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Eminence Legend B102 DIY Cab Help?

Discussion in 'Amps and Cabs [BG]' started by Dylan Bretz, Jun 25, 2018.


  1. Dylan Bretz

    Dylan Bretz

    Jun 25, 2018
    Ohio
    I'm designing a cab using WinISD for the Eminence Legend B102. It's a 200 watt 8ohm driver. I'll be using it for coffee house and bar room gigs, so pushing tons of wattage is not a huge concern. Matching the right tone is more important to me. The B102 is nice because it has a pretty large frequency range (44Hz - 4KHz) which is great for my upright bass playing as well as my 5 String (High C).

    Here's the problem:

    The Transfer Function Magnitude graph looks great when the cab is 2.4 cu ft. and tuned to 45Hz. Real smooth graph with F3 at 44Hz. But the Maximum Power graph dips way low (only 22 watts at 65Hz). But when I compensate for the Maximum Power (1 cu ft. at 90Hz; power still dips down to 82 watts at 120Hz) the F3 moves up to 78Hz and a bump forms around 115Hz. Any suggestions to find a suitable cab size? And am I making too big of a deal about the Maximum Power??

    Thanks,
    - Dylan
     
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    You have discovered one of the challenges to designing a cabinet that respects the mechanical power handling of the speaker. It's a very real issue for us designers.

    Now the bigger problem, or the other limitation which makes the mechanical power handling more of an issue is the low sensitivity. This means that you will bump up against the mechanical power handling limitation more often.

    The number you arrived at seems a little low though, you might go back and double-check that you have all the numbers entered correctly (including the correct units for each number). I don't use that program, but I will go back and maybe hand calculate a few data points when the results don't match what I expect.
     
  3. Rick James

    Rick James Inactive

    Feb 24, 2007
    New Jersey
    You're not making a big deal at all. That driver just isn't good for electric bass. The reason is the short xmax. You'll never handle low C with enough output unless you're using at least two if not four of them. The Beta 12LTA would be better, but I wouldn't be asking even a twelve with less than 4.5mm xmax to handle low C.
     
  4. Dylan Bretz

    Dylan Bretz

    Jun 25, 2018
    Ohio
    I went back and re-entered all of the parameters into WinISD, double checking for units. I also entered the parameters WinISD Pro to see if that made a difference with the calculations, but both attempts I made spit back the same numbers at me.

    I am not familiar with hand calculating with the given parameters, but I feel confident that I've put in all of the parameters correctly, so I don't think that is an issue.

    Any ideas?

    - Dylan
     
  5. Dylan Bretz

    Dylan Bretz

    Jun 25, 2018
    Ohio
    I play a high C so I really just need to get the driver to handle decent down to 41Hz. The Xmax is short on the B102, but I picked one up for a steal of a price that I just couldn't turn down. That leaves me trying to figure out how to compensate for the Xmax, but I can't seem to find any happy medium with a decently low F3 and minimized distortion - without making my volume .35 cu ft. (but that seems unreasonable).

    - Dylan
     
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Simple answer... you can't compensate.
     
    Stumbo likes this.
  7. Dylan Bretz

    Dylan Bretz

    Jun 25, 2018
    Ohio
    Thread solved! haha

    I was afraid of this, but I figured as much. Thanks helping!
    - Dylan
     
    Stumbo likes this.
  8. BadExample

    BadExample

    Jan 21, 2016
    Injiana
    Are you using the latest version of winISD pro? The not pro version is buggy.
     
    agedhorse and Stumbo like this.
  9. Dylan Bretz

    Dylan Bretz

    Jun 25, 2018
    Ohio
    I'm using the latest version, so that shouldn't be an issue. I'm guessing I just have to cut my losses on that driver!
     
  10. BogeyBass

    BogeyBass Suspended

    Sep 14, 2010
    It's not software it's 102 driver. Older version is buggy with newer operating systems. But still works fine. New version is compatible with newer operating systems. Thats it. Nothing new and special. Same formulas same functions

    And yes the 102 does like a large cabinet to get flat response. But as you found power handling is horrible in such large volume.

    Happy medium with the 102 is around 1.3 to 1.6 cubic feet and keep the tuning around 48 to 50hz

    Its about all you get with 102 and as mentioned sensitivity is low. Best application is 2x10 pair if you want power handling . with a pair you can do about 1.3 cubic per driver and tune 45 to 48hz

    Realistic F3 in 1 cubic will always be 65 to 75 hz regardless of driver with musical instrument type speakers

    More to be gained in 2 cubic like you found but efficiency and bandwidth at that point is found with a 12" driver its it average typical volume for 12" with 55 to 65hz still being achievable f3

    To really dip down a 15" driver in 3 cubic feet brings you closer to maybe 48 to 55hz. Real big boys are your large box 15 inch drivers in 4 cubic feet. And same as well tradeoff off power handling in 4 cubic to maybe touch 48/50hz

    With typical Efficiency Bandwidth Product (EBP) of 80 to 100 musical instrument speakers these are typical volumes. And deep F3 only come from ...airspace.

    .9 to 1.6 = 10" efficiency = 92/96dB
    1.6 to 2.4 =12" efficiency = 94/98dB
    2.6 to 3.2 small box 15" = 95/101dB
    3.2 to 4.4 large box 15" = 95/101dB

    Dont worry plenty EQ in modern amps
    And 2nd harmonic in the 80s is more important than the 40hz and is more audible.

    It's why your classic peg 810 with sealed drivers only in .9 cubic per driver with F3 maybe at 75hz lol still makes many many players happy. It hits 80 hz just fine. Efficiency per driver and power handling is ok. But it uses 8 speakers so more headroom.

    Ive done drop D C and A to absurd levels with 810s but just used 2 of them.
     
    Last edited: Jun 25, 2018

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