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Thread: Originating point of sound from a speaker

  1. #11
    Senior Member cvjoint's Avatar
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    Quote Originally Posted by Captainobvious View Post
    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.
    I think it just gives strength. Instead of displacing air think sand, move the cone the same displacement and see how much sand falls out. Should be the same as a flat "cone". Aka the SD is larger with concavity but the air displaced (volume) is the same.
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  2. #12
    Controller AL9000's Avatar
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    Quote Originally Posted by Chad View Post
    Voice coil.
    Woofer + Tweeter: Physical time alignment - diyAudio

    Ask yourself this...

    WHERE does the electrical impulse become a mechanical movement?

    Some use the VC former/cone joint.
    If this were true, then you wouldn't need a cone. The VC creates the movement, but the cone produces the actual sound (pressure wave).
    Look at post #6 in that link you provided
    According to what I've learnt the acoustic centre for a driver moves in position relative to the frequency it is reproducing. Therefore any 'aligning' be it physical or electrical is only relevant to that one frequency, or rather you could say frequency band because the acoustic centre will most likely remain within acceptable limits over certain frequency bands.
    Last edited by AL9000; 08-22-2012 at 09:36 AM.


  3. #13
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    Quote Originally Posted by AL9000 View Post
    If this were true, then you wouldn't need a cone. The VC creates the movement, but the cone produces the actual sound (pressure wave).
    Look at post #6 in that link you provided
    The sound producing cone would not produce sound unless something moved it...like the voicecoil. I would agree with comment you could use the cone/vc glue joint if the cone were rigid enough. Sometimes it's easy to forget the cone is not completely rigid. It's not something that ranks high up on my list of importance however.

    That quote was horrible to quote. Using that logic you would have to claim the acoustic center moves dependent on the volume knob as well, due to excursion.

  4. #14
    Controller AL9000's Avatar
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    So if you pluck the string on a guitar, one could say that it's your finger making the sound?


  5. #15
    Founding Member benny's Avatar
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    The string ain't gonna pluck itself.

  6. #16
    Controller AL9000's Avatar
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    I'm not trying to be argumentative, it's just coming out that way :wtf:


  7. #17
    Founding Member Subwoofery's Avatar
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    Let's just say that the finger is the electrical impulse sent to the voice coil

    Kelvin

  8. #18
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    Quote Originally Posted by AL9000 View Post
    So if you pluck the string on a guitar, one could say that it's your finger making the sound?
    We are talking about the timing so it has to start at the beginning of excitation, yes that difference can be super tiny but it's there. I wouldn't sweat it though. Unless you are way off, there are bigger problems.

    You could say a planar driver is the only exception because the coil is built into the diaphragm.
    Last edited by durwood; 08-24-2012 at 12:46 AM.

  9. #19
    Junior Member Hot rod's Avatar
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    Would a difference of an inch or so even matter with reference to time alignment? All of the speakers would be off the same amount roughly.

    My own experiments do not reveal a discernable difference of 1", however my install is still very, very rough, so I cannot surely say it does not matter.

    Durwood's post seems to answer my question, but if the point was brought up to begin with, it seems to me that it might indeed make a difference. That is not to say that I believe the voice coil should be considered the point of origin for sound, and therefore should be used as the point of measurement, because I do not. My question, I suppose, has more to do with the principles of TA.
    Last edited by Hot rod; 08-24-2012 at 08:54 PM.

  10. #20
    Senior Member cvjoint's Avatar
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    It does matter in some extreme cases, overall importance increases in the size of the driver and decreases in the distance to the speaker. Worst case, you have a 10" midbass in door. A typical 2" coil could be a few inches from the edge of the cone and that's quite a bit in near-field like that

    I think one of the main points was sort of diluted in the discussion. I get that it is important where the sound first originates but that's not the only or even the most important reference for time alignment. Say the voice coil was .1" and attached to the cone at the edge of it somewhere. Even if the cone is not the stiffest there is it is still an active cone, it produces sound. Why align in reference to the first active part of the speaker, and not the average point where sound is generated? It is the same mistake someone would make by time aligning a speaker based on one frequency when the driver reproduces a whole bunch of them. Aren't we interested in the entire output of the speaker?
    2001 Honda S2000
    Head: Pioneer P99 + Samsung Galaxy S3
    Amplifiers: 3,000w+ Zeff class G/H power
    4 way: Aurum Cantus AST2560 Air Motion Transformers, BG Neo8-s Planar transducers, Peerless XLS 10" MAC midbass woofers, Tympany LAT700 x2

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