Difference between "electrostatic" and "ribbon"?

Oh, there's a big difference.

An electrostat has a diaphragm, usually a polymer, stretched tight and between two charged stators. The stators need a high voltage supply to charge them.

A ribbon is a strip of aluminum (usually) that is sometimes corrugated, that hangs between rows of permanent magnets. The ribbon cannot be stretched tight and it sits in the magnetic gap between the magnets. You'll have magnets turned to the positive on one side and negative on the other. You'll pass the signal through the ribbon.

You'll also find quasi-ribbons with foil conductors stuck to a membrane of some type, and you'll also find planars which are sort of a combination. A planar will have something like a stator, but with a bunch of magnets on it. The diaphragm will have a conductor etched onto it, so the driver will move back and forth similar to thhe action of an electrostat.

Another interesting variation is the AMT, or Air Motion Transformer. It has a planar-like diaphragm folded like an accordion hung between magnets.

In headphones, you'll find electrostats from Stax, Sennheiser, Koss and a few others. There are a number of planars, but the Audez'e models are popular now. Ergo makes an AMT (see Duggeh's review). And no one has brought to market a ribbon headphone, though I've seen a couple of prototypes.

I build a pair of ribbon speakers a few years back - they're wonderful, but it's hard to get bass out of them. Also have picked up a pair of ESS AMTs and Quad ESL-63s. Haven't had any Magnepans (planars) yet, but will pick up a pair one of these days.

Another interesting alternative technology is plasma. There were some plasma tweeters marketed some years back and, IIRC, even a pair of plasma headphones, but I can't remember the details. There are also a couple of DIY plasma tweeter projects if you're interested.

And while on the topic, look up field coil speakers. They have a cone and a voicecoil like a conventional speaker, but use an electromagnet instead of a permanent magnet. You'll find them manufactured by Supravox, Fertin and a couple of boutique manufacturers.

Oh I heard about the mysterious plasma tweeters about 5 years ago.  Couldn't scrounge much up about them though at the time.  DIY plasma you say?  Do tell....

I tend to think of electrostat, ribbon, and dynamic drivers in terms of "density" of sound and "speed." (also microdynamics, "life")

 

Density:

 

dynamic>ribbon>'stat

 

Speed:

 

'Stat>ribbon>dynamic

 

I find that electrostat headphones have much better chance of preserving the speed (also microdynamics) while sacrificing less in tonal density and impact relative to electrostat speakers.

Here's the DIY plasma tweeter: http://www.plasmatweeter.de/eng_plasma.htm

Thanks for your answer! It is good for reference, It helps me out of the problem.

Thx Erik!