Planar Speaker Asylum

RE: Hi Jim - I use lspCAD to model Maggie XOs. :-)) nt

130.76.32.167

In Reply to: RE: Hi Jim - I use lspCAD to model Maggie XOs. :-)) nt posted by andyr on October 22, 2009 at 21:06:30

Andy,
I haven't seen the lspCad software before, looks like it is audio specific software.
I derived the 3.3R fourth-order cross-over "Old School" last night while listening to some John Hiatt.
The input voltage is known, and there are two unknowns - the ribbon voltage (Vr) and the voltage between the two caps (V1).
KCL at Vr
Vr/R + Vr/L7*S + (Vr-V1)*C4*S = 0
KCL at V1
(V1-Vin)*C1*S + V1/L1*S + (Vr-V1)* C4*S=0
Solving for V1 = f(Vr) in the top equation, and substituting for V1 in the lower yields (after some manipulation)
Vr/Vin = (R*L1*L7*C1*C4*S^4) / [ R*L1*L7*C1*C4*S^4 + (L1*L2*C1+L1*L7*C4)*S^3 + (R*L7*C4 + R*L1*C1 + R*L1*C4)*S^2 + L7*S +R ]
There are four zero's at the origin, and four poles which are the roots of the denominator polynomial.
regards,
Jim

Edits: 10/23/09

Follow Ups:

Haha - although my first degree was in applied maths, that sort of stuff is waaay above me now! :-)) ... - andyr 13:31:36 10/23/09 (0)

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