Why Don't All Mids/Midbasses Have Flat, Filled-In Cones?

[kelticwizard]

Why are we even dealing with diaphragm materials in a cone shape anymore? Not so big a deal with woofers and subs, since the depth of the cone is such a small percentage of wavelengths it carries.

But once something plays above 500 Hz or so, cone depth becomes a reasonable fraction of the wavelengths being carried, not to mention such issues as time smear, etc.

I have been told that the center of cone, with respect to depth, even shifts with frequency. That certainly cannot be good for imaging.

Technics came up with a brilliant solution with the SB series of flat face woofers some time ago, but has done nothing with it since.
HoneyComb Speakers

So unless you want to do it Technics' way, (and presumably pay them royalities), that leaves the filled-in cone. I know Cabasse had a model with a filled-in cone some time ago, but why aren't all high quality manufacturers coming up with them?


I tried filling in a cone of a speaker with that same soft foam stuff you use for weatherstripping-spray it on and it dries semi-hard. It made the frequency response worse. Not surprisingly.

But surely, with the thousands of materials available today, and more always coming down the pike, speaker designers can find a way to fill in the cone so the face of a mid is flat.

If filling in the cone with only one material won't work, how about a nice layer job of inexpensive materials cut into cone shape? The resonances can cancel each other out. Once glued together, a hole can be cut into the center-not puncturing the front-for ventilation purposes. Once the cone is made, you will not even need to have an outside diaphragm material-just the cone itelf would do, attached between the voice coil and the surround.

With expensive materials like Kevlar being used for diaphragm materials, it just seems to me that by now this is one problem that would have been solved. Does anybody have a good reason why it has not been?

[johninCR]

The ratio of rigidity/weight is much much higher with a cone shape than with a flat shape. Even modern materials aren't rigid enough to make a flat speaker cone work well.

[Magura]

Dont the top of the line nautilus sport a flat faced bass unit??

Magura

[DcibeL]

The only speakers I have seen with flat faces have been car subwoofers, such as the Phoenix Gold Titanium Elite. As far as I can tell, the Titanium elite uses a regular cone design, with a metal plate over the front. It also has 3 super-cool led's mounted on it

[454Casull]

What about an inverted cone? It would have the same rigidity as a "concave" cone, wouldn't have sound bounce around on the inside, and would save some space (i.e. basket arms wouldn't have to be so long).

[bigparsnip]

There are I believe actualy quite a few of the B & W speakers which use flat woofers in their designs, even as low down as the 600 series models. There ae also a number of older drivers before the Technics ones which were flat, in particular the KEF B139 which first came out back in the 70's I think.

[roddyama]

You can't forget this one from KEF (B-139)

Photo from Planet10's site

[bigparsnip]

I guess this may have been the one you were talking about Magura?

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[Seth Smith]

Phase Technology's PC series has been using flat pistons for over 10 years now. If there really was something there, I figure somebody would have done it by now.

[Magura]

Originally posted by bigparsnip
I guess this may have been the one you were talking about Magura?

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Dribble...dribble...drool.

Yes, thats the one.

Magura