um, sorry, jimmy, but why are you suggesting a dynamic mic for recording an acoustic guitar? the complexity of the acoustic guitars dynamic range is best served with a condenser mic. i have found that dynamic mics are a bit bland sounding and lack the harmonic overtones associated with acoustic guitars. my new low budget LDC is the mxl v67. on acoustic guitar is hard to beat! before i was mic'ing my acoustics with my mojave ma200 on the 14th fret, a a stereo pair or rode nt5's on the 5th fret and right behind the bridge. gives a great one, but was a bit on the bright side. i bought the v67 due to the price and bought a pair of sennheiser e614's on the cheap and found that for AG, these are a winning combo. hell, the v67 alone is simply amazing. for the OP, i would recommend a pair of the v67i. it is a dual voiced LDC that has a dark/bright switch that enables either the front side of the capsule or rear for 2 distinct sounds. a stereo pari for capturing the 14th fret and the bridge would definitely bring out the voice of your martin. run those into a good preamp and enjoy a slice of sonic nirvana.Scott, not to be a d1ck but, why would you even suggest buying a $40 mic when an SM57 is much better than a pg81?