I'm thinking one of the keys to a good speaker for classical is that they are "fast" and able to keep up with all the details inherent in large scale classical recordings, symphonic or orchestral recordings in particular. Rigidity is another factor.
Planars and electrostats probably have an inherent advantage in regards to speed and rigidity, but I have heard "box" speakers that are fast and detailed as well, though the fact is that many box designs are not, so you may have to be more careful.
The Triangle speakers I have heard come to mind as a good example of a fast box speaker design. The material used in the cone of the bass driver is a key factor as I understand it. Lighter materials are inherently faster and more re-active.
I think the polymer woofers used in many B&W bass drivers and the paper cones used in Triangles are representative of the two ends of the spectrum in regards to the physical properties inherent in bass driver cone materials. Paper drivers can be lightweight and fast, as in Triangles. Polymer is not perhaps as light weight but perhaps more rigid?
Planars and electrostats probably have an inherent advantage in regards to speed and rigidity, but I have heard "box" speakers that are fast and detailed as well, though the fact is that many box designs are not, so you may have to be more careful.
The Triangle speakers I have heard come to mind as a good example of a fast box speaker design. The material used in the cone of the bass driver is a key factor as I understand it. Lighter materials are inherently faster and more re-active.
I think the polymer woofers used in many B&W bass drivers and the paper cones used in Triangles are representative of the two ends of the spectrum in regards to the physical properties inherent in bass driver cone materials. Paper drivers can be lightweight and fast, as in Triangles. Polymer is not perhaps as light weight but perhaps more rigid?