pay 12 times more than a minidsp, as a bonus get worse measurements! 
but atleast its less silly than his 10k (?) fullrange driver speakers (http://shinshu.fm/MHz/06.94/images/zs9B1pMl.jpg)
Honestly rabbit, I never took NP as a serious speaker designer. He's a tinkerer at best and does it to entertain himself which is fine.
All things equal, competent loudspeaker design is EXTRAORDINARILY difficult, and requires resources, time, dedication, and most importantly a keen understanding of the importance of directivity control, and psychoacoustics. Very few loudspeakers achieve that - most brag about their stout cabinetry, or lack thereof (with regards to OB designs).
NP's expertise in analog circuit design is well established. Yes, he deviates from the norm there as well but he does have a good understanding of the importance of low IMD, and the importance of concentrating on the harmonic distortion
spectra more than any other aspect - which is where he ties in psychoacoustics. At least he
publishes that data (and its reaffirmed by 3rd part measurements), so you can make an informed decision prior to purchase. This is in stark contrast to many loudspeaker designers who cower and hide (not all, but most).
I find it distressing how we (the enthusiasts/the audiophiles) breed incompetence by not demanding accountability. If we did demand it from all designers be it loudspeakers, analog and digital equipment, just imagine?!
There is a reason why a buy/sell section called AudioGON exists. It should really be called AudioTarot.
Best,
Anand.
