Flat cone drivers?

Again:

haemphyst wrote: That's what honeycomb materials are all about... the BEST stiffness to mass ratio available for a given construction material. If I recall correctly, Blaupunkt had a flat "full-range" honeycomb speaker a few years ago, they worked really well... After I blew em up, I took them apart to test their actual strength. I was able to stand on one without it crumpling. Granted, I was WAY smaller then, but still, the diaphragm only weighed a few grams.

As far as the "oil tank" example, (and they're natural gas, not oil) A sphere IS very strong, but not against internal pressure. Is is, granted, stronger than most other shapes for internal pressure, but it is FAR better suited for external pressures. Read here. An icosahedron or dodecahedron is FAR stronger. A "Buckyball" would be stronger still. I STOOD on those diaphragms, and they did not bend. This is the point I want to get across. Flat diaphragms are not used as much because of the price. Honeycomb materials are VERY expensive to manufacture. A regular cone can be made by the THOUSANDS for pennies each, (certainly less than a dollar each) and they are strong enough for a woofer cone. There is a reason they use honeycomb aluminum to build AIRCRAFT, not the least parts of which include the wings... A flat diaphragm can exhibit a FAR BETTER stiffness to mass ratio than most anything out there, IF the materials chosen are chosen and implemented correctly. As far as round enclosures? Look at Gallo Loudspeakers. (There are others as well, but the names escape me presently.) They were doing round enclosures years ago. Spun aluminum, usually, they were not round for the strength, they were round for the dispersion characteristics, and the woofer section happened to be round, simply to match the mid-hi globes.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

dwarren wrote: Steven Kephart wrote: It just isn't a practical design.  There are no performance benifits, so the only reason to use it is for the cosmetics.  Plus a cone shape has a MUCH better stiffness to weight ratio. Out of curiosity Steven, do you have any experience with the Arc flatlines or even the E.D. flat cones? I thought that with a flat cone, more stiffness was achieved? I might add that I owned a pair of PPI pro flat pistons and although they blew constantly (not necessarily due to cone design) they did sound decent.

I haven't played with the Arc flatlines.  But I am VERY familiar with the ED flat cones which were notorious for having cone/former joint problems.  Their failure rate was very high, as was the cone's moving mass.

haemphyst wrote: That's what honeycomb materials are all about... the BEST stiffness to mass ratio available for a given construction material. If I recall correctly, Blaupunkt had a flat "full-range" honeycomb speaker a few years ago, they worked really well... After I blew em up, I took them apart to test their actual strength. I was able to stand on one without it crumpling. Granted, I was WAY smaller then, but still, the diaphragm only weighed a few grams.

Acutally, I believe a cone shape made from the same material would still offer a better stiffness to weight ratio.  Here's a picture of Dan Wiggins standing on a paper cone: http://www.adireaudio.com/Files/StandingOnBrahmaCone.JPG  A honeycomb shape is a great solution when forced into dealing with a flat surface.  But there is still quite a bit of material being used.  And of course there is the price issue you mentioned.  And you still don't have any performance benifits from using that design.  In fact there are some compromises that can effect the outcome as ED found out.

wouldn't you also lose surface area with a flat cone compared to traditional designs?fiberglass reminds me of peanut brittle... but fiberglass tastes better!

sprawl85 wrote: wouldn't you also lose surface area with a flat cone compared to traditional designs?

I read somewhere that the surface area difference is negligable and it is the cone diameter that is more important because it is pushing a cylindrical volume of air. Any truth to that?

Nope. It's a hemisphere, and it won't matter what size the diaphragm is.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."