Thiel Owners

Kenazfilan - the Bose 901 was a huge marketplace success at the time we were developing our initial ideas and prototypes. Audiophiles and specialty stores nearly universally rejected them as gimmicks, but there were some valid ideas in there. The crossoverless multiple driver does preserve phase relationships, which are only partially obscured by the small differences in distance to the reflecting walls. The short distance between the speaker and wall minimizes the distance difference between the reflected wavefront and front-firing direct radiator. The equalizer does not introduce phase shift and the sealed bass rolls off at 12dB / octave, which is quite benign. I concur with your speculation that the design might sound like hash with higher order crossovers introducing baked in phase shifts. 
I would love to see impulse response and other "normal" tests on the 901.It might fare fairly well at low levels in a highly damped room. But, those CTS drivers were driven far beyond their linear excursion and the dust-cap "tweeter" was very ragged, and the room perimeter drive is inherently problematic and so forth and so on. I am amazed at their success. Bose spent more on advertising than on product. And it worked for them.

 The 901 was, I believe, the only speaker that Jim dissected to see how other designs coped with the intrinsic constraints and trade-offs of the art. It definitely served as encouragement that we could do better.

tomthiel

Might you be able to provide any history of the cs .5.   This speaker, which I like to think of as the baby Thiel was my entry into the world of Thiel.   I had a pair in my main rig from 1996 to 2011 before graduating to a pair of 2.4s.   My cs .5s are now in bubble wrap in my crawl space, to be turned over to my son when he is ready for them.

i sold the Bose 901 between 1979 and 1981.  we also had Dahlquist, Maggies, and Infinity among others.  they were horrible sounding in all respects.  we used to say that the more you spent on bose,  the worst they sounded.  we actually liked their little 301 for what it was.  when a guy came into our store with a Molly Hatchet or AC/DC album under their arm,  we would immediately show them the 901 as we knew they were pretty much indestructible.  If he came in with classical then it was either Maggies or DQ-10's.  they were wretched speakers in my   opinion

Jazzman - I know a little which I'll be glad to remember. You might read Stereophile's 1995 review when it was introduced, https://www.stereophile.com/floorloudspeakers/223/index.htmlI find it nearly incredible that this little, inexpensive speaker performed so very well - compare that review with products costing high multiples of its $1k+ / pair. The .5 was my last production engineering product before leaving Thiel for New Hampshire. It got the same 1" MDF walls and interior cabinet bracing, which resulted in the deadest of any Thiel product ever. The Vifa drivers were entirely Thiel-designed with the fancy magnet structures, and the "paper" woofer cone actually had multiple-fiber reinforcement and damped coating, which made it behave extremely well. The crossover, although quite simple, has the same high-purity copper coils, polypropylene caps and low-induction resistors as the rest of the family. The .5 got a full technical paper, and its attributes, performance and measurements could easily be read as applying to a $10K speaker with the exception of its bass extension. The CS.5 was an exercise is how inexpensively we could produce an full-bore Thiel speaker.
On a personal note, in 1997 I introduced a pair to the resident musical theatre producer of my new-home rural New Hampshire village, which led to more pairs, and the founding of a small local Performing Arts Foundation. I am on the board and produce musical events at our Arts Center, using Thiel speakers, which were originally borrowed .5s, then my 2.2s and now 1.6s since my 2.2s are in the redevelopment studio.

Your son is very fortunate to ge those .5s. There are plenty of spare drivers and parts to last his lifetime. I have .5 drivers here for comparative analysis and they are really exceptional. Do note that electrolytic caps can deteriorate in storage and might best be replaced before putting them back into service if more than 30 years has elapsed. I'm glad you asked.

Tom,

Thanks much for the background on the .5s.   Much appreciated.
My son has another year of grad school, then it will be time to be looking for an affordable amp to pair with those puppies as a graduation gift.