Freeheel Posted April 4, 2013 Author Report Share Posted April 4, 2013 Hey Mike, I'm decoding for the outputs. The editors would have something to say if they got unmatrixed mid and side tracks on channel 1 and 2. So "no" to decoding for the cans. And that means that the separation is controlled by the matrix so I would assume that the tracks are kept fully separate before matrixing (I think that is what you meant by max separation?) When I've seen this effect, the levels of mid and side mic have been equivalent at the preamps as well, if that makes any difference. Cheers, Brent Calkin Quote Link to comment Share on other sites More sharing options...
Constantin Posted April 4, 2013 Report Share Posted April 4, 2013 Are you closer to a solution, yet? This one is quite interesting. I would agree with those who thought it would be the MS matrix, or the mixer's headphone amp or the stereo buss. With the latter two it means it should also occur when MS is not engaged. Did you try regular stereo linking? Also I don't think it's a phase issue. MS stereo can be folded down to mono easily because the two S signals (0deg and 180deg) will cancel each other out, leaving you with the M signal which will be in the middle, not on the left, if the matrix still works. It it's the 8 mic crapping out, the matrix wouldn't know and would go on decoding, the regular M and the silent S. The M would still be in the middle. So it can really only be the matrix, as I see it Quote Link to comment Share on other sites More sharing options...
Freeheel Posted April 4, 2013 Author Report Share Posted April 4, 2013 Hi Constantin, All your observations are bang-on, I think. It's definitely not the headphone amp since the right side meter cuts when the sound cuts. Leaving, as you say, the matrix and the outputs. The outputs have never done this under any other circumstances, so I'm leaning toward the matrix as the issue as well. I've been a little busy to see if I can replicate the problem at the end of an airport runway. I tried with my noisy old diesel Landcruiser, but I couldn't trigger the problem. Maybe I should try some low sine tones fed straight into the matrix, at least that's easily done and repeatable.. quite frustrating, really Cheers, Brent Calkin Quote Link to comment Share on other sites More sharing options...
Brhoward Posted April 5, 2013 Report Share Posted April 5, 2013 This is an interesting problem. A few questions... Is the microphone stationary? Is one lobe of figure-8 pointed at the source in question? Are you in an open space or are there reflective surfaces? Also, does this occur only when the loud noise is moving? If so, then one side of the figure-8, before the matrix, might be going 180º out of phase, the two sides might cancel each other out. just a thought... Quote Link to comment Share on other sites More sharing options...
Constantin Posted April 5, 2013 Report Share Posted April 5, 2013 Also, does this occur only when the loud noise is moving? If so, then one side of the figure-8, before the matrix, might be going 180º out of phase, the two sides might cancel each other out. just a thought... Yes, that's possible, but what I find most baffling is that the entire right side is lost. If the fig-8 mic somehow manages to cancel itself out (which would in itself be very weird), why doesn't the 50 stay in the middle? Quote Link to comment Share on other sites More sharing options...
Freeheel Posted April 5, 2013 Author Report Share Posted April 5, 2013 The Mic is generally stationary and the mid is on axis and the figure 8 diaphragm is 90° off axis. (as usual) It usually has happened in wide open spaces -no reflections. This has always happened when the sound source is moving and seems to be independent of mic position (I've tried moving it to different angles) The effect has always occurred when the moving vehicle is at it's closest approach. And Constantin, again you are bang on, if it's a figure 8 mic phase thing, why doesn't the 50 stay in the middle? Cheers, Brent Calkin Quote Link to comment Share on other sites More sharing options...
Constantin Posted April 7, 2013 Report Share Posted April 7, 2013 Hey Brent, just to let you know, I was thinking about your very intriguing problem an whipped my 442 out of storage and set-up an MS rig. I didn't try to emulate your problem, but I tried to verify what we said above. So yes, if two channels are stereo linked for MS and you kill the 8, the 50 will stay in the middle. If you only monitor MS in your headphones and don't stereo-link, and then kill the 8, you will only have a signal in the left side, because you have to pan channel 1 to the left, 2 to the right, for it to work in the cans. In linked mode, channel 1's pan pot controls to pan of both channels. Channel 2 controls have no function. So, to cut a long story short, since you said you were linking them, this really only leaves the MS matrix. Or, perhaps, the pan section of channel 1. but tha latter can easily be verified without MS. Time to call SD, I think. Sorry for waffling on Quote Link to comment Share on other sites More sharing options...
Brandon Pert Posted April 10, 2013 Report Share Posted April 10, 2013 Have you tried a mkh40 instead of mkh50? I've experienced phase issues when using a hypercardiod in a drive by situation. Can anyone shed some light on the differences between hypercardiod and cardioid patterns as the mid mic? Quote Link to comment Share on other sites More sharing options...
Matti Posted April 10, 2013 Report Share Posted April 10, 2013 This has nothing to do with the maths of mid/side recording or matrixing per´se, rather something wrong with the setup or user -saying this in constructive sence Matti Quote Link to comment Share on other sites More sharing options...
