mechanical sound?

Discussion in 'Archived Threads 2001-2004' started by PaulDF, Nov 6, 2002.

  1. PaulDF

    PaulDF Second Unit

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    Last night for something to do I decided to play some low tones through my main speakers to see how low they would play. To my suprise the 10hz tone was easily audible. These are quite low end speakers by the way, with 6.5 inch drivers, so I am assuming the sound was more like a mechanical sound created by the cones moving... Am I right? Must be since a 10hz tone is definitely not audible. Does this mean my speakers are super cheap, or will other respectable speakers do the same thing?

    BTW. How do I measure the rolloff now?
     
  2. Tim Hoover

    Tim Hoover Screenwriter

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    From your description, it may be a cabinet resonance. It doesn't necessarily mean your speakers are of poor quality - good designs often place the resonance point out of the speakers' response band, so the cabinets don't resonate with actual program material.
    It could also be the woofer spazzing out at being asked to play something so low [​IMG]
     
  3. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    That could be damaging the speakers if you attempt to play 10hz test tones through your speakers so I wouldn't push it.

    I think what you are hearing is probably the driver bottoming out or some sort of distortion. Even subwoofers have filters to prevent them from playing frequencies as low as 10hz.

    To measure roll off you could play test tones in a sweep and graph it and then calculate the slope of where the volume drops.
     
  4. Manuel Delaflor

    Manuel Delaflor Supporting Actor

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    I think you are listening to THD, probably in the orders of 200% or so. In other words, when you put that 10Hz fundamental the cone of the speaker is only able to respond with a 100Hz tone harmonic of the fundamental (it can be another frequency, Im speculating here).

    To measure the roll of in those circumstances you need RTA software which allow you to test for THD too. Search on Google for Spectralab and read the instructions.
     

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