@Bob-Stephens really does use a floating neck that does not come in contact with the soundboard. His dulcimers also have a false bottom, so both top and bottom are free to vibrate. You can see some pictures here on his website and also in some of the pictures he has posted to FOTMD . He uses a metal rod that runs the length of the neck to enhance stability and reduce the need for excessive bracing of the soundboard.
He is a member here and has explained the evolution of his design principles elsewhere, so I won't go into more details (which I don't understand, honestly). One of those discussions is Floating Fretboards .
David Beede uses the same floating fretboard principle on his octave dulcimers. (Or rather he did, until he stopped building.) The fretboard is attached to the body with two or three metal dowels that drive sound vibrations directly into the sound chamber. I have one of these little dulcimers and am constantly amazed how much volume can emerge from such a small instrument. It's like the dulcimer version of Taylor's GS-Mini. The "decoupled tailpiece" principle that David used on his full-size dulcimers is similar to a "discontinuous" fretboard to which Ken refers.
I have not yet played a dulcimer by Bob Stephens but I have a wooden, nylon-string dulcimer on order and will surely post a video or two after it arrives. (I have to specify "wooden" because he is now making dulcimers using 3-D printing for nearly everything but the top.) I ordered one because I love the idea of a dulcimer specifically designed for nylon strings and look forward to exploring the different tonal possibilities of that instrument. Bob worked with Aaron O'Rourke on the nylon-string dulcimers and has been working with Butch Ross on the steel-string dulcimers. You can find them demonstrating those models on YouTube if you search for a moment or two.
And here is Steve Eulberg demonstrating an earlier version of the nylon-string dulcimer . When he turns the dulcimer on its side with the camera from above (1:17-1:27), you can see the space in between the neck and the soundboard.
Dusty T., Northern California
As a musician, you have to keep one foot back in the past and one foot forward into the future.
-- Dizzy Gillespie
updated by @dusty: 02/01/24 03:15:23PM