Good question. First tried one near the HDMI input on the projector. Nothing. Nada. Which was a surprise, as by now they had worked great everywhere else. So I pulled out the Synergistic placement guide. Ha! Says to place ECT near the connector on the SENDING side! Sure enough, that’s the place! No idea why, but then I have almost no idea why this stuff works in the first place.
The story is dither. Which could be. I’ve x-rayed ECT, HFT and PHT and can see what’s inside. Exactly how and why I don’t know but dither seems to play a role.
Why it matters which end it goes, that I totally do not know! Because I have tried these things all over the place and with very consistent results. But with video projectors anyway they seem not to do much on the projector itself but do improve video when used on the video source.