Why does my F# boom?

Discussion in 'Amps and Cabs [BG]' started by NighthawkGS, Aug 18, 2019.

  1. Hi... At the risk of asking too many questions... Here's one about a boomy stage... I did read a ton of the existing threads first.:-(

    Last night, played a pub gig that we've done maybe 10 times before. The Bistro in Hayward CA--long square room famous for some sound difficulties. The last two times, since they tore the ugly beer-stained carpet off the stage and refinished or replaced the flooring, I'm getting horrendous booming centered on F#, with a bit also at F and G.

    4 string P-bass, fairly new D'Addario nickel wound strings, fingerstyle, entirely different rigs both times. (EDIT: No PA support. ALSO, 1st time using the MG800 at 4ohms...maybe this was the biggest difference... ;)

    Problem is also pretty bad playing up an octave, ex: 9th fret of A string.

    Tried moving rig around a bit, but never more than 5 feet from back floor or eight feet from the side wall.

    Tried EQ options available on genzler Magellan mg 800, including semi parametric EQ.

    MY QUESTION: Would a milk crate under the cabinet do the trick? Or should I experiment with HPF or a outboard parametric EQ? (HPF sounds kind of interesting in its own right, but would hate to lose any additional low end, and, the problem is also pretty bad an octave higher, as mentioned above.)

    For cabinets, was using pair of small 1 x 12s this time, and fairly big 1 x 15 previous time with same problem... 1 x 15 has casters.

    Seems quite likely the problem is the stage, but can't test until next gig.

    Thanks! ;)
    Last edited: Aug 19, 2019
  2. bobyoung53

    bobyoung53 Supporting Member

    Rooms are tuned just like soda bottles, they're like a column of air and you are exciting the room with the F#, I once played a room every weekend for a while where the C boomed way over anything else and it was really irritating. I stopped playing the C, had to. The room must be just the right length for F#, the room i played in with the C was long also but obviously shorter than yours.
    TolerancEJ and SoulReflection like this.
  3. If it's booming an octave up then it's too high to do anything with a HPF , 3.5ft from the wall might have done something.

    Parametric cut centered on the F#2 92.5hz frequency should sort it.
    Wisebass, pcake, onda'bass and 8 others like this.
  4. My amp's semiparametric only goes down to 150 Hertz, guess I could locate and try a cut at 185 Hertz, since the problem is still pretty bad an octave higher...

    Or, I could just stop playing F#s. ;)
  5. Stumbo

    Stumbo Guest

    Feb 11, 2008
    You can try a piece of carpet under your cab or a pad like an Auralex.

    An HPF may help to keep everything else that vibrates below around 60-70hz that also may be exiting the F#.
    SoulReflection likes this.
  6. bwildt


    Mar 21, 2017
    Wichita, Kansas
    Could be the stage or it could be the room. It could be just where you are standing. These booming notes can be annoying. Has anyone commented on how it sounds out in the room? It could be just a problem on stage. Are you carrying the room with just your amp or do you also have PA support?

    Most of these possible solutions have already been mentioned.

    Problem limited to stage:
    Try to elevating the speaker cab or moving it to another spot on stage. Be careful with EQ changes to tame the stage if the bass sounds OK out in the room. You may have to live with it.

    Problem on stage and out in the room:
    Try cab placement as above and also try EQ. A true parametric EQ might be needed, as the EQ on your amp may not have a narrow enough Q (frequency width) parameter to notch just the offending note. You might need an outboard EQ.

    If you are using PA support, it could be interaction between the PA subs and/or your bass cab. It might also only happen in specific areas of the room. If the mixer has a true parametric EQ, you might be able to notch the frequency there.

    Bass frequencies can be really hard to control due to room reinforcement and cancellation nodes.
    Jesuguru, bbh and NighthawkGS like this.
  7. The 92.5hz is the fundamental of the octave up from your low F# and the biggest chunk of energy in that low F#. If can hum it nearish but not too near the bottom of your range that'll be the one.
    Wisebass, bdplaid and Stumbo like this.
  8. Wasnex


    Dec 25, 2011
    You could try to setup some boundary cancellation to help tame the resonance. This is achieve by placing your speaker 1/4 wavelength from reflective surface like the floor and walls. 1/4 wavelength at 92.5hz is around 3', so you need something taller than a milk crate.

