Which methods exist for converting stereo to mono?


The typical way stereo signals are converted to mono is by summing left and right (and perhaps attenuate the result).

Obviously, the sum approach does a poor job capturing the side material, as the greater the difference is, the more the input signals will cancel each other out.

Are there any other (perhaps more creative) methods that will allow the side events to make it through in a mono conversion?

Michael Hansen Buur

Posted 2015-06-26T11:42:37.290

Reputation: 3 612



Off the top of my head..

Sum - Adds Signals; any sounds present in both signals are reinforced by a varying amount, depending on how in-phase they are.

Subtract - Subtracts one signal from the other(same as inverting the phase of one, then adding it to the other); any sounds present in both signals are attenuated or cancelled out completely, depending on how in-phase they are.

You could add (Sum + Subtract) together, but you would be left with one of the input channels(L or R) being attenuated.

The only method I can think of is to delay one of the stereo channels, then add it to the other, to limit the reinforcement.
You could even try applying a stereo delay to just the mono element before summing.

Marc W

Posted 2015-06-26T11:42:37.290

Reputation: 2 042

Thats not going to work - it leaves me with either L or R as result: (L + R) + (L - R) = L. However the delay idea is interesting.. perhaps delaying the side signal before summing with the mid could work – Michael Hansen Buur – 2015-06-26T15:43:31.043

Yes, you're right. How did I miss that? That's what I get for rushing an answer! I'll edit it in a bit. – Marc W – 2015-06-26T19:58:43.257