One question that people might ask, would be ‘Why is there still any interest in Pro Logic, when in the world today, we have AC3 sound compression?’ Beyond AC3, we also have AAC sound compression, which gets used in MP4 Video Files, or by itself, in M4A Audio Files.
The answer I would give is as follows. As long as our player or player application supports AC3, it will definitely be better able to output 6 channels of sound from such a compressed, digital stream.
But it can happen to us that our speaker amplifier only accepts two analog channels, which would have been called Left and Right. In such a case, If our speaker amp possesses a Pro Logic decoder, the player of our AC3-compressed stream still has the option, of Pro Logic encoding its stereo output.
In that case, our speaker amp will still try to decode that into surround sound, with as many speakers as we have connected to this amp.
But, If we do that, we are subjecting the sound to a loss in quality, because the sound has been collapsed into analog stereo first.
Yet, to substitute some other, Back-Front component for the surround channel, which is being fed to the Pro Logic decoder, does not really hurt the quality of the surround decoding more, than using Pro Logic already would. And so I would see no hesitation in doing so, if the need arises.