Jim Merrill makes traditional guitars modeled after the great 1930's Martins and probably comes as close as anyone in replicating that sound. They can be described as warm, sweet, harmonically complex, loud and with great sustain. But in addition, they have that three dimensional "hollow" sound that typically only good older instruments that have been played for many years usually have. Merrills are made with top flight materials  and workmanship has over the years developed to the highest levels.  Merrills have a deeper neck angle than most modern instruments so they can confound guitar techs that are not used to looking at them, but this deeper angle is part of the formula for the great old Martin sound they achieve. They take quite a bit of time to get but the wait is well worth it.