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can someone critique my design

Discussion in 'Amps and Cabs [BG]' started by JacksonsMen, Feb 13, 2006.


  1. ok, someone that has a bit more experiance with this than i do... im planning to build a 1x15 cab, and thought that i was done with the designing phase, but reading something about tuning frequencies and what not, i thought it best to have someone whith more knowlage look over my info

    the Theile Small on the speaker (Emi Legend B15) are
    Qts: 0.45
    Vas: 7.6ft^3
    Fs: 40.00htz
    Re: 6.55ohm
    Le: .51
    Xmax: 0.3mm
    Z:166ohm
    Qms: 11.44
    Qes: 0.47
    SPL: 102.00dB
    Pe: 300W
    BL: 16.20
    dia: 15.00in
    Sd: 0.086m^2

    this is the gain plot that i have so far for it, does anything here send up a red flag?
    [​IMG]
     
  2. didnt realize it, but in that picture you cant tell that it peaks out at +.4dB@80-99htz
     
  3. No, but it is difficult to comment without knowing box volume and tuning freq. What are they?
     
  4. oh, my bad. box is tuned to 37htz with a volume of 7ft^3
     
  5. 7 cubic feet? for a 1x15 cab? That is huge.... are you sure you want this?
     
  6. VAS on it is 7.6, and WIN ISD tried to make it 10.6. if my math was corrct, which im pretty sure it is, interior dimensions were 24"x24"x20" . Exterior dims are right at 21.5x25.5x27.5.......which now that i atcually think about is huge......maybe a couple alternate designs are about to hit the works

    :edit:
    i just ran some numbers and realized that if i knock it down to 5.667ft^3, even down to 4.772ft^3 and still get a very similar gain plot
     
  7. Try 3-3.5 cubic feet... 40 hertz is not as important as you think. Most basses do not have a lot of output in that region; 80 hertz is much more important. I find 40 hertz at -6 db to be sufficient.
     
  8. even if i do play on the low b quite a bit?, and on a very quick ISD plot, 80htz is at +1dB, 40htz @-8dB, and 31htz at a wopping low of -13dB
     
  9. Yes.. let me explain: most of the output from your bass is not fundamental freq. but harmonic. That would be 80 hertz for a 4 string and 60 for a 5 string. This is true for allmost all bolt-on basses; some neck-through basses put out more fundamental. And to assure you even more: the graphs in winISD are measured halfspace, wich would translate to outdoors... for indoors you can add 3 db in the bass region.
    Also a tip: download the alpha version of winISD: it has a lot more functions than the beta version; also some minor bugs but you will learn to work around those. Especially the cone excursion graph in the alpha version is very helpfull; provided you understand that x-max is less important than x-mech.
     
  10. teach me Obi Wahn... ive never gotten too technical about boxes, since all ive ever built were copies or basic car audio boxes. as far as the halfspace, i figured it was a bit off, but i didnt figure it for 3dB of variance.

    what is x-mech though, ive never even heard of it
     
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Do not use the B15, it has inadequate xmax and Vd for bass, use the CB 15. Even better, wait until the Deltalite II 2515 is available, better performance than the CB 15, weighs five pounds.
     
  12. I am certinly not the Obi-wan of cabdesign here on talkbass... that would probably be Billfitzmaurice...
    x-mech is max cone excursion before damage occurs.. x-max is max cone excursion before distortion. Since the human ear is not very sensitive to distortion in the bass region you better use x-mech as your guide. 'farting out' occurs just before x-mech, not x-max.
     
  13. gotya....yeah, i have noticed the inadequate xmax on the b15, but i already had one here, if/when it fails i will probably get a cb15 for it, and make necisary changes to the cab if need be
     
  14. hmm, again, just ran a rough shot at ISD, and it seems like the CB15 has much worse response than the b15, although more capable......does that make any sense to anyone?
     
  15. All driver designs are compromises... in this case Eminence chose a hard cone suspension for the B15; this makes for a very efficient driver but at the expense of x-max. The suspension on the CB 15 is a lot more loose; thus the driver is not very efficient but it can take a lot of power before x-max since the voice coil is longer.
     
  16. ah, i see.... well when i plugged the TS perams for the CB15 into the settup i already had for the B15 it was a different plot, but not an entirely bad one, so ill stick to it, build the cab, put the B15 in, if it fails or i dont like it, ill swap for the CB15
     
  17. Regarding the design differences between the B15 and the CB15:
    - The B15 is for those who are somewhat short in amp power so they need the most efficient driver out there. I would not reccomend it for amps with more than 100-150 watts.
    - The CB 15 is designed for those with more than 100-150 watts at their disposal.
     
  18. yeah, my amp is only rated at 250W@4ohms, but i rarely run it at even half volume with the preamps at 0/10 and 3/10 respectively
     
  19. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Ordinarily I'd also be leaning towards a speaker with a better excursion characteristic. But if the B15 is lying around doing nothing, and you're prepared to accept that it could fail, then go ahead. You learn something every time you build a cab. It'a all experience and in this case, there's no considerable money being flushed away.
     
  20. thats what im going on, this thing should be done this weekend if i get any time after our gig, so ill be sure to update asap