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"thunderturd?" i hope not spent too much $$ for that.. need help

Discussion in 'Amps and Cabs [BG]' started by frankz, May 27, 2011.

  1. frankz


    Sep 29, 2009
    put a bass rig togather and have used it for about 4 rehearsals now and it has some glaring problems i was hoping to get some help on... anyhow bass is Ibanez btb 505 with ibanez pickups (i know) going thru art prochannel into crown 402... the cab which is suspect between that and the pickups is the prob.. is an 1977 acoustic 406 2x15 with eminence 3015s in it.. not the low freq ones the up to 6khz ones.. anyhow the thing should be awesome but it has what i call "holes and booms" for example you can hit a B note on the E string and shakes the house down hit a G on the same string and its quieit... now! i did put insulation in the cab (didnt cover vents) but it has sides and opposite side of vent... i asked earlier about the wisdom of this and got 50/50 answers .... prob is in order to remove insulation its a bit of a (treck to rehearsal space haul out blow out blah blah blah) and that might not even be the problem... any ideas?? getting complaints and i know its 4x the cab i was using (new acoustic 4x10 with blown driver) .... please help
  2. Did you try moving the cab to a different position in the practice room ?

    You may be experiencing cancellation of certain frequencies.
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    +1. The worst place to test a cab is in small room. The other question is was the cab modeled to see if the 3015 drivers would work in it. You can't stick any driver into any box and get a good result.
  4. KramerBassFan


    Jan 3, 2009
    I'd imagine the old Acoustic 406 cab would do better with Beta 15's than 3015's, but what do i know.
  5. rpsands


    Jul 6, 2007
    Phoenix, AZ
    The acoustic is almost certainly tuned way too high for 3015's - combine that with poor damping and you've got a recipe for a nasty sounding cabinet.
  6. 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)
    Whew! When I saw the word "thunderturd", I thought... oh, nevermind.

    It's not unusual for room modes in a small room to result in narrow-band dips of 12 dB or more at some bass frequencies. My guess is that's the most likely cause.

    Try changing the position of cab and/or your ears relative to the room boundaries in all three dimensions, and see if that helps. I say "all three dimensons" because the notch could be caused by a floor-to-ceiling mode.

    If you wanted to experiment with a lower tuning frequency, you might try reducing the port's cross-sectional area. Stuffing a piece of foam the length of the port and maybe 1/3 its width and a wee bit more height than the port (should have a good friction fit) into the port would be a quick-n-dirty way to reduce the port area and thereby lower the tuning frequency.
  7. frankz


    Sep 29, 2009
    thanks for input.. ill try pointing it so its not 90 degrees to the walls might help abit.. yeah the cab was a very clean empty find and i wanted light soo 3015s seemed to fit no way to actually model it.. actually doubt if acoustic modeled it in '77. well its my rig for now i may yank the insulation out of the top cab or reduce it a bunch to see if i can get more mids.. other than getting it set up the 3015s are monsters used to run a 4x10 with one side of the crown 8ohm vs 4ohm i know but they are way more sensitive that might be part the prob also... anyway i got monday to mess with it....btw (opening for the Rev. in august) very stoked so need to get some tones going.......... gonna try the 1/3 port reduction also.. didnt know which way that went if bigger port lowered the tuning or raised it..

    btw... just wanted to add.. the 3015s are crazy clean and powerful its all a tuning/ and i really need better pickups in bass.. issue.. probably also i got used to not needing to control dynamics as much with my old 89db spl speakers .. didnt wanna give the impression i was raggin on the speakers they are 3x better speakers than i am a bass player ive played them at 400watts - 200 each and cant imagine running bridged.. but i will soon as i get a bananna clip pigtail :)
  8. KramerBassFan


    Jan 3, 2009
    The insulation would add mids, not remove them. Removing the Insulation would only make it worse, i'd imagine.

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