Experience with HFTs

There was a very extensive discussion about Schumann Generators (SGs) over the past week and in some thread I saw a mention of HFTs.

Unlike SGs, HFTs appear to interact with the music in a room similar but opposite of Acoustic Panels purpose. I can’t really put those panels or bass traps in because of my room layout and these appear to be small, and not require electricity, but I can’t understand why I would put them on a speaker- the speaker company should have taken its own acoustic properties into account. Also how would you put them on a wall?

Can your please relay your experience with them positive or negative and what you purchased and total investment? Synergistic Research appears to be a leader with these things. Always looking for ways to improve the sound without breaking the bank.