Quote Originally Posted by cradeldorf View Post
Don't take this as a negative attitude but are you saying that the phram can push enough air through those tiny slots to actually create a back pressure against the air that's in the horn tube which has a much larger volume than the slots? It just sounds as if physics would say that it would take a lot of air movement through the slots before you could build up pressure against whats in the tube. Or maybe I just don't understand enough yet. 604B's had a 1000hz crossover point? other than the horn mouth being slightly different, the throat I believe was the same size.
Altec 604 Duplex Speakers and related
There is no need to worry about negative attitude etc. We all are beyond that.

Coming to the subject.....yes the air thru the phase-plug slots is enough to find resistance in the horn pipe. It is also to do with frequency. Actually these drivers are very much like a rugged-ized microphone. Forget about this, think of a 515 in a 825/828, and think of the cone movement...and how little it is !
Yes you are right by saying that you have not yet got the feel of this subject.