Need Help to calculate Thiele/Small values

[andrew01]

Hi,
I have some drivers i wish to use but only have some of the T/S
values.I need the rest of the numbers to enter into WinISD to calculate a box .
Is there a way of calculating the other values or do they have to be electrically measured ? ( I don't have any facility to do this )

This is what I know :

200mm bass driver
Fo = 41hz
Q = 0.44
Vas = 45 L
Z = 8 ohms
SPL = 90dB / 1W / 1M

Thanks

[kelticwizard]

If yu use the "short" version of WinISD, I believe you can just enter those numbers and leave the rest blank. It will give you a curve..

At least in the older version I downloaded a couple of years ago.

To be on the safe side, if you can borrow a simple meter from somebody, you can measure the DC resistance, (Re), very easily.

Finally, if you absolutely have to get Bl readings, etc, Bullock and White's freeware BoxModel will calculate the value for you. Link. I'll calculate them later tonight if you have trouble.

[andrew01]

Thanks.
Yeah I'll be able to measure the Re OK...

I've already tried entering the values I have into WinISD but it won't save the entry or calc anything without the missing values..

[kelticwizard]

Measure that and I'll give you the various values from Bullock and White's BoxModel, (co-author Bob White is a member here).

Meanwhile, having downloaded the old version of WinISD-the one where you don't have to go have all the parameters to get the bass curves-I'll give you a picture of what the speaker will do in which size box anyway. Incidentally, the wonderful speaker writer David Weems has said that to get the bass curves, all you need is the info you already have. I really don't know why WinISD has decided to get so fussy all of a sudden.


Blue = 28.4 L Closed Box, Qtc = 0.71

Red = 59.9L, 37.5 Hz tuning. Port is 10 cm diameter by 20.1 cm length

PS: I only do this Metric stuff as a courtesy because this is an international forum, nobody over here actually uses that system, lol.

I believe I have the entire download file for the old WinISD on my hard drive somewhere, so if you have an ICQ number I guess I can send it over to you. I have an old, inactive ICQ number from years ago. I remember the username, I think I can reactivate. Or maybe I can open up a Yahoo messenger account, or something. Anyhow, Email me if want the old version of WinISD which does not require all those parameters to give you the bass curve. I'll find some way to get it over to you.

[simon5]

I don't know what version of WinISD you're using, but the newest one will let you use incomplete parameters sheets.

I'm talking about WinISD Pro alpha 0.50a7

I entered what you gave and I got :
Qms: 3.939
Qes: 0.495

Then I estimated Sd to 250 cm^3 and Re to 6.0 so I got :
Mms: 29.7
BL: 9.62508
Dd: 7.02
Cms: 0.5076
Rms: 1.94147
USPL: 91.25
Znom: 8.000
n0: 0.6089

Good luck!

[kelticwizard]

Simon:

Mine was downloaded June of 2003.

And you don't even have to go through any additional calculation, all you have to do is fill in the info Andrew has to get the bass curve.

[richie00boy]

I'll be putting a simple spreadsheet with graph on my website soon, just for those occasions when you don't have tons of parameters. I've also written a guide to measuring/extracting the most useful parameters, which can be used by beginners and experts alike. It's just going through some checking before I post it up.

[kelticwizard]

Rich:

I'll certainly be looking for it.

Would that be located here?

[AndrewT]

Hi Richie,
that seems very helpful.

[simon5]

Yeah I know you don't have to fill additional parameters to get a basic curve, but I prefer to estimate Re and Sd so I can get a SPL curve.

BTW, a small tool when you don't have alot of parameters is here :
http://www.linearteam.dk/default.aspx?pageid=newdriver

Qts, Vas, Fs and you're good to go.