Speaker cone shape

jasonbourne52396 posts04-22-2021 1:21pmManger makes flat diaphragm drivers that use the "bending wave" principle for phase coherence.

Great transient response, but frequency response is all over the map. His website dedicates much time to transients and location by transients, but seems to ignore all the other mechanisms for location that are frequency based. I guess it comes with the marketing territory. I can certainly appreciate the engineering of the driver. I have only heard them at an audio show. They were good. Not great, good. I found them no more or less realistic than other implementations.

For some reason, as to which one of you will no doubt enlighten me, they sound even better when the 6.5" are wired out of phase with the 8" & 4".

If you've copied an original crossover design then that driver would have been reverse polarity as well. Capacitors and Inductors alter the phase of the signal so it's not unusual to allow the signal for one driver to go 180˚ out and correct it at the driver. 

My only answer to your original question is that air doesn't flow through a driver so you can't apply the physics of a wing to a loudspeaker diaphragm. It needs to be stiff and light which is why a cone is a good choice of shape for a woofer or mid with a conventional voice coil. Electrostatic speakers are able to have flat diaphragms as the electromotive force is spread across the whole surface area.

If you don't already own a copy The Loudspeaker Design Cookbook by Vance Dickinson is a good primer for the subject... more practical than theory but a good jumping in point. If you really want to get into the mechanics of sound diffraction then the Master Handbook of Acoustics is as good a place as any to start.

"...Lincoln Walsh was a pioneering expert on radar design back in the Forties! I think he may have invented the perfect speaker!..."

A good example for this thread on speaker cone design. Walsh's full range driver was very interesting but the cone was so big that there were problems with cone break-up and distortion at high levels. As a mechanical engineer, you can quickly surmise that all electro-mechanical  drivers have trade-offs, nothing yet is the perfect radiator but the state of the art is still very very good. 

The Walsh Ohm speaker sounds awful. It's a novel design, but next to anything else it's terrible. Explain to me how a single voice coil driver made from three different materials firing downward can have a wideband, high fidelity frequency response. Short answer...it can't...and doesn't.

Sony has had flat diaphragms. Morel makes a dome drivers. Mount a woofer backwards, magnet out and the box gains some volume. Drivers designed with a round cone have the advantage of basic rigidity. Different frequency based cone geometries are chosen for dispersion characteristics.... everything is a compromise. 

Many new drivers have an inverted dome style for the diaphragm. Different materials and diaphragm treatments are also part of the mix.

The best motor design I've ever heard was the extreme underhung topology that was the NeoRadial developed by Aurasound back in the 1990s. Total voice coil immersion in the gap, very linear response, extremely low motor distortion...and very expensive to manufacture due to the amount of steel to house the motor. Over hung coils just cant do what underhung can do for low distortion control of the moving mass. The latest JBL Dual Differential motors is probably the closest with a braking effect from the coils as they reverse direction.

They are shaped that way to add strength and rigidity to the center coil or a more accurate pistonic motion during use to decrease distorion and flexing of the cone during movement.