Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Speakers, loudness, and electrical input

  1. Feb 26, 2015 #1
    What is the formula for speaker input/output?

    On a related topic, on a motor an input of x (electricity) equals output of y (movement) and an input of y (movement) equals output of x (electricity)
    x=y and y=x
    Is the theory of x=y / y=x applicable to speakers? x=electricity y=loudness
  2. jcsd
  3. Feb 26, 2015 #2


    User Avatar
    Science Advisor
    Gold Member

    You have forgotten to include efficiency. The output of any device will never be equal to the input. And of course some types of motors will not work as generators. But you have the general idea correct. I don't believe there is any magic formula for speakers. The input to output relationship is usually a manufacturers spec and will vary from one transducer to the next. Loudspeakers are generally not considered very efficient at all.
  4. Feb 26, 2015 #3


    User Avatar
    Gold Member

  5. Feb 26, 2015 #4
    the standard measurement is 1 watt at 1 meter to get the sound pressure level that varies with speaker efficiency.
  6. Feb 26, 2015 #5

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

    Just a thought -
    Speakers having DC resistance around 80% of nominal impedance are condemned to low efficiency as converters of electrical to mechanical energy..

    a search on "theory of loudspeakers" should be fruitful.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook