My experience with "salad bowl" horns
My experience with Great Plains drivers 1" and 1.4"(basic Altec 902 and 288) has led me to use the 650hz round wooden tractix horns with 1" drivers crossed over at 1.6khz and the 1.4" drivers on 500hz round wooden horns crossed over at 800hz.
1" on 650hz salad bowl sounded bad at 800hz, usable but not desirable to me due to strain on lower frequenies and loss of upper HF response.
1.4" on 500hz salad bowl sounded good at 800hz and decent enough HF response(to approx rated 18khz top end) to allow me to not have to bother with tweeter.
1.4" on 500hz salad bowl crossed over at 1.6khz had much better voicing than the 1" driver on smaller horn, but I found too much zing on the top HF response.
After listening to both horns at their best crossover setting left me thinking the 1." driver sounded nice, but when using the 1.4" driver on the larger horn I left the 1" and 650hz horns sitting in the closet for now.
Bill H. at Great Plains sells the 902 and 399 drivers manufactured new for decent prices.
In comparison of the 1" drivers (Altec 902 and JBL 2426), I found the JBL better in the upper midrange but needing a tweeter for upper HF.
The Altec goes higher, but with less magical midrange of the JBL.
Many choices here, I prefer the Altecs due to availability and cost.
I run small SET triode amps most of the time.
Hope this helps some!
Regards, Ron