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Best-ever T/S parameter spreadsheet.
Best-ever T/S parameter spreadsheet.
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Old 14th February 2004, 09:52 AM   #21
Circlotron is offline Circlotron  Australia
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Default Latest version

This version calculates the changes in Qes, Qms and Qts when a known mass is added for Vas measurement.

Thanks to GM for the info provided in this post. http://www.diyaudio.com/forums/showt...195#post325195
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Old 20th March 2004, 10:25 AM   #22
Circlotron is offline Circlotron  Australia
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Default Latest latest version

Diagrams added.

Previous version instructed user to ignore calculated F1,F2 voltage which made it a bit hard to find the two frequencies at which this voltage occurs.
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Old 6th April 2018, 08:53 AM   #23
Circlotron is offline Circlotron  Australia
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I can hardly believe its been just over 14 years since I fiddled around with and then posted this spreadsheet. Is there anyone out there that actually built some speakers using this?
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Old 6th June 2018, 02:56 AM   #24
keithostertag is offline keithostertag
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I'm new at this and just found your spreadsheet. Wow, it's been around a long time! I'd like to use it as part of my learning...

Two initial thoughts/question:

1) Will it matter if the signal generator I use has a 50 ohm output impedance? (it was designed for RF applications. ) Also, I'm a bit surprised that your example shows "Oscillator volts" equal to 16.575- seems pretty high, but I haven't tried it yet.

2) Where do I get F1 and F2, the plus and minus 3dB points from Fs?

Thanks!
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Old 16th June 2018, 01:29 PM   #25
Circlotron is offline Circlotron  Australia
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Quote:
Originally Posted by keithostertag View Post
I'm new at this and just found your spreadsheet.
1) Will it matter if the signal generator I use has a 50 ohm output impedance? (it was designed for RF applications. ) Also, I'm a bit surprised that your example shows "Oscillator volts" equal to 16.575- seems pretty high, but I haven't tried it yet.

2) Where do I get F1 and F2, the plus and minus 3dB points from Fs?

Thanks!
Just include the 50 ohms of your signal generator as part of the resistance in series with the speaker and put the total value in the spreadsheet.

The "oscillator volts" was actually the output from an amplifier, so probably higher than a normal oscillator.

For F1 and F2, once you find the maximum voltage across the voice coil at resonance, in this case 0.411 volts, write that voltage in cell B:10. The -3dB voltage then appears in cell B:16. Adjust the frequency above and below the resonant peak until the voice coil voltage drops to cell B:16 value. F1 is the below-resonance frequency for this voltage and F2 is the above-resonance frequency.

Also, with the speaker facing upwards, make sure you have the back of the magnet sitting on something heavy, for example a brick lengthwise. Don't block any vent hole though. If the speaker is not firmly supported this will affect the measured Q figures.

Hope this helps. Let us know how you go!
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Last edited by Circlotron; 16th June 2018 at 01:35 PM.
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Old 16th June 2018, 01:47 PM   #26
keithostertag is offline keithostertag
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Thanks!

I'm guessing: if I use a modern amplifier between my signal generator and the speaker I won't need to be concerned with additional series resistance in the calculation because modern amps have such low output impedance, is that correct?

I questioned the 16 volts because I've read that for T/S parameters we need small signals, like around 1 volt p-p?
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Old 16th June 2018, 01:57 PM   #27
Circlotron is offline Circlotron  Australia
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You could try it with both high and low voltages and see if there is any worthwhile difference. Post your results here! If you used a series resistor of say 1000 ohms then the amplifier output impedance you could completely ignore. Flat frequency response is important though. Bass and treble controls are a liability.
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Old 18th June 2018, 04:06 PM   #28
keithostertag is offline keithostertag
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Finally got through one set of calcs. The biggest thing I learned is how difficult it is to get consistently repeatable results- not sure if it was due to Fluke DMM not handling AC measurements over a range of frequencies, maybe temp drift for the scope as well as the amp and signal source, whatever. I suppose since it is a brand new driver that it could still be settling in (I didn't' do any kind of actual burn-in for it).

I was using an old inexpensive Beckman sig gen which has no readout and a sloppy dial, so some type of freq counter is needed. I used my scope mostly, but also a cool free freq counter Android app on my phone from Keuwlsoft, good displaying freq it can hear, in my case 60Hz to over 5KHz.

Also, circuit interactions do seem to matter. I fed the sig gen into my Crown amp- the output would vary a little depending on the freq. I finally decided to measure the amp output open circuit at the Fs to use with the spreadsheet- difference wasn't very much.

Measuring Re is tricky- I did in two methods and since one was close to the published specs I went with that.

Looking over the calculations vs the published specs, I show a lower Fs, lower Vas, and higher Qts. Maybe someone could look over my results (in attached photo) and respond to anything you notice that might be significant?

In a few weeks I will be getting a DATS V2 system to compare.

These calculations are for a sealed box? I don't know how to use these calculations to determine the best cabinet volume for a vented system using this driver..

Keith

Click the image to open in full size.
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Old 18th June 2018, 10:36 PM   #29
whgeiger is offline whgeiger  United States
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Default N.B.: Projected (Effective) Cone Area Calculation

The volume displacement (Vd) of a typical cone driver may be approximated by that occupied by a frustum of a cone, i.e.

Vd = π Ec (Ds˛ + Ds Dc + Dc˛)/12

and also

= Ec Sd

where
π = 3.14159
Ec - Cone Excursion
Dc - Cone Diameter
Ds - Surround Diameter
Sd - Projected Effective Radiating Surface Area

Thus

Sd = π (Ds˛ + Ds Dc + Dc˛)/12

Regards,

WHG

Last edited by whgeiger; 18th June 2018 at 10:44 PM.
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