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roystr 14th January 2005 01:46 PM

what do these abrieveations mean?
fd = Fs
Qes = Qes
Qmd = Qms
Qtd = Qts
Vd = Vas
or this paragraph??

"Usually, only drivers which have low Qts (0.25 - 0.4) , Qes (0.3 - 0.4) and Fs values are suitable for transmission line systems."

im guessing here but i think ill need to know what that all means if im to become a speaker builder. granted my goal is to make a few for myself((book shelf,and maybe a suround system to replace my polks)) and maybe a set or two for my brothers . im not realy into the thought of learning all that ive been reading about in here,though i have the feeling i may learn it anyways if im to understand what you guys are talking about most of the time.



x. onasis 14th January 2005 02:46 PM

I'd say you're guessing right.

These are Theile/Small parameters (and Martin King's equivalents), they define the electrical and mechanical properties of drivers to aid designing. A simplified explanation here.

Yes, there is much to learn if you want to become an expert or even understand most of the advice traded here. Vance Dickason's Loudspeaker Cookbook book is a place to start, or poke around the True Audio site where this review of John Murphy's book is from.

OTOH, you could just tell us exactly what you want to build and ask for recommendations for careful though, this hobby is as addictive as it is fun.

x. onasis 14th January 2005 03:17 PM

And check out this thread.

(Onasis wonders where Halojoy is lately.)

AndrewT 14th January 2005 03:21 PM

in your equivalents, d appears to substitute s.
But Vas is the volume of air that has the same spring stiffness as the cone has due to spider and surround.
Vd is the volume of the cone area(Sd) times the linear cone displacement(xmaz).
regards Andrew T.

Keld 14th January 2005 03:54 PM

A search around the www (world wide wait) is recomended, books have been writen about your the "simple" question,
not that I dont want to help you ,but the subject is over my head:)



Originally posted by x. onasis

(Onasis wonders where Halojoy is lately.)

Keld also wonders how wheels are turning for Halojoy AKA gromanswe.
he was here but he disappeared:lickface:

Timn8ter 14th January 2005 04:22 PM

Those are Theil/Small parameters. They have been around for many years now as a explanation of a drivers characteristics in mathmatical terms. This allows designers to simulate (rather accurately) how a driver will behave in a particular enclosure. It appears that you'll need to do some reading as explaining T/S parameters in detail is probably too much for a forum posting (or should be ;) ). Vance's book is very good although for a beginner it might be a little overwhelming. You could check out "The Great Sound Stereo Speaker Manual" to get the basics of speaker design then move on to more updated and detailed material.

roystr 15th January 2005 11:33 PM

tim,i ordered that book used last night.
it was a 4th edition,kinda old,but im sure lots of information for a newbie like me.


Timn8ter 16th January 2005 12:03 AM

Re: tim,i ordered that book used last night.

Originally posted by roystr
it was a 4th edition,kinda old,but im sure lots of information for a newbie like me.


Yes on both counts. Transmission line theory has come a long way since Weems but the rest of it is still pretty good.

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