DEEP AND WIDE.
Part of the inspiration for the SRM450's horn design came from listening to big high-output studio monitors. They had smoother on-axis response and lower distortion because they used an exponential horn design that kept the air impedance constant and the sound smooth as silk. Today's widely used "constant directivity" horns control dispersion relatively well, but their straight walls generate reflections that cause distortion.
However, on big studio monitors, the off-axis pattern control wasn't great.
Pattern control can be loosely defined as "similar off-axis response at a wide range of frequencies." Lots of speakers claim "90° horizontal dispersion." But when you examine their polar patterns closely, you discover that they don't achieve 90° dispersion at all frequencies (drawing at left). In real world, as opposed to the laboratory, when you walk into a live venue, you spend most of your time standing off-axis to the speaker system. When a speaker has uneven dispersion (poor pattern control) at higher frequencies, full-range sound projects straight out like a beam. That's great for the listeners right in front of the speaker, but off-axis listeners get muddy, dull, uneven sound.
Poor pattern control (grey areas) is the result of uneven dispersion at various frequencies. The speaker may do ok at 1kHz but "beam" increasingly narrow patterns at higher frequencies.
So here was the problem: how to take advantage of an exponential horn's smooth response, but solve the problem of high frequency beaming.
The solution was a combination multi-cell aperture throat and exponential horn geometry to obtain the desired dispersion pattern and lower distortion.
Thanks to the efforts of a pair of the world's best acoustic scientists, we were able to retain the finned horn's dispersion advantages while reducing distortion problems. Our researchers provided the mathematical calculations and modeling that led us to create a two-piece vaned horn throat aperture and a separate exponential/conical horn. By placing the phase plug of the driver right next to the fins, we minimized reflection problems.
The design also resulted in a very large horn mouth that provides excellent power response at the crossover point. Stand up to 45 degrees off-axis and you still get wonderful, full-range performance.