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Fix for a boomy cab

Discussion in 'Amps and Cabs [BG]' started by Phendyr_Loon, Dec 8, 2011.


  1. Phendyr_Loon

    Phendyr_Loon

    Sep 4, 2010
    Through research, I've gained the knowledge of mid frequencies and unarrested standing waves creating unwanted "boomy" overtones.

    I recently built two cabs to these specs. http://www.eminence.com/pdf/Basslite_S2012_cab.pdf

    I lined the 5 interior walls between the bracing with 1" foam. Since I'm still experiencing boom at moderate volume, should I add a bit more lining to the cabs? I think I have some egg crate mattress topper around here, I was thinking that I could fix the sound with that.
     
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
  3. Phendyr_Loon

    Phendyr_Loon

    Sep 4, 2010
    Oh, I left that out. It's the 2.7 cu. ft. cab, i believe it is tuned to 47hz.
     
  4. will33

    will33

    May 22, 2006
    austin,tx
    Those really shouldn't be boomy assuming they're built to spec and the tuning is right. Too high of tuning gets boom. The lining is to damp midrange cancellations and your 1" should be sufficient. Any more than 2" would be too much.

    Try positioning the cab differently. Next to a wall adds 6db in the lows, in a corner adds 12.

    Most amps are also anything but flat in response so mess with the tone controls. If your amp has a fender tone stack, search how to use it.

    If you built the sealed version, perhaps it could use more stuffing.

    Which version? Tone settings you're using? Rig placement? Bass? All that stuff. It's a good thing to play it outside, then move it indoors to hear the effects of positioning, boundry loading, etc.

    Basically provide some more details and we can get it sorted out
     
  5. will33

    will33

    May 22, 2006
    austin,tx
    What did you line the first inch with? Closed cell foam won't damp the sound but rather shrink the box....just a thought.
     
  6. Phendyr_Loon

    Phendyr_Loon

    Sep 4, 2010
    The foam I used is similar to what is used in kitchen chair padding. It feels like egg crate foam but just without the peaks and valleys.

    I actually ran out of that stuff 3/4 of the way through each cab and ended up finishing out most of the back wall will egg crate remnants anyway.
     
  7. will33

    will33

    May 22, 2006
    austin,tx
    If you can easily blow through it, like an air filter, it's ok. I'd start by making sure your bass and amp don't have any extra lows dialed in, then mess with positioning, just to make sure it isn't boundry loading giving you the boom. If it's still too boomy, lowering the tuning (longer pipes) will roll the lowend out more.

    Basslites aren't a really aggressive uppermid/trebly sounding driver. If that's what you're looking for, you may need eq to get it.
     
  8. Phendyr_Loon

    Phendyr_Loon

    Sep 4, 2010
    Thanks Will33, I'll mess around with positioning. As I can remember I got good tone from my cabs in the past by positioning my amp in the corner.
    I'm using a Eden WT 300, it fairly new to me so I'll screw around with the parametric eq on the mids.
     
  9. will33

    will33

    May 22, 2006
    austin,tx
    Your profile says jazz bass, some effects and an Eden amp. Take the effects out of the chain, plug straight into the amp and make sure the contour/enhance knob is all the way down to get a better idea of what the cab is really doing. It's a different cab, you may have to adjust your other stuff differently. I don't know where you are, it might be cold, but play the rig outside to get a point of reference as to what positioning is doing to it. Depending on your tonal preference, it should sound "ok" or a little thin/weak in the lows outdoors.
     
  10. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    You might try lowering the tuning frequency. That tends to tighten up the low end a bit, though it can also lower the fartout threshold.
     
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    You can see the boom in the response chart hump centered at 90Hz. The 2012 gives best results in a 3.5 to 4 cu ft box tuned to 40-45 Hz.
     
  12. Joe Smithberger

    Joe Smithberger Supporting Member

    Mar 8, 2002
    Canton, Ohio, USA
    Newbie question:

    What could I potentially do to a commercially made cab to lower the tuning?
     
  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Extend the ports.
     
  14. Bass Unique

    Bass Unique

    Nov 3, 2011
    Wiltshire
    or it can raise the fart out threshold if this was only a problem on the bottom notes. Displacement is naturally a maximum at the lower frequencies. Port tuning lowers displacement at that frequency. Go too low though and it will fart out about 2.5x the frequency.
     
  15. Bill,

    In a small cab with a tube port in the back panel, would lengthening the tube be "extending the port"?
     
  16. BogeyBass

    BogeyBass

    Sep 14, 2010
    Do you have pictures of your cabs?

    2.7 is the volume after you subtract port and driver volume?

    otherwise if its the volume without subtracting,
    you could have a much smaller box
    and the foam your using is taking even more volume.

    47hz is a ok tune for a large box, little high for small box
    using the 2012.
     
  17. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Yes, but don't expect too much from a small cab. You can go low with high sensitivity, or you can have a small cab, but you can't have a small cab that goes low with high sensitivity.
     

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