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Building a sealed 4x10 cab...

Discussion in 'Amps and Cabs [BG]' started by Stewbone, Nov 19, 2002.


  1. I have a sealed 4x10 cab 'cause it's all about punch- I run it with a 1x15 EAW w/ JBL 2226H driver (the 4x10 has Eminence Betas). Trouble is, the cab's made of panels of a a Luaun and foam sandwich that isn't a real classic example of expert joinery. It's kind of falling apart!

    I'd ike to build a new cab out of Birch ply, but I'm interested in finding the best plan for one, since I'm going to re-build someone else's job. Why not go it one better, right? So I'm wondering if anyone has the dimensions for the SVT 8x10 sealed refrigerator- the one with the sealed chambers of 2- 10's each?

    I don't know even how important dimensions actually are for a sealed box, since we're not too worried about "throw", or any of that, I guess. Any ideas?

    Stewbone.
     
  2. The only thing to be worried about is that you keep the internal volume of the cabinet the same as the old one. If you want separate chambers for the speakers (good idea, but adds weight) just get each chamber an equal part of the cab volume.

    You could try to redesign the cab, but you'd have to have the exact specs on the speakers.

    Regards,
    Joris.
     
  3. Aha- I was wondering about that membership thing...!

    So, seems as long as I actually bisect the space inside the cab with my chamber wall, that should be equalizing the two. My only (biggest) question really was concerning the best design idea for a sealed cab. I was going to go with the Ampeg idea, only half of the 8x10, since it's reliable old hat.

    Eminence B's are in the cab now, and they make their specs available. I'm going to need to know exactly what to do with all those Fs's and such! Or I could just go with a re-build of what I have here. Maybe Ampeg uses Em B's?

    Thanks for the reply, Joris, looks like I may have to slow down a bit, here! Then again,...

    Stewbone.
     
  4. The Eminence Beta 10 requires a large volume for correct sealed box operation. The Eminence Legend BP102 goes down a little lower, and requires slightly less cabinet volume.

    The Beta 10 B2 Butterworth gives you maximum flat response and requires 1.96 cubic feet per driver. The D2 Bessel alignment requires 5.48 cubic feet per driver, but gives the best transient response.

    You can reduce the volume by 30% by stuffing the sealed box with fiber fill at the rate of 1 pound per cubic foot of volume. For example, a 1.5 cubic foot volume stuffed with 1.5 pounds of fiber fill will appear to the driver as a 1.96 cubic foot sealed box.
     
  5. So, how much volume exactly does a Beta 10 require? I want to build it with a baffle (sealed) between each set of two speakers, and have little idea of what all the Thiele-Small numbers actually translate to concerning building requirements.

    How do I find an optimal plan for this undertaking, Bgavin?

    Stewbone, the seeking.
     
  6. RobOtto

    RobOtto

    Aug 15, 2002
    Denton, TX
  7. The smallest sealed volume for a Beta 10 is 1.96 cubic feet. This provides a Butterworth (B2) sealed alignment which gives the most extended bass response.

    If you use 1.5 cubic feet of volume, and stuff it with 1.5 pounds of fiber fill, you can get an effective volume of 1.96 cubic feet. Sealed cabs are very forgiving, even to large errors in volume.

    Better to err too large than too small, though. The larger cabs have better transient response, but all sealed boxs have better transient response than vented boxes.
     
  8. bgavin you have often mentioned alignments , as for example B2 Butterworth, and I would like to know if it is possible to get a listing of specific alignments and of their use. And how to calculate them for a speaker
     
  9. I keep several alignments in my spread sheet that can be downloaded from my signature belows. The formulas in my spread sheet are easy to follow. I have much more on my site in the /Reference/Music/Speaker Design/ directories.

    Vented flat response:
    SBB4 - larger box, lower tuning, higher F3, best transient performance (tightest punch)

    QB3 - smaller box, higher tuning, lower F3, slightly worse transients

    Discrete - Sometimes called Butterworth or B4, but this is not entirely correct, as these exist only for a single Qts value. There are several formulas for calculating maximum flat response. The WinISD program uses this one.

    Sealed boxes:

    Qtc = 0.500, 2nd Order, most critically damped, largest box, flat group delay

    Qtc = 0.577, D2 Bessel, best non-flat group delay (best transients), large box

    Qtc = 0.707, B2 Butterworth, maximum flat response, compact box, average transients

    Qtc > 0.707 is C2 and other alignments, worse low end response, prone to big booming, worst transients

    There is an excellent text on vented and sealed alignment in Dickason's "Loudspeaker Design Cookbook".

    [ edit ]

    I favor the SBB4 vented alignment because it offers the tightest bass and the lowest tuning frequency. This is always the free air resonant frequency (Fs) of the driver for the SBB4 alignment. I choose drivers based on Fs for the job at hand. A 4-string bass driver (for me) should have an Fs of 41 Hz in SBB4, since I won't be going below low E.

    My subs are Fs = 20 Hz, and I expect to routinely reproduce 26 Hz generated by the dbx 120a synth I recently acquired. My JBL E-155 in-work project is Fs = 30 Hz because that is where it landed. I've been wanting to tinker with an E-155 because it is ideal as a very small stage monitor with PA support.
     
  10. thanks, the problem with your ref. sheet is that i don't have excel

    How are the SBB4 and QB3 calculated?
     
  11. Hey, pardon my abject ignorance (really), but what exactly are transients? In very base terms, please...

    I'm looking, by the way, for a pretty tight, punchy box that can reproduce down to C# with Beta 10's; and I understand from the Eminence website that these speakers are optimized for lead guitar, but suitable for bass guitar... Thanks for your forbearance!

    Stewbone, the knave.
     
  12. Allright- I've got a lot of information here, thanks for everything! I can get on and find whatever else I need, here. I appreciate your time and the sharing of your knowledge. It will go to the making of music worth doing and adding something good to someone's life. Isn't that cool?
    Many thanks,

    Stewbone. :)
     
  13. Rockbobmel

    Rockbobmel Supporting Member

    Stew,
    Did you build the 8-10 or 2/4-10s?