Point well taken...but... if you want to take your OBs to the next level 
Thanks to Scott F, Poultrygeist, Richard, BoJonJovi and Godzilla and JRKO from
http://www.diyaudio.com/forums/full-range/196808-beta-12lta-beta-12a-2-open-baffle-concept-viable-3.html for sharing your knowledge, experience and encouragement-enabling me to begin my journey into the OB world. Of course, all DIYing involves risks of time and money, such as buying expensive drivers for the wrong enclosures and/or room size, or attempting to passively cross a three way speaker system when truly cost effective results might only be achieved by at least bi-amping the mids and midbass drivers.
But here’s what I’ve got to work with and what my goals are. I just hope that I won’t get laughed out of court:
OBs, I’m told, should have at least have 4 ft of space behind them, and ?? ft to either side of them. In any case, while this won’t be a problem in my 18’ x 14 living room, I have another speaker system planned for that room. And though that room is uncluttered enough to accommodate both speaker systems, my crazy idea is to build a pair of OBs for one of two fairly cluttered bedrooms. One room is 12 ft x 11; the other is 17 ft x 9.
I’ve read that putting speakers (most or all types of?) along the longer wall is not advisable. If yes, why is this so? In any case, at least I can get rid of stuff along one of the longer walls in the bigger room to allow placement of speakers there.
Regarding placement and listening position in the 12 ft x 11 bedroom, I’d be sitting in my small easy chair in front of the north wall, with my single twin bed to the right of me. The bed is 24” high and my ears are 35” above the floor. For listening sessions, I could slide the right OB away from the west wall where I’d normally keep it to then be in front of the doorway. However, the place for the left OB would be impossibly cluttered, leaving no more than 3 ft behind it-before encountering my left floor standing TV speaker behind my 32” TV, none of which I want to part with. And there would be only a few inches between the left OB and the East wall and the 32” TV to its right.
While I’m no one’s kind of speaker designer, presumably the need to maximize the OB’s distance from boundaries allows fuller wavelength excursions for low frequency response from, say, what those Eminence Alpha 12” LTA drivers, can generate-though I lack the first year college physics to understand the entire event. Sadly, unless I’m wrong it would seem that neither of my bedrooms have adequate space to draw decent LF response from those Eminence Alpha 12” LTA in OBs-at least down to 70Hz, to where my sub can take over. Yes or No?
Likewise, note the amount of space needed even for Jon Ver Halen’s Tiny OBs.
http://www.lowther-america.com/Cabinets/Open_Baffle_Speakers/, which otherwise would have worked for me. As stated here, the TOBs go down to 65Hz and even in my smaller bedroom I might have room for one of my Rythmik 12" sealed servo subs.
http://www.rythmikaudio.com/technology.html built by Jim Salk
http://www.salksound.com/salkrythmik%20-%20home.htmAnd so, in my crazed pursuit of using OBs in one of my small cluttered rooms, I cobbled together this
system idea, which I hope won’t cause more problems than I think it might solve, as follows: The pair of sealed 15” midwoofers that I will be using in my three-way living room system. They are a pair of GPA Altec 416-8Bs
http://www.greatplainsaudio.com/downloads/416-8B%20Spec%20Sheet.pdf They would be in the same low diffraction, 3 cu. ft sealed cabinets designed by fellow diyaudio.com
member Gary Dahl for use with another speaker project. Gary’s sealed boxes keep the 416s within their 700Hz to 70Hz comfort zone, thereby minimizing IM distortion. Gary, Lynn Olson, Jon Ver Halen among others have long known the Altec 416 to be a very unusual driver, and enjoy its almost “magical” sonic properties of this “PA” speaker in almost any kind of enclosure.
http://www.diyaudio.com/forums/multi-way/100392-beyond-ariel-781.html and
http://www.enjoythemusic.com/magazine/equipment/1009/lowther_high_efficiency.htm Thus, to overcome the OBs’ room boundary issues for adequate low frequency response in very small rooms, I would place an Eminence Beta 12 LTA OB atop each Altec 416 midwoofer box.
There’s only ~0.3db difference between the 416 and the Beta LTA, so active crossovers are obviously not needed, at least for level matching. And aren’t sealed boxes the most forgiving of placement restrictions? If so, then their handling of everything from 700Hz down to 70Hz should take most room boundary problems off the Beta LTA OBs. Correct?
As for highs, while expensive it appears that the best solution by far would be a pair of 9” RAAL Lazy ribbons
https://www.madisoundspeakerstore.com/ribbon-tweeters/raal-lazy-ribbon-9-ribbon-tweeter/ Along with excellent dispersion, their > 100db sensitivity would again remove the need for active
crossovers.
Question: Depending on which of my two small bedrooms I’d be installing these hybrid OBs-and on which wall they are placed along-I’d be sitting between 7.5 ft and 12 ft away in one bedroom and between 8 ft and 9 ft away from them in the smaller bedroom. Gary’s Altec sealed midwoofers cabinets are 26” w x 15” d x 20” h. But assuming on-axis placement is desirable, how wide and how high does the OB panel for the Beta 12 LTA need to be, with each panel sitting atop each Altec midwoofer cabinet?
Obviously, these numbers would also impact placement for the RAAL ribbon tweeter, being either to the side or atop each Beta 12 LTA OB.
Another question: Would I be compromising a lot on sound quality if don’t at least partially crossover this system actively?
Btw, I would drive the system with my First Watt F4 amp
http://www.firstwatt.com/f4.html via a tube preamp like this
http://www.kandkaudio.com/line-stage-2/ As for Lowthers (in OBs atop the Altec midwoofers?), I’ve heard it said that most people either love them or hate them. Whether that be due to the “shout”-though apparently due to a problem with the driver’s whizzer that was banished more than 15 years ago-or the break in period or other personal listening preferences, I wouldn’t know. However, I’ve certainly been long interested in hearing them, particularly the Alnico models. But to best of my knowledge no has ever once done a Lowther show in New York City. Nor could I find Lowther owners there-or on Long Island, where I live-who might let me hear them.
On the other hand, everyone seems to love the sound of OBs in general; ditto for Alnico drivers, such as the GPA Altec 416s-particularly in low diffraction sealed boxes that cut their low end off below 70Hz. Despite having to contend with 3 cu ft midwoofer boxes in my bedroom, I’m hoping that I might have hit upon “a best of all worlds” system that works in at least one of my bedrooms.
But did I overlook anything?
Anything else good or bad about my bedroom speaker system idea?
How good do you think it might sound?
