In Reply to: Yep posted by smallpond on May 12, 2003 at 19:44:25:
Hi JayThe phase problem is a minor one in Olson's implimentation (see p. 238 of Acous. Eng.) and in mine (if you are still awake after reading my long post above, hey you asked :)). Some cancellation has shown up in measurements, but due to the fact that you have to move the test mic back to a point where the two horns can react, it becomes difficult to seperate any speaker anomalies here from room effects. The fact that the measurements vary quite a bit according to mic location indicates that my room is adding more to the measurements in this respect than the crossover overlap, however there is no reason to feel complacent unless anechoic measurements are done, and none of my buddies have one.
As to Bert's concern that the rear output would be considerably less than the front, this too is not verified in Olson's example nor in mine. The throat of the horn on the front driver should be less than what one would use when applying the classic optimum throat size formula, and this is in order to optimize the front horn for higher frequencies (and it looks like Olson's design could have used some fine tuning here), with the added effect of some attenuation which as luck would have it balances mine out fairly well, with some more experimentation due here. This is just fine tuning and perhaps the least of your problems in a double loader IMHO. Bruce Edgar has pointed out that if you push the horn into a corner, the bass will improve but the mid bass will suffer. Conversely pulling the horn out of the corner and more into the room causes the bass to suffer and the mid bass to improve. This effect makes much more of a difference in the bass/mid bass area than what I can identify as phase cancellation from the two horns.
Paul
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