This looks new: Speaker Purifier?

[Ammonite Audio]

Martin Colloms tested the Russ Andrews speaker Zapperator some time ago and found it to have little effect with his normal reference system, but revisited it later when HiFi Critic did an extensive piece on speaker cables and the effects of RF interference. In that test, he was astounded to find that cheapo bell wire (awful sounding on its own) was elevated to something like "really quite good by any standard" when the Zapperator was added. So, as ever, YMMV and these things have to be highly system-dependent, but I would not be too hasty to dismiss them out of hand.