I need to design a contour network for a woofer and have been desperately looking for a formula. I found one at www.lalena.com but he is not sure if it's correct. Any information would be great..
sardonx
sardonx
Loudspeaker Design Cookbook by Vance Dickason - I have the sixth edition from 2000. Beginning at p. 147, there are descriptions of circuits for:
dooper
For situation a), a parallel RL circuit is used, and for situation b), a parallel RC circuit is used. Which network do you need the formulas for?
dooper
Dooper,
I'm interested in situation A. It's for the SS 7 inch revelator.
The response starts to rise at 800hz and tops out at 1800 with a total rise of about 4db.
I'm interested in situation A. It's for the SS 7 inch revelator.
The response starts to rise at 800hz and tops out at 1800 with a total rise of about 4db.
1. L (in henries) = 0.15916 / f - in this case f = 400 Hz.
2. "R is selected so the combined impedance of the total circuit equals the amount of maximum-needed attenuation (or average if the rise is not well-defined), where:
Z = (RX) / ((R ^ 2 + X ^ 2) ^ 0.5)
Z = total circuit impedance
X = component reactance at frequency of maximum attenuation"
For an inductor, X = 2 * pi * F * L.
Dickason suggests R = 5 ohms would result in 4.8 dB attenuation.
The book has more info, formulas, and examples. It's well worth the money 🙂
EDIT: The formulas on the Web page you posted appear to be the same as the ones in Dickason's LDC.
Cheers,
dooper
2. "R is selected so the combined impedance of the total circuit equals the amount of maximum-needed attenuation (or average if the rise is not well-defined), where:
Z = (RX) / ((R ^ 2 + X ^ 2) ^ 0.5)
Z = total circuit impedance
X = component reactance at frequency of maximum attenuation"
For an inductor, X = 2 * pi * F * L.
Dickason suggests R = 5 ohms would result in 4.8 dB attenuation.
The book has more info, formulas, and examples. It's well worth the money 🙂
EDIT: The formulas on the Web page you posted appear to be the same as the ones in Dickason's LDC.
Cheers,
dooper
Member
Joined 2003
Sardonx,
I used the 7" revelator in my previous system and as I recall, for the circuit you are asking about, L was .2 and R 2-3 ohms. I am not certain about either value...optimum reponse on your baffle may require different values anyhow.
I also used a very subtle series RLC trap across the VC tuned to the ~800Hz impedance glitch in the rev. I don't remember those values at all, but the overall result of the two networks was much flatter reponse. You're on the right track...keep going.
Paul
4-way dipoles
I used the 7" revelator in my previous system and as I recall, for the circuit you are asking about, L was .2 and R 2-3 ohms. I am not certain about either value...optimum reponse on your baffle may require different values anyhow.
I also used a very subtle series RLC trap across the VC tuned to the ~800Hz impedance glitch in the rev. I don't remember those values at all, but the overall result of the two networks was much flatter reponse. You're on the right track...keep going.
Paul
4-way dipoles
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