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Four PI Thermionic & 1K6a012dB [message #34309]

Sun, 02 December 2001 14:51

John B.
Messages: 3
Registered: May 2009

Esquire

I have the four pi thermionic plans, and I've already started assembling the boxes - parts are and will be on order. I fully intend to build the four pi's, but would like my knowledge as complete as possible.To this end, I do, however, have a question.

Using the spice tools and circuit models you provide; and other number crunching and plotting tools:

No matter how I analyze and model the system I seem to predict a 3 or so octave wide notch in the response centered at about 2000Hz. Am I correct? The notch is apparently crossover generated, and I can't find any component of the system which compensates, or for which it compensates.

I imagine this is probably a more complex issue than I am assuming - what with phase cancellations and so forth. But it bothers me :) and inquiring minds want to know.

Thanks.

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Compensation for compression horns [message #34310 is a reply to message #34309]

Sun, 02 December 2001 19:23

Wayne Parham
Messages: 18726
Registered: January 2001

Illuminati (33rd Degree)

The crossover is asymmetrical, so the electrical crossover points don't line up. There is also top-octave compensation in the tweeter circuit, which attenuates the lower region much more than HF. This is all done on purpose to make the overall response curve as flat as possible. The crossover was carefully designed to provide good response, both on axis and off, with uniformly collapsing directivity that is matched at crossover and constant above that.

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