Posted by JBen (A) on August 31, 2010 at 20:24:58

In Reply to: RE: Ferrite Bead? posted by gymwear5@hotmail.com on August 31, 2010 at 13:52:35

G5, I am having a laugh here imagining you holding a truckload of ferrite sticks in you hands :-))

What chokes did you get? Also, what slopes are you using, as in "similar to" 1st design, 2nd or other ?

In bi-amping, I have 2 modes that I can choose:
1. Both, the tweeter and the mid/bass panel get line-level filtered signals from the power amp. I think that this is what you use, though you may have active filtering and I use passive filtering (along the lines of what Davey did).
2. The tweeter still gets line-level filtering but the mid/bass uses the speaker level xover inductor (and caps, if called for).

I have not used #1 for a while. I seem to remember that if I used 1st order for the tweeter and 2nd for the low panel, the chokes worked better both on the respective "negative" side of the speaker terminals. But I never wrote it down. In reality, it was so clear that I did it by ear. The determining factor was always what I called "synchronicity". It is hard to explain but basically it means that there is one set of polarity combinations where:
1. The tweeter yields the usual benefits of the chokes (including cleaner highs)
2. The tweeter choke also improves imaging from the upper mids to the extreme highs. This may not always be obvious. Some music makes it easier to detect the effect, if their recording captures a rich sound stage.
3. THEN you add the choke to the mid/bass. If the terminal placement is "correct", the imaging improvements shown at first by the tweeter, are coordinated down the frequency range. If not, try the other.

In other words, the only role of the choke for the lower panel is to synchronize with the "whatever it is" that the tweeter choke did, with regard to imaging. (I suspect that it is phasing related.)

This, BTW, is why I believe that it does not matter that there already is another inductor* in the loop (with regard to regular xovers, or my bi-amp config #2 above). It seems that there needs to be the additional "complemental" choke action for the best imaging features to manifest themselves. The other term that came to mind in the initial days of discovery was "alignment".



*For the benefit of others : chokes = inductors = coils. The names, as used, vary for a range of reasons but their basic build is the same. "Chokes" does tend to be the most common name for high frequency coil applications.