Randy,
I doubt we'll be at RMAF this year - too much going on. We might have our speakers there though. It all depends on what kind of arrangements we can make with other demonstrating manufacturers between then and now.
As far as the ribbon issue goes...there's quite a bit involved technically. On a certain level a ribbon and a soft dome tweeter are similar. They are both designed to operate in a controlled "break-up" mode. That simply means that both of their diaphragms are designed such that different parts of the diaphragm move independently of the others. Specifically, at the lower end of their operating range the entire diaphragm operates in unison - like a solid piston moving back and forth. As frequency is increased that changes. In the ribbon, the center of the diaphragm tends to operate more and more independently from the outer parts. As frequency continues on up, the moving surface gets smaller and smaller such that only a small area at the center is moving,
In the soft dome tweeter, the opposite is occurring. As the frequency increases, a "ring shaped" area located near where the voice-coil attaches behind it...is the part that continues to move. There comes a frequency wherein the center of the dome hardly moves at all.. It's from this very concept that the new Vifa/ScanSpeak "ring radiator" tweeters evolved. The thinking is..."Well, if the center of the diaphragm doesn't move anyway - get rid of it. Doing so will lower the total mass of the system and allow the tweeter to go higher in frequency."
Well...this obviously is true as they're making them and they work, but...there's no "free lunch." They do go out to 40kHz or more, but how important is that really? Removing that center part reduces the total air load on the moving surface and thereby reduces the drivers ability to push air at lower frequencies. The same concept is true with woofers. All else being equal (excursion limits), bigger cones (more cone area) make more bass. Because the center has been removed on these tweeters, they are notorious for producing high distortion when operated below 2kHz and are essentially useless below that point.
But I digress. Why would a ribbon be potentially inferior to a dome then? Well with the dome, the outer supporting suspension that supports it and keeps the voice-coil centered in the magnetic air-gap, is "de-coupled" from the center of the diaphragm where it attaches to the voice-coil. Because of this the suspension can be optimized to do its job with less fear of interaction with the rest of the moving diaphragm. Then that permits the center part to be optimized to do its job with a high degree of control and precision as well. Therefore, the two distinctly different and necessary jobs can be engineered to a higher degree of accuracy.
With any typical ribbon, both of the above mentioned functions must be integrated into one moving element. Although on a certain level it simplifies the design, it is also likely that compromises will be made.
As an example: A bicycle with a rigid frame that depends on rubber tires to dampen road vibration is simpler and will work, but it's likely to provide a rougher ride than one equiped with shock absorbers and offers the same rubber tires as well.
Hope this all makes sense.
-Bob
