Discussion in 'General Electronics Chat' started by justin77, Apr 3, 2010.

  1. justin77

    Thread Starter New Member

    Apr 3, 2010
    I like to know the usual efficiency rate for a subwoofer.
  2. kkazem

    Active Member

    Jul 23, 2009

    I don't know that there is a "usual" efficiency for a sub-wooferr. Also, it's not clear if you're only asking about the speaker itself, or the speaker + amplifier efficiency. However, there are some things we can deduce about it. First, efficiency is defined mathematically as (100%*Power Out/Power In). This can be rewritten as (100%*Power Out/[Power Out + Power Loss]). It can be thought of as a measure of the relative amount of power loss compared to the output power. Power lost, in this case, is manifested as heat. So, if you place a thermocouple on the subwoofer or even just your hand, and feel or measure very little heat above the ambient temperature, then the subwoofer is highly efficient. There are three main components to this heat loss: a) The core loss in the magnet (stator), b) the resistive copper loss in the coil(armature), and c) additional copper loss due to the skin effect of ac signals.
    Well, that's about all I can tell you except that the power in is easily measured, but the power out is a bit harder to measure as it involves some physics in addition to the measurement of the sound pressure. But it can be done.
    Good luck,
    Kamran Kazem