Johnnyb53 wrote: "I prefer a lower crossover point from a 15" speaker, but if it works, it works."
He's referring to the 1200 Hz crossover point between the Altec Model 19's 15" woofer and 1" horn-loaded compression driver.
At first glance, Johnnyb's objection makes sense... and if this were just about any other speaker I'd agree. But there's a reason behind that 1200 Hz crossover point. It's rather interesting in my opinion, so here goes:
The predecessor of the Model 19 was, if memory serves me, the Valencia. The Valencia had essentially the same driver complement I believe (15" woofer, 1" compression driver on a 90-by-40 degree horn), with a crossover point around 600 Hz. This was a very good speaker, but someone at Altec had a highly unorthodox idea for a way to improve on it: match up the output of the woofer and horn off-axis as well as on-axis at the crossover point.
To do this, it was necessary to raise the crossover high enough so that the woofer's radiation pattern matched that of the horn. Actually the woofer's pattern at the crossover point is in between the 90 degree horizonal and 40 degree vertical pattern of the horn, but the net effect is a very good match.
While intuitively 1200 Hz seems way too high for a 15" woofer, the Model 19 is considered by many to be the finest speaker Altec ever made. So obviously the Altec engineers knew what they were doing.
If I were to trace back over time the basic concept behind my own designs, I think the Altec Model 19 would be the point of origin. Applying the concepts of the Model 19, JBL made the landmark Model 4430 studio monitor. Earl Geddes' Summa is conceptually an update of the Model 4430, and my stuff is an offshoot of Geddes' work.
So while I've never owned a pair, I have a soft spot for the Model 19, and great respect for whoever first came up with the idea to take a 15" woofer up to 1.2 kHz against all conventional wisdom, and thereby matching up the directivity of woofer and horn in the crossover region.
So Johnnyb I don't blame you one bit for raising an eyebrow over that 1200 Hz crossover point... but there was a method behind the madness!
Duke