The musical soundtrack for many films includes bass instruments that produce very low notes.
After the 1980s, film scores increasingly used synthesized instruments, including synth bass keyboards, which incorporated very low-pitched notes.
As well, since they are sound effects, they may have a longer duration or sustain than many low-pitched musical notes, which makes them harder to reproduce accurately.
Also, the separate recording allowed a straightforward installation of extra dedicated subwoofers, and removed the need to upgrade the main speakers.
Later formats such as Dolby Digital retained the LFE channel, although this is more through convention and backwards compatibility than necessity, as digital formats have greater dynamic range than the magnetic analogue recordings on 70 mm prints, and modern sound processors have a bass management system to redirect bass from all channels to a subwoofer.
In the 1990s surround sound home theater systems became available to enhance the experience of viewing DVD and Blu-ray films.