Speaker cone shape


Why are speakers cone shaped, apart from rigidity? To my mind the air being pushed by a cone would radiate at an angle inward toward the axis of the speaker and collide in the centre, which seems inefficient to me, and likely to cause some distortion of the sound. This may also cause interference to adjacent speakers on the same baffle.  Would there be any advantage to having the surface flat, assuming you could maintain rigidity without increasing the mass? There must be modern capable materials out there.
Is the fact that the speaker is cone shaped that causes the volume to change counter intuitively as you move left and right in front of the speakers? What I mean by counter intuitively is when you move left the right speaker sounds louder and visa versa.
chris_w_uk
Nobody's mentioned amt drivers yet, 'til now.

Absolutely effortless....*S*  

Oldhvymec, +1 on the 2496....sweet.

(*hmmmm* Initialed, 'o.h.m.'...ohm.....interesting....;)...)

The old Ohm Walsh's large cones were a breakthrough, but suffered from the tech of the era.  The newer ones are very good, but the interpretation of their designs 'cheat' a bit on the original concept......

I do too, but in a different fashion. *G*  Just got to go there...*S*
Having done some research on this when I was making custom speakers, I can tell you shape does not seem to effect radiation pattern. They all create a pressure wave that expands outward in all directions as it travels. It does not collapse inward. Think ripples on a pond. The waves you see are not in the same direction as the stone that caused them.  You can mount a woofer backwards and it still performs the same if polarity is reversed. I hope this helps you visualize what’s happening at the air/cone interface. 
Thank you vinylfan62! Someone finally came up with the right answer. Talking about lay instinct gone awry. Air is not moving. It is pressure fronts that are moving. A flat woofer radiates exactly the same way as a conical one. The physical characteristics of the drivers are different but that is all. This might lead to different driver behaviors and distortion characteristics. Nobody has been able to out perform the conical driver in bass and midrange applications for dynamic drivers.  It is an inherently stiff structure so it is easier to keep it light. Attempts at using alternative  structures have been relative failures. The old paper cone still reigns supreme but you also have composites, metal, ceramic and diamond cones and domes. You also have various suspension types, voice coil formers, methods of ventilation and voice coil cooling (ferrofluid), and basket structure. There is no magic in any of this.

The real problem for dynamic drivers is that their dispersion characteristics change dramatically with frequency relative to the size of the driver. The frequency band is not dispersing uniformly but continuously changing. Some people believe speakers that disperse uniformly over a narrower area have better imaging characteristics as opposed to speakers that will disperse widely but unevenly across the frequency band. 
   
Put a whole bunch of small...say 3"...full range drivers in an array of some sort that will move enough air to get to 85+ dB and be prepared at the amazing sound...with no crossover interference...that all these little drivers working in unison can create. 

Faital Pro makes some pretty killer little full range drivers for about $20 each.