old speaker parameters vs. Thiele-Small parameters

[Joao]

I'd like to get the rules how the engineers calculated their speaker enclosures.
Nowadays they use Thiele-Small parameters. Taking a look on old brocjures from Altec, JBL, Jensen, RCA .... there are no Thiele-Small-parameters listed because this was the age before - some call it the golden age of audio.

What parameters did they use and how they calculated the enclosures?

Does anyone can deliver / give me parameters from
RCA MI1444
RCA MI9449 (CX)
Jensen G610
Jensen H530
or from some old Fieldcoil drivers of this generation?

Thank you for your help and passion.
Joao

[Hoerninger]

Hi Joao,

there is a set of electromechanical parameters which can be used for such problems. They have their origin in mechanics and electricity as parts of physics. The mechanical parameters are not widely known, and there are often made electrical analogies. The german Feldkeller has quite a reputation for this subject, you will find literature in university libraries.

To be more concrete D.B.Keele gives in "Low-frequency horn design using Thiele/Small driver parameters" an example, which is fairly readable.
http://www.xlrtechs.com/dbkeele.com/...TS%20Paras.pdf
In table I On page 13 there is a comparison between electromechanical and Thiele/Small Parameters.
Hope this was helpful
____________
Regards
Peter

[Robh3606]

Just look at the old enclosure brochures most have charts and rudimentary explanations.

http://www.lansingheritage.org/html/...1968-plans.htm

http://www.lansingheritage.org/html/...960s-plans.htm

http://alteclansingunofficial.nlenet...rs/TL_264A.pdf


Rob

[Joao]

Peter,

thanks for the reply. Do I understand it right, that Thiele/Small developed their parameters from the physics of mechanics?
Noticed that you're from Germany as well. If you like we can have a phonecall for discussing more.
Regards
Joao

-------------------------------------------------

Rob,
thank you for your reply. The pdf-file is a great link.
Regards
Joao

[10 Watt Street]

Good book on this topic: HOW TO BUILD SPEAKER ENCLOSURES by Alexis Badmaieff and Don Davis

[Joao]

Good book on this topic: HOW TO BUILD SPEAKER ENCLOSURES by Alexis Badmaieff and Don Davis

Thanks for the tip.
Regards

Joao

[Steve Schell]

Joao, I will forward your post to a friend who might be able to provide some information, at least in regard to the RCA woofers. The ones you mentioned were intended for horn loading, and have very light cones and extremely strong motors. The same design "recipe" applied to most of the old Jensen, Lansing, etc. field coil woofers.

[Joao]

Hello Steve

thank you for forewarding this. I'm just anxious about the response.
My RCA's (MI 9449)and Jensen (H222) indeed own very light cones and strong motors.
I use the RCA coax in a vented cabinet and the Jensen in an open baffle (back bent baffle). The Jensen is supported with an Eminence woofer.
The Eminence owns lght cones as well and are, in my opinion, one of the best woofers of new construction.

So my idea is to construct a new driver, permanent and field coil, with the parameters of the mentioned drivers. As well I want to understand the world of old designers and how they calculated the cabinets for those drivers.

Regards
Joao

[Bill W]

Measurements using the mass method

Def_BassUnit 'RCA'

Sd=993.147cm2
fs=55.8Hz
Vas=197.993L
Qms=4.884
Qes=0.373
Re=13.3ohm
Le=0.6mH
Xms=2mm
Mms=56.7g
Bl=26.624Tm

Performance in vented enclosure:

Vb=150L fb=55.0Hz Qb/fo=1.426

101.2dB 1.8W 4.92V

Hope this Helps, Bill ( RCA-fan)

[Joao]

Bill,

thank you for the posting and parameters. Do you know the magnetic flux density of the firld coil? What driver from RCA is this MIxxxx?
I'm wondering that they are low voltage... thought that those drivers use 110V?!

Regards
Joao