Placement tips for Synergistic Research HTFs

Speaking of SPL meters, having spent more time with resonators of various types and SPL meters than the average bear, I feel it’s only right to mention that resonators are not only effective in various locations on walls of the room -which is almost always where it’s suggested they be placed - but also ANYWHERE in the 3D space of the room where a sound pressure peak happens to be located. And which can be easily found with...you guessed it!  - an SPL meter and test tone. By dissipating the unwanted energy of standing waves, reflected waves, echoes, etc. the resonators are reducing the comb filter effects present in an untreated room, including comb filter effects produced by acoustic anomalies in the 3D space of the room. In fact the tiny bowl resonators and similar devices could be hung by string from the ceiling slightly out from the wall and not touching the wall - and be equally effective. In fact, Franck Tchang’s original acoustic resonators were not tightly coupled to the wall, but rested gently on a bracket, presumably so the metal bowls would be free to resonate.

I have found over the past 15 years or so that the geometry the material and its placement on surface boundaries are the 3 greatest influences of surface control.

If you have placed devices on flat surfaces or walls and you are pleased with the outcome you can take this whole thing to a higher level by removing adhesive damping materials and attaching your device right to the wall or other surface. You can do this with the aid of a threaded insert placed directly into the wall and your device also threaded screwed into the wall. You can now adjust the resonance point on the wall by ever so slightly adjusting the tension of your device to the wall or surface. 1/16 of a turn can be clearly discerned..or even much less depending on the surface.
Same method will also benefit all things internal and external to speakers and electronics. This method gives you more control over all things within your room boundary including the walls. All these devices and surfaces are passive radiators and all make their own sounds. While compressive waves are the largest wave component in any audio room the wave type and boundary area influenced by what Todd and others are reporting on and there greater benefit are not compressive. Tom

To briefly summarize this discussion of tiny little bowl resonators and similar devices:

A number of applications for these tiny little resonators and transducers have been identified, not only when used directly on objects and room surfaces but in the 3D space of the room, and even when used in other rooms.

1. Vibration of walls and other room surfaces
2. Vibration of component chassis
3. Vibration of speaker cabinets
4. Dissipation of acoustic wave anomalies such as reflected waves and standing waves
5. Dissipation of RFI/EMI energy

We also found that the material itself is important and that pure metals like good, silver and platinum and copper have their own unique sonic signatures. Of course we also know there are a lot of other techniques for calming vibrations on wall, components and speakers, constrained layer dampers like Marigo VTS dots, for example and the out of production Tekna Sonic dampers. You can also give vibrations a chance to escape the confinement of speakers or component simply by placing hard cone on top, point up. 

I count at least four manufacturers of these tiny little bowl resonators currently, including your humble scribe. The first of course and the person who should get most of the credit is Franck Tchang who introduced the whole idea around 15 years ago.

On  the devices I make that I designed to enhance mechanical grounding of a cello I have measured over a db in gain. In my audio room I place one of the same discs on top of each sound panel with the major feature facing up at the ceiling..I now use a single 3mm or 5mm magnetic sphere that fit nicely in the cup center. I use 1 each on my mono amps same way..the bass is better for sure..on the sound panels the ceiling is lifted. If you use steel bearings in the cup use nothing smaller than s110 or you damp the device. Tom