I recently bought an electro-acoustic measurement system called Clio. I still have a lot to learn about using it to do fancier measurements like THD, Polar Plots, etc., but I have been using it to do some basic frequency plots for the Project May effort and tonight I thought I'd give it a whirl on the popular JBL 2397 "Smith" horns.
Here is a plot of the JBL 2441 driver on the 2397 horn. The Blue plot is on axis and the Red plot is 30 degrees off axis. These plots have what is called 1/12th Octave smoothing. With smoothing it averages the response within the specified octave rate. The overall response is pretty flat (no speaker really measures flat at this resolution), and the 30 degree off axis response is surprisingly good. Realize that this horn is not really meant to be used below 800Hz.
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