Brandon, Josh have commented on how the TH-50 sounded at the Southern GTG a while back, actually it was that event that sort of inspired this project. Thebuckman has one also and has chimed in as well on it in his house.
On that subject;
Mike has taken a measurement at the shop this morning which I thought would be interesting to post.
Keep in mind this is a big room (like 80 feet deep , 20 foot ceiling etc if I remember).
Here is a TH-50 and DTS10 measured in the demo area of the shop IE: same room, same drive Voltage, same distance etc.
This was with a different measurement system than before (EASRA with an Earthworks mic and pre) so the graphs look a little different.
In any case, it should give somewhat of an idea what the difference is sound may be like between them.
It would appear that in the 11 Hz to 20 odd Hz range, the DTS10 produces about 15 to 20 dB more sound (20dB being 100 times more).
Mikes comment was you can hear that too haha.
Noah asked how does acoustic levitation work.
Well, sound travels in two components, pressure and velocity, the minimum and maximum for each are separated by 90 degrees in phase. A radio person might recognize that radio waves travel similarly, a Voltage and Magnetic field, each separated by 90 degrees.
If one sets up a standing wave between a source and reflector or uses two opposed sources, the position of these pressure and velocity maximums are stationary in the interference pattern that is produced.
If you place a small obstruction in that sound field and it is intense enough one can levitate. The object has to be about 1/3 wl or less in size and the intensity has to be about 150dB to levitate Styrofoam, about 160dB for more interesting things like ceramic and approaching 170dB for lead.
Anyway, when you place something in that field, gravity pulls it down.
The acoustic pressure is high BUT is alternating so that pressure cancels out.
90 degrees away, you have the velocity maximum, here is the levitation force and as Noah guessed, it is like an airplane wing in a real way. The air velocity is forced to travel around the object, this is the longer path the top of the wing feels.
Here, a spherical object is pulled radially but that force BUT gravity is pulling down too.
Now the object sinks slightly so that it is in the lower part of that velocity field and so that radial force now is an upward component to it.
Stable levitation happens when that upward force is greater than the object mass and the sample sits in the bottom of the levitation well.
Humorously, one can have too much intensity, if you levitate something like 5 min epoxy (or experimental ceramic heated to 1500 degrees C in a furnace) a too high intensity squashes the sample into a disc, thick at the edges and thin in the center.
Levitating a cockroach with excessive SPL causes high speed rotation, at a lower level one could observe a very confused bug as it tries to run to no avail.
Why zero G?
Well the velocity of sound increases with temperature and passing sound from a room temperature source into a really hot furnace is no easy task. In fact, my first horn modeling software was written so that it accommodated a temperature gradient, later altered to reflect the use with loudspeakers.
Anyway, it is much harder to levitate at high temperatures so in the sounding rocket and shuttle flights, the purpose of the levitation was only to position the sample without any contact. NASA's interest was in making new forms of ceramic and glass which could not be made in a container due to contamination from a container or nucleation, (crystallization triggered by contact with a solid). The experiments were flown on Shuttle flights STS-7 and STS51a and then when the shuttle exploded, all of that work was put on hold and a few years later Intersonics closed it's doors without having that work.
Unfortunately the Servodrive woofer business (concert sound) I had started as a side endeavor , was not robust enough to save the company. Japan and Germany (science agencies) purchased several ground based levitators near the end, we thought if we could do high temperatures in one G that this might save the company but it was not to be..
It was some short time after that I started going on line and eventually ran into (electronically) Noah on an old forum called the Bass list.
Anyway, hope that helps.