Concentric drivers

@mulveling  😃 *kazoo fanfare*  And thanks for that byte of info yours unruly was unaware of, but not now... makes it work, despite itself. *L*

Flip phase, and a crossover tweak.  'Pepperpot' backside shaped to act as a default waveguide, audible Magik...(google that...;)...).

That's why I like Walsh drivers.  Simple, just stack vertically and cross proper. *S*  The rest is mechanics and material magic.

...and beats having to move speakers Really Fast to compensate for Doppler fx.

Something for your and all's late Sat./early Sun. :

We always called it intermodulated distortion.  I always thought adding a sub and cutting off the two bottom octaves helped.  I have no measurements to back that up.  Do most single driver speakers usually get set up with a sub.  I would lump the Tannoys in there(concentric driver).  Now, when I hear Tannoy speakers they sound real good!  It would be fun to experiment with them.

So what does "Doppler effect" sound like? Like talking through a moving fan?

Every driver reproduce a range of frequencies. So why don't all driver produce "Doppler effect"?

All drivers change phase throughput their frequency response. Is that the same thing?

It has been said that it is inaudible or does not affect sound in any appreciable way.

For most speakers today,  doppler is not a real problem.  It does exist and can be measured.  It would most accurately be described as FREQUENCY Intermodulation distortion.  When drivers are used and ran over a very large frequency the drivers move at very different rates and that causes the doppler effect.  As drivers have improved,  natural crossover points in 2 way designs has lowered overall and most 3 way plus designs have never had real issues.  Of course, there are always exceptions, but overall, Frequency intermodulation distortion is not an issue in todays speakers.