Home made Dolby Pro logic

Dolby Pro logic by yourself?

I remember when in ’90s came first recievers with Dolby Surround / Dolby Pro logic. Everybody were excited from it and everyone use this function on recievers, with every stereo input like a movie, music etc. Of course, it takes short while and everybody use the stereo output back again. This reproduction is interesting but not for every input.

But!

It can happend, when you just want this 5 channel audio output made by yourself. In one sentence it can explain the principle of Dolby ProLogic as a subtracking left channel from right (or oppositely), use it as back speakers and extracting from stereo source mid tones (voices etc) for center channel. Yeah, this is true. In back left and right speaker you have ONLY MONO AUDIO LAYER.  This is first version of Dolby Pro Logic. So, lets see how you can easy do „by hand“ this 5 ch (5.1) from basic stereo input. I choose for this example part of the song from Archive, album Controlling Crowds. The name of the song is Funeral:

Source sample input sounds like this:

1.) In the first step I exported surround channel by substracking left channel from right. You have to do in most of the applications one step before: extract left and right channel to mono layers. After this you can substract it. The result sounds:

2.) Second step is making center channel by using some special filters like center channel extracting or just using simple graphic equalizer. I choose in Adobe Audition effect called CENTER CHANNEL EXTRACTOR:

And thats it! Simple oldschool Dolby Pro Logic. 🙂

Left and right channel is original source. Center is our step 2, surround is step 1 and you can also extract only low pass to the LFE channel.

Most of the reciever in own setup can make just simple delay (ms) between front right and left channel and surround channel. This makes chorus (reverb) feeling.

Imagine! This all steps makes in 90s recievers realtime. 🙂