What are the differences between steel-string acoustic and Spanish guitars?
The most prevalent differences are in the neck joints, the bridge designs, the bracing systems, and the nut widths.
Neck joint: The neck joins the Spanish guitar at the 12th fret whereas it joins the steel-string (folk) guitar’s body at the 14th fret. The neck joint on Spanish guitars are unified and built into the body. On a folk guitar, the neck is attached to the finished body with a dovetail joint, and usually has a truss-rod (running through the neck and into the body) for added reinforcement and intonation control.
Bridge design: On Spanish guitars, the strings are strung through horizontal holes then tied. With folk guitars, the strings are usually secured by pegs wedged into vertical holes.
Bracing: The bracing on Spanish guitars is usually of a radial fan system. Since the string tension of steel-strings is about three times greater than that of Spanish guitars, steel-strings usually employ a stronger, less efficient ‘X’ bracing system.
Nut Width: The nut width on Spanish guitars is much wider than on folk guitars, usually by about 4 to 5 millimeters.