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DIY 2x10" - little help needed

Discussion in 'Amps and Cabs [BG]' started by mikeboth, Aug 4, 2002.


  1. mikeboth

    mikeboth The last thing you'll ever see

    Jun 14, 2002
    Tallinn, Estonia
    Operator: prophecysound systems
    I'm working on plans for a DIY 2x10" with horn and need help / advice on a couple of points:
    - regarding the 'tuning' frequency for a ported box, are there any 'rules' I should be following as regards tuning frequency vs. Fs? Currently I'm planning on tuning my box to 39Hz (to avoid 'farting' problems with low E).
    - with rectangular ports, is it ok to make them as wide as the 'face' of the box? I've tweaked my numbers so that the port length is 1.8cm, which is the thickness of the MDF I'm using; this would be very convenient, but I'm unsure if there any rules I need to follow here.

    BTW, I'm going to be using 2 Eminence beta 10s, and doing up some plans for future DIYers (assuming the end result is not something to be ashamed of!). I'm hoping to use this box for jazz combo rehearsals and pair it with a 1x12" or 1x15" for gigs.

    Oh! And kudos to Liam aka Psychobiker for his assistance thus far. :D

    MikeB
     
  2. AFAIK if you keep the proper port area for the length required you should be fine. At least that's the way it seems to work in the WinISD software. That's also true of most of the dimensions of a cab. Keep the volume constant and tweak the dimensions to make something you want. I think I've heard that you shouldn't have 2 identical dimensions in the equation also - something about standing waves...?

    But I'm sure that Bgavin or someone will come along here and have a bit more information.
     
  3. Every driver has a few different alignments for what you are trying to accomplish. The Beta 10" is essentially identical to the Carvin PS10 used in the Carvin RL210, etc cabs.

    The Beta 10 requires 4.1 cubic feet net volume to realize its full potential. If you stuff it into a tiny cabinet (RL210) it cuts the bottom off the low end, and it sounds just like... a Carvin RL210.

    My spread sheet shows one alignment, which is the optimum flat alignment for lowest flat response. Others (Avatar) go for the EBS (extended bass shelf) which is putting a small volume driver into a large cab to extend the bass response.

    The Avatar uses the Delta 10" which is optimum in only 0.67 cubic feet, but has very poor low end response. Essentially nothing below 80 Hz. The EBS alignment is effective at extending the low end, but introduces significant group delay as a consequence. This is what makes a bass driver sound "muddy". The opposite is a sealed cabinet, which makes the bass as tight as it can be for that driver.

    Tuning frequency is determined by the driver parameters and the enclosure. It is not arbitrary.

    Master the book "Loudspeaker Design Cookbook" by Vance Dickason. Once you understand this book, you can build something that will sound good. Unless you are experimenting just for the fun of it, I encourage you to buy a cab for serious playing.
     
  4. mikeboth

    mikeboth The last thing you'll ever see

    Jun 14, 2002
    Tallinn, Estonia
    Operator: prophecysound systems
    Actually, I *am* experimenting for the fun of it. :D Your spreadsheet it very useful - thanks a lot for putting it together. I purposely steered away from the higher-powered Eminence 10" drivers for the reasons you mention - lack of low-end response. It has been interesting to play around with WinISD and run through the trade-offs required as regards efficiency, low-end response and group delay, but I think I've finally settled on a design that I'd be happy with - it certainly won't be the smallest 2x10", nor the lightest nor the loudest, but I'm willing to accept the end result.

    I ended up with a nominal 130L box (60cm wide x 44.5 cm high x 60cm deep using 18mm MDF) tuned to 41Hz; the response is down -3db @ ~ 59Hz, and group delay is around 9ms for low E. I still need to work out the volume differences for bracing, the drivers etc, but this is the design I'm going to try out.

    MikeB