More to do with "seen" resistance?
"The Yamaha AST unlike any existing amplifier, is an amplifier that can have a negative resistance figure in its output impedance.
The voice coil impedance of a conventional speaker is approximately 6 ohms, and the AST can apply a negative resistance to eliminate this voice coil resistance portion.
As a result, with the combination of the AST-Amifier and the AST System exclusive speakers, the resistance between the amplifier and speakers will become approximately 0 ohms and the electrical current will be able to run infinitely (condition close to superconductivity).
In other words, the amplifier output voltage will directly drive the speakers, hence making it possible to provide a powerful driving force and damping power of steady speed operation."