Freeheel Posted April 11, 2013 Author Report Share Posted April 11, 2013 Hey Brandon, I have heard that the rear lobe of a super cardioid mid mic can cause weird imaging since the rear lobe is out of phase with the front lobe. Apparently a cardioid mic's rear lobe is not out of phase. This is internet hearsay from a nature recordist site - I would love to hear if anyone of our group has experience with this. Interesting thought, though I don't know if it could cause the issue I'm having. And Matti, please tell me if you have any guesses as to what what my setup or user error is... if you tell me it's the user himself, I may take some offense... Cheers, Brent Calkin Quote Link to comment Share on other sites More sharing options...
Constantin Posted April 11, 2013 Report Share Posted April 11, 2013 A cardioid doesn't have a rear-lobe. So no phase issues there. The only possible user errors I see are: - Confusing MS linking with MS monitoring (Brent already said that's not it) - Plugging the mics into the wrong input, the 50 into 2 (or 4) instead of 1 (or 3) - Engaging the phase switch - Using the pan pots Quote Link to comment Share on other sites More sharing options...
Freeheel Posted April 12, 2013 Author Report Share Posted April 12, 2013 user errors -nope, -nope -nope -and nope. I just spent the day running m/s boom while recording horses on a nice quiet farm. Sounded beautiful. No planes, no cars, just birds, horses and a burbling brook. And no Harleys, so no problem.... cheers, Brent Calkin Quote Link to comment Share on other sites More sharing options...
Brandon Pert Posted April 12, 2013 Report Share Posted April 12, 2013 While smaller than a super-cardioid a cardioid does still have a rear lobe. I agree there is probably something wrong with the hardware here.. I'm curious if anyone has any facts on supers or hypers vs. cardioids in a m/s rig? Quote Link to comment Share on other sites More sharing options...
Constantin Posted April 12, 2013 Report Share Posted April 12, 2013 While smaller than a super-cardioid a cardioid does still have a rear lobe. I agree there is probably something wrong with the hardware here.. I'm curious if anyone has any facts on supers or hypers vs. cardioids in a m/s rig? If you mean the "butt cheeks" (very sorry for that tern), then cardioids may have two rear-lobes, but no, they don't have what's known as rear lobes. I don't have any facts regarding the use of a hypercardioid vs cardioids in an M/S rig, but only personal experience. I use the cmit with the Schoeps 8 sonetimes. It's nice for docs, etc., where you want a "proper" boom mic, but also want to be ready to record atmos at a moment's notice. It sounds nuch nicer then than a mono rig, but I much prefer M/S with a cardioid mic. It sound wider and more natural Quote Link to comment Share on other sites More sharing options...
dudsound Posted April 18, 2013 Report Share Posted April 18, 2013 For the most accurate and natural stereo image, a cardioid microphone should be used for the mid signal. By progressively using "tighter" microphones instead of a cardioid, eg an MKH50 or 60, the resulting stereo image looses clarity and sounds more like three separate areas, hard left, centre and hard right with "holes" in the image between them. I did know one recordist who used an MKH70 with a 30 in an MS configuration, but that seemed pretty pointless to me and I think his boomswinger thought so as well. A hypercardioid like the MKH50 is probably the best compromise between being a very versatile microphone you would use anyway for a variety of situations, and one that is able to present a reasonable stereo image in an MS configuration. Brent, whilst I assume you are supplying your tracks in AB stereo because your production has specified this, and unfortunately many editors are very poorly informed about how to use MS stereo so supplying stereo in that form is a risk unless specifically requested or agreed to by post, you are of course loosing the main advantage of MS stereo which is the ability to manipulate the "width" of the image after the event or even discard that element with the knowledge that you still have a mono version, the mid signal, which is as good as you would ordinarily supply. Equally, if you are recording dialogue in MS you are also including additional noise/atmos, (which may be desirable), from the S microphone when you submit in decoded AB stereo form, and of course this cannot be minimised after the event, unlike MS stereo. Dudley Quote Link to comment Share on other sites More sharing options...
Freeheel Posted April 18, 2013 Author Report Share Posted April 18, 2013 Hi Dudley, I agree that the 50 makes a slightly notchy stereo field, but for for most static ambiences, it doesn't really hurt. I'm just trying to create a soundfield with some width and life to it, not trying to create a scientifically accurate match to what is actually happening. I mainly like M/S for the common reason that the most important mic element is pointed at your sonic subject. I rarely record dialogue in M/S, but did record one entire feature doc that way as all interviews were done on the fly in an interesting sonic environment. For that I delivered 2 tracks of decoded AB and 2 tracks undecoded M/S for full flexibility. It kind of freaked the post guy out but he figured it out and it's neat, 'cause the director's off camera lines come from off the side of the screen and it sounds rather natural. And all the dialogue has a nice natural ambience about it. Not something I would try everywhere, but in a quiet Kurdish village with a background of calls to prayer, and farm animals murmuring in the background, it was pretty nice. As an aside, when delivering M/S as AB, the stereo width can still be controlled. You just use the pan controls. A/B (from decoded M/S) panned to center will result in just the Mid mic. (the sides cancel) A little cumbersome to use two channels as one mono track, but you could bounce it down to a single mono track in a DAW pretty quickly. Cheers, Brent Calkin Quote Link to comment Share on other sites More sharing options...
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