@larryi I have only heard two or three OB designs but uniformly, they all exhibited a thinness, a lack of weight or gravitas, that left me wanting for more. I'm not saying they can't scale the heights but I haven't heard it.
Cube Audio Nenuphar Single Driver Speaker (10 inch) TQWT Enclosure
Cube Audio (Poland) designs single drivers and single driver speakers.
Principals are Grzegorz Rulka and Marek Kostrzyński.
Link to the Cube Audio Nenuphar (with F10 Neo driver) speaker page:
https://www.cubeaudio.eu/cube-audio-nenuphar
Link to 6Moons review by Srajan Ebaen (August 2018):
https://6moons.com/audioreview_articles/cubeaudio2/
* Frequency response may vary and depends on room size and accompanying electronic equipment.
Principals are Grzegorz Rulka and Marek Kostrzyński.
Link to the Cube Audio Nenuphar (with F10 Neo driver) speaker page:
https://www.cubeaudio.eu/cube-audio-nenuphar
Link to 6Moons review by Srajan Ebaen (August 2018):
https://6moons.com/audioreview_articles/cubeaudio2/
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Parameters (from Cube Audio):
Power: 40 W
Efficiency: 92 dB
Frequency response: 30Hz - 18kHz ( 6db)*
Dimensions: 30 x 50 x 105 cm
Weight: 40 Kg
* Frequency response may vary and depends on room size and accompanying electronic equipment.