Thanks gordy and I will try that - but is there any other way of doing it that does not effect levels?

Erm.. it doesn't affect levels - what this explanation is saying is if Vegas simply combined the left and right waveforms, the volume level would become (100% + 100%) = 200% - by halving the volume as part of the combine function, it brings it back to 100% (ie no change at all).

Cheers

gb

Right click on the audio track header (the bit with the name, volume slider etc) and choose 'duplicate track'

Right click on the audio event of the first track and choose "channels>left only".

Right click on the audio event of the second track and choose "Channels>Right only"

Ah yes - I guess if the left and right channels are completely discrete sources with no shared information and absolutely no overlap of events, then the combine function *would* half the volume.....

In which case the method suggested by ibliss would be better.

I mainly use the combine channels function with interviews recorded using a stereo tie clip mic where there is a lot of spill from the left and right axes. Mono-ing the signal in these circumstances reduces the risk of the interview dissapearing altogether as a result of phase cancellation when played through equipment that has been incorrectly set up for stereo.

Cheers

gb

A mono signal played back through a stereo system has "half" the signal from each original channel going through two channels, so you end up with the full volume in the end anyway.

Creating a mono version increases the loss in case of phase cancellation. If the left & right playback are identical then you risk total cancellation. Having unique left & right channels will avoid cancellation. Cancellation occurs when two identical signals are out of phase.

That being said, any semi-competent audio engineer will test their setup for phase cancellation before the event, or they don't deserve to be paid.

"If the left & right playback are identical then you risk total cancellation"

No! I know you know what you are talking about, I think that sentence must have slipped in by accident!

If the left and right channel are identical and you combine them to mono, the total level will go up by 6dB.

If there were identical, and one side was phase inverted then they would cancel each other out when combined.

Yes, that's what i was talking about. If the two channels are identical you risk cancellation when the sound system is set up incorrectly so that the two channels are out of phase. Hence the gist of my entire reply. ;) This is the situation that gordyboy was worried about, and having identical channels makes the cancellation worse in this case than if the channels weren't identical.

So, in context of my reply to the situtation, that sentence was very deliberate.

Actually I was thinking of the scenario where your stereo mix is being played through a mono set up and phase cancellation occurs...

and the client goes bananas because all the dialogue has dissapeared from his expensive video production!

gb

If you do have a stereo source you can check for cancelation problems with the "downmix" button on the mixer window. Always a good thing to do before finishing a project anyway.

Larry

Um--is that what that there phase-reversal button is for, on the Vegas audio tracks?

Phase reversal reverses the entire audio track. If you have a stereo audio track then it reverses both left & right, which doesn't check for out-of-phase.

Probably the safest thing to do in gordyboy's situation is to create a mono audio track, the place it at -0dB on one side of the stereo mix and place an identical copy at -6dB on the other side. That way, a normal stereo playback will have the same material in both speakers, just louder in one than the other, which can be corrected with balance. A mono playback will mix the two together for overall -3dB, which is just a bit quieter and can be adjusted with volume. Out-of-phase playback will be -6dB instead of cancelled. And, in the case of mono playback in which the technician only plugs in one of the channels, you still get the full audio.

Or, better yet, have the tech check for phase cancellation before the event opens, as should have happened anyway. It ain't hard ... red wire to the red terminal ... If you want a laugh i'll tell y'all my Carnegie Hall story some day.

Time to read up on why M/S recording was invented to capture stereo audio in a way that doesn't create problems in mono...

Different mike setup and a bit of processing to get from Mid/Side to Left/Right.

Not a new concept, works very well.