anyone know the possible answer to this?

[skidder652003]

So at tonights gig, on a wooden stage I should add, we were trying to set up the PA at soundcheck and my bass was horribly boomy
(fender P, ampeg SVT and 410, Di'd to desk and 2 tops & sub) but heres the weird thing, ONLY when i played an "A" note!
I tried it all over the neck and every time i hit an "A" there would be a horrible follow on boominess to the note which completely disappeared if I played any other note.
Its never happened before, we eventually overcame the worst of it by switching the polarity of the sub (Mackie 18 thump).
Any clever folk out there who might know the reason?

[ambient]

I'm guessing that something in the room was resonating in sympathy with the frequency of your note.

[zbd1960]

Agree, sounds like you found a very precise resonance with the stage and/or room.

[Lozz196]

Yep, the plastic window effect thingy in my living room resonates rotten with a B when played on the A string. Not too bad with the B on the E string though, but it hates the afore-mentioned.

[Phil Starr]

Ha ha I know how loud you play Steve.

You'd obviously set off a room resonance somewhere. You might also have been getting some feedback off the sub. Reversing the polarity might have fixed that but left the room resonance so that you only lost some of the effect.

[tonyquipment]

Ever heard the Beatles - I feel fine ?

That starts off with feedback A note because of the feedback resonance

The only other way around this I reckon potentially detune slightly so it doesn't boom when you hit the A note ?

[cytania]

I think room resonance works with certain cabs. Room 3 at Magnet got a huge boom out of my Barefaced Compact (E flat). In desperation I patched the amp into a Peavey 8x10 that had been left there and the boom went.

Edited September 11, 2016 by cytania

[Spike Vincent]

You've found a very specific resonant frequency.Was the sub on the stage as well as your cab ?

[tauzero]

[quote name='cytania' timestamp='1473596270' post='3131468']
I think room resonance works with certain cabs. Room 3 at Magnet got a huge boom out of my Barefaced Compact (E flat). In desperation I patched the amp into a Peavey 8x10 that had been left there and the boom went.
[/quote]

Were the two cabs in exactly the same place? I think placement would have something to do with it.

[skidder652003]

[quote name='Spike Vincent' timestamp='1473608287' post='3131590']
You've found a very specific resonant frequency.Was the sub on the stage as well as your cab ?
[/quote]
yep sub was also on the hollow wooden stage, next time it'll be on the concrete floor!

[skidder652003]

[quote name='Phil Starr' timestamp='1473590297' post='3131375']
Ha ha I know how loud you play Steve.

You'd obviously set off a room resonance somewhere. You might also have been getting some feedback off the sub. Reversing the polarity might have fixed that but left the room resonance so that you only lost some of the effect.
[/quote]

You think we were loud then, the sub is ridiculous!

[landwomble]

You need a parametric eq to notch out the resonance

[funkgod]

Cus yours is a 4x10 In this case, one good thing you can do to help that will give best results is get the bass cab off the stage floor !
Good big lockable wheels help as they add an air gap.

i do pa hire, and the same prob happens alot, and the best thing is a stand.
easy for combos, 2x10, and 4x10 (not so easy with 6 and 8x10) .
it has to be a stand, not a box of some sort like the drummers plastic bass drum case, it will still be there just not as bad and add boom.
I always for the last 25 years use a stand, used it with my old set up, a trace 4x10 and trace 350, and now with a swr redhead 2x10 some times with a swr 2x10 ext cab, so i can have the redhead on a stand and the 2 x 10 on the floor under it, and if i get boom unplug it or put it on the stand, done.
This also helps do two things,

1, because the cab is high, about back height, you can hear what you are playing much much clearer and.... you dont have to have it as loud on stage, win win.
2, if you set up next to the drummer and he uses a monitor you can put his monitor under the stand saving stage space,
for functions you can wrap black cloth around hiding the stand and the bass drum monitor just leaving your cab in the air, looks very tidy, win win.
so recap... win win + win win= win win win win


folds up, and you can use it for all sorts,
if you dont use it your guitarist will, if he does not clame it the key player will, and if he does not the sound guy will for the desk, so is just dam handy to have.

