So I ran across this, which helped quite a lot, but doesn't get into enough detail, IMO.

http://www.enjoythemusic.com/diy/0709/open_baffle.htm

He talks about the baffle size being a tone shaper, but you guys talk in this thread about certain drivers needing certain baffle distances. How do you know whether to leave 5 inches on each side of a 15" woofer or 8 inches or another dimension? Do tweeters and midrange/fullrange need smaller baffles due to the frequencies they radiate?

Anyone got links to beginner friendly guides to speaker design? Specifically OB would be nice, but general info is great as well.

I think I can get my head around the acoustics part as I work with acoustic amplifiers daily, I just need some guidance when it comes to speakers. The hard part will be the crossovers, at least to understand, since I have zero experience with building electronics.

Yep...I listened to this bastardization tonight. Go ahead and laugh it up. Cheap electrolytic, cheap solid core inductor, connections twisted together. First order filter at 200Hz. It actually doesn't sound terrible. Poor but not terrible.

• Imaging is wonky, midrange weirdness too
• Surprisingly decent tonal balance. I think it's on the bassy side of things though. But not that muddy
• I'm getting fairly good bass extension. Good impact down to 40Hz based on my warble tones
• I do not seem to get any better/more bass by placing the woofer baffles together, as opposed to pulling them apart. Not intuitive, knowing what I know about OBs. Perhaps something to do with their acoustics centers still being close to the end of the baffle?
• Might be worth it to look into structural upgrades. I don't think I'm hearing any resonances, but you can feel 'em when you touch the cabinet. Still has some peaks and nulls I feel. Might just be room modes, although I don't think my space is too mode-y.
• Not that easy to listen to. This was less of a problem with the BK12 unadulterated. No joke, I think my Marantz is giving out on me sonically. I need a new amp(s)

I'll measure tomorrow.

Will do.

So I was talking to the Exit Level Audio guy (forgot his name) and open baffles came up. He recommended I look into some Alpair driver (forgot the name again). Any opinions on that? I'm still weighing my options on what I want to use. Transplanting the Fostex makes the most sense. But I know once I cut the baffle it's going to be a PITA to try to make a larger cutout for a larger driver. So it better not suck.

He also recommended I check out the Open Baffle forum on AudioCircle. I'm flipping through there right now to see what's up.

I skipped Alpair because of their low efficiency and low impedance.  Also they lie big time on their published FR graphs, and that doesn't gel well with me (what else are they lying about?)

Pulled 'em apart. Big time improvement.

• Imaging is quite a bit better; Separation is better; easier on the ears
• Just noticed a MAJOR null in bass response around 80Hz. Using the Aphex Twin track called "Ageispolis", which BTW is a great track for detecting mid-bass and upper-bass smoothness/quality
• Other than the above point, I'm really starting to like the open baffle bass
• These still tend to fall apart during complex passages. I think it's the FE126's fault actually. Funny how even humble headphone systems can be better than speakers in this regard
• Good representation of space and reverberant qualties. I bet this would be even better with tubes 
• Vocal shoutiness/harshness might be back a a little