building zobels


I've seen a number of references to (I think) some instructions by Sean on how to build a zobel network, but after a number of searches I can't seem to locate the info.

Can someone direct me to the thread...or send the instructions?

thanks
fishboat
Clio09,

"Based on what you said it appears to be after the crossover."
Based on what I wrote, the A-C Zobel appears BEFORE the x-over. :-)

Anyway, I'm no expert in this never having built my own speakers. So, it would be safer for me to say that I don't know whether or not before or after the xover makes a diff. I think that we might need a 3rd person in the know to straighten us (atleast me!) out.

Just thinking out loud: they say that the speaker manuf uses a Zobel to make the speaker load freq insensitive to the amplifier. I looked @ the ckt in the link provided by Distortion & if I work out the impedance xfer function of the Zobel & draw its Bode plot I see that there is a pole @ DC (0Hz) & a zero at 1/RC. This zero negates the pole at DC such that the eff freq response is flat over freq. So, if the values of R & C are chosen such that the zero cuts in well below the -3dB point of the speaker, the amplifer will see a constant (over freq) impedance. So, maybe it does make sense to have the Zobel across the speaker binding posts (rather than across the woofer terminals). So, I wonder why, then, all the diagrams in the literature show Zobels directly across the woofer terminals?

The Alpha-Core Zobels works in the range above audibility to maintain a stable load for amps that are sensitive. Another use of the Zobel is to make drivers appear more linear/resistive. In the first case, you want it to be seen by the amp while, in the second, to be seen by the network.

Kal
Kal,

Does the quality of the resistors that make up the Zobel with the Alpha Core cables matter as it relates to sound quality? I was wondering if it made sense to use better quality resistors, although with the way the Zobel is integrated into my cable it might be hard to swap out.
I doubt the quality of the resistors would make any difference since they are operating/effective at frequencies beyond normal hearing range.

Kal