Convert audio to 5.1 as in this other thread...


I’m a new user of this forum and Audacity. I know to use the beta software to be able to map my wavs to different channels.
Please direct me to a post if this question has already been answered.

I need help using audacity to accomplish the following:

I would like to convert a stereo file into mp3 (yes, I know I won’t get 5.1 quality nor magically create the extra channel information).

For this line:

old left - old right(3dB down) + 15ms delay - 10dB = new left surround

I assume he means to bring the right channel down 3db, invert it, combine it with the old left, add a 15ms delay, then bring it down 10db

Is this correct?

Can someone explain to me what this means? Or how to do it in audacity?

old left + old right + 18dB per octive filter centered at 180Hz (crossover, your wave form will look like this “~~~~~ ___________________” )

  • 2dB @ 80Hz .7 octive wide + 3db @ 180Hz .8 octive wide

Any help appreciated!

<<<18dB per octive filter centered at 180Hz>>>

Cool. That’s how he got the LFE Low Frequency Effects channel from the main show. You could probably do the same thing with Effects > Low Pass Filter at 180 Hz. He was doing a very specific frequency equalization curve. Yes, you need to be able to translate the instructions to the Equalizer tools.


He’s not been very clear with that line, (and I’m not an expert with surround sound)
He may mean that, or he may mean:

(old left mixed with inverted old right) amplified by -3dB (minus three)
mixed with (+)
(old left with inverted old right) amplified by -10dB (minus ten) and delayed by 15 milliseconds.

Either of these interpretations will produce a kind of fake surround sound, but they will sound different. Experimentation is called for.

Combine the left and right into a mono channel (in Audacity 1.3.12 you can do this with “Stereo Track to Mono” from the “Tracks” menu).
Then apply an Equalization filter that looks something like this:

Wow! Didn’t expect such great replies.

Thanks for taking the time to do this. I will come back and post my results soon so others may benefit from this. Thank you.

Ok. I said I’d be back and here I am.

I tried two different sets of two things.

Using the bass equalization vs the low pass filter sound almost the same and close enough for my needs. Although, I understand that the equalizer is likely more precise.

As for doing the right surround the way you suggested, or the way I thought, they both sound slightly different but I have no idea which is better. I might try just playing the surround alone to see which sounds better unless someone has a better idea to determine which to use. Either way, they both sound better than sending the same “front” sounds to the “surround” speakers.

One thing I had difficulty with was the delay in Audacity. I tried to set 15ms but the lowest I could go was .01s . As well, there were other settings such as # of echoes that I left at the default.

All things aside, this is much much better for me and my audience (maybe not for hardcore audiophiles).

0.01 seconds is 10ms

The default setting on Audacity’s delay for # of echoes is 5, if you only want one (“a delay”) set this to 1.
and change the “decay amount” to 10 if you want “-10db” level for the delay (default is 6).
Leave the other settings at default.

Hey Guys,

Thanks for the help.

I am on the route to automating this here:

Thanks again,