Every movie you see that says Dolby Stereo has 4 channel matrixed surround sound. The simplified home version was called Dolby Surround and only extracted the surround channel from the existing 4 channel matrixed surround. It is a simple matter to generate an LFE to go with it. The 70 mm 6 track was comprised of left, center, right, surround and two LFE channels. Before Dolby Stereo, you either had optical mono soundtracks or magnetic 6 track (there were some older formats that were 4 track). But there was only one surround channel. The two extra tracks were either mid right and mid left or LFE. 5 front channels kind of made sense with some of the very wide format movies presented on very large screens.

The 1985 and 1993 mixes should be matrixed as well. Some of the later matrixed surround contains 2 surround channels. Dolby Surround equipment can extract 1 surround channel. Dolby ProLogic can extract 1 surround channel and the center. Dolby ProLogic II can extract 2 surround channels and the center. There have to be 2 surround channels to extract or it will just duplicate the single surround channel. LFE is usually mixed with the surround and cut off between 80 and 120 hz. The LFE channel isn’t necessary as most systems will direct the low bass sounds to the subwoofer and filter them out of the surround channels.

The original 77 Dolby Stereo was included in video releases before 1985, including multiple LD releases. I am currently working on a way to extract the original multi channel audio from the stereo source. If it works I should be able to create a 4.1 channel AC3 or DTS file for the original audio. From my first attempt with the 1985 soundtrack, I think I can extract a full 5.1 channels from it and the 1993 soundtrack.