I think I know what you are looking for. A purist single driver system driven by a SET amp with no negative feedback. That means no crossover and no whizzer, as a whizzer is basically a mechanical crossover. You are okay without a super tweeter, as extension and linearity above 5k is less important than maintaining coherence in the treble and upper mid-range.
To get this done, a 3 inch wide-band driver may be just about ideal for mids and treble. A Tabaq transmission line quarter wave type design or for bigger bass, a Frugel Horn XL back loaded horn type of design using the Alpair 10 driver.
These are well engineered designs and are available for DIY. The commercial designers often times borrow from the DIY community...but in doing so they normally get away from the purist approach and add things like super tweeters, whizzers, baffle step correction, bass woofers, resistors, etc.
To get this done, a 3 inch wide-band driver may be just about ideal for mids and treble. A Tabaq transmission line quarter wave type design or for bigger bass, a Frugel Horn XL back loaded horn type of design using the Alpair 10 driver.
These are well engineered designs and are available for DIY. The commercial designers often times borrow from the DIY community...but in doing so they normally get away from the purist approach and add things like super tweeters, whizzers, baffle step correction, bass woofers, resistors, etc.