Metal speakers. How are they?

I notice that aluminum and magnesium cones have become very common, including in some high quality systems. What's the story on these things? I am considering purchase of a speaker that has Seas 7-inch magnesium woofers, in MTM configuration.

These speakers will replace Dynaudio Gemini MTM speakers whose little 5" woofers are great, but just won't keep up with my three MG1.6 + SW front speakers. I have contemplated rear subwoofers, but there just is not space. The Dynaudios were used for many years as the high end of a biamped system, and they were fine for that purpose.
I generally love speakers designed with the SEAS drivers even though I haven't been able to listen to all of them. They generally produce pristine sound that is quite beguiling and musical (live feel: piano sounds exceptionally good). According to one of the replies to my post, the SEAS drivers are hard to design with and one needs to choose the brand carefully.
Materials don't (shouldn't) matter. At an introductory seminar (Rosine Audio -Skokie, IL), Arnie Nudell (founder of Infinity and Genesis speakers) was asked if diamond coated drivers would sound good replied: "Drivers made of horse-shit would sound good if they were linear in their frequency range"...
I respectfully submit that materials DO matter. Metal cones can and do ring and have harsher break-up than (conventional) treated paper. This said, there are excellent metal performers -- the "21" Seas are amongst the best. Best,
Gregm..."Harsher" breakup? The literature says that the drivers do have a resonance that needs to be controlled by crossover design, but that this one relatively easy to deal with peak replaces the multiple resonances that occur with cone breakup with other materials.
I've heard the W18E001 woofers in two different speakers that were really excellent. I agree with Greg above that cone materials obviously make a big difference.

Personally, I think S. Linkwitz plays with a deck with a couple more cards than most of us and here is a nice piece he wrote up on drivers including the W18E001.

I remain,
Thanks for the good info. Seems as if the SEAS W18E001 is about as good as it gets.
I agree with greg about the slight harshness, but all in all i think metal cones can make fantastic speakers

Regarding the horse-pucky reference, one of the things that has to be taken in consideration is weight and rigidity.
Maybe if you tolled the horse crap out real flat and fasioned it into a cone and used some sort of hardener to it, then maybe a horses but can be the source of sonic beauty! :)
Slaps: Maybe mix a little beryllium with the pony's oats?
Dweller, thats not a bad idea. Maybe a pinch of powdered ceramic as well
There are many great Metal Drivers out there.The problems with ringing have been addressed and the set I use now have no such artifacts.I heard of one designer that stated he could tell what the driver material was just by the sound.

I thought I use to until I received a new set of Metal Drivers for my NEARs which have eliminated the Metal artifact.

Wilsons are Metal ,atleast the Inverted Domes are and I use an Inverted Dome also. They need to be implemented right which is key to everthing in audio I think.
I like the sound of metal cones - look at all the musical instruments made from metal. Since we are trying to recreate alive music, make sense to me to use the same material.

We need the sound of wood (paper cones), and metal to cover all the sounds of live music.

They satisfy certain audio needs we have - but after awhile, I miss the sound of a paper cone, so i go back and forth - with a few sets of speakers.
Sorry Eldartford, I missed yr question. I meant the frequency where cone break-up occurs. That doesn't seem an issue in your case as you can easily play the seas in its optimum range, crossing to the tweet above that.
Mr Linkwitz's site is, indeed, a mine of info. OTOH, if you're interested in a passive dipole implementation using a seas magnesium mid, check out the Point75.

That site has is a mine of information for diy -- probably the best quick-reference site around.
I like metal...but it has to have spandex and hair spray to sound its best...long live Diamond Dave! ON a more serious note...I prefer the natural tonal quality of treated paper...