Decibels

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  • 11-19-2009, 08:56 PM
    farfromphile
    Decibels
    Hey guys, I was just thinking about something I heard quite some time ago. If you double your power output, you gain 10dB. For every speaker you add from the same amount of power, you gain 3 dB. So, if you add a second subwoofer the same as the first one you'll gain approx. 13 dB. 10 from doubling power and 3 from another speaker. Can anyone confirm if this is right?
  • 11-19-2009, 09:05 PM
    Mr Peabody
    Decibels aren't as easy as the little quotes people repeat and it tends to start and argument because some hear the 3dB thing where others hear the 10dB thing. Here's a good link I keep for just such an occasion, a good explanation of dB's: http://www.phys.unsw.edu.au/jw/dB.html
  • 11-19-2009, 09:07 PM
    02audionoob
    The 10 dB concept is a theory on how much increase it takes to create the perception of double the loudness. Double power is +3 dB.

    Two sources (in this case, subwoofers) that are the same loudness as each other will be 3 dB louder than only one of them, regardless of the proposed idea that there's now twice as much power.
  • 11-19-2009, 09:50 PM
    Smokey
    Quote:

    Originally Posted by farfromphile
    If you double your power output, you gain 10dB.

    As 02audionoob said, if you double the power output, your gain will be only 3 dB.

    This chart from Mr. Peabody's link explain it better.

    http://www.phys.unsw.edu.au/jw/graphics/LI.GIF
  • 11-20-2009, 06:25 AM
    bfalls
    However, if you're looking to increase your bass output a lot of advantage can be had by placement. I believe I heard that for every room boundary you place your subwoofers next to, you gain 3db. A maximum of 9db gain by placing it in a corner. Of course that will depend on your listening position and whether you're sitting on a peak or in a trough.
  • 11-26-2009, 08:00 PM
    hermanv
    Standard amplifiers are voltage sources so If you parallel a second speaker you will double the current draw from the amplifier and thereby double the amplifier power output.

    Thermodynamics says there is never a free lunch.