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

  1. #41
    Join Date: Jun 2008

    Location: N. Ireland

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    I'm Steve.

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    Quote Originally Posted by Qwin View Post
    Yeh, but you do have the user guide loaded, don't you?
    I have had my version 1 DATS for several years and the manual has separate quick start guides for XP/Vista/7. It talks you through setting up the audio, according to the menu differences in the three OS versions, what you are doing is the same thing on them all. I don't understand your problem, are you saying you have Windows 10 and your manual does not cover 10?
    Hi, I missed the settings in the guide earlier as previous post. Note to self.. RTFM...properly Steve

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  2. #42
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    Capture.jpg


    Will this do?
    Steve
    They swim... the mark of Satan is upon them. They must hang.


    FLAC / WDTV Live / Cambridge Audio / Tannoy VX12

  3. #43
    Join Date: Jan 2013

    Location: Durham - UK

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    I'm Ken.

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    Quote Originally Posted by aquapiranha View Post
    Capture.jpg


    Will this do?
    Steve
    Yep, that is similar to what I use.

    Check out the many YouTube clips on using the added mass method with DATS, I just checked out 4 of them and folks were using anything from 6.08g to 230g. 150g by one on a 12" stiff sub driver.

    My advice would be to add weight till the suspension just starts to sag, measure that and use a bit less. You don't want the driver to bottom out and travel is not great on some, just a few mm.
    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 / Nord MC500 Power Amps/ Modified semi-active Yamaha NS1000M Speakers / Stello CDT100 Transport / NAD M51 DAC.

  4. #44
    Join Date: Jun 2008

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    Quote Originally Posted by Qwin View Post
    Yep, that is similar to what I use.

    Check out the many YouTube clips on using the added mass method with DATS, I just checked out 4 of them and folks were using anything from 6.08g to 230g. 150g by one on a 12" stiff sub driver.

    My advice would be to add weight till the suspension just starts to sag, measure that and use a bit less. You don't want the driver to bottom out and travel is not great on some, just a few mm.
    Will do thanks for the advice

    Steve

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


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  5. #45
    Join Date: Oct 2016

    Location: Bolton, England

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    For added mass you need enough to shift the resonant frequency by 10% - 25%. Simply laying the driver on its back can shift the resonant frequency by 5% or more, so I wouldn't recommend doing that.
    As for calibration, you need to put it into context. 1% accuracy is, in my opinion, more than good enough to work with. Most of the box/port parameters are a bit woolly anyway due to the unknown stiffness of the cabinet walls, the quantity/quality of any wall lining that might be used etc., etc. Typical temperature and humidity variations are enough to shift the parameters by more than 1%, so I wouldn't bother spending a lot of money on a 0.01% calibration resistor.

  6. #46
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    Quote Originally Posted by RothwellAudio View Post
    For added mass you need enough to shift the resonant frequency by 10% - 25%. Simply laying the driver on its back can shift the resonant frequency by 5% or more, so I wouldn't recommend doing that.
    As for calibration, you need to put it into context. 1% accuracy is, in my opinion, more than good enough to work with. Most of the box/port parameters are a bit woolly anyway due to the unknown stiffness of the cabinet walls, the quantity/quality of any wall lining that might be used etc., etc. Typical temperature and humidity variations are enough to shift the parameters by more than 1%, so I wouldn't bother spending a lot of money on a 0.01% calibration resistor.
    Ok thanks. I see what you are saying about gravity etc. So standing the driver as it would be in a box and use masking tape to secure the weight? I could do that, I have not seen anyone doing it but it does make sense.i wonder though if the DATS software has been written to accommodate gravity? This is a lot more complicated than I thought it was going to be with so many differing opinions! tha is for the advice btw.

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  7. #47
    Join Date: Oct 2016

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    You could just forget about added mass and use the test box method. Didn't you say you had a box that the drivers fitted?

  8. #48
    Join Date: Jun 2008

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    Quote Originally Posted by RothwellAudio View Post
    You could just forget about added mass and use the test box method. Didn't you say you had a box that the drivers fitted?
    I have the original cabinets made by Tannoy. I will look into how that is done thanks

    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

  9. #49
    Join Date: Jan 2013

    Location: Durham - UK

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    I'm Ken.

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    Quote Originally Posted by RothwellAudio View Post
    For added mass you need enough to shift the resonant frequency by 10% - 25%. Simply laying the driver on its back can shift the resonant frequency by 5% or more, so I wouldn't recommend doing that.
    As for calibration, you need to put it into context. 1% accuracy is, in my opinion, more than good enough to work with. Most of the box/port parameters are a bit woolly anyway due to the unknown stiffness of the cabinet walls, the quantity/quality of any wall lining that might be used etc., etc. Typical temperature and humidity variations are enough to shift the parameters by more than 1%, so I wouldn't bother spending a lot of money on a 0.01% calibration resistor.
    The calibration also applies to the Resistance/capacitance/inductance measuring accuracy and is the main reason for doing it.

    Once calibrated, it is way more accurate than your average digital multimeter.

    Isn't the point of added mass, to measure the difference between free air and loaded states?
    You have to do this in the test procedure.
    So as long as the attitude of the driver is the same for both measurement the difference in resonant frequency between Horizontal and Vertical should not effect the results. Or am I interpreting it incorrectly?
    Last edited by Qwin; 11-06-2018 at 12:18.
    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 / Nord MC500 Power Amps/ Modified semi-active Yamaha NS1000M Speakers / Stello CDT100 Transport / NAD M51 DAC.

  10. #50
    Join Date: Oct 2016

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    Quote Originally Posted by Qwin View Post
    The calibration also applies to the Resistance/capacitance/inductance measuring accuracy and is the main reason for doing it.
    Once calibrated, it is way more accurate than your average digital multimeter.
    Yes, there's nothing wrong with making the test equipment as accurate as it can be. My point really was that the whole Thiele/Small approach to vented box design isn't as accurate as the computer read-outs might lead you to believe. Certainly, you can enter lots of data and the computer will crunch the numbers and give you the -3dB point to 100th of a Hz, but it's really only a guide.
    Quote Originally Posted by Qwin View Post
    Isn't the point of added mass, to measure the difference between free air and loaded states?
    You have to do this in the test procedure.
    So as long as the attitude of the driver is the same for both measurement the difference in resonant frequency between Horizontal and Vertical should not effect the results. Or am I interpreting it incorrectly?
    Yes, you measure the driver in free air and again with some added mass or mounted in a test enclosure. However, the free air resonance changes if you have the driver laying face up. The change seems to be a lot more for some drivers than others, but certainly more than 1%. Personally, I wouldn't want to go to the expense of calibrating the system with a 0.01% resistor and then introduce bigger errors by doing the measurements with the driver face up.
    Quote Originally Posted by walpurgis View Post
    Laying a driver on its back will alter the resonance anyway, as the cone weight then bears fully on the suspension. So I'm not sure how an accurate reading can be done this way.
    Neither am I.

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