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Designing a box, input appreciated.

Discussion in 'Amps and Cabs [BG]' started by SomeBum, Sep 20, 2001.

  1. Sep 20, 2001 #1
    SomeBum

    SomeBum Guest

    Sep 20, 2001
    Hello,

    I'm currently planning a box which will have 2 15" PA Drivers. Normally I'd just go for a standard one on top of the other box (ported) but I was wondering if anybody had any other suggestions as to a design that might be more effective.

    I've seen Foldback speakers with what looks like wooden square ports, with a sloping 'floor' of the port and a small gap for air coming out of the box. Does anyone know what this type of design is called?

    I might be confusing a lot of people somewhat so I'll just clarify what I mean for the first thing. I plan to make the box like this:

    I---------------I
    I I
    I 15" I
    I I
    I 15" I
    I I
    I Port/s I
    I---------------I

    Never before have I seen such fantastic ascii art :)

    thanks if anybody replies to this.
     
  2. Sep 20, 2001 #2
    Hategear

    Hategear Workin' hard at hardly workin'.

    Apr 6, 2001
    Appleton, Swissconsin
    Put some nice wheels on it.
     
  3. Sep 20, 2001 #3
    jasonbraatz

    jasonbraatz Supporting Member

    Oct 18, 2000
    Milwaukee, WI
    you know what'd be killer?


    make the top 15" normal, add a tweeter, and then make the second 15" a folded horn type.


    so you'd have big bass up front, and big bass far away.


    jason
     
  4. Sep 20, 2001 #4
    Joris

    Joris

    Jan 20, 2000
    Zevenbergen, The Netherlands
    The cab you're talking about is a folded horn type. It's not possible to design one yourself. Try to find an example and copy it exactly, including the brand and type of speakers.
     
  5. Sep 20, 2001 #5
    bgavin

    bgavin

    May 3, 2001
    Orangevale, CA 95662
    Give yourself instant gratification: buy one instead. :D

    However, if you are planning on building with PA drivers, you must be looking for sound reinforcement bass response, which is real loud but not particularly low. You can install PA class drivers in a wide variety of boxes that are all too small, and the loss of bass response will not be a problem at all because the loss is below voice range. Design them for small size and ease of carry.

    IMO, give up on the folded horns, etc. If you want more noise, add another driver. That will give you more noise and power handling capability than a marginal front loaded short horn which is more difficult to accomodate and harder to haul around.

    Our band uses Peavey mains which consist of 2x15, a mid-range horn, and high ranger tweeter horn in a cabinet with built in wheels. We have two of these and they are not too heavy, are easy to move and sound great for voice use. They make lots of noise too.

    If you REALLY want to make a lot of PA noise, use a pair of JBL E130, a JBL 2490 or 375 midrange driver and horn assembly, and a bullet tweeter. I ran this PA for years and it is capable of destroying the reproductive systems of most adults from a block away. It was tiny, modular, and easy to carry. The downside is the cost.

    Skip the folded horns, and my advise is skip building unless it is a skill you already have, along with all the tools.
     
  6. Sep 20, 2001 #6
    Joris

    Joris

    Jan 20, 2000
    Zevenbergen, The Netherlands
    I agree. If this will be the very first speaker project you're gonna do, get ready to be disappointed. Start with something small instead, like a 2-way bookshelf hifi cabinet.

    Folded horns are for sound reinforcement. Not for stage use. They "throw" the sound out into the audience, quite a few yards away. And they're a pain in the b*tt to design, build, and haul around.

    If you want to play it easy, build a closed box. You can hardly go wrong on those.
     
  7. Sep 20, 2001 #7
    SomeBum

    SomeBum Guest

    Sep 20, 2001
    Actually this isn't the first build I've participated in. I have a large 6 cubic feet 2 x 15" Box (with subwoofers, not PA Drivers) that I built so I know what I'm doing, just having not used PA drivers before I though perhaps there was a few tricks I could employ for better performance.

    I'll be porting the box to increase the response in the low end.

    As I said earlier, my intentions are to build a simple one on top of the other box, looking around on the net I think folded horns are doable for me but probably not worth the trouble especially as I'm not intending this for sound reinforcement, just simple amplification of bass for practising and maybe behind me gigging.

    Incidentally, at what frequency do people generally select for a two way crossover to a 15" PA Driver and Horn? (and I do realise that frequency response varies with driver).

    Good idea about the wheels btw, this will be one heavy heavy box. I'm hoping to get away with about 4 cubic feet but if bass response is less than desired (when I simulate it in a box design program) I guess I might have to increase the size.

    thanks for your suggestions