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Bass Cabinet Speaker Wiring (2x12x15) - I Need Your Help!

Discussion in 'Amps and Cabs [BG]' started by Drifter_Bass, Aug 31, 2017.

  1. Drifter_Bass


    Apr 5, 2017
    MPLS, MN
    Hello TB.

    I have a vintage Sears BXL200 bass cabinet that has 2x 12" drivers and 2x 15" drivers, like the one you see below (not my picture personally but that exact same cab - you can faintly see how the speakers are positioned in a rhombus/diamond configuration). All 4 drivers are the originals and they don't have much life left in them - it took very little time for one of them to blow.

    I want to upgrade all 4 drivers and wire them to the single input at 8ohms - this is where I need help. I want to integrate some sort of crossover in-line that would take the high-end stress off the 15's and the low-end/sub-frequency stress off the 12's.

    I have a few ideas but I ultimately want to know:
    1. What is the best/most-sensical way to wire this up so that I can plug my bass amp into a single jack and drive the speakers safely?
    2. What ohms would the 4 drivers need to be, in this situation, to arrive at an 8ohm jack?


    Thanks for reading - any suggestions are appreciated! :)
  2. Not suggesting that throwing new speakers in an old cab is the way to go, but this is kind of a cool project if you can pull it off.

    If you haven't already modeled this cab with different speakers to see what might work best, or least worse, then you might want to start there, and/or get someone who's good at it to help. It is an unusual combination and back in the day no one cared about or knew about speaker modeling, let alone be able to do it with just a slide rule.

    I'm not sure, what with the crop of speakers these days, that trying to do a crossover is really necessary. I say that because 12s and 15s are so similar in size and the power ratings on even 12's are so good these days that it might not matter. Size is not really as much of a consideration in what frequencies a driver will handle in this brave new world. Just be sure the two 12's as a pair can more than handle 1/2 of the max amp power output. A crossover might actually make things worse. And will certainly complicate matters to a high degree. The design of the cab may influence the use of a crossover as well. I think you'd be fine without it.

    For straight up wiring, (without the complication of a crossover) you can go with 32 Ohms each driver, all wired in parallel.
    Or if you can't find appropriate 32's in your sizes, you can wire two 8's in series (16) and the other two 8's in series (16) then wire the resulting combinations in parallel for 8 Ohms. Can't think of a combination off hand that uses four 4 Ohm or four 16 Ohm drivers and gives you an 8 Ohm cab. Whatever you do though all of the drivers should be the same impedance.

    Be sure to post this when you finish it and give us a report.
  3. Drifter_Bass


    Apr 5, 2017
    MPLS, MN
    Thanks for the advice! Is there a reliable way I can easily model speakers in this cabinet? Are you referring to a digital computer program or physically testing different drivers in the cabinet and taking some sort of measurement?

    I agree that throwing brand new drivers in a cabinet like this is more foolish than not, but I am in this for the project and learning opportunities - and hey, I might end up with a roaring cabinet at the end of it! I also have a friend with loads of bass/gtr speakers that he basically giving me so I don't have much to lose in the way of "brand new drivers".
  4. Yes, I was referring to digital computer modeling.

    Well the price is right on those drivers then.
    Back in the day, I don't think a lot of the cab builders did much more than "we've got a bunch of these speakers, lets throw them in a cab and see what happens." I'm sure some of the big speaker companies like E.V. or Klipsch had guys with pocket protectors. But while hippies were trippin' on acid in the sixties, there were a handful of scientist and engineers who got their "high" from trying to figure out the relationships between the speaker and the box it was mounted in.

    i wish you well with your search for the roar.
  5. 1. Measure the interior dimensions to find the volume of the cabinet.
    2. Select two 12 inch or two 15 inch speakers that will work in a ported box of that volume.
    3. Cover the two openings that will no longer be used, and install the port(s) the design calls for in the baffle.
    4. Find out that it is not really very good.

    5. Remove the speakers, and ports, and convert it into a stylish retro looking liquor cabinet.
    Last edited: Aug 31, 2017
  6. BassmanPaul

    BassmanPaul Inactive

    IMHO putting new drivers in that cabinet would be akin to lipstick on a pig. it’s not, and never has been a professional speaker cabinet. Save your hard earned money to put towards something decent. Mixing twelves and fifteens in the same box is questionable design for a start. Sorry.
    agedhorse and Munjibunga like this.
  7. seamonkey


    Aug 6, 2004
    You can just throw in whatever drivers fit. That's all sears did.

    Better drivers than you'd expect for the price
    MCM Audio Select 12" Woofer with Paper Cone and Cloth Surround - 175W RMS at 8ohm | 55-2952 (552952) | MCM Audio Select

    There are 8 and 4 ohm versions. They go on sales all the time for even better pricing.

    If the cab is cheap wood (particle board) it may not be able to handle the weight of these drivers.

    You could use the same drivers and build yourself a dynamite cabinet. See Bill Fitzmaurice's site as he some times specifies MCM drivers.
    agedhorse likes this.
  8. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    the 12" dont need alot of power if you run a crossover then you can run 2 pairs of speakers at 8ohms, for a total of eight ohms.

    to get a 8ohm load you need 2 speakers in parallel 16ohms each

    for the 15" use a pair Eminence Delta 15B its a 16ohm driver in parallel will provide 8ohm load.

    for the 12" use pair Eminence Legend V1216 its 16ohm driver in parrallel will provide 8ohm load.

    using a crossover combined load will be 8ohm.

    all else falls run each pair to its own seperate jack so you could use external amplfier or active crossover instead of passive.

    likewise you could fill the 12" holes and just run a standard 2x15
    a16 ohm pair be 8 ohms
    8 ohm pair be 4 ohms in parallel

    dont use series loads with tube amps
  9. PawleeP


    Oct 8, 2012
    East Coast
    Are you saying don't use series for tube power amps because of a possible open load situation if a speaker burns up? Sorry if this is off topic.
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    You might want to check the dates of the posts you are responding to, as well as noticing that BogeyBass was banned a year ago so he "can't" answer your question (though 808State appears to be related to BogeyBass in some way).
  11. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

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