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Newbie seeking input on a DIY cab.

Discussion in 'Amps and Cabs [BG]' started by bw79072, Aug 9, 2012.

  1. bw79072


    Nov 11, 2010
    Greetings from Texas!
    I have lurked here for a couple years, trying to absorb everything I could from the vast knowledge
    bass (pun intended)...BTW, (many props to BFM, GB, JohnK10, etc, etc) and have now gotten to the point where I have
    a few solid concepts, but need some clarification on a few things that I have not been able to find
    in the other threads.
    Although I have played alot of rigs over the better part of 35 years, I never really paid any attention
    to the science(s) behind speaker cab designing. I am about to embark on my 2nd custom
    DIY cabinet (the 1st one looks awesome, but sounds like crap), which will be very similar to JohnK10's
    Starliner. I have tried WinISD, but I find that BassBox 6 Pro works better (for me, that is), so all
    figures come from that. Here's the plan...

    The concept parameters:
    A lightweight 2x15 loud enough to stand on it's own on most gigs with little to no PA help.

    Driver choices:
    Eminence Legend cb158, BassLite2515, 3015 (non-LF)

    The box:
    Total internal volume is 7.279 cu. ft., tuned to roughly 45hz, depending on the driver.

    One thing I'm confused about...I've seen the term 'displacement limited to XXX watts'...am I correct
    in assuming that that is the max power your cab can handle at low frequency where the driver(s)
    reach Xmax and any power applied over that will only bring doom and despair?

    For instance, If I use the 3015's, cab tuned to 44.27hz with (2)-4"x0.75" tubes, with no fill, BassBox
    shows maximum cone displacement of 6mm between 80-90hz with 800 watts. Is that the displacement
    limit figure?

    Would it be correct to assume that this box would run fine with just about any head up to the
    750-800 watt range, so long as I pulled the low-bass back a tad?

    I have several head possibilities in mind, but, more on that later..gotta get the cab ironed out first.
    Any thoughts, ideas, opinions, etc. will be greatly appreciated.
  2. will33


    May 22, 2006
    You're looking the right spot there 90hz-ish, but it seems that should be more around 500-some watts with those speakers. With WinISD it's based off a constant sine wave, which a bass guitar signal isn't, so you can usually hit them a little harder than the program predicts. Is BassBox geared more towards representing a plucked string sort of signal? When you pluck a string, there's a big amplitude/power spike in the first few milliseconds of hitting the note, then it tames down to much less as the note rings out.
  3. bw79072


    Nov 11, 2010
    Ok, I think I may have finally gotten the hang of using WinISD...

    According to ISD, using BASSLITE C2515s, in a 45hz, 7.279cu.ft. cab, should yield a displacement limited 225 watts and average roughly 124db. Since the 2515s are rated at 300w each, would it be safe/sane to to feed them anything over the 225 and just EQ accordingly? I was thinking maybe a Tour750 or something in that genre...
  4. will33


    May 22, 2006
    Sure. The displacement limit is where they run out of xmax, generally defined as 10% distortion. The point where they become audibly distorted. When you hear that, it's the limit, just back off a little. Can use any size amp with them, just listen for the distortion limit. They'll quite loud by then (124db). Note the basslite is a 4ohm driver, so you'd have either a 2 ohm or 8ohm 215. I'd probably wire it for 8ohms with a big amp.
  5. bw79072


    Nov 11, 2010
    Yeah I just noticed the ohm issue...lemme see what it says with the Deltalite 2515s...I could just as easily and more cheaply use the Legends, but am trying to build in a little 'schleppage factor'...

    HMmmm, 8ohms + big amp = room for another cab....yummy. LOL
  6. Soulfinger


    Sep 20, 2004
    Houston, TX
    I'm doing about what you're doing (also in Texas), except I think I'm going to do two 1x15s. I'm going for somewhere between 3.5 to 4.0 cu. ft. per box, tuned to 45Hz. I haven't looked at the 2515s---I think I'm going to use the Faital Pro 15PR400. They might not go quite as loud as the 3015's, but they'll get plenty loud, and with less power.
  7. SBrown


    Dec 5, 2008
    Auburn, CA
  8. bw79072


    Nov 11, 2010
    Ok so I’ve been messing around with ISD trying to learn its in’s and outs…a couple days ago I was playing with some cab volumes and tunings, when, I thought I’d just put in the basics and let the program do all the work…here’s what I found….

    I chose 2 - 3015s in a 45hz box…ISD gave me a box size of about 6cu. ft. using 2 – 4” port tubes…
    Then I got to looking at the graphs and ***!!! Displacement limit of…wait for it…ONLY 650watts??? HOLY CRAP! And if fed the 900 watts the two drivers are rated for combined, it says I would be rewarded with a liver-shattering 130db!!!

    Question 1: are these actual, for real, honest to goodness numbers?

    Question 2; is this approximately what GB’s Dually design does? If so, I’m headed for the lumber yard for some plywood!

  9. astack

    astack Supporting Member

    Nov 12, 2011
    St. Louis, MO
    Hmm, could be reasonable for the Kappas, but I'd check the other graphs before getting too excited. My guess is something is getting traded off for that. Maybe a pretty high f3? And you're reading the excursion limit from the graph with the dip, yeah (if that makes sense)?

    Also, check port speed - you're probably in chuff city right now. Give it more port to make GB happy :)

    Otherwise, sounds like you're doing your homework well. :cool:

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