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Old 4th November 2005, 01:25 PM   #1
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Smile Hi all, Just joined, and i need some advice...

Hi, ive been having a browse of over the last few days, and ive tryed searching, but i still have quite a few questions.

one thing at a time though...

i am aware of the basics, i'm not a complete noob, but some things i have never really touched on before.

so, anyway my first question is this:

I plan to build some (2 pairs) of MTM style speakers. I have the drivers already, they are drivers that were used in some of the B&W DM600 series.

They are approx 5" diameter, and have the yellow woven kevlar cones.

first things first though, i dont really have any information on these speakers, so i need to measure/calculate the Thiele/small parameters for them.

i have looked into software, and i have stumbled across a piece of software called sample champion, which looks like it will do the job, although it doesnt look particularly easy to use.

is there any other software/methods that are worth considering?

Thanks in Advance

Andy
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Old 4th November 2005, 01:29 PM   #2
SY is offline SY  United States
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One of the most popular is Speaker Workshop. And it's free. Beware that it is NOT trivial to get going the first time, but with a bit of persistence, you'll be amazed at how powerful and effective it is.

Run right out and get a copy of Joe d'Appoliti's book on measuring loudspeakers. It is far too easy to get results that are nonsense and d'Appolito will help you understand where the traps are.
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Old 4th November 2005, 01:42 PM   #3
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You don't need to go to the complexity of Sample Champion / CLIO / LMS /Praxis etc: to measure the TS parameters.

There's two basic ways to do it. One involves fitting the unit under test into a sealed box of a known volume and measuring certain parameters in and out of the box. The other (which I use) is to apply a known mass to the cone and once again, performing some calculations based on measurements of the unit with and without the mass.

There's an Excel spreadsheet and document, originally by Matts Kellberg, which makes the added mass method very easy to use.
(It's worth practising on a few drive units to get a feel for things though. You'll need a sine wave oscillator and an ac and dc meter for the test, although a sound card based oscillator is OK).

If you want a copy of the doc and the spreadsheet then send me an email and I'll send them to you.
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Old 4th November 2005, 01:54 PM   #4
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hi, thanks for the reply.

i have seen speaker workshop, but isnt it windows 95/98 only?

i dont think i could bring my self to install win 98 agin!! hehe

also, any more information on the book? what is the title?

i have read most of a book by Martin Colloms (i think thats his name) a few years ago, although it was a good read, and provided lots of information, it didnt really touch all the decision making aspects of loudspeaker design.

thanks again
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Old 4th November 2005, 01:58 PM   #5
SY is offline SY  United States
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Quote:
Originally posted by champ222

i have seen speaker workshop, but isnt it windows 95/98 only?

i dont think i could bring my self to install win 98 agin!! hehe

also, any more information on the book? what is the title?
Neither could I. I'm running it under XP Home and XP Professional.

I can't remember the book's specific title (I'm not at home at the moment), but it's available from Audio Amateur press. It shouldn't be too hard to chase down with a minute or two of googling. Or Amazoning. The title will be obvious.
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Old 4th November 2005, 02:02 PM   #6
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sample champion has a plug in that is specifically used to measure T/S parameters. it uses either of the methods you desribe, the known volume box, or the known mass.

i assume it is using the same method?
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Old 4th November 2005, 02:10 PM   #7
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Yes it does exactly the same thing as in the doc and spreadsheet I've just mailed you.
If you do a Google search for something like 'measure thiele small parameters' you'll get a lot of other useful information.
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Old 4th November 2005, 02:11 PM   #8
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thanks again, i have googled the book, and i'm on the case.

how did you get speaker workshop working on XP?

i tried it on win2000, but it gave me an error message, something about a 16bit subsystem or something.

i havent tried it on my XP pro install, i assumed it would be the same?

thanks again
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Old 4th November 2005, 02:13 PM   #9
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Quote:
Originally posted by champ222

how did you get speaker workshop working on XP?
I'm rather software-stupid, so perhaps someone else can diagnose. For me, I just installed it and it ran fine.
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Old 4th November 2005, 02:39 PM   #10
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thanks for your help guys, i'll try and get hold of that book, and i'll maybe try speaker workshop too on win xp.

i'll have a go at measuring the T/S parameters too.

for the free air measurements, do i need to construct some sort of jig to hold the driver?
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