Speaker 101 - tweeter and cone materials

Brian Cheney at VMPS has an interesting discussion on woofer cone material at http://www.vmpsaudio.com/d-cones.htm

He is obviously very knowledgeable and entertaining, but keep in mind that his point of view is not the only valid point of view. For example, he slams metal cones in general, while many other people rave about the SEAS Excel line of magnesium drivers.

Sigfried Linkwitz also talks about driver material in his comparisons of various woofers and tweeters at http://www.linkwitzlab.com

For me, if I can see the driver, I want it to be something sexy. Metal, Kevlar, woven carbon fiber, or ceramic. Preferably with a nice pretty phase plug. If I can't see the driver, I don't care what it is made of.

Oops, the second link should be http://www.linkwitzlab.com/x-mid_dist.htm

Brian C. probably slams metal cones because I believe he generally eschews complex x-overs. With metal cones and their nasty break-up characteristics you really need x-overs with steep (real steep) slopes so that resonance and break-up nasties aren't audible. Well executed metal cones (both aluminum and magnesium) can sound quite good. You really need to hear them to decide if you like them. My preference is treated paper cones but metal cones have a certain detailed character that can sound quite interesting on good recordings.

Can you tell me what you mean by "x-overs with steep slopes"?