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Q. for Wayne - Spice Models [message #34609] Mon, 31 December 2001 05:17 Go to next message
John B. is currently offline  John B.
Messages: 3
Registered: May 2009
Esquire
Wayne:

How do you derive the LCR values for the mechanical reactances shown in the crossover document. I'd really like to be able to generate them for other drivers.

Thanks,

John B.

Determining mechanical reactance values for Spice models [message #34610 is a reply to message #34609] Mon, 31 December 2001 14:39 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17606
Registered: January 2001
Illuminati (33rd Degree)
You can find equivalent circuit values by backsolving the formulas Fr = 1/2πLC and Q = √LC/R using the impedance graph and/or Thiele/Small parameters. For example, if you know that impedance at resonance is 50 ohms and the resonant frequency is 40Hz with a Q of 5.0, then resistance must 50 ohms and inductive and capacitive reactances must be equal at 40Hz.

A similar procedure is used to determine reactance values for the impedance peaks caused by horns, where the frequency and Q of resonant events is not expressely stated. In this case, the impedance graph is used to determine resonant frequency and Q values for each peak that is to be simulated with a corresponding tank circuit. Q is relatively easy to determine - it is resonance divided by bandwidth - so the frequency of each peak is divided by the width of each peak (at 70% amplitude) to determine its Q. This gives you resonant frequency, Q and amplitude, which is everything you need to know to express the reactive nature of a device.

Re: Determining mechanical reactance values for Spice models [message #34625 is a reply to message #34610] Wed, 02 January 2002 02:44 Go to previous message
John B. is currently offline  John B.
Messages: 3
Registered: May 2009
Esquire

Wayne:

Thanks, and a happy new year!

John B.

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