Experience with HFTs

I use a few in conjunction with other room treatments. After much experimentation I've settled on six being optimum for my room. I use three on each side of room, perhaps five feet behind listening chair, spread out evenly from top to bottom. I've also tried them at many different locations, didn't work for me. In location I have them add sense of greater spaciousness of room, when in fact my dedicated listening room is already fairly deep, that being 25' length, then opening into kitchen. I don't like them anywhere close to speakers, mids sound less natural, more tipped up. Also, don't like them centered anywhere in room, pulls soundstage unnaturally  forward. I prefer judicious use of these along with other diffusion products, in my case, RPG Skylines cut into quarters placed at first reflection points. More subtle than the HFT's here.

I have been using 20 HFT’s in my system since around June 2021. 20 of these buggers. That makes level 4.  I am enthralled! My sound stage has expanded and moved forward and in some instances is like I have headphones on. Sometimes I need to make sure my surround is not on. My bass is better. More separation of vocal And instruments. This all in 2 channel and no subs. EVERYTHING I throw at my system drops my jaw, regardless of source.

20 is about where I'm at. Two speaker kits plus however many room. This is after years of experimenting with various panels and tube traps. HFT are far more effective than those old school treatments. Plan on adding some diffusers some day but for now I am like you, swimming in it. 

The recommended placement program works great, but within those recommendations they are surprisingly responsive to positioning. Mine were put up in pairs and sometimes one at a time, with each one being moved slightly an inch or three and always noticed a change sometimes surprisingly big. One on the back of my old Talon Khorus speakers went from great to awful by moving a mere 2"!   

The champeen of HFT is David Pritchard, who used to be a quite active poster. He had dozens in his listening room, all over his mom's place, and even in his car!

I used to have so many HFT’s, probably 30+ and many more of my DIY creations.

Until I found the Stillpoints Aperture ll’s. They make the room sound so much more real, the HFT’s sound fake when compared. Though a lot more money, I now have 8 of them. And, I also have 20" ASC tube traps in the 4 corners.

I sold off all of my HFT’s.

ozzy

I have 18 HFT's.  Two are missing or fell off and are lost.   My wife hates them and everyone that comes to our house tries to take them off the walls.  I can say that I have not followed the exact guidelines due to the room structure.  I probably have 11 on the ceiling beams.  I am not putting them on my speakers...sorry, I do not want even a smudge of putty on them.  I am also in the process of adding Vicoustic Cinema round absorption panels.  I have the Townshend podiums and Shuman Resonators.  

In my case, the Shuman Resonators have no impact on my music or sleeping habits.  Townshend Podiums a slight improvement in the soundstage.  HFT's - can't really say they help or hurt.  Please don't say I did not follow the exact placement locations as instructed by SR.  Someone would have to prove to me scientifically that those locations are the only place they can be.  Now, if the HFT's came in white, then I might be able to follow the guidelines.  Fuses are a definite impact on my music.  At this point I have so many tweaks I don't know which ones work and which ones don't.