Yes, this is an audiophile tweak alert, but even music lovers can only go $30 wrong with this, and I think even they may be pleased.
If you can stand to lose $30 on an audio tweak while waiting for the perfect automatic DSP equalization device, I encourage you to try a pair of these. These are basically short pieces of Litz wire with the strands connected together at one end to a short piece of solid-core copper wire. Attach the solid-core copper end of one to the negative speaker terminal of each speaker. For the adventurous, cut the solid-core connecting wire of each down to just long enough to fit through the hole in the binding post for posts with holes or around the post for posts without holes and then re-attach your speaker wire as usual. Gently bend the body of the Ground Enhancer just a bit so that it is not touching the speaker cabinet but sticks out into free space. That's it. Now listen.
I recently got crazy and tampered with perfection, adding just a single pair of Ground Enhancers in the living room Harbeth M40.1 system attached to the ground/black terminals of the two speakers.
The result--I kid you not--was more depth, clearer imaging, more space around the instruments and the whole presentation, the proverbial blacker backgrounds, smoother-more-natural-and-lower-distortion-yet-sounding high end, both punchier and more defined bass, cleaner transients (e.g., more differentiated and clearer hand-claps in an audience). Somehow, low bit-rate internet streaming is quite improved in terms of reduction of the irritation from digital artifacts; it's the difference between pleasantly listenable and involving. No, it's not a night-and-day difference, but I'd estimate than even a novice listener would hear the effect right away and not hesitate to classify it as an improvement and not just a change in the sound. And that's listening from the next room. In the sweet spot . . . well, make sure you wear your Depends.
The recording producer who heard my living room Harbeth system a few months back and pronounced my M40.1s the best box speakers he'd ever heard after less than two minutes listening would have swooned indeed if he'd heard the system with these installed on the back of the M40.1s. I can just see him writhing and drooling on the floor as I tell him, "no," my M40.1s are not for sale and, "yes," you'll probably have to wait several months to get a pair since they seem perpetually backordered.
If you like what the single pair of Ground Enhancers do sonically, you can add more at other spots in the system to further enhance the effect. In my basement audio room I use one Ground Enhancer on each component in the system from sources through speakers. And this is a system which already had a dedicated electrical system, star grounding to a copper stake in the ground, and all DNM speaker cables and interconnects with the DNM High Frequency Tuning Network (HFTN) filters at each end of every wire. The HFTNs are nice improvements as well, but they are more expensive by a factor of 10.
In my admittedly sighted A/B tests, adding another EVS Ground Enhancer to an as-yet-untreated component always further improved the sound and subtracting the same Ground Enhancer(s) always took the sound down in quality a notch. Other than the speaker and amp grounds, these were especially effective on the EVS-modified Oppo BDP-105 and the Logitech Squeezebox Touch.
Scoff if you like. You ARE putting little antennas on all your system grounds and thus feeding all sorts of RF into the system, right? Bound to audibly degrade the sound if it does anything audible at all, right? In fairness, some reviewers have heard nothing much from the EVS Ground Enhancers, and others have heard an improvement at first and then decided they liked the flashier "more extended" highs they had before better and removed the Ground Enhancers. I try removing one or a stereo pair now and again, but it only takes a few seconds to decide that the difference they make in my system is an improvement, and one worth far, far more than $30.