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Building a cab

Discussion in 'Amps and Cabs [BG]' started by TrevorOfDoom, Mar 6, 2014.

  1. TrevorOfDoom

    TrevorOfDoom Supporting Member

    Jun 17, 2007
    Austin, TX
    I've got my mind set on building a cab, and i'm planning on aping the style of the Bag End S15, with a few modifications.
    I'm thinking of making it 18"x18"x18", using a Bag End 15" speaker, with a 5" port.
    Since I can't read WinISD to save my life, I'm curious if any of the cab gurus can guide me, help me figure out if this will work.
    I imagine it'll have a bit more low end than the regular BE S15, but still be very mid-centric.

  2. I'm definitely not an expert on this, but I will tell you that you should at least try to use software to help design your cab if you're changing the size. That being said, if you're using the same dimensions as the Bag End 1x15 and you're using the proper Bag End 15" (there is probably more than one model) you'll be close. try to figure out what thickness/type of wood used, the type of bracing, and dampening material as well. Also the port might not just be a 5" hole, it might be a tube inside which you would also have to use, and it needs to be the proper length. I'm assuming with a couple google searches you should be able to find most if not all of this info, and if you're lucky a couple of image searches might show you the inside of someone's cab.

    This is one area that people should definitely do their homework, because building a cab is quite the process, and doesn't it suck when you put all that work in and the thing sounds like crap.
  3. TrevorOfDoom

    TrevorOfDoom Supporting Member

    Jun 17, 2007
    Austin, TX
    Bag End only uses one model of 15" speaker, they use 3/4" ply, and their port is just a round hole in the back of the box.
    The Bag End S15 is 18"x18"x15", so I'm adding 3" to the depth, which will hopefully deepen the sound.
  4. Raf Seibert

    Raf Seibert

    Dec 16, 2013
    Off the top of my head, I'd say that a perfect cube, 18 x 18 x 18, might not be the best shape for a speaker enclosure. Internal standing waves, and all that jazz.

  5. StraightSix


    Nov 23, 2011
    Exactly right - a cube is about the worst possible dimensions for a speaker cab.
  6. Chapbass


    Dec 11, 2003
    Chicago, IL
    If you're looking to go the DIY route, why not use some designs like a fEARful or something, and then do the construction yourself? Its been proven, but you still get to make it your own and put your own signature on it.
  7. ^^ +1

    It's so easy to find professionally designed box plans these days - I highly recommend you check out greenboy.us/fEARful or Bill Fitzmaurice before getting started.

    There are lots of others out there too. There really is a science behind it, and it really does make a big difference in the quality of the final product.

    I built a fEARful 15/6 tube last year and I will never purchase a speaker cabinet again. Done right, you can't lose.
  8. Jools4001

    Jools4001 Supporting Member


    If you're really going to make a better mousetrap, then you either need to learn all about how to do it properly, or accept that other people with more knowledge and time invested in it have got there before you. You are extremely unlikely to make a better product than they've already come up with on your first attempt.

    The web abounds with tested speaker designs...fEarful, Bill Fitzmaurice, builders on this forum that do know their way around WinISD.

    BTW... What are your goals? Beware going for it on a cost basis, because although building your own cab CAN be cheaper if you do it right, and give you a product comparable to more expensive commercial designs, it still ain't cheap if you want to do it properly.
  9. TrevorOfDoom

    TrevorOfDoom Supporting Member

    Jun 17, 2007
    Austin, TX
    While I dig the fEarful idea, i already own the Bag End speaker (came from my BE cab).
    I want it to pair well with my Bag End S15L.
    My idea was to build a copy of the small S15, but add some size to bring down the mid push that those cabs have.
  10. Cool. Definitely don't want to poo-poo your idea and understand the desire to re-use the speaker you have, but watch out: you go and build yourself a cab and you are going to open yourself up to a whole new universe of GAS.

    Regarding your plan to copy the design of the cab you have and change the dimensions to get a certain effect: my feeling is that it will be a lot of effort and potentially a lot of expense in pursuit of a result that will be unpredictable and suboptimal at best.
  11. TrevorOfDoom

    TrevorOfDoom Supporting Member

    Jun 17, 2007
    Austin, TX
    So no cube. Could i build it 18"x18"x16" and be safe? A little extra room for a little extra oomph?
  12. 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)
    Normally I'd have thought that a 5" diameter hole in the back of an 18" x 18" x 15" box would tune it too high for electric bass, but apparently Bag End's woofer is fine with that, so I don't think the woofer would have a problem with your increasing the depth of the box a little bit deeper than the factory box. The tuning frequency will move down about 3 Hz as you deepen the box by 1" (assuming you keep the port diameter and depth the same).
  13. Wait...
    You took a Bag End 15" speaker out of a Bag End cab suitable for it? Isn't that like trying to fix something that isn't broken?

    Since you're doing it anyways, if you make the front of the cab square (edit: or any shape.) be sure to place the driver off-center to reduce internal resonance. As Billfitzmaurice would tell you, "Symmetry looks good, sounds bad."
  14. bobcruz


    Mar 10, 2004
    Alameda, CA
  15. TrevorOfDoom

    TrevorOfDoom Supporting Member

    Jun 17, 2007
    Austin, TX
    I have a spare speaker.
    I blew it and it was cheaper and faster at the time to just buy a new speaker.
    I recently had the blown one reconed so now i'd like an additional box for when i need it.

    Since i don't rightly know what i'm doing, i guess i'll just build an 18"x18"x15" box like the small Bag End and just call it a day.
  16. StraightSix


    Nov 23, 2011
    That sounds like the best idea - copy the dimensions and ports of your existing Bag End cab and you won't go too far wrong.

    Good luck.
  17. TrevorOfDoom

    TrevorOfDoom Supporting Member

    Jun 17, 2007
    Austin, TX
    I take that back: i'm building the 18"x18"x16", unless someone can tell me why I shouldn't.
    I'd like the slightly bigger box to offset the inset handles i've got, and hopefully it'll give me a bit more booty.
    I'll try and find the T&S specs for my speaker, let the experts know how it goes. Thanks!
  18. TrevorOfDoom

    TrevorOfDoom Supporting Member

    Jun 17, 2007
    Austin, TX
    okay, last time:
    how about I build a cab 18"x20"x16", 5" circular port?

    Bag End uses the Eminence Legend CA158, as near as I can tell. However, BE claims slightly lower power handling, I think as a way to build them in a smaller box than the manufacturer's recommended size.

    I used fdeck's program that Bob Cruz suggested, and the only problem I had is that I have no idea what the port is tuned to on my cabinet, nor do I have any idea how to calculate that on my prospective cab.