They're wired parallel/series for 4ohms and I'm crossing at 200hz and 4khz right now. I'll play around with the XO this week as well as trying them mirrored with the tweeters on the inside. No complaints so far.

Great job!

I saw your post about -> "16 NSB, 8 PT2 tweeters per side"...
I'm starting a project with these same speakers for a friend.
I have PT2 tweeters that I will give him and I ordered those
NSB's to play around with.

Got any tips for integrating the NSB to PT2?

crossover you use?
sealed vs. open baffle sound ?

"Got any tips for integrating the NSB to PT2?

They seem to integrate themselves pretty well. As I mentioned before, it's helpful to have some way of boosting/attenuating the individual lines in the array. If you really wanted to go whole hawg, having some EQ available to flatten the HF rolloff above 10khz would be pretty cool.

"crossover you use?"

I'm using an active 3-way XO (Ashly XR2001). If I remember right, I think I had the XO at 150hz and 3.5khz in the end for the NSBs, but it seemed to work well with a pretty large deviation from those points too. Probably a taste thing.

"sealed vs. open baffle sound ?"

I don't have room to get speakers away from walls in here, so my dipole experiments have been less than successful. I built the NSB arrays as OBs initially, but ended up closing off the backs. Alot of people with the room to do it in, have had good success running them as dipoles however, so that'd be up to you and whether or not you can take adavantage of it.

These new arrays are sealed. I went for a standard Qtc of .7 with some fiberglass to soak up reflections back thru the cones. I won't be doing anymore dipole speakers in here except for quick listens to hear the drivers.