Sigma DM-15 Acoustic Guitar The Sigma DM-15 is a steel-stringed acoustic guitar whose design is oriented towards the well-known guitars of traditional american manufacturers. Therefore, the body of the Sigma DM-15 is quite close to a D-14 guitar and consists in this model completely of mahogany, with a solid mahogany top. The mahogany neck of the Sigma DM-15 features a fingerboard made of Micarta with 20 perfectly fitted frets. The great playability and the direct steel-string sound with its straight decaying notes and fast attack makes the Sigma DM-15 to an charismatic acoustic guitar of great value.