Does lower CR equal lower efficiency? Will directivity collapse sooner (without a diffractive throat geometry), resulting in a lower HF cutoff? Could that be why the MSL-4 uses such a low crossover point? I had the idea to mount a midbass driver (or two) in the aforementioned fashion, then affix some kind of throat or smoothing guide to the front of the driver. No rear chamber access panel, no double-walled horns! Then, I'd coax the HF horn in the midbass mouth. Have any experience in that direction?