M-S vs. X-Y for field use

[Doug Boze]

Hey all,

I've been away for a long, long time (where does the time go?) and want to get back into my old hobby. I've been lurking here most of a month, trying to get a grasp on what's what and what species of lily is being gilded at the moment, and it's bewildering.

I have a Canon XL-2, CAVision matte box with two trays, bellows lens hood and rod system, a Manfrotto 503 head and either Amvona (el cheapo) CF sticks or, for brute work, Bogen 3183 sticks, an AT-825 single-point stereo mic inside an old-style Rycote WS-4, which is attached to the right-hand pan handle location using an amazing birch dowel (pat. pending).

My hobby has been railfanning, shooting trains around the Pacific Northwest. At one time I even thought I might make it a living, being on layoff, but about the same time work reared its ugly head and I went back to my day job as a machinist.

Looking at where things are today, I think I'm getting an idea of what I want as far as an upgrade to the HD world. So many things to upgrade, including audio. The AT-825 has served me very well, and the newer BP4025 would seem the logical upgrade unit. But I've been reading about M-S stereo, and now I only know just enough to be a hazard to my own judgement. I know the advantage to it as far as having an honest interview mic (not that I've ever done an interview) but the concept of spacial manipulation interests me.

Is it worthwhile to go the M-S route for my application? I was thinking of a pair of AKG Blue-line mics, using the CK94 and CK-93 and a Rycote WS AE kit. It's much pricier than the BP4025, but I was going to replace the WS-4 with a WS-3 anyway. The specs of A-T's BP4025 are very attractive, and the old AT-825 has been an amazingly sensitive, quiet, and forgiving mic. I'd be rather concerned about dynamic range and max SPL: wheel flange squeal will loosen one's teeth, I kid you not.

BTW, some years back I thought the Rode NT-4 was the bomb due to its specs. Well, the one I had was a bomb, so much so that I have zero interest in their product line. Maybe it was a factory reject that made it to market or maybe somebody damaged it and it was returned. Horrible device, yet all I read are lauds?

[Brian P. Reynolds]

I prefer XY rather than MS, sorry to hear your experience with the NT4 was not good, I personally love the results it gives for location stereo.
If you do use MS and are going down the unmatrixed form be VERY careful that everyone that can edit / change / mix / have access to it fully understands MS and its pitfalls. If someone is unaware that it is MS they can destroy a mix very rapidly.

Perhaps a bigger decision for stereo sound with pictures should the sound image pan with the picture image OR should the screen be regarded as a window (like a house) and any sound image should move across it.

Some of the older MS mics were capable of handling VERY high SPL's ie; Sony ECM 969 were often used for grand prix cam FX mics..... BUT they had a very poor s/n ratio, great for car racing but poor for general FX recordings.

[Steven Reid]

Doug, I regularly use the BP4025 with pleasure. Most reviews hail it as a superb mic for recording ambiance, e.g., in nature. I don't disagree. Indeed, it is an astonishingly quiet mic and, paired with my Sound Devices 302 with its quiet preamps, it will yield a freaky quiet, beautiful stereo image.

Its 1" LDC capsules are fixed at 120*, IIRC, so the stereo image is wide. Anything close might sound a little weird.

I used it once to record scratch audio at a very loud rock concert using the 10 dB pad. It performed flawlessly. No distortion.

Audio guru Ty Ford, who chimes in here from time to time, once wrote an exemplary review of this mic; it nudged me toward a purchase. I can't seem to find a link at the moment.

Hope this helps.

[James Kuhn]

Caveat: While my 'profile' states 'Major Player', it's merely a function of quantity of threads I've commented upon. I'm not an expert!

It would be helpful if you could let us know what you're planning to record? I've always been told dialog should be captured in 'monaural' and 'Nat Sounds' (background) in stereo. That said, if you're planning to record chamber music in an acoustically clean environment, one of the numerous X/Y, M-S, Decca Tree, Blumlein Array, etc., would be some of the microphone configurations you can experiment with. Remember, the 'audio string' begins with the microphone. GIGO.

I'm sure some of the real audio experts will chime-in and provide more detailed and substantive information.

Regards,

J.

[Brian P. Reynolds]

I have assumed trains.... Original post 3rd paragraph

[James Kuhn]

OP: "My hobby has been railfanning,..." Past tense? Maybe I read too much into it?

J.

[Mike Beckett]

(Assuming this _is_ railways/railroads...)

