Mono mixing/compability (Interleave/phase) tutorial help needed

Hi Erik, I will try to answer some of your questions. Firstly I use a different set-up and it might prove to be better for your case too. I believe it is best to check for mono compatibility through a separate small mono speaker. And a single speaker at that. Mono sounds better coming from a single point source. This is better than mono coming from your two main speakers. Also the small speaker especially at low volume is excellent for checking what I call the critical mix.

I have got it driven from a small Hi Fi amp which has a mono switch which sums the stereo input signal to mono. I send that amp the stereo signal from a spare headphone output on my digital mixer but many interfaces would have a headphone out as well.

The reason that this is good is I only have to turn down my main monitors and turn up the small mono speaker control and it is there all working and automatically in mono. In Sonar you could insert Channel Tools for example over your main mix buss and have it set for mono with the two sliders in the centre. I am not sure how Sonar works switching the main buss interleave button into mono. With Studio One it definitely sums the two outputs to mono. You would need to check that Sonar does the same. 

I do it at the mix stage, mastering is way too late. Mono synths are going to sum well and wont give you any issues. It is the big wide stereo pads and things that you need to check and you can listen to see how robust they still sound in mono and also if their volume drops at all in mono. If something almost disappears in mono then it might be using phase flipping effects to create the image you are hearing. You may need to do some work on the stereo effect so that it sums better in mono. eg polarity invert one side etc.. If you have created a stereo interleaved track you may need to convert it to two mono tracks in order to do things on one side easily and not the other.

The small speaker will also stop parts getting lost that you may have panned to the extremes of the stereo image. You will still hear them clearly in stereo on your main speakers but in mono they might end up a bit soft compared to everything else especially stuff that is panned centre. So you simply bring their levels up slightly and then you will find those parts are easily heard in the small mono speaker again and not changed very much in stereo. So you have satisfied both speaker systems now instead of one.

The small mono speaker at low volume will do more for your mixes than anything else. I spend more time on the small mono speaker. I find when I get that sounding very very good the music sounds absolutely killer back on the main speakers up loud again. Everything is perfectly in balance. Of course you still need your main speakers in stereo and up loud to check bass and reverb levels and other things like that.

Hi Erik once again. Sorry I forgot to mention that M/S techniques don't have much to do with all this mono stuff at all. It is a stereo miking and recording technique that uses two microphones set-up in a certain way in order to capture a stereo image.

It does have the ability to alter the stereo width after the event. It can be used in a mastering situation too where the final stereo image can be converted to M/S and then separate processing is applied to the M/S signals and then the M/S signal is turned back into stereo again. What it does allow you to do is to effect things that are either panned centre or the extremes without effecting the other so much. 

It is not so much directed at mono compatibility though. What it can do though is to remove the stereo stuff that is panned and leave the mono centre signals in place but that is not the same as summing L+R. For straight ahead mono you simply need to sum L and R signals and feed that into some sort of amp and out to a small speaker. (Unless the amp has a mono switch and many older Hi Fi amps did and they are ideal for this) 

A simple summing solution could also be wired into the stereo plug that goes into your stereo headphone out. . ie two 100 ohm resistors are soldered to the TIP and RING parts of the plug and joined at the other end to create an effective mono signal. That and the earth form your unbalanced mono feed.

I believe it is best to check for mono compatibility through a separate small mono speaker.

I'll second that. A dedicated Auratone-type speaker is really useful, not just for checking mono-compatibility but also as a sanity check for your mixes. But if you don't have one, you can get by with just clicking the interleave button on your master bus to fold your stereo mix to mono. If it sounds bad, don't panic - it always does. But there's bad and then there's "where'd the bass guitar go?" bad.

If you want to experiment, insert the Channel Tools plugin on your master bus and invert the phase of one of the stereo channels (simulating a worst-case mono-incompatibility scenario). Right away you'll hear the center-panned bass and kick disappear. But now put on your headphones -  it sounds a little weird but the bass is back! That's because the left and right channels aren't being blended and therefore aren't cancelling each other out.