When I set them up originally I did use an SPL app on my phone (yes, crappy I know), and did check the difference between 0° and 180° on the HSU, which is closest to my LP. The difference was, if I remember correctly, somewhere between 1.5db to 2.0db, and I went with the better result ( which I, of course, can't remember- and I've been working out of town for three weeks, to return Sunday
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Due to negative WAF ( and other things too), I will be moving my setup to another place. The room it's in now is a funky space- imagine a 16x12 rectangle with a 6x6 rectangle off the front right corner. It's also got a coffered ceiling. My new room will have a more traditional layout. I'm just imagining having two subs up front then being able to optimally place a 3rd would give me more even response throughout the room. I know it'd be cheaper to roll with what I've got, but I'm definitely not opposed to dishing out for some more woofage!