DIY speakers that impressed you compared to production speakers

My first speaker build did it. A pair of FF85K drivers in oversized cabinets, made from plans I found online in Japanese. I knew nothing about the physics. The treble was amazing. No bass though to speak of, truly. Smoked my pair of B&W DM602S3 speakers. Philip Glass’s piece for solo violin & Bang on a Can’s cover of Brian Eno’s Music for Airports were revelatory; the music hung in the air.

I was sold on single-drivers at that point because of their point-source nature, and, while I didn’t know it at the time, I was enjoying the dispersion of the very small & light cone of the FF85K. I have become an advocate & collector of very small & light-coned single-drivers.

I have since built conventional two-way speakers, but I have always come back to single-drivers. The only two-way alignment I want to try now is a sealed or vented coaxial.
 
My first speaker build did it.
Similar for me-it's why I became a loudspeaker design engineer, I couldn't afford some big Altecs (15 + horn, I forget the model). So I got into building my own as I had woodworking tools. The massive speakers I used in college had 15" pro woofers and horns. 117 dB in my dorm room from a little NAD 3020 playing Rush "Signals"-as I've posted elsewhere that's as loud as I measured Van Halen's 1984 tour from row 30 in Chicago! Nothing commercial was even available like that, and no pro speaker would have fit.

Another DIY design I really like is the Focal Aria 5. You could really hear into the music with those.

Now I'm getting the bug to build some big speakers with a big horn, something smooth to as low as possible, and use Audyssey to EQ the power response droop.