2 definitions for I

  IHF : Institute of High Fidelity: Institute founded by American manufactuers of audio equipment, devoted to the improvement of audio technology, standardization of test and measuring methods, etc. "IHF" in audio specifications means that values were obtained in measurements according to IHF standards.
+ Associated link: http://www.classicaudio.com/gloss/

  Impedance : This is the resiatance of the speaker, measured in ohms. A low impedance takes a large amount of power from the amp, and a high impedance takes less. Low impedance speakers (below 6-8 ohms) are harder to drive, and high impedance speakers are easier.