Hello Jorge I tell you: Low-low frequencies, this margin contains the fundamental notes of the sensation of rhythm, too much reinforcement in this band can make the music threat (very strong of low) .Mid-this band contains the low-value harmonics of some instruments: piano, tuba, etc. of a tube if it is between the 1-2khz band, the impression is of a metallic tube the excess produces fatigue shortly after. Applifier If you have, brands (manufacturer) of the speakers, radio etc.