(the simplest type, except for no crossover)
2.3's have about 23 components for each speaker, but "simple" is subjective. :)
"that apparantly used a very simple, minimalist, first order crossover design...a resistor or capasitor or something" The Extrema has the simple crossover you speak of, the EA 1 has I think 6-7 components per speaker but its been 8 years so I'm not sure anymore.
Dennis Had's Soliloquy SM2A3 uses a minimalist crossover design specifically intended for use with low powered SET amps (it's 11 ohms and comes with a caution to not exceed use with amps of greater than 25 watts). At the same time he designed the Soliloquy 5.0 with identical drivers, cabinetry size, etc but with a different crossover for more powerful amps.
Full-range, single driver, horn speakers have no crossovers, but usually have sonic limitations at the frequency extremes (you can only ask a single driver to do so much...). Very large panel planars and electrostatics (such as the big Sound Labs) also have no crossovers, unless they are combined with a dynamic sub-woofer in a hybrid design.
Phase-and-time aligned speakers (such as Vandersteen) use first-order crossovers, which are less complex in design that higher-order crossovers. First-order crossovers do not, however, guarantee better sound reproduction that high-order crossovers -- it's the total design execution that's ultimately responsible for the audio quality.
I'd like to clarify Jond's comment:
It is my understanding that the Reference 3a de Capo uses 1 element (high pass) to protect the tweeter. As far as I know, this is the simplest x-over used on a multi-driver system. Most 1st order x-over systems use multiple elements.
However, to your original post: I'm not so sure that this will make the speaker sound dynamic (my de Capo's aren't spectacular in this respect). OTOH the resultant flat impedance curve is definitely tube amp friendly - especially for SETs. Also, phase shift is minimized and many people believe that to be beneficial.
To me, the more crossover parts a particular speaker utilizes equates to more mistakes made by the designer in the speakers conceptual design stages. Hence speakers with lots of parts were not properly designed to begin with. The only way to do a minimal x-over parts product is to do ALL the math prior to building it. Look into the Green Mountain Audio designs.
Here's a few more to add to your list.
Brentworth Sound Lab. I like this companie's thinking. This sure resembles the design theory behind my current speakers.
Royal Devices loudspeakers This company doesn't use crossovers on the woofers of their speakers. They look great..I wonder if they sound as good as they look.
Audio Note Loudspeakers. Looks like very simple crossovers to none at all used in these speakers.
Carfrae Horn speakers
Contrast audio loudspeakers (Ukraine).
In construction uses scheme with only one capacitor. Need to hear but you can imagine if you read reviews.
Own components from naturall materials and more than 20-ty years of experience in designed and manufacturing.
The Seas A23 kit uses a single capacitor, single resistor:
Of course, there are a number of "full range" designs which have zero electrical crossovers.
One interesting approach lately is a WAWB - Woofer Assisted Wide-Band. This pushes the one crossover point down to the 200-300 Hz range.
While a 1st-order crossover does require fewer parts (perhaps just a single capacitor and resistor) than a 2nd, 3rd, or 4th-order, a loudspeaker with a 1st-order x/o does not necessarily have a simple one. Thiels are often mentioned (as they are above), but they actually have very complicated crossovers. The reason is, their crossovers perform far more than mere 1st-order filtering. There are a great number of parts used to tailor, manage, and compensate for the characteristics of the drivers used in Thiel loudspeakers. Just look at a schematic for one!
On the other hand, the Eminent Technology LFT-8b, which also employs 1st-order filters (one at 180Hz, another at 10kHz), contains only a few extra parts for driver compensation. That speaker’s x/o schematic is posted on the ET website.
Many of these minimal crossover speakers use mid/woofers with an abnormally high voice coil inductance .The SEAS A26 are an example of that.So to claim there is no crossover on the mid/woofer is arguably misleading.It is just that a first order crossover is built into the voice coil .The mid/woofer in the A26 kit for example [the 26RE4] has an inductance of 3.8mH.Most similar drivers have an inductance of more like 1mH.I suspect the Audio Note drivers would be much the same.
The Totem Element speaker line doesn’t use any active or passive crossovers.
I’m not sure why people misread this. Their actual quote is:
No active or passive cross-over parts in the woofer section
You can read it on their website here:
In this respect it is like the Seas A26 kit I posted above.