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Thread: Originating point of sound from a speaker

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    Founding Member pocket5s's Avatar
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    Question Originating point of sound from a speaker

    For several weeks I've been reading on and off all kinds of technical stuff on drivers, phase, arrays, etc. and one thing that I see in many of the diagrams I come across is the lining up of speakers voice coils when talking about time alignments and such instead of the front of the speaker. This is assuming cone drivers BTW.

    Unless I'm crazy, the sound comes from the cone and not the vc, yes? Assuming that is the case, is the vc used because that is the furthest back on the cone the sound can originate?

    Take a 6" driver and a 3" driver mounted on a common baffle. The deepest part of the cone on the 6 could be a good inch or so further away than the 3", so is that why the TA is measured from there as opposed the edge of the cone?

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    Senior Member cvjoint's Avatar
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    To me it only makes sense that the entire cone is active. In fact, as a rule of thumb the SD gets measured using the top of the surround on a half-roll type, so the surround is half active as well. As long as it moves air, it generates sound. It is probably better to think of a cone as infinitely small dots producing sound. In effect what you have then is time alignment on one channel and an infinite amount of speakers! The average distance from the listening point to the dots is probably the best measure.
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    Founding Member pocket5s's Avatar
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    The whole cone certainly makes sense (and seems obvious) and I can see some logic in the surround radiating sound as well.

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    Founding Member benny's Avatar
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    I believe the sound is said to originate at the coil because it is the first part of the moving assembly to be energized.


    And I could also be talking through my hat.

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    Controller AL9000's Avatar
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    Since sound is a pressure wave, I would think that it originates at or in front of the cone. Another thought...if different frequencies have different wavelengths, does the source originate at different spots depending on the frequency being produced?


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    Founding Member Subwoofery's Avatar
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    Quote Originally Posted by AL9000 View Post
    Since sound is a pressure wave, I would think that it originates at or in front of the cone. Another thought...if different frequencies have different wavelengths, does the source originate at different spots depending on the frequency being produced?
    I seem to remember having read that high frequencies originate from the center of the cone while lower frequencies originate from the spot closer to the surround.

    Kelvin

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    Senior Member cvjoint's Avatar
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    Quote Originally Posted by Subwoofery View Post
    I seem to remember having read that high frequencies originate from the center of the cone while lower frequencies originate from the spot closer to the surround.

    Kelvin
    Wouldn't it make more sense for the oscillation of the cone to define the frequency, not parts of the cone surface? What happens when you chop a cone into a smaller one? Small speakers can reproduce low frequencies too. They may not be as efficient but that's another story. If my theory of the cone as an assembly of dot speakers is true, then coupling could be the reason why efficiency goes up when neighboring "dots" join up together.

    I would think that the VC-cone joint only matter in the sense that the cone may be more flabby at the extremes. If the cone is strong enough, I don't see whether it would matter whether the coil is 7", 4", 3" in diameter or a solid piston for that matter.

    A flat cone may be more desirable since every piece of the cone radiates sound in the same plane. I imagine cones are concave to have a stronger geometric shape and move the break up higher. Planars succeed in having this more favorable flat surface at the expense of stiffness: produces shrieking sounds under high output, and of course gets a huge cut in excursion as well.
    Last edited by cvjoint; 08-21-2012 at 06:19 AM.
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    Controller AL9000's Avatar
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    I wish there was some way to see a driver work via a fluid dynamics program.


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    Big Daddy Chad's Avatar
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    Voice coil.
    http://www.diyaudio.com/forums/multi...alignment.html

    Ask yourself this...

    WHERE does the electrical impulse become a mechanical movement?

    Some use the VC former/cone joint.
    Last edited by Chad; 08-21-2012 at 10:30 PM.

  10. #10
    Member Captainobvious's Avatar
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    Quote Originally Posted by cvjoint View Post
    Wouldn't it make more sense for the oscillation of the cone to define the frequency, not parts of the cone surface? What happens when you chop a cone into a smaller one? Small speakers can reproduce low frequencies too. They may not be as efficient but that's another story. If my theory of the cone as an assembly of dot speakers is true, then coupling could be the reason why efficiency goes up when neighboring "dots" join up together.

    I would think that the VC-cone joint only matter in the sense that the cone may be more flabby at the extremes. If the cone is strong enough, I don't see whether it would matter whether the coil is 7", 4", 3" in diameter or a solid piston for that matter.

    A flat cone may be more desirable since every piece of the cone radiates sound in the same plane. I imagine cones are concave to have a stronger geometric shape and move the break up higher. Planars succeed in having this more favorable flat surface at the expense of stiffness: produces shrieking sounds under high output, and of course gets a huge cut in excursion as well.
    Interesting stuff!
    I suspect you're correct about the cone geometry being used as a mechanism to provide strength. The problem with the flat cones is a significant loss in SD for a given size. The cone shape not only provides more strength and therefore the ability to use thinner (and lighter) material, but it also gives you more surface area.

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