What do Loudness Controls do?

Loudness controls on sound equipment were originally designed to compensate for the human ears loss of frequency response at low volumes.

When sound is played softly the human ear does not hear lows or high quite as well as it does when the same sound is played loud.

Loudness controls were originally designed to compensate for this deficiency but boosting the bass and highs a little bit but were only supposed to be used at very low volume levels.

A few manufacturers have made equipment that have automatic loudness controls that automatically turn the amount of loudness increase up or down when you turn the volume control up or down, but most are just on or off.

It seems like many of the loudness controls nowadays just act as a bass boost. And most listeners just turn it on cause it seems to add more bass not knowing why it was there in the first place.

An audio purist would probably NEVER be caught using the loudness control!