I've been interested in modelling the Pi designs that use the piezo tweeters (using AIM-Spice), and have a couple or so questions:

Using what data I can find regarding the CTS piezo, the model is: "...like a lossy capacitor to the amplifier...". The circuit is basically a capacitor in series with a resistor, with the resistor representing the dissipation loss. The question is - would the resistance actually take part in an AC analysis model? If so, does anybody have any idea of an appropriate value for this resistance given 2.83V across the terminals?

How are the Vin and source impedance values chosen in the models provided in the Pi Crossover Spice circuits? Am I wrong in thinking that the series impedance would actually be quite low, and an input voltage of 2.83V is the reference standard?

A question regarding the mechanical Q of the 2 Pi Tower speaker, I calculate an Fr of 45 and a Q of around 7. Is that correct?

Thanks for any info.

John B.

About the source voltage and impedance in Spice models, you can set this to whatever values you prefer. Source voltage is whatever you want it to be, and source impedance can be modeled using an input resistor.

As for the mechanical resonance of the two π tower, the cabinet is 4.5ft3 and the Helmholtz frequency is 40Hz.