What is the best cord for the SM58 and Prologue 12H?
The difference between Hi-Z (high impedance) and Lo-Z (low impedance) is clearly defined in a Shure book available on-line. This book also explains the differences of microphone connectors and cables. Please go to:
Microphone Techniques for Music - Sound Reinforcement
The proper cable for an SM58 or Prologue 12H will be based on the type of equipment to which you are connecting the microphone.