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8th December 2013, 06:02 PM  #1 
diyAudio Member
Join Date: Jun 2009

Calculate Resistance from Z and Phase?
My mind must be slipping today. If I have a known impedance with a known phase shift, what is the equation to calculate the parallel capacitance and find the resistance without that phase shift?
Example: 6 Ohms impedance, 30 degrees. I need to find that capacitance value and remove that to then find the resistance at zero shift. Last edited by kouiky; 8th December 2013 at 06:17 PM. 
8th December 2013, 06:19 PM  #2 
diyAudio Member
Join Date: Nov 2003
Location: Brighton UK

Hi,
At 30 degrees the real part is (cos) 0.866xZ R, imaginary is (sin) 0.5xZ. rgds, sreten.
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8th December 2013, 06:42 PM  #3 
diyAudio Member
Join Date: Jun 2009

Does this work for calculating the resistance component of a speaker driver when the Z and phase are known?
Last edited by kouiky; 8th December 2013 at 06:55 PM. 
8th December 2013, 09:01 PM  #4  
diyAudio Member
Join Date: Mar 2003
Location: Haarlem, the Netherlands

Quote:
mag(Y)=1/mag(Z) phi(Y)=phi(Z) G=mag(Y)*cos(phi(Y)) Rparallel=1/G B=mag(Y)*sin(phi(Y)) Cparallel=B/(2*pi*f) Hence, using cos(x)=cos(x) and sin(x)=sin(x): Rparallel=mag(Z)/cos(phi(Z)) Cparallel=sin(phi(Z))/(mag(Z)*2*pi*f) With mag(Z)=6 ohm, phi(Z)=30 degrees: Rparallel~=6.92820323 ohm Cparallel unknown because the frequency is not specified. Examples: f=1 Hz > Cparallel~=13262.91192 uF f=1 kHz > Cparallel~=13.26291192 uF 

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