Perhaps these work as well as the Walker HDL's. I get similar results (even) with high end speakers and high end wire. Perhaps they're similar concepts, delivered by two different companies.
Bybee quantum filters for speakers
enjoythemusicreview
Review in summary:
"To put it into perspective, imagine the following scenario. Money is no object and you have the opportunity to purchase $20,000 worth of the finest cable/interconnect. Let me make this perfectly clear: $320 worth of Purifiers will make for a far greater sonic improvement in your system than would all of that cable. In hindsight, cable is a band aid - the Purifier the cure. "
Review in summary:
"To put it into perspective, imagine the following scenario. Money is no object and you have the opportunity to purchase $20,000 worth of the finest cable/interconnect. Let me make this perfectly clear: $320 worth of Purifiers will make for a far greater sonic improvement in your system than would all of that cable. In hindsight, cable is a band aid - the Purifier the cure. "