I imagine adding a third woofer would create a situation where the outer two interfere with each other around 400Hz. I've considered the 3 woofer vertical "array" as "do-able" for a while now...using 2226J's the nominal z would only be 5.33 ohms, and parallax issues won't be too bad, as the relative distances from the woofer to listener might not vary much.

Add a fourth woofer to the array, now we're still looking at an easy 4 ohm load, with 4 jbl2226J's in parallel. But UNLESS you position the woofers along an arc like Pro Arrays, parallax issues will become more prominent. Maybe not an issue for "home hi-fi". And stuffing a horn in there somewhere for the HF, along the vertical axis, is going to force an even larger gap between at least two of the woofers in the array.

Intuitively, I'm thinking the array format is designed for SPECIFIC pro sound applications, and will create more problems than it will solve if implemented poorly. I'm not clear what characteristics it has that would be so desireable for home use that acceptance of the self-interference and parallax issues would be considered worthwhile. Sam

ps, when the "benchmark" is the performance of a pair of 4 Pi Pro's, you have to get pretty fancy to do any better:) and NOTHING ELSE that fits in such a small footprint is available, period.