T/S parameters. Help!!!

I´m a newbie in the Speakers world and I want to ask you a few questions.
The most important, I´m sorry for my written english. I know that I need to improve it.
Well, I live in Argentina and due to our economical situation, is imposible to import speakers from others countries (Vifa, Audax, etc)
Even a book like "The Loudspeaker Design Cookbook" it´s imposible to find it.
Anyway I bought a couple of speakers (8" woofer, 8 ohms, polypropylene cones,bell melting, Re=6.9) made it here.
Yesterday I was measuring the impedance. Afortunatly I didn´t have problems. But I´m a litle confused. I found fs at 48 Hz (Zmax=23.51 ohms). And I started to search f1 and f2.
According to www.speakermania.com/transd/find.html, f1 and f2 are the frecuencies where Z=R1 where R1=(Sqrt(Zmax/Re))*Re. With this I found R1=12.734 Ohms and f1=38 Hz and f2=59 Hz. Then fs=Sqrt(f1*f2)=47.32. Everything ok!!!
If I follow the ecuations that appears in the mentionated page I have:


Due to this values I decided to use other method that apears in www.sound.au.com/tsp.htm and:

The question: Which´s right??? What I´m doing wrong???
Any help will be appreciated.
Marcelo (Higo)
from Buenos Aires
If building speakers is something you intend to do some more of, I'd suggest that you download a copy of Speaker Workshop from...


(it's free). It does automatic impedance measurements, TS pararameter estimation, acoustic measurements and much, much more. The software only really comes into it's own if you build a jig; see


... for more details about the jig.

Hope this helps,