Convert electrical power to dB(SPL) for speaker?

Discussion in 'General Electronics Chat' started by blah2222, Dec 13, 2012.

  1. blah2222

    Thread Starter Well-Known Member

    May 3, 2010

    I am wondering if there is a good way of calculating a speaker's dB(SPL) at a certain volume level if you know the its rms voltage/current/power?

    Other factors would also be speaker diameter and distance from which observer is listening from but I'm curious as I don't really want to by an SPL meter if it's not necessary.

  2. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    The datasheet of a speaker spec's its SPL so there is not much to calculate but its power and distance.

    The size of the magnet and the smallness of the gap between the moving voice coil and the magnet assembly affect the sensitivity of a speaker.

    Some cheap speakers produce a high SPL at only one frequency and many hifi speakers produce a lower SPL at all frequencies.

    A cheap speaker focusses higher frequencies into a narrow beam. A good speaker has a wide angle for most frequencies.
  3. tubeguy

    Well-Known Member

    Nov 3, 2012
    An example of a speaker sensitivity spec would be 90db@1watt/1meter.

    To calculate SPL for increased power you add 3db every time you double the power at the same 1 meter distance. The speaker would produce 93db with 2 watts, 96db with 4 watts etc..

    To calculate SPL for increased distance you subtract 6db every time you double the distance from the speaker.
  4. bertus


    Apr 5, 2008