Double top implies that there are simply two components to the soundboard, two independent soundboards glued together under pressure. In actuality all double tops are three layered; the inner top, outer top, and a middle core which at this time is usually composed of wood, Nomex Honeycomb.
With the Nomex Honeycomb core, it makes the top lighter while maintaining structural integrity, increasing responsiveness, sustainability, projection, and enhances the clarity fundamentals and overtones of the instruments.
The first double top with a Nomex core is created by Matthias Dammann in 1995. It is also referred as ‘sandwich top’ or ‘composite top’.
The advantages of having double top guitars are clarity of the individual notes, much more sustain, better balance, and an improved projection in front of the instrument. Even small bodied instruments can fill a room with ease.