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Thread: measuring Thiele-Small parameters - what am I missing?

  1. #21
    Join Date: Nov 2011

    Location: wirral

    Posts: 184
    I'm frank.

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    You'll need more than 5-15g to measure VAS, aim for around 60% of mms-just don't exceed mms.
    If you dont know the mms run T&S sweeps while adding mass to the cone and stop when Fs has dropped by 25%. V2 will tell when there's insufficient added mass to drop Fs by 25%.
    I prefer the enclosed vol method myself.

  2. #22
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 1,185
    I'm Andrew.

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    Yes, the amount of mass to be added will depend on how big the speaker is and the mass of its cone. The resonant frequency needs to shift enough to do the calculations (even if the calculations are handled by software) and the minimum usable shift is about 10%, though 25% would be better.
    The point I was trying to make is that 324g is way too much for most speakers.
    Yes, the test box method is probably better but necessitates some tedious woodwork.

  3. #23
    Join Date: Jun 2008

    Location: N. Ireland

    Posts: 2,485
    I'm Steve.

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    Quote Originally Posted by RothwellAudio View Post
    Yes, the amount of mass to be added will depend on how big the speaker is and the mass of its cone. The resonant frequency needs to shift enough to do the calculations (even if the calculations are handled by software) and the minimum usable shift is about 10%, though 25% would be better.
    The point I was trying to make is that 324g is way too much for most speakers.
    Yes, the test box method is probably better but necessitates some tedious woodwork.
    So if I block the ports of the current enclosure, and I know the volume of it, would that work? Thanks

    Sent from my SM-G960F using Tapatalk
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  4. #24
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 1,185
    I'm Andrew.

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    Quote Originally Posted by aquapiranha View Post
    So if I block the ports of the current enclosure, and I know the volume of it, would that work?
    Yes, I suppose if you already have enclosures for the drivers then it's all a lot easier.

  5. #25
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,468
    I'm Ken.

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    As mentioned earlier DATS makes this easy, weight depends on size of driver.
    I got the girl at the Post Office to stick my role of masking tape on the Postal Scales, which displayed in divisions of 0.1gm. a roll of tape or similar, is used to evenly distribute the weight around the dust cap of the driver.
    I've used this method several times and got results similar to the manufacturers nominal spec.
    You get a complete list of T&S parameters returned.

    DATS also plots Impedance v Frequency and has an accurate Resistance/Capacitance/Inductance meter built in.

    V2 also measures ESR at 3 frequencies.

    For the asking price it's a great tool.
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + AT 33PTG II / AQVOX Phono 2 CI / Pro-Ject Pre Box RS / ESP Active X-Over / Nakamichi AVP1 Power / Modified semi-active Yamaha NS1000M Speakers / Stello CDT100 Transport / NAD M51 DAC.

  6. #26
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 1,185
    I'm Andrew.

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    Quote Originally Posted by Qwin View Post
    a roll of tape or similar, is used to evenly distribute the weight around the dust cap of the driver.
    I've used this method several times and got results similar to the manufacturers nominal spec.
    How did you fix it in place? Did you have the driver vertical or horizontal?

  7. #27
    Join Date: Jun 2008

    Location: N. Ireland

    Posts: 2,485
    I'm Steve.

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    Quote Originally Posted by RothwellAudio View Post
    How did you fix it in place? Did you have the driver vertical or horizontal?
    The one I saw had it on its back. The DATS has arrived at last so I will try to give it a go over the weekend if I have time

    Sent from my SM-G960F using Tapatalk
    They swim... the mark of Satan is upon them. They must hang.


    FLAC / WDTV Live / Cambridge Audio / Tannoy VX12

  8. #28
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,468
    I'm Ken.

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    Quote Originally Posted by RothwellAudio View Post
    How did you fix it in place? Did you have the driver vertical or horizontal?
    Driver pointing up, stood on its magnet, I stood mine on a small footprint pedestal (non magnetic bookshelf speaker stand) so there would be no reflection back off the table top etc. I stood this well out into the room in clear space, to minimize any reflections.
    The tape just sits on the cone under its own weight, masking tape tends to have a sticky edge which helps keep the role in position, it self centers to an extent within the convex cone of the driver. I used different size/weight of tape role depending on the driver size being measured. Parts Express recommend using a role of tape on their product info. video, check it out to see how they recommend doing it.
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + AT 33PTG II / AQVOX Phono 2 CI / Pro-Ject Pre Box RS / ESP Active X-Over / Nakamichi AVP1 Power / Modified semi-active Yamaha NS1000M Speakers / Stello CDT100 Transport / NAD M51 DAC.

  9. #29
    Join Date: Jun 2008

    Location: N. Ireland

    Posts: 2,485
    I'm Steve.

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    So, having installed the DATS software following the quick guide, I see on the video some other settings require adjusting too. However, the video shows windows 7 and I am using 10, so I emailed support to see if there are any differences. Once I have the answer I will perform the tests using a roll of tape as they recommend. Of anyone has any other input or advice I would be grateful for it.

    Steve

    Sent from my SM-G960F using Tapatalk
    They swim... the mark of Satan is upon them. They must hang.


    FLAC / WDTV Live / Cambridge Audio / Tannoy VX12

  10. #30
    Join Date: Jun 2008

    Location: N. Ireland

    Posts: 2,485
    I'm Steve.

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    Quote Originally Posted by aquapiranha View Post
    So, having installed the DATS software following the quick guide, I see on the video some other settings require adjusting too. However, the video shows windows 7 and I am using 10, so I emailed support to see if there are any differences. Once I have the answer I will perform the tests using a roll of tape as they recommend. Of anyone has any other input or advice I would be grateful for it.

    Steve

    Sent from my SM-G960F using Tapatalk
    Oh, and another potential issue...I weighed a roll of tape on two commer I am scales at work and they both reported 324g. Bow, they cannot display increments of 1g and so I imagine they are very nearly the same. The scale at my local post office says 329.2g so which do I use! I am getting scale paranoia... I wonder how much difference a couple of grams either way would make to the readings?

    Sent from my SM-G960F using Tapatalk
    They swim... the mark of Satan is upon them. They must hang.


    FLAC / WDTV Live / Cambridge Audio / Tannoy VX12

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