An SM57 runs flat from about 125Hz to about 4kHz. Definitely not the best choice for tracking low frequencies!
What you probably want to use for tracking is a large diagphragm condenser mic. These are often flat to about 20-30Hz.
A less expensive option would be to use something like a BLUE Ball mic, which is flat to about 40Hz, or the Kickball -- though the Kickball has a tailored response that is not true; there is a diode that emphasizes frequencies between 40-80Hz.
You might want to try doing what I do when I track bass guitar. I use an SM57 centered on one of the cones, and a large diaphragm condenser positioned to pick up the most bass frequencies. Then I combine the two.
Another option you might want to try is placing an omni mic, knee level, about 15' from the cabinet. You will get TREMENDOUS low frequency response from this mic, but you will want a close mic, too, for a more direct tone. Bring up the omni to taste, or use a lowpass filter.