Excellent build. Aluminium faceplate reduces vibrations which may come from the front baffle to the tweeter. Troels Gravesen and others have measured the distortion to be extremely low even down to 1.5KHz, thus allowing for low crossover frequencies in 2-way designs.
It's a fabric dome, plus it's a ring radiator, all of which gives it a more mellow sound. It works very well for almost all speaker projects mated with all sorts of midbass drivers. I will be using it in 2-way designs with the SB17CRC and SB17NRX drivers.