Hmmm. I do a lot of railway videos. I am not an audio expert by any means, but I get by, and have more direct experience of recording steam and diesel locomotives than a lot of people on here I'd guess.

I've always used mono shotgun mics, currently a pair of AT875R microphones. Cheap and cheerful, Nattrass Approved(TM) and great shotguns. One of them is camera mounted, and the other lives inside a Rode Blimp and is operated by someone else, recording into a Tascam DR-60. If a train is passing by, you just pan the mic along with it and you get pretty good sound. Trains are loud beasts, and you don't need to be within a foot of the subject like you do for voice recording. I can be 100s of yards away across a beach, field, hilltop etc. and still get great sound.

Results are pretty good, I have to say. Occasionally I do a pan in post to simulate stereo on cliched shots of a train passing at distance from the camera, but normally it's just mono. And nobody notices.

I did dabble with a similar AT8022 X/Y stereo microphone. It's great for music, ambient etc., and I've kept it for this purpose. If you go into a forest or other environment, or a music performance of some sort, the ambient recording is just excellent.

But it's total pants at recording "trains through the landscape", as it's just too quiet until the train is almost upon you. You either have the mic mounted, static, pointing in the mid-point of the pan (for example), and you only get any meaningful sound when the train's really close. Or you pan it with the camera, and it just sounds weird, but still way too low volume to be of any use.

It's not a levels setting or anything like that. It's just not the mic for the job of recording a distant sound getting closer then passing. At least, not for me. Of course, the BP4025 could be way better than the AT8022. I just don't want to waste £500 finding that out! I would love to hear any advice from people with actual experience of recording trains in this way.

I really would suggest that music in an auditorium or studio etc. is very different from recording this sort of subject, and should not be taken as a recommendation that the same mic works in train audio recording. The AT8022/BP4025 would be great if you had it strapped to the train to get good engine noise, but I think that's as far as I would go.

One thing I do take comfort in is that nobody has ever, ever complained about my sound - and sound is super-important for train people, take my word for it! The only issue I've ever had is wind, I do end up in some really gusty locations, and at times even the Rycote S-Series windshield isn't enough.

As I said, specific advice in this recording field would be very welcome!

[Steven Reid]

Mike, I enjoyed watching a few of your train videos. I noticed (from my very small sampling) that you're performing simple pans, L-R or R-L, and, hence, I can appreciate your remarks on using a camera mounted shotgun. Yet, what about recording a train through a proper stereo mike on a field recorder located close to the tracks, you and cam at a distance, then sync in post?

[Seth Bloombaum]

I don't know much about trains!

But someone has to step in to promote M-S! I use M-S regularly for ambience recordings of various types, in many cases this is the room sound to mix with direct microphone sources for music. Have I made that clear as mud? I do a fair amount of live sound work with multitrack recording, and a stereo mic in the audience really brings these recordings to life. Even more if the "audience" is singing along...

Also have done quite a bit of recording/video of acoustic music, using a single M-S, or an ORTF or X/Y array.

These days, it's mostly M-S, for the convenience of the single mic body (ORTF and X/Y with two cardoids), and the magic of dialing the stereo spread.

Have done quite a bit with a friends Beyerdynamic M-S, a beautiful mic, but unaffordable for mere mortals. I purchased a Nattrass Approved (TM) Sony MS-957 a few years ago, and it has been a workhorse. It decodes to stereo in the mic, so dialing the spread in Post is somewhat more involved, but can be done by dematrixing the stereo back to M-S. Quite possible with a bit of headscratching.

I like M-S! One of the advantages is an absolutely seamless degradation to mono. There's an involved explanation to why this is so, but the short story is that when left and right are summed to mono, what you're left with is the signal from the cardoid that supplies the "mid" signal (M-S = Mid-Side), with no potential for comb filtering or other phase artifacts, such as you get with X/Y, or even moreso with ORTF.

On the other hand, in my practical experience, the phase artifacts so often referenced in summing X/Y or ORTF to mono don't seem to sound bad to me on good monitors, even though the math predicts horrible results.

My all-time favorite stereo image is ORTF. But the convenience of a single M-S mic wins in most of my shoots, with ORTF coming out for small acoustic performances direct to stereo.

A train is not a singer/songwriter... but I'd be interested to hear comparisons of these different stereo techniques with the train. Get yourself a couple of mic bodies, a pair of cardoid capsules, a figure-8 cap and a mounting bar, and you can try them all!

The conventional wisdom is that stereo be done with a fixed mic/array, not panning. But we all swivel our heads with the train, why not pan the mics too?

