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Thread: Decibels

  1. #1
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    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?

  2. #2
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    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

  3. #3
    Retro Modernist 02audionoob's Avatar
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    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.

  4. #4
    Suspended Smokey's Avatar
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    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.


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    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.

  6. #6
    Forum Regular hermanv's Avatar
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    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.
    Herman;

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