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2x10 Cab Design - WinISD Curve Question

Discussion in 'Amps and Cabs [BG]' started by Roundwound, Nov 28, 2005.


  1. Roundwound

    Roundwound

    May 13, 2004
    Peoria, IL
    I decided to design and build a 2x10 bass cab for the fun of it. I have other commerical cabs I can use, so this is not a do or die project. Using the lite version of WinISD (not pro) I plugged in the specs for the following driver:

    Warrior 10

    Problem Question
    Here are the results for one design I came up with. My question follows the data:

    Number of drivers : 2
    Box type : Vented
    Box size : 3.700 ft^3
    Tuning frequency : 32.00 Hz
    Vent : 1 vent(s)
    2.73 in length for each
    3.00 in round


    Freq Gain SPL
    [Hz] [dB] [dB]
    20.00 -24.13 77.88
    25.00 -12.59 89.42
    30.00 0.81 102.82
    35.00 2.87 104.88
    40.00 0.31 102.32
    45.00 -0.17 101.84
    50.00 0.03 102.04
    55.00 0.42 102.43
    60.00 0.81 102.82
    65.00 1.12 103.13
    70.00 1.34 103.35
    75.00 1.48 103.49
    80.00 1.54 103.55
    85.00 1.56 103.57
    90.00 1.53 103.54
    95.00 1.49 103.50
    100.00 1.43 103.44

    However, for this result and any other frequency tuning/volume combination I played with, the db/gain curve goes up sharply right before my desired frequency tuning, sort of like a ski jump. Is this a common result or an anomaly? Or is it just a "boom" effect that I can insulate out? I double-checked the speaker specs I typed in, and there doesn't seem to be a problem.

    I know the design provided is for 32 HZ tuning...The 31HZ results indicated just a little bit more of a negative relative gain/db curve than I wanted in the 50-40 HZ range, but maybe I'm being picky. My priority is to build a midrange bass cab that can at least attempt to handle a low b and not fall out too much on the low notes (60-31HZ), since I will use it mostly standalone for worship music and an occassional rock jam in small venues. It will be a 4ohm cab running through my Peavey Firebass 700 head (475w@4ohm, 700w@2ohm when my 2x12 is added as a "sub").

    Any questions, comments, help, etc. is appreciated.

    Thanks!
     
  2. Disclaimer: I'm not an expert so everything I say take with a pinch of salt. I have built a single driver cab with winISD.
    Based on what I learnt doing that:

    The hump you describe is normal, box size is a factor. I think some designers purposefully put the hump in there to get extra power at that freq and give the cab a certain voicing.

    I very much doubt you will be getting the performance you hope for based on the figures ie. 102db at 35hz (1 watt presumably)

    That would be great performance for a pair of much larger speaker at that freq, as far as I know.

    Remeber, the sensitivty rating of a driver varies over frequency. Ideally you need graph plot to see this...eminence provide them for their drivers. The warrior may have an average sens. of 99, or just at say 2000hz (where it might be at its most sensitive), but its most likely response will drop off below 100hz, quite significantly as you approach 30hz...

    for example
    http://editweb.iglou.com/eminence/eminence/pages/products02/speakpro/kap10.htm

    notice how this driver is about 10db down at 50hz than at 200hz - and thats without taking into consideration issues with the box.

    Also check the group delay window in winisd... the higher the delay value the bigger the 'mud' factor.

    There might be more expensive 10inch drivers out there which are loud and do go low though... partsexpress have many manufacturers.

    Rolling your own is fun though.


     
  3. The Clap

    The Clap

    Jan 5, 2004
    Scottsdale, AZ
    You're tuning way too low at 32hz, that's a full octave below the speaker's Fs. Also, 3.7ft for a box to contain 2 speakers with a combined Vas of just over 1ft is much too large. These aren't particularly high quality speakers; you shouldn't worry as much about graphing them in WinISD for low end extension, because it just won't be there.
     
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Stay away from those drivers, they have a poor reputation. Do it right, use BP102s or Beta 10s or B102s, and accept the results WinISD gives you. You'll likely end up around 2 cu ft per driver, tuned between 40 and 50 Hz. Flat response below 60 Hz won't happen but that's OK, it's supposed to be like that, 'tis the nature of the beast. Never even consider a driver with a Qts higher than 0.5, nor less than .25.
     
  5. Roundwound

    Roundwound

    May 13, 2004
    Peoria, IL
    Thanks for the great information. I know they're not the best drivers (plus someone is giving them to me for free) and I'm not expecting a lot out of this first project, but if it's usable for some limited applications I'll call it a success. You all are right, I should keep the tuning to a level that's right for the speakers. If the speaker performance was really that good for a 10 at those low HZ levels we'd all just own one cab. And I'll check that group delay window for the mud factor.

    Just thought of an idea...Perhaps I should just build the cabinet around the BP102 that Bill mentioned (even MSC states the Warrior is close to that spec), throw these free Warriors in initially and install BPs when I get a hold of some. I know Eminence has some cab plans for their speakers; I'll check that out, too.
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Don't worry about it below 100 Hz. The only thing about the BP102 is that it dies at 2.5kHz, so not much midrange to be had. If used with a midrange driver it's quite good, but can sound dull on its own.