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
I imagine many of you are not old enough to remember the Leak "Sandwich" loudspeakers from the early-1970’s; Leak was one of the British companies that never really took off in the U.S.A. in a big way.

Leak’s claim to fame was their flat-face drivers, very similar to the legendary KEF B-139 woofer (used by David Wilson in his mid-70’s WAMM, and ESS in their TranStatic 1), but with a round mounting frame rather than the B-139’s oval one. Leak argued that the cone shape of dynamic drivers causes them to have unacceptable levels of cone break-up, so they developed drivers which had flat front faces, the faces being created, as is that of the KEF woofer, out of expanded styrofoam.

One of the Leak models got a pretty enthusiastic review in 1971 by J. Gordon Holt in Stereophile (at the time, the only subjective hi-fi reviewer and magazine in the U.S.A., 1971 being a year before Harry Pearson started The Absolute Sound). I was in the market for new loudspeakers, and luckily for me there was a Leak dealer in San Jose, a little 1-man shop.

I gave the Leak an audition, but ended up choosing a different loudspeaker. I agreed with Holt’s assessment of the Leak, but found them to be no match for a couple of other the speaker I had also auditioned, both of which contained ESL tweeters: the Infinity 2000A and ESS Transtatic 1. I also heard the Infinity Servo-Static, but didn’t have the two thousand bucks they sold for.

Cone break-up is an important issue, but only one facing loudspeaker designers. And addressing the issue by making drivers with flat front faces only one way to do so. Richard Vandersteen goes to great lengths to minimize cone break-up, but the lack of that break-up does not by itself guaranty good sound.
I don't perceive flat speakers to have any inherent advantage in breakup. If anything a cone has more stiffness in the vector of movement.
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.