Concentric drivers

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.

No