2. misc-audio
  3. 148618-129691

How HFTs and other miniature tuning devices might work?

After living with some SR HFT room tuning devices for about a month now, I only know one thing for sure. They work. Specifically, they seem to work by improving image specificity, which flows on to other areas such as image size, soundstage dimension and finally subjective tonal balance. 

As I listen, I ponder the question of how and why these devices may be doing what they do. I have come up with an answer but it's only speculation. Could it be that...

The sound waves projected from the back of speakers (in my case ML electrostatics) are normally reflecting off the back wall, and then returning to the listener's ears at the listening position. The highest frequencies are the most directional, and they are the frequencies which the listener uses to focus on, as the source of the sound. Normally these highest frequencies would be reflecting off many "spot sources" on the wall behind the speskers.

If a device were placed on the wall which synthesized even higher frequencies from the highest frequencies, then those ultra-high frequencies would become the most directional ones. The mind's focus would then be on the position of that single device, as the source of the sound. Could it be that high frequencies entering the HFT (or similar device) are divided (or dithered) into ultra-high frequencies (perhaps by a grid or mesh), and then projected out of the device, amplified by its horn-like structure? The effect would be to make one "spot source" (the highest frequency source) the focus of attention, rather than many spot sources. All lower frequencies would subjectively appear to originate from the same point source, based upon the detection of the source of the ultra-directional highest frequencies. In that way, the tiny devices could influence image placement and soundstage dimensions.
whostolethebatmobile

Showing 2 responses by millercarbon

millercarbon's avatar
millercarbon
12,531 posts
 
What is it with tweaks that attracts kooks? I guess because its hard to imagine how they work they seem nutty and so people assume they must be nutty and next thing you know sure enough kooks are coming out of the woodwork all over with one nutty idea after another. Most nutty seeming ideas are in fact nutty. As are most kooky seeming kooks.

Which is especially nutty when with something like this it turns out there's a really serious and near universally accepted idea behind it. Dither is widely used in digital and in video. In both of those its used to improve resolution. Which is exactly what we hear with the various HFT versions. 

A main difference seems to be the dither in those applications is universal. Software, in other words, distributes the dither uniformly throughout the entire work. ECT, PHT and HFT on the other hand, the dither they introduce (if that is indeed what they are doing) is localized. Or at least that would be my explanation for why they work better in some locations than others, why it makes a difference how many are used, etc.
millercarbon's avatar
millercarbon
12,531 posts
 
Give the man an A for effort.

You're close. Ted Denney himself has said it has to do with dither. Pretty sure dither is mentioned somewhere on the Synergistic Research website as well. And when you start talking about how it might work, the horn and the grid or mesh, well surely you have looked and seen the mesh? If not then go take a look. You might not see it on every one as its a pretty small opening, but look at the Wide Angle HFT the opening is widest and the mesh quite easy to see.

You must have missed my review and posts about this several months ago. X-ray images show the different HFT types all have a horn with a chamber behind the throat. The chamber is partially filled, with different materials for the different types. Or at least material of different density. That's all you really know from x-ray, density. It looks to be loosely packed or at any rate is not solid or uniform. 

My impression is vibrations cause this material to rattle around creating a somewhat random noise which the horn amplifies and sends out into the room. It is this sonic dither that helps randomize modes that would otherwise interfere with our perception of the very fine detail we get our sense of spatial awareness from.

Bear in mind that while talking about HFT, that the PHT and ECT construction is exactly the same. Those work placed both on the outside as well as the inside of components. SR also has the same type device used pointing down inside their footers. ECT are supposed to be Electronic, PHT Phono, and HFT High Frequency. But all these devices look the same, and by using them different places I can say for sure they all work the same everywhere. (And I mean everywhere- turntable motor, tone arm, laptop, iPod, video projector.... everywhere!)  

I think Ted is being honest about dither. That HFT broadcast some sort of sound into the room seems inescapable. A randomized dither could be improving the sound by breaking up very small high frequency standing waves. Beyond that however is very hard to say.
More to discover