Thiel's naming has been called confusing, although it is quite logical from inside the system.
There are a few different series, which developed organically over time:
O the original O series which was sequential, first product, second product, etc. without regard to what it was. That series ran through the O4a (second generation of O4) andO3b, third generation of O3. The next iteration of the O3 was dubbed Coherent Source by Peter Moncrief of International Audio Review.
That CS name stuck and all subsequent floorstanding coherent speakers fell into the CS series, with the 3 being the 10" 3-way flagship. The CS3.5 was the 5th generation of the 3 and was replaced by the 3.6 and 3.7. The CS2 appeared as a smaller, less expensive model to inherit what we learned from the 3. The O4 - 6.5" 2-way became the CS1 series which ran consecutively all the way to the 1.7. The model 2 had much longer runs without upgrades than the 1 or 3 which received the bulk of Jim's development energies. The CS2 was an 8 inch x 3" x 1" ported design which ran more than 10,000 copies before the CS2.2 in 1990. The 2.3 and 2.4 sported the coincident-coax as a proof of concept while the CS3.6 produced robust sales and received internal, non-heralded upgrades. Note that in Thiel-land a new model designation means at least new drivers. When products received internal upgrades, they had names like 3.6.1, etc. but only dealers knew of those designations.
When home theater came along more series were added to the mix.
SCS (Small Coherent Source) the bookshelf - satellite series got the first coincident-coax 6.5x1"driver which ran to SCS4. MCS was Medium Coherent Source, often used for center channel, etc.
The Personal Coherent Source was an executive - desktop little thing of its own.
The SubWoofers were designated SW, but with upgraded room interaction software became the SmartSub or SS series.
What holds true is that each number model series remains a consistent entity such as CS3 = 10"x3 way, etc. and the post decimal number is the generation with 2 being the second, as in CS2.2 etc. Each model retains its distinct personality and attributes, but grows in quality as new technologies and solutions were developed.
The CS1 had a full series from CS1 to 1.2, 1.3, 1.4, 1.5, 1.6 and finally the 1.7. The CS2 generations always ran longer for marketplace and R&D reasons. So it topped out at 2.4. The next generation was named after Jim's death and was called the 2.7 due to the radical coax driver and asterisks woofer it shared with the 3.7. Except for that model 2 number skip, the numbering is fairly consistent. Way, way many products for a small company.
