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Pi Alignment ? [message #47463]

Thu, 11 August 2005 23:49

hitsware
Messages: 51
Registered: May 2009

Baron

How does one determine 'Rou' ? .........mike

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Re: Pi Alignment ? [message #47464 is a reply to message #47463]

Fri, 12 August 2005 01:36

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

It's best to measure the T/S electro-mechanical parameters, and use the reciprocal of Qts as Qd.

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Re: Pi Alignment ? [message #47466 is a reply to message #47464]

Fri, 12 August 2005 10:31

hitsware
Messages: 51
Registered: May 2009

Baron

Thanks!
Obtaining the T/S parameters is what I'm working on.
I have a 'woofer tester' that does a good job (agrees with the classic 1K Ohm method)
BUT
For some reason it goes bonkers on certain drivers (Fs 4Hz AND -Qts!)
So I'm trying to streamline my manual method.
I'd like to use the Fl & Fh = -0.707 Zmax method for Qts (since my scope has a specific graticule for this purpose) and absolute values are not needed (Zmax is set @ full scale):
Qts=((Fs/(Fh-Fl))*(Re/Zmax)...........Actually 'Qo' ????
Anyways then comes Vas (using added mass).
But if it could be calculated at this point it would be slick.
So Rou=1-(((Zmax/Zmin)-50)/10) doesn't work anymore ?
Technology Marches On ! ................. mike

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Re: Pi Alignment ? [message #47467 is a reply to message #47466]

Fri, 12 August 2005 12:07

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

The Rou method is easy, and in many cases provides a pretty good approximation. But I think the sealed box method is better for large woofers, and added mass is better for midwoofers and other speakers with stiff suspensions.

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Re: Pi Alignment ? [message #47468 is a reply to message #47467]

Fri, 12 August 2005 17:26

hitsware
Messages: 51
Registered: May 2009

Baron

>I think the sealed box method is better
>for large woofers, and added mass is better
>for midwoofers and other speakers with
>stiff suspensions.

Yea......Maybe too stiff of suspension is
what throws the W.T.
I tried the closed box method on it and
managed to get a -Vas
(I knew they were mind expanding):)
The drivers I'm playing with (the kind
used in grocery store ceilings) are all
hi-Q.
Anyways I came up with the below and it
matches the W.T. pretty well.
Used Futtrups app as a go-between.
Thank You again ............ mike

Quick and Dirty

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