HFT High Frequency Transducer

Is any body experiment with these tweek, that treat the listening room ?  5 of these would supposed to give an improvement.  Do we have to continue to 15 or 20 ?  Because they are not cheap !
All the answers you need can be found here -- and yes there are benefits to more

But you could make your own :-)

I use the Synergistic Research HFT's in my listening rooms. This is after trying to go the more traditional way of improving room acoustics with GIK acoustic products.

For me the advantages of the HFT approach is: easier to install and to dial in the optimum location of the devices, they are not visually distracting, and if you move you can easily take them with you.

Since they come with a 30 day trial, I think many audiophile rooms would benefit with an audition. and if you do not like them the cost to return them is under ten dollars. It is a fun and educational  weekend experiment.
David Pritchard
folkfreak.  But you could make your own :-) ...
What is the recepe ?  Is it easy to make ?
folkfreak;  it is crazy how a little copper bell can make huge improvement.  Also "acoustic resonator" are in the same shape.  May be if they were 10 times less expensive, they would sell ten times more ?
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.

@millercarbon absolutely -- DIY is a fools errand but our OP seems constrained in the pocket book 😏

I just posted some advice on how to further improve the impact of your HFTs, ECTs and so on by optimizing the power to your Atmosphere’s and FEQs ... give it a try
Everyone's on a budget. Given enough time and effort most of us eventually realize the biggest bang for the buck is a holistic approach that includes tweaks like HFTs and cones and interconnects and power cords right up there with the more traditionally recognized components like amps and speakers. 

The thing of it is, there are now so many different products capable of producing so much improvement so cost-effectively that the greatest challenge today is to develop the listening skills and evaluation experience to be able to make effective choices. I mean, look: BDR Cones, SR HFT and Blue Quantum Fuse are all incredible values for the improvement in SQ they deliver. But the only way of proving that, and the only way of knowing which is best for your system in its present state is to, as folkfreak said, give it a try.

Just be sure to follow Audiophile Rule Number One: Never buy anything you haven't first auditioned, unless it can be returned no questions asked.

btw oops my bad, I got the special above wrong. Its buy 2 get 1 free.

The most cost effective then would probably be something like buy one HFT pack of 10, and one Speaker Kit, and get one HFT Wide Angle Kit free.
The speaker kits are one kit or 6 per speaker, but I know from experimenting you can get really good results with half that, or 3 per speaker. Actually these things are so effective even just one or two is amazing and really makes the speakers disappear. Guess I will find out next week what a full kit treatment will do!