Why does my old PE515 microphone have so much more volume than the SM58 and Please explain the use for high or low impedance in microphones.
The PE515 is likely wired as high impedance. The SM58 is low impedance. If you connect the SM58 to a Shure A85F low-to-high impedance transformer, it will be as loud, if not louder than the PE515. In general, a high impedance microphone will have an output level around 20 dB greater than a low impedance microphone.
To learn more about impedance, please go to: www.shure.com/faq
Enter the search keyword "impedance".
Have fun reading.