Originally Posted by
mgadei
… I found this thread, and because till now I did not have the oportunity to thank you "officially" Swerd, I thank you now, for this great thread.
De rien . Thank you for your efforts at making the printed circuit board. I hope someone here finds them useful.
Originally Posted by
mgadei
I think is a well designed crossover, although, I have a little reserve with the 3.9uF over the tweeter. I kept a place on my printed boards for an aditional resistor with this cap. I will test when they will be ready.
I discussed your question with Dennis Murphy by email. He said he will have to look into his old files and get back to me with an answer.
In brief, mgadei wonders about the 3.9 µF capacitor (C3061) in the tweeter circuit:
In post #8 of this thread, GordonW asked a similar question:Got an impedance plot for the system? My only concern, is the 3.9uf cap going directly to ground, on the tweeter. Looks like it might have a pretty significant impedance dip at high frequencies. That kind of capacitive load might make some amps have problems...
My answer (post #11):We were concerned about that, but no problems have appeared in use with 3 different amps: a small 30 wpc Marantz stereo receiver, a medium Denon 75 wpc HT receiver, and a large B&K 200 wpc external 2-channel amp. A predicted impedance plot (from LspCAD) is seen below. The blue trace is the woofer (Net 1), red is the midrange (Net 2), and green is the tweeter (Net 3). The lowest point is around 3 kHz. Note that nothing below 100 Hz shows on this plot.
I would also add that the tweeter is active at 5 kHz and higher. At those frequencies, the impedance is no lower than 10 ohms. The lowest impedance (about 4 ohms) for the entire frequency range shown appears around 3 kHz, where the mid range operates. So, I don't see any low impedance for the tweeter that could be attributed to the location of that 3.9 µF cap. And with the amplifiers I've used, I have not encountered any problems.
This does not directly address the question, but I hope it shows how it doesn't appear to be a problem.