It is really sad to see more and more dogmatists spoiling this forum, which I thought was meant to create an easy way to exchange our experiences: EXPERIENCES, not theoretical arguments. In case of the open baffle loudspeakers and the voiced criticism that the back-aiming sound wave is out of phase (probably correct) one concludes that because of this, they are "wrong". This sounds almost like evangelical argumentation. My point would be, that all music, lest the one played back in a recording studio, is "out of phase". Case in point: a symphony orchestra. It is usually stacked 15 meters back or even more (in case of the Mahler orchestra) and often also lifted towards the back by several feet. While playing the same theme, the sound from the 1st and 2nd violin strings will arrive earlier at the orchestra seat than the woodwinds, and the brass even with more delay. Guess what? Our brains accommodate for this with delight, as it gives it all the spacial clues it needs to relax and enjoy: it's called "psycho-acoustics", and the late Herbert von Karajan endowed a continuing research grant to explore and correctly describe it's effects. Our ears are not oscilloscopes!
Which brings me to my actual contribution: I am totally in love with my Linkwitz LX521 speakers (https://linkwitz.store/category/lxspeakers/), powered by Dr. Frank Brenner's active analog 4-channel signal-processor/amplifier system (same URL "PowerBox 6pro NCore Precision Analog"). I had listened to Siegfried Linkwtz's original Orion speakers at several audio shows, and was blown away. At the 2006 RMAF I was about to buy them, when Siegfried's wife told me that he was working on an even better design (in a report of the event STEREOPHILE gave the Linkwitz room "best-in-show", btw). Then, at the 2012 Burning Amp (if I remember correctly) the LX 521 was shown (with passive crossover and powered by 4 PASS LABS amps): Nelson Pass had set up the display himself (he and Siegfried were long time friends; and yes: Nelson uses this open baffle system himself, apparently even while it's "wrong"). That's when I made the plunge: I ordered the construction materials and SEAS speaker sets from Dr. Brenner (the pre-cut birchwood ply panels need to be glued together and internally wired, which is actually a lot of fun) and after a few weeks, I gave the raw chassis to my local MAACO paint shop to have them painted in Lexus Pearl White with extra glitter. You can look at them here (before they moved into the music room): https://linkwitzlab.com/LX521/PhotoGallery.htm (mine are the white ones, 5th entry from the top). And then the magic happened: once properly placed (4 feet from the back (which is actually our terrace sliding door) and 3 feet from each side wall, the musical event unfolds between the speakers and somewhat behind them: one seems to "look" onto a virtual stage, whether it is solo voice (Maria Callas, Lyle Lovett, or Boz Scaggs), string quartet (Bush Quartett EMI C147-01668/70), or Steely Dan, jazz piano (Oscar Peterson "We get Requests"), or Mahler #2 (Klemperer, ERC). Most remarkably: there is no sweet spot! I can move mack and forward, stand up and even go to the back of the room: the musical event is firmly locked between the speakers and stays focused, unlike the MBL Radialstrahlers which fill the room with sound that is omni-directional. In fact, if I open the terrace door, Maria Callas seems to sing on the terrace as if she was standing in front of the pool. Unreal! In conclusion: On his website, the late Siegfried Linkwitz (we became friends towards the end of his life) gives everyone an in-depth primer about psycho acoustics and how this discipline has influenced the design of his incomparable speakers, and Dr. Brenner is carrying on the legacy by providing future-proof support electronics which make the magic happen: and all that for a price less than a Lyra Atlas cartridge!
[ProJect LP10 Carbon TT with Benz Micro LPS; MSB Platinum V Signature CD player/DAC; Supratek Grange Preamp; Linkwitz 6Pro NCore analog data processing/power amp; Linkwitz LX521 4-way active speakers]