Decible calculatin'?

Discussion in 'Amps and Cabs [BG]' started by Nomadic Herder, Oct 8, 2001.

  1. Is there any kind of formula with which one can calculate how many decibles an amp is capable of?

    And can anyone tell me how many decibles my Ampeg B3158 (100 watts to a 15 and 50 to an 8) can put out? And how many of those are before it distorts?
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    It's not calculated from the amp specs, but the speaker specs - the SPL rating.

    Let's say a cab has SPL of 100 dB 1W/1m and a power handling of 100 W RMS.

    That's means if you put 1 W into it you get roughly 100 dB.

    10 times the power give you + 10dB.

    So you get 120 dB with 100 W power.

    Another way of calculating it:
    Twice the power gives you +3 dB

    1W = 100dB
    2W = 103dB
    4W = 106dB
    8W = 109dB
    16W = 112dB
    32W = 115dB
    64W = 118dB
    128W = 121dB

    This also shows the logarithmic relationship quite clearly.
  3. Conclusion: you need to know the speaker's sensitivity first (the "dB-at-1W-at-1m" figure)

    The maximum SPL is always the "power-at-the-verge-of-clipping".
  4. HeavyDuty

    HeavyDuty Supporting Curmudgeon Staff Member Gold Supporting Member

    Jun 26, 2000
    Suburban Chicago, IL
    Then, if you're like me and suck at advanced math, go here .
  5. Steven Green

    Steven Green

    Jul 25, 2001
    Pacific NW
    What if you have two cabs that have a different dB/SPL rating?

    I have a Eden 410XLT which is 106 @1w/1m


    118XL which is 100 dB @1w/1m

    and 625 W rms driving them?

    What would my total SPL be?
  6. Steven Green

    Steven Green

    Jul 25, 2001
    Pacific NW
    Also, is that MAX or not? If not, what is MAX?