just had a quick look, these are very strong, height and width adjustable. (look for "keyboard table")
look for a strong square tube leg rather than a round tube leg
worth a go, Hope it helps,
something like this....
[url="http://www.ebay.co.uk/itm/PROFESSIONAL-KEYBOARD-TABLE-STAND-DJ-EQUIPMENT-NOTEBOOK-TURNTABLE-MIXER-FOLDABLE-/281424882678?hash=item41863aebf6:g:iKYAAOSwSHZWcwWg#ht_6648wt_1028"]http://www.ebay.co.u...#ht_6648wt_1028[/url]

Edited September 12, 2016 by funkgod

[phil.c60]

Exactly the same thing happened to me on an outdoor stage a couple of weeks ago. Whenever I hit an A (and a few of the songs in our set were in A....) the harmonica player who was at the other end of the stage almost had a fit! He could feel it through his feet. We were only [playing a short set of 45 mins so I just put up with it as I was using someone elses rig - a Markbass 2x10 combo on top of a matching 4x10. Resonance was clearly the issue.

[Happy Jack]

I saw the latest incarnation of Doctor Feelgood at the Half Moon in Putney about five years ago. Yet again, it was the 'A'. Every time the bass player hit it, the whole room just rang.

A few months later I saw The Jetsonics (feat. Low End Bee) play the support slot at the same venue and warned Adam about the rogue A. Didn't make a blind bit of difference, the whole room just rang. Again.

[Low End Bee]

[quote name='Happy Jack' timestamp='1473687316' post='3132246']
I saw the latest incarnation of Doctor Feelgood at the Half Moon in Putney about five years ago. Yet again, it was the 'A'. Every time the bass player hit it, the whole room just rang.

A few months later I saw The Jetsonics (feat. Low End Bee) play the support slot at the same venue and warned Adam about the rogue A. Didn't make a blind bit of difference, the whole room just rang. Again.
[/quote]

At least it shows I was in tune for a change.

[ivansc]

I bought one of the auralex foam and wood speaker stand thignies for just this reason. Anywhere that has major resonance issues it is usually cured fro me by sticking my cab on the auralex.

[url="https://www.amazon.co.uk/AURALEX-ACOUSTICS-GRAMMA-ISOLATION-GUITAR/dp/B0002D0B4U"]https://www.amazon.c...R/dp/B0002D0B4U[/url]

But bass direct actually stock them!

QUOte:
[color=#020202][font=Helvetica, Arial, sans-serif]
The Auralex® BabyGRAMMA™ v2 Amplifier Isolation platform is a smaller version of our classic GRAMMA™, which is trusted by chart- topping recording artists on-stage and in the studio. The BabyGRAMMA is designed for compact guitar, bass and keyboard amplifiers.[/font][/color][color=#020202][font=Helvetica, Arial, sans-serif]
• A tighter, more focused low-end[/font][/color][color=#020202][font=Helvetica, Arial, sans-serif]
• Hear the true sound of your amp, loudspeaker or subwoofer[/font][/color][color=#020202][font=Helvetica, Arial, sans-serif]
• Instantly improve your sound on-stage or in the studio[/font][/color]

Edited September 12, 2016 by ivansc

[Happy Jack]

[quote name='ivansc' timestamp='1473692807' post='3132312']
I bought one of the auralex foam and wood speaker stand thignies for just this reason.

[/quote]

I use Auralex stands routinely, and they're a great cure for 'boom' off a hollow floor or stage.

Not sure they can do much about resonant frequencies though. If the room is going to ring when it hears a particular frequency, then allowing that frequency (along with all the others of course) to be heard more clearly is not necessarily the solution.