all of them?

Some basses have 'dead spots' where the note is quieter or less distinct tonally. May also have what I call 'live spots' where the unique combination of woods and frequency and string gauge/ tension exposes it more. You might even be able to hear that acoustically. A good setup will compensate for or mask these spots somewhat.

My Jazz bass has live spots G and G# (E-string 3rd and 4th fret) and a pronounced dead spot C# (D-string 11th fret) which is not there on the corresponding note on the other 3 strings. (The acoustic guitarist in one band had a dead spot on the low G but a live spot on the low G#, which wasn't fun :-(

pasta4lnch · #16 01-06-2011, 09:05 AM

I believe its called a "standing wave" if a wave bounces back off the wall back onto itself at 180 degrees it cancels out, but if they overlap it will double in volume . . . probably not what's going on w/ the OP though, but who knows . . .

jesterbass · #17 01-06-2011, 05:46 PM

Quote:

Originally Posted by Chrisk-K

When I play my basses at my home, the A note on the E string is much louder than other notes, especially when I use a neck pickup on my Js or a P pickup. I've tried different amps and cabs and the result is the same. Interestingly, the open A note doesn't show the same symptom.

Is this caused by "room resonance"? That is, does my house material somehow increase the amplitude of the A note? Is there a cure?

I have that too. It happens on all As. And it is NOT the bass or its setup. (In fact one of my basses does have dead spots and other boomy spots but not related to A). Recently I changed room in my house, and it still happens. Both rooms were approximately same size, so I believe it is a problem with the dimensions of the typical small bedroom. Unless my stereo (where I listen my bass from since I don't have an amp/cab at home) has a weird tendency to amplify A more, highly unlikely.

SurferJoe46 · #18 01-06-2011, 07:06 PM

A compressor won't correct this - but a Notch Filter will.

You can selectively dial down any freq that sets a room to parasitic resonance or echo or harmonics.

One room I play has a sweet spot for a D# or E on the E string at the 11th-12th fret. It happens and I just turn on the Notcher and dial it in and it's gone.

No more Earth-shattering Ka-Boom!

Groove Doctor · #19 01-06-2011, 09:44 PM

+1 Notch filter (which is a semi-parametric EQ with a narrow Q)

Chrisk-K · #20 01-06-2011, 10:06 PM

I'm the OP. It's not the problem of the bass because I get this booming A with all my basses and all my amps.

I don't like hot pickups and the neck J pickups of my Geddy & Lakland and the P pickups of my P and Spector are almost flushed to the body.

I did some experiment. When I played basses in my wooden-floored living room, the A note boomed even more loudly. When I play basses in my carpeted basement, the booming is still there but a little bit weaker.

Here's an interesting thing. I laid down on the floor, facing the ceiling, and played basses. I did NOT hear the booming A at all! The A note sounded like other notes. Can anyone interpret what's going on here?