DIY? Yeah, uh, no. Not even. And you know something is true when it comes from someone who really, really wants it to be otherwise. Because these things work so well, and I really, really, REALLY wanted to be able to make a bunch and save myself a few grand. Really. And its not like I haven't done stuff like this before. I've made my own active shielding, which on the speaker cables and interconnects works about as well as the SR, which I know because I have the SR Active Shielding too. Unfortunately with HFT's its a lot harder than the copy cats make it out to be.
Having access to x-ray it is easy enough to see what's going on with these things without taking one apart. None of the DIY attempts comes even close to Ted Denny's design. All they do is mimic the shape. What they leave out is what's inside, what probably (near as I can figure) generates dither.
So if you want what they do you just have to buy them. And lucky you, highend-electronics just started a buy one get one free special on HFTs. I know because I was just ordering some more and they told me about it. They seem to be one of the bigger SR dealers around. Not affiliated, just a guy who believes too many places today get by on getting by and make great customer service rare, so when I encounter it I like to spread the word. And Betty has provided me with some of the best.
I would start with the regular HFT. You will find even just a single one front and center produces a noticeable effect. My suggestion, experiment with placement. Move it up or down a few inches. They work great and consistently anywhere near where they recommend. But if you listen carefully you will probably notice you are able to tune things like the sparkle on cymbals or the fullness of strings with very small adjustments. You can also try them on your speakers. If you do you may be surprised. One placed near a tweeter moved the whole sound stage back a rather dramatic amount! It was awesome! But unfortunately also lost a lot of presence resulting in a too recessed sounding presentation. Turns out this was NOT one of the recommended placements, and now I can understand why! Lol!
Synergistic uses the same technology in their PHT for phono and ECT for electronics. Also in their footers. Haven't tried the footers but the PHT and ECT are all extremely effective giving consistently good results everywhere I have tried them. And I have tried them all over my stereo, laptop and video projector. Again, experiment. Only way to know.