Constant Beamwidth Transducers (Dayton/DB Keele) - There are two CBTs you can buy as manufactured products: the CBT36 kit and the CBT24 kit/
complete speaker, both offered by Dayton. The CBT24 is on sale for $1495/pr as of February 2, 2019. For mini-monitor money, you can get a bleeding-edge driver array, albeit limited by driver performance. I would personally love to see someone stick in Vifa TG9s or some other widebander with smoother dispersion and FR. Rick Craig of Selah Audio also does custom CBT work at a much higher price range. The CBT
isn't a line array. Despite its looks it is as far as one can get from a line source. The curvature and gradually-decreasing SPL (called "shading") emitted by drivers as one moves up the array come together - as someone described brilliantly on DIYAudio -
a "slice" (like an orange) of the wavefront of a perfect point source placed on the ground plane. Project an imaginary line backwards from each driver at the angle at which the driver is pivoted. Do you see the slice of a sphere now? Exceptionally uniform coverage both vertically and horizontally. No floor bounce because the speaker is on the ground plane. Floyd Toole mused that it could be the
"perfect" surround loudspeaker due to the uniformity of coverage allowing similar sound over a larger seating area.
There is more discussion on another ASR thread.
Note that the CBTs will require subs and ideally DSP to equalise driver response. Don Keele (ex-JBL, designer of the JBL biradials before the CBT array for audio) has an excellent lecture series that examines the properties of CBTs: