TS parameters when changing Flux Density

f4bok · 23rd December 2008, 02:48 PM

Hello

I have 4 Altec 421-8H baskets with 416-8B Cones
I know the TS parameters of the original 416-8B speakers with its Flux Density of 1.1 Tesla
Now, new flux density with 421-8H basket and 416-8B cone is 1.44 Tesla
Is it possible to calculate new TS parameters since we know original parameters and original and new flux density ?
Is New Bl = (1.44/1.1) * Bl(416) ?

Thanks
Bruno

John Sheerin · 23rd December 2008, 06:06 PM

In simplified theory, yes, that would be correct. In reality it would be correct if the flux distribution through the gap region was the same as for the 416-8B (so the ratio of flux density was the same at all points). If the top plate thicknesses are different between the speakers, then this will probably not be the same. If you build the speakers, just measure the parameters to find out what BL really is.

Ron E · 23rd December 2008, 11:53 PM

You will roughly cut Qes in half, which will double efficiency.

f4bok · 24th December 2008, 08:06 AM

Hi

Thanks for your answers
Yes, the best way is to measure new parameters, but I was wondering:
Do Cms and Rms depend only of mechanical characteristics of the cone?
In that case:
Fs should be the same (1/(2*PI*SQR(Cms*Mms))
Also Qms (2*PI*Fs*Mms/Rms)
Also Vas (Rho*C²*Sd²*Cms )
And Qes should be (1.44/1.1)² smaller, is that what you mean Ron E ?
If Cms and Rms do not change, measuring new Bl instead of estimating it (1.44/1.1) should be enough ?

Rgds

Ron E · 24th December 2008, 11:33 AM

Quote:

Originally posted by f4bok
Hi

Thanks for your answers
Yes, the best way is to measure new parameters, but I was wondering:
Do Cms and Rms depend only of mechanical characteristics of the cone?
In that case:
Fs should be the same (1/(2*PI*SQR(Cms*Mms))
Also Qms (2*PI*Fs*Mms/Rms)
Also Vas (Rho*C²*Sd²*Cms )
And Qes should be (1.44/1.1)² smaller, is that what you mean Ron E ?
If Cms and Rms do not change, measuring new Bl instead of estimating it (1.44/1.1) should be enough ?

Rgds

Yes.

Rms should not change much unless former is conductive. Cms is just springiness, nothing to do with motor.

Measuring Qes, Qms is easier than Rms or Bl.

23rd December 2008, 02:48 PM	#1
f4bok diyAudio Member Join Date: Aug 2004 Location: lyon	TS parameters when changing Flux Density Hello I have 4 Altec 421-8H baskets with 416-8B Cones I know the TS parameters of the original 416-8B speakers with its Flux Density of 1.1 Tesla Now, new flux density with 421-8H basket and 416-8B cone is 1.44 Tesla Is it possible to calculate new TS parameters since we know original parameters and original and new flux density ? Is New Bl = (1.44/1.1) * Bl(416) ? Thanks Bruno

23rd December 2008, 11:53 PM	#3
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	You will roughly cut Qes in half, which will double efficiency. __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

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23rd December 2008, 06:06 PM	#2
John Sheerin diyAudio Member Join Date: Nov 2003 Location: Pittsburgh, PA	In simplified theory, yes, that would be correct. In reality it would be correct if the flux distribution through the gap region was the same as for the 416-8B (so the ratio of flux density was the same at all points). If the top plate thicknesses are different between the speakers, then this will probably not be the same. If you build the speakers, just measure the parameters to find out what BL really is.

24th December 2008, 08:06 AM	#4
f4bok diyAudio Member Join Date: Aug 2004 Location: lyon	Hi Thanks for your answers Yes, the best way is to measure new parameters, but I was wondering: Do Cms and Rms depend only of mechanical characteristics of the cone? In that case: Fs should be the same (1/(2PISQR(CmsMms)) Also Qms (2PIFsMms/Rms) Also Vas (RhoC²Sd²*Cms ) And Qes should be (1.44/1.1)² smaller, is that what you mean Ron E ? If Cms and Rms do not change, measuring new Bl instead of estimating it (1.44/1.1) should be enough ? Rgds

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