    Here's a related article: arqen.com/acoustics-101/speaker-placement-boundary-interference/
    Wisebass, Jesuguru, bdplaid and 5 others like this.
  9. I was off in my guess at 1/4 wavelength. Indeed just over 3ft from baffle to wall should do something.
    bdplaid, Wasnex and sawzalot like this.
  10. /\/\3phist0

    /\/\3phist0 ( ͡° ͜ʖ ͡°) mmm Woody! DHDIK? Sweet Treets. Supporting Member

  11. nnnnnn


    Oct 27, 2018
    Have you tried playing Gb instead?
    basscooker, RockDoc, Alik and 33 others like this.
  12. Sounds like the rooms resonant frequency is somewhere between the notes you mentioned are booming. It's likely due to the carpet change. If nothing that's been mentioned works maybe try putting something around your amp to dampen the sound a bit? There must've been something about that old carpet that tamed the resonant frequency, but the new carpet changed that.
  13. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Don't worry about it. Rooms do weird things, and what's happening on stage may not be happening in the room at all.
  14. /\/\3phist0

    /\/\3phist0 ( ͡° ͜ʖ ͡°) mmm Woody! DHDIK? Sweet Treets. Supporting Member

    34" pretty darn close.
    Last edited: Aug 19, 2019
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  15. S.F.Sorrow


    Dec 6, 2014
    Yep, like others have said: It's the room, nothing to do with your gear. Google standing waves. A HPF will not be any help at all unless you want to ruin your tone in the process.

    I assume acoustic treatment of the room is out of the question so that leaves the second best solution: A fully parametric eq (not semi-parametric) with narrow, surgical notch bands. Studio grade rack gear, meaning expensive.

    At least it's a regular gig so you know the room and the problem frequency which makes it possible to try to adapt your dynamics (playing F# softer or semi-mute the string with the next finger to avoid the tone building/feeding).

    On the cheap you might get an improvement using an inexpensive graphic eq with a band in the vicinity of F# but it's not ideal and the wide bands will also affect nearby notes (probably even more than the problem frequency) and mess with your tone.

    A carpet will do absolutely NOTHING at these low frequencies but if they replaced the flooring (and probably more importantly, whatever is below the flooring) that could certainly have changed how the room behaves acoustically.

    Milk crate under the cab can help against general boominess (so can moving the cab away from the wall) but it won't fix standing waves in the room at specific frequencies. It won't hurt to give it a try though, it certainly won't make it worse and you could get lucky and cancel out some nastiness. Less boominess is always a good thing.
    bdplaid, Mugre and NighthawkGS like this.
  16. Honkey tonk

    Honkey tonk Turn it up Supporting Member

    Feb 10, 2019
    Lower 48
    Phase out the fundamental
  17. Turbo Sparky

    Turbo Sparky Supporting Member

    May 14, 2018
    South Eastern U.S.
    Have played a few venues with a less than perfect stage/riser. I've found the less bracing used, other than simple rectangular/square framing, the greater the chance of "boom" (hyperresonance).
    Raising the cabs can help, but once I got an always-on HPF...*Broughton*…
    Dialing in/out the "boom" is but a knob away...like 3 seconds away..."Lows" are not "lost," but are rather more clear and even...
    One of the best $95 I've ever spent on gear.
  18. Sparkl


    Apr 23, 2011
    The room you play in seems to have a resonating point centered around the f# and its octave aliquotes. There really isn't much you can do unless you try to use some pro grade eq filters that can phase or detract energy from that note and the aliquotes until the room feedback becomes glued with the output of other notes.

    A much easier option is to simply turn down the volume of the band. At a certain volume the sound and room feedback will clear out and then let the owner know that removing the acoustic treatment was definitely a bad idea.
    bdplaid and Honkey tonk like this.
  19. Sparkl


    Apr 23, 2011
    Dampening won't fix things since it isn't the high frequencies in question but rather the low mids.