Minimum Xmax for bassguitar speakers.

Discussion in 'Amps and Cabs [BG]' started by Goose55, Mar 11, 2020.

  1. Hi,
    I've got my eye on a vintage bass cab 2x12. It doesnt realy look like a bass cab, it's a bit smaller. The speaker are Eminence Gamma 12A. On the site of Eminence the specs show that they are 300 watts with a Xmax of 16 mm. And that 16 mm looks a bit low. But still it can handle 300 watt per speaker. The specs also say that its usable for bassguitar. The guy selling the cab have used it for many years for bass.
    What do you guys think? Isnt 16 mm a bit low?
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    16mm??? That's huge... I think you mean 1.6mm?

    It depends very much on the application, how much power you need to handle, how loud you need to be and how low you need to go.

    Everything is a tradeoff of many interrelated variables.
    rogypop and Inara like this.
  3. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    16mm would be huge.
    and would be a muddy subwoofer

    Gamma 12A has a Xmax of 1.5mm
    the period makes big difference

    smaller gap height would mean more bandwidth and high sensitivity
    meaning sensitivity is high around 98 dB and bandwidth has enough high end for full range use

    Gamma12a is discontinued driver likewise the 15" version or Gamma15a also discontinued
    both of these drivers used larger magnets and had high sensitivity
    and were very very typical bass drivers for alot of bass combos

    they were replaced with the Beta 12a2 and the Beta15a for
    recommended manufacture /oem use

    metalworks and cone is about same cost, price per pallet is lowered
    by reducing magnet weight. and the 12" and 15" perform about the same
    sensitivity is slightly lower.

    anyhoo blah blah blah
    point is the driver specs were most likely done with older gap/voice coil height for Xmax
    10% distortion is measured or assumed to a set mathematical calculation .

    now its common to use laser measurements for xmax.
    so actual advertised xmax will tend to be higher than the older measurement calculations

    these 1.5mm coils would most likely measure anywhere from 2.5mm to 3.5mm with a laser
    or would be similar to performance as a typical beta

    the gammas just have higher sensitivity
    which means a little more output or max SPL before hitting distortion.

    they will have the same typical 40 to 70 watts of power handling per driver below 100hz
    just like a beta.

    so 300 watts thermal, 2x12 would be about 140 to 220 watts of power handling before 10% distortion or what is considered xmax.
    depending on how you EQ and play your bass
    this is totally normal for 3mm drivers or in this case an older measured 1.5mm driver.
    xlim before driver damage would assume 6 to 10 mm

    the SVT810 only has 3mm drivers but with 8 of them it can do 400 to 500 watts before distortion
    if you measured the gap it probably be closer to 1.5 to 1.8mm xmax
    Last edited: Mar 11, 2020
    Pulverizor likes this.
  4. rogypop


    Jan 10, 2009
    Many good bass guitar drivers live in 5 to 8mm xmax range. This is just one of the factors. As already mentioned, 9+ mm is a subwoofer range and those loudspeakers usually suffer the lack of upper mids and lower sensitivity thus require bigger amps and dedicated midrange drivers. Loudspeakers are all about compromises.