Bybee Labs has been producing their
QSE(Quantum Signal Enhancer - to place on component chassis) and
iQSE (internal version for inside of electronics) for several years. Based on the concept of aligning the polarities of protons and electrons within the magnetic field for more efficient energy transfer, these upgrades have developed quite a following. Bybee has now adapted these concepts to the loudspeaker in the form of the
Quantum Clarifier ($100 each).
Use of the Quantum Clarifiers entails getting at the back of the speaker drivers (dynamic type - not for ribbons or electrostatics) where you can magnetically attach one of the 'Clarifiers to each mid-range driver and/or woofer. The results are across the board: better top and bottom extension, information retrieval, realism. An easy (in most cases) DIY upgrade for most speaker systems. If you don't mind opening up your speakers, definitely something to consider.