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Thread: A very weird upgrade? The PMR (Passive Multi-vocal Resonator)

  1. #41
    Join Date: May 2016

    Location: Much Wenlock

    Posts: 516
    I'm Gary.


    Quote Originally Posted by walpurgis View Post
    As in parabolic microphone.

    Not really this is a parabolic reflector, at the focal point the sound will be amplified, the object in front is the acoustic collector.

  2. #42
    Join Date: Jun 2015

    Location: London/Durham

    Posts: 1,501
    I'm Lawrence.

    Default A very weird upgrade? The PMR (Passive Multi-vocal Resonator)

    I think the interesting fact about this is that some people like the effect of it. It's a bronze bowl which would have the effect of reflecting waves (but not necessarily to a single focal point like a parabolic bowl as it seems to have different degrees of curvature within it suggesting multiple focal points. It is made of metal and when excited by certain frequency sound waves will resonate and produce a ringing sound with harmonics not unlike a bell. I believe early metal dome tweeters suffered from ringing but this was at circa 20khz+ and thus outside the range of human audibility. Given the mass size and thickness of this I imagine the resonant frequency would be well into the audible range so it must do something. It can't be tuned to cancel out room effects in every room it is used, so either it produces a positive result in certain rooms, and the people who rate it happen to have heard it in these rooms, the remainder have not, or it produces a certain result in all rooms and the people who rate it like that effect in a similar way that many people like the "good" distortion produced by valve gear which wouldn't measure well but sounds nice to me certainly. I find it hard to imagine why a metallic ringing would make me prefer the sound but then if someone suggested to me why don't we charge a grid in a glass tube with a vacuum and then use a heater to emit electrons through the grid to a plate and thus act as an amplification device on the voltage of the grid, I would probably think they were nuts.

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