Sound
Sub-bass
Also called subs, rumble
Sub-bass is the lowest audible region, roughly 20 to 60 Hz: the rumble under a film score, an 808 kick or a pipe organ’s longest pipes. It is felt in the chest as much as heard.
Few instruments play this low, so sub-bass is most obvious in electronic music, film sound and organ recordings. A product that rolls off here still sounds full on most pop and rock, which is why a missing bottom octave can go unnoticed for years.
Small speakers rarely reach it; a Subwoofer or a large floorstander does. Sealed IEMs and planar headphones often extend further than open dynamic headphones, whose bass rolls off gently.
In a Frequency response measurement, sub-bass extension is where the line drops away at the left edge. Reviewers call this bass extension: how low the response reaches before it rolls off.