Whizzer cone drivers

Charney offers several choices for their full-range driver.  I've heard the Voxativ and AER driver in their Companion line of speakers.  I like the AER more than I do the Voxativ, but, both drivers are excellent in that speaker.  I find the Charney single driver full range system to be more naturally balanced and less peaky than the Cube Audio Nenuphar system, but, the Nenuphar Basis (two way system with a powered woofer) is a different beast and I really like that system--vibrant, rich, and capable of filling a very large room.  These whizzer cone systems do demand careful speaker placement and listening on the preferred axis (i.e., small listening window), but,  all speakers really do have a small ideal listening window anyway.

I have Moth Audio Cicadas on my TV system, I stare at those whizzer cones all day! 

My wife wanted me to buy the Cicada's way back when (her favorite color is Red).

DeKay

Single driver for the widest frequency range.

I hate even seeing them. Though they can balance out a driver, I feel that the driver was inadequate, to begin with. You are trying to get something out of a speaker than what the cone sans the Whizzer can produce. It is a cheap bridge from say having a single-driver system, compared to a two or three-driver system. I have a meter that graphically shows me a graph including the immediate frequency and the sustained fall-off. You can get an app for your celliophone that shows you a similar representation, 'Decibel X'. I have the ability to take an individual speaker out of the circuit and see what is left. and yes there are tones made by the larger speakers that MIGHT in some ways fill in the upper tones, but I build crossovers with the intention of taking those frequencies OUT and leaving it up to the next higher-frequency speaker to take over. If you don't like what a bookshelf speaker sounds like you have the option of getting a stand-mounted or floor-standing speaker, to begin with.