REW FDD Motional impedance parameters

[Bernard]

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]

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]

Thank you John for this very quick answer.

 

[Bernard]

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]

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.