Speakers able to go down to 0.5 ohms?

Not sure what your getting at but I think the Sound Lab A-1's and Apogee Scentilla both have an .5 ohm impedance at some point in their operating range.

Dave

Very few amplifiers are capable of properly driving such a low impedence speaker.
I too am not sure what you are really asking. One wouldn't ask what speaker is able to..., but either what speaker does, or what amplifier is able to drive such a speaker.

Adding to the above list, the Cello's biggest speakers operated at about one ohm.

Richard

Original CLSs.This is the Aflac trivia site--Right?

Sound Lab A-1's go down to around or slightly below 2 ohms in the very high treble, to the best of my knowlege.

I used to use Strathearn ribbon drivers in homebrew speakers, and they were a .55 ohm load.

Amplifiers that can drive such a load include the Electron Kinetics Eagle 2 (which is what I used on the Strathearns) as well as the InnerSound ESL amp (stable into a .33 ohm load). I think the Claytons are also stable into .5 ohm loads (Disclaimer - I peddle these two lines, which is why I'm familiar with 'em). I'm sure there are many others.

It's too bad the amp-killer early Apogees and early CLS's aren't still being made, as these days there are relatively affordable amps that can drive 'em.

Duke