REW FDD Motional impedance parameters

Bernard

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May 22, 2017
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120
Hello John,

The excellent Scanspeak Excel spreadsheet "VENTED-FDD" which can be found here https://www.scan-speak.dk/toolbox/
uses the AMS parameter that I do not find in the list of TS parameters.
You give the RAMS value that Scanspeak calculates from the AMS value in the spreadsheet.
I don't know how to calculate this AMS parameter.
In your great generosity, could you add this value in an upcoming beta?
Merci John!
Bernard
 

John Mulcahy

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Apr 3, 2017
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7,213
That's an earlier version of the model using a series RL network for the frequency dependence rather than parallel. To convert from the parallel LCES // ΛES to a series LCES + RAMS version changes both L and R, though the change in L is typically small. For the conversion define Q = ΛES / LCES then RAMS = ΛES /(1 + Q*Q) and the new LCES is LCES*Q*Q/(1 + Q*Q).
 

Bernard

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Thread Starter
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May 22, 2017
Messages
120
That's an earlier version of the model using a series RL network for the frequency dependence rather than parallel. To convert from the parallel LCES // ΛES to a series LCES + RAMS version changes both L and R, though the change in L is typically small. For the conversion define Q = ΛES / LCES then RAMS = ΛES /(1 + Q*Q) and the new LCES is LCES*Q*Q/(1 + Q*Q).
Hello John,
Not many people should use this sheet but I can't find the ΛES parameter in the Thiele-Small parameter calculation results anymore in the last beta version... and that bothers me!
Best regards.
 

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
7,213
When dual added mass was implemented REW changed to the LOG model, which is a better fit to the physical mechanisms of driver mechanical behaviour.
 
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