Megasound, as technology People & Technology

Megasound was a proprietary theatrical sound system developed by Warner Bros. in the early 1980s. It added extra speakers to the theater — specifically aimed at delivering extreme low-frequency content at high volume — on top of the standard Six-Track Dolby Stereo mix carried on 70mm prints. Only four Warner Bros. films were released with Megasound encoding.

The system was never adopted as an industry standard and left no trace on home video releases. It exists primarily as a historical curiosity — an early attempt at what would later become the subwoofer channel (the ".1" in 5.1 surround) and eventually Dolby Atmos height channels.

In the wiki

Film	Page	Summary
Outland (1981)	Physical Media Releases (Outland)	70mm blow-up prints carried Six-Track Dolby Stereo with Megasound; one of only four Warner films to use the system