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Old 23rd December 2008, 02:48 PM   #1
f4bok is offline f4bok  France
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Default 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
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Old 23rd December 2008, 06:06 PM   #2
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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.
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Old 23rd December 2008, 11:53 PM   #3
Ron E is offline Ron E  United States
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You will roughly cut Qes in half, which will double efficiency.
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Old 24th December 2008, 08:06 AM   #4
f4bok is offline f4bok  France
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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*C*Sd*Cms )
And Qes should be (1.44/1.1) 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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Old 24th December 2008, 11:33 AM   #5
Ron E is offline Ron E  United States
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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*C*Sd*Cms )
And Qes should be (1.44/1.1) 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.
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