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If my crossover poing is 4k with a 16 ohm tweeter and I exchange it for the same tweeter only this one is 8 ohms where does the crossover point go? Up or down? (Woofer is 8 ohms) Thanks for any help. I have been wondering this for quite a while. BC
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"For a 1st order crossover f=1/(2*pi*C*Z) so the frequency and impedance are related. For a 2nd order crossover f= 1/(2*pi*sqrt(L*C)) and so the frequency is independent of the impedance. However the Q of a 2nd order filter is dependent on the impedance (Q = Z*sqrt(C/L) )."
DJK, Its a 3rd order and I have absolutely no idea what you are saying (unfortunately for me)
You will need to change the value of every part in order for it to work properly.
He could add an 8 Ohm resistor in series with the tweet, keeping the load that the XO sees at 16 Ohms. The net result would be attenuation of the tweet, which may or may not be needed.
My question was does the crossover point go up or down (or maybe a 3rd option)? I am not really asking if I can effectively use the crossover with the 8 ohm tweeter.
Sorry, I didn't mean to get off onto a tangent.
Actually, DJK already answered your original question.
If your crossover is first order, (6dB/Oct), the load will affect the frequency. An 8 Ohm load on a crossover designed for 16 Ohms will halve the frequency. Instead of 4K, it would be 2K.
If your crossover is second order (12 dB/Oct), the loading does not affect the corner frequency as much, although it will affect the slope.
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There will be an incorrect transfer function based on the original third order components. Each stage of the crossover will depend on the following stage. If you change out the driver with a different impedance, the frequency will change at each stage which will make the crossover not do what you think it might.
Play with the numbers on the crossover designer on diyaudioandvideo http://www.diyaudioandvideo.com/Calculator/XOver/
PeterZ
Thanks a lot.
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