Mike Beckett, above, writes about how the distant train was inaudible using a stereo mic until it was quite close. I'd try to find a valley with road crossings - the valley echoes the sound of the train, the road crossings so as to hear that magnificent (steam?) horn. Record the sound at 3am when other sources are quiet? This would allow boosting the gain in recording and/or post with less general background sounds. Put this alongside some daytime video...

[Mike Beckett]

Steven,

Thanks - I did try that, but the problem is you really don't hear much until the trains it's on top of the mic. I will always use off-camera audio where I can, for wind protection and not removing risk of camera rattles such as buttons being pressed or my feet crunching in gravel.

Because a shot tends to last quite long, a close-up mic would not capture very much sound. I did once think off putting a whole series of audio recorders along a site, but I'm not made of microphones or money!

Seth,

great suggestion - I could absolutely experiment more, but I'm very limited in locations in this country, so the valley idea is out. Not much happening at 3am really either :) The things I film are rare/one-off movements, so it's hard to record sound from other times. I have dubbed sound sometimes, and nobody has yet noticed, not even the most die hard train nerds!

The problem with this sort of thing is the distance from the sound source to the microphone, as well all know there's no such thing as a zoom microphone.

I don want to hog this thread too much though, I defer to the OP who may or may not have the same questions/issues as me.

[Bruce Watson]

Originally Posted by Doug Boze

Is it worthwhile to go the M-S route for my application?

Depends (of course).

I'm certainly not an expert. And it's been awhile since I studied this stuff. But what I remember is that mid-side works by eliminating phasing. The stereo image is formed solely by loudness variation. And this in turn lets you decide how wide to make the stereo separation in post when you do the decoding of the two mic tracks to stereo. That convenience is a big attraction and part of the reason for mid-side's continuing popularity. That, and it sounds quite good.

Mic systems like x-y and ORTF capture the phasing information. Because the stereo field is in part dependent on the phase differences, the width of the stereo field is defined at capture time. So you have to be spot-on in mic placement at capture since you aren't going to materially effect the stereo field in post. What you supposedly gain by giving up this flexibility is better stereo imaging and "a more natural sound".

In reality, people turn this into a religious argument. It comes down to mid-side having its adherents, and x-y (and the variations) having its adherents. Which side you decide to join is a personal decision. The only help I can give to someone trying to decide is the advice to try recording and listening to both. Trust your ears, trust your instincts. You'll make the right decision, for you.

[Brian P. Reynolds]

If you are doing ANY production that is in stereo.... it doesn't matter if its XY / MS / AB / ORTF or any other form ALWAYS check the mix in mono as well........ALWAYS ....NO exceptions !!!!!!!!

[Jim Andrada]

Another M-S Fanboy here!

I use it a lot for orchestral recordings and vary the M mic according to what sounds better - omni works fine for quite a lot of things things.

I will say that I like X-Y beter for acoustic guitar and it's a toss-up for classical piano. Of course you could write a thick book about mic-ing the piano.

I use a pair of Schoeps mics into a Sound Devices 302/702 and have never gotten any complaints about sound quality.

Would like to try ORTF but just haven't gotten around to it yet.

Never done trains though.

[Rick Reineke]

A high-quality X-Y stereo mic is most likely best for the OP's application. High-quality portable preamps are also a must. Setting up a multi-mic array takes time, skills and is a PIA to lug around.. to remote locations.

[Doug Boze]

Thanks for the replies, fellows. I responded to this thread many hours ago but my post was lost (took too long to type it, I reckon).

I think I'll stick to the single-point stereo mic like the A-T BP4025. While it isn't as sensitive as the AT-825, the other specs make for a very attractive mic. For my part, I do love to capture the ambiance of the location, whether it be wind rustling the leaves or sighing through tall grass and sage, birds or babbling brooks, or roaring rivers and falls, I believe that a sonic picture is worth detailing.

I'm a bit puzzled as to what separate pre-amps would bring to the package. I've never had trouble with the camera's own. Well, except very early in my experience, in the mid 90's when I had a consumer Hi-8 thing. I was at a profoundly quiet place, almost anechoic, and wondered what I was recording.

I was recording HISS, that's what. Bands of it at about 15KHz which, I'm sure you'll recall, was the limit of Hi-8 AFM. I created an FFT filter in post to mask it. Haven't troubled to do so in the digital age, but I do normalize the sound levels in post. That's it. Keeping it simple and stupid. So, in other words, for HISS to KISS, ha ha!