Gauges 10-14-22-30-38-48. Rare Phosphor Bronze Acoustic Guitar Strings are a departure from the standard good-quality bronze string currently available--not necessarily better but possessing a new different and stronger voice. Hand-carved archtops dreadnoughts and good steel string acoustic guitars of rosewood maple and mahogany benefit from a distinct improvement in tone depth and sustain with a fatter louder sound and a deeper bottom.