# Thiele-Small consistency to other software



## Stereodude (Feb 6, 2010)

I have a Dayton Audio DATS. I've used it to measure one of my subwoofer drivers, an Adire Audio Tumult Mk I.

I also exported the impedance sweeps from the DATS and imported them into REW and tried using the Thiele-Small parameter calculator in REW. I get different T/S parameters between the DATS and REW.

I've attached the impedance sweeps and a screen shot of the T/S parameters from each program.

Any ideas why they are so different? Which one is correct?


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## Stereodude (Feb 6, 2010)

Also, REW generates L2 / R2 and L3 / R3 values which I believe is the Wright electrical impedance model. If I used modeling software that only support L2 / R2 (Leach electrical impedance model) how do I convert the Wright L2 / R2 + L3 / R3 values to a set of Leach L2 / R2 values? I suspect it's not as simple as adding them up since they're in series.


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## Mike P. (Apr 6, 2007)

> I have a Dayton Audio DATS. I've used it to measure one of my subwoofer drivers, an Adire Audio Tumult Mk I.


Just curious, how did the results from the Dayton Audio DATS compare to the published parameters from Adire?

​


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## Stereodude (Feb 6, 2010)

Mike P. said:


> Just curious, how did the results from the Dayton Audio DATS compare to the published parameters from Adire?
> 
> ​


None of them are in agreement with each other.

Adire Specs:
Re: 3.2ohms
Fs: 19Hz
Le: 4.2mH
Qms: 4.30
Qes: 0.39
Vas: 160L
SPL: 87.1 (1W, 1m)

However, it's possible the Adire specs are not small signal parameters, but large signal parameters or some blend of the large signal & small signal parameters. The DATS is measuring small signal. I have to presume that REW is also generating small signal parameters since the impedance data was obtained at low power levels by the DATS hardware.


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## JohnM (Apr 11, 2006)

Did you really add 415g to the cone? Seems like an awful lot to add, would like to see the mdat file of the measurements.


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## Stereodude (Feb 6, 2010)

JohnM said:


> Did you really add 415g to the cone? Seems like an awful lot to add, would like to see the mdat file of the measurements.


Yes, I really added 415g. It's a big 15" subwoofer. The DATS software complained that I didn't add enough mass when I used less mass.

I don't have .mdat files since I didn't make the impedance sweeps with REW. I imported the sweeps from the DATS into REW. They're in the first post.


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## Stereodude (Feb 6, 2010)

Maybe the REW T/S parameters are correct. I measured a sub I built with the Tumult and compared it to a model simulation of the Tumult using the REW T/S parameters and get this (1/6th smoothing). Green is the model and purple is the close mic combination. Prior to this set of T/S parameters from REW I couldn't get the model to match the actual sub.


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## Low-Q (Oct 11, 2009)

JohnM said:


> Did you really add 415g to the cone? Seems like an awful lot to add, would like to see the mdat file of the measurements.


That one also went through my mind... I experience that putting the driver in a sealed enclosure provides the most accurate results. Adding mass has just messed up the measurements for me.

Also the added mass method will alter the position of the voicecoil if the driver is placed horizontally on a table. It cause less BL, higher Qts, and higher Fs (Due to the extra tension to the spider and rubber surround).

Vidar


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## Stereodude (Feb 6, 2010)

How exactly are you attaching mass to a driver when it's held vertical and gravity is working against you?


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## JohnM (Apr 11, 2006)

Typically the mass would be much smaller, and stuck in place. The shift in Fs doesn't need to be as large as in the measurements posted.


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