jasonhou Posted November 24, 2020 Share Posted November 24, 2020 I read the discussions about M/S here and just want further clearfication. My understanding is that M/S is actually Sum/Difference - M=L+R, S=L-R. So when materstering with an M/S EQ, adjusting the M channel actually affects everything in the mix, right? For instance, EQing the M channel in order to bring the upper-mid of the vocal would also affect the guitars panned to L and R. But EQing the S channel wouldn't affect any true mono sound panned to the center, right? Thanks! Quote Link to comment Share on other sites More sharing options...
David Nahmani Posted November 26, 2020 Share Posted November 26, 2020 M is not everything, it's only the center (it is lacking the information related to the differences between the L and R signals). EQing the M channel affects only the center, not the sides. EQing the S channel affects only the sides, not the center. So you're correct in that the S channel wouldn't affect a mono signal (if L = R then S = L - R = 0). Quote Link to comment Share on other sites More sharing options...
jasonhou Posted November 27, 2020 Author Share Posted November 27, 2020 M is not everything, it's only the center (it is lacking the information related to the differences between the L and R signals). That's my previous understanding as well until I did the experiments below. I panned 3 true mono sounds to Hard Left, Center and Hard Right and then bounced into a single stereo file. Then I used several plugins with M/S capability to examine the contents of the M and S channel. I can hear all 3 sounds in the M channel. I can only hear the sounds panned to Hard Left and Hard Right in the S channel. I then tried with 3 true stereo sounds, panned to Half Left, Center and Half Right (all with stereo pan mode). I can hear all 3 sounds in the M channel. I can hear all 3 sounds in the S channel. Quote Link to comment Share on other sites More sharing options...
Solution David Nahmani Posted November 27, 2020 Solution Share Posted November 27, 2020 That's my previous understanding as well until I did the experiments below. I panned 3 true mono sounds to Hard Left, Center and Hard Right and then bounced into a single stereo file. Then I used several plugins with M/S capability to examine the contents of the M and S channel. I can hear all 3 sounds in the M channel. I can only hear the sounds panned to Hard Left and Hard Right in the S channel. I then tried with 3 true stereo sounds, panned to Half Left, Center and Half Right (all with stereo pan mode). I can hear all 3 sounds in the M channel. I can hear all 3 sounds in the S channel. Yes, what you describe is the expected behavior. None of this is contradicting my statement: M is the center signal (If you feed a stereo signal to two speakers and place an omnidirectional mic right in the center of the two speakers, you can record that center signal (M = L + R). What you're losing when summing L+R is neither the Left, Right or Center signal, it's the positioning of the L and R signals in the stereo signal (which is, in other words, the difference between L and R, so in essence, the Side signal). Also I'm not sure what you mean by "true stereo". I don't believe I've ever heard this term. Any signal panned hard left or right is going to end up being a mono signal, so it doesn't really matter if you started with a stereo or mono signal. You can also consider that the wider the stereo the more L and R are out of phase. When L and R completely out of phase, the M signal contains nothing (M = L + R = 0). So take a mono signal, send it to two Auxes, one panned hard left and the other hard right, invert the polarity on one of the Auxes, encode to MS, you'll get double the original signal in the S signal (S = L - R = L - (-L) = L + L = 2L), but nothing in the M signal. (M = L + R = L + (-L) = L - L = 0) Quote Link to comment Share on other sites More sharing options...
jasonhou Posted November 28, 2020 Author Share Posted November 28, 2020 Yes, what you describe is the expected behavior. None of this is contradicting my statement: M is the center signal My misunderstanding in the past is that the M channel is equal to mono elements panned in the center. So this is not true because elements panned to the sides also present in the M channel, just without the spacial information. What I've been taught in the past is that EQing a vocal in the M channel won't affect the guitars panned to the sides at all. So it's not true. Also I'm not sure what you mean by "true stereo". I don't believe I've ever heard this term. Any signal panned hard left or right is going to end up being a mono signal, so it doesn't really matter if you started with a stereo or mono signal. True Stereo is a signal consists of 2 related channels, with correlated material. Not like Pseudo Stereo, which only duplicates a single channel. That's what I mean. In the 2nd experiment I didn't panned the stereo sounds Hard Left and Right, but in the mid-way. I just wanted to hear how they behave in the M channel. Thank you for taking the time to have this detailed discussion. I really appreciate it. Quote Link to comment Share on other sites More sharing options...
David Nahmani Posted November 28, 2020 Share Posted November 28, 2020 My misunderstanding in the past is that the M channel is equal to mono elements panned in the center. So this is not true because elements panned to the sides also present in the M channel, just without the spacial information. Yes, that is correct. What I've been taught in the past is that EQing a vocal in the M channel won't affect the guitars panned to the sides at all. So it's not true. I'm not sure what you mean here, are you EQing a mix containing both vocals and guitars? Normally to EQ your vocals you would insert the EQ on the vocal channel strip so that the EQ affects only the vocal signal and none of the other signals on the other tracks (no matter where it's panned). Thank you for taking the time to have this detailed discussion. I really appreciate it. You're welcome! Quote Link to comment Share on other sites More sharing options...
jasonhou Posted November 29, 2020 Author Share Posted November 29, 2020 I'm not sure what you mean here, are you EQing a mix containing both vocals and guitars? Normally to EQ your vocals you would insert the EQ on the vocal channel strip so that the EQ affects only the vocal signal and none of the other signals on the other tracks (no matter where it's panned). I didn't clarify that I was talking about M/S EQ during the Mastering process. I've been taught that EQing the M channel would only affect lead vocal, snare, kick which are at center but not any sounds panned to the sides like guitars, hi-hat etc. I now learn this is not completely true since the M channel does contain contents that are panned. Quote Link to comment Share on other sites More sharing options...
David Nahmani Posted November 29, 2020 Share Posted November 29, 2020 I didn't clarify that I was talking about M/S EQ during the Mastering process. I've been taught that EQing the M channel would only affect lead vocal, snare, kick which are at center but not any sounds panned to the sides like guitars, hi-hat etc. I now learn this is not completely true since the M channel does contain contents that are panned. Got it. Yes, in that case what you're saying makes sense. Quote Link to comment Share on other sites More sharing options...
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