Decibels........Important???

Discussion in 'Archived Threads 2001-2004' started by Nick_Murphy, Jun 18, 2002.

  1. Nick_Murphy

    Nick_Murphy Agent

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    Now I'm such a newbie when it comes to this decibel crap, haha! Anyways, i'm wondering if it's important to research when looking for a new reciever. I've always understood that it refers to the amount of current/power running through a reviever. Now is this the same thing as the amount of amps powering the speakers, which just means it's a higher current reciever? Can someone please slap me in the face with a big ol trout? haha, thanx!
     
  2. Dustin B

    Dustin B Producer

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  3. Allan Jayne

    Allan Jayne Cinematographer

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    For the consumer, decibels is a way to compare two or more amplifiers or speakers or complete sound systems. For technicians and engineers, decibels is a convenient way to monitor sound levels or power levels to avoid overloading circuits or broadcasting too weakly.
    On an absolute scale, it requires test equipment to measure decibels as it pertains to the loudness of your sound system or the number of watts being delivered. There are probably some benchmarks or standards such as so many watts equals so many decibels on an absolute scale but I don't know what they are.
    If you have more amplifier watts but less efficient (less sensitive) speakers you won't necessarily get louder sound compared with someone who has fewer amplifier watts but more efficient speakers. Speakers may be rated as delivering so many decibels of audible output for so many watts of input. Good speakers tend to be inefficient, perhaps for 100 watts of input, there may be less than five watts of output. One watt of audible output in mid-range, around 500 to 2000 Hz, is earsplitting to hear if you are standing within five feet of the source.
    If I remember correctly, three decibels more means twice as much power. If an amplifier delivers 100 watts plus or minus 3 dB, there is a reference frequency, usually 1000 Hz, where it can deliver 100 watts but at some frequencies usually near the top and bottom of the specified range it is only guaranteed to deliver 50 watts (and some frequencies it might deliver 200 watts). Speakers, too, have frequency response curves (assuming a constant power input) that can be described in decibels. I am not sure how it relates to twice as loud. If I remember correctly, one decibel is the smallest incremental difference in loudness that the average person can detect. The original unit of measurement is the bel, named after Alexander Graham Bell. More often than not, finer gradations were needed and the decibel, one tenth of a bel, is used more often.
    The scale of decibels is such that if you increase the number of decibels in even steps, the loudness increases in even steps but the amount of power needed increases exponentially (steps of 3 dB: 1, 2, 4, 8, 16 or steps of ten dB: 1, 10, 100, 1000, etc.). Mathematically this is refered to as a logarithmic scale.
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  4. Blake R

    Blake R Stunt Coordinator

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    One important thing to remember about the decibel is that it is a relative measure of power, voltage, sound pressure level, etc. The reason electronic engineers use them is it makes it possible to make simple linear plots of amplifier frequency response on a logarithmic scale. It also allows you to perform algebraic operations with non-linear quantities.
     
  5. Vince Maskeeper

    Vince Maskeeper Producer

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    Nick,

    I'm unsure where you saw a decibel rating on a receiver or amplifier product. The decibel is a specific measure of difference in signal-- and in the audio world is used to measure several different things (both input and output). There are several scales of dB in the audio world as well.

    I wonder exactly where you saw a decibel rating in a receiver specification- and wonder maybe if you misunderstood what the rating was trying to say. Most receivers will be rated in wattage output- not overall decibels. Sometimes the dB factor is used to qualify other specifications (such as freq response)-- but you don't see decibel as an outright specification.

    Maybe you could ellaborate on what you saw and where- and someone here might be able to help you understand what the spec is saying.

    -V
     

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