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Old November 30th, 2014, 04:04 AM   #1
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more than one mic for the Z1U.

Can anyone tell me please, would it be possible to improve the captured audio on a Z1U by using 2 mics, one connected to each XLR socket?
I'm using it for train videos and want to get a good stereo effect from the speakers when replayed to a TV. I am looking at a mic separation of about 5 feet.
Many thanks.
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Old November 30th, 2014, 04:34 AM   #2
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Re: more than one mic for the Z1U.

Yes using 2 mics will give you 2 audio signals but they will NOT be stereo and will possibly cause phase problems in post production.

You will need a stereo mic to deliver good results Rode do several that would be worth looking at, like RØDE Microphones - Stereo VideoMic X
(I haven't tried one but I do own a Rode NT4 and very happy with the results)
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Old November 30th, 2014, 05:18 AM   #3
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Re: more than one mic for the Z1U.

Thanks, Brian.
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Old November 30th, 2014, 09:00 AM   #4
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Re: more than one mic for the Z1U.

Depending on the type of microphones used and the direction they are pointed, you can have stereo, but widely spaced mics are prone to phasing problems.

I would use either a single-point stereo mic, or a coincident-positioned matching pair of cardioid mics as a starting point for your videos of trains. That would be easier in the field to deal with, position, wind-protect, and eliminate phasing issues.

There is a lot of info on the internet about stereo mic techniques to get you going.

Last edited by Jay Massengill; November 30th, 2014 at 10:30 AM.
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Old November 30th, 2014, 09:29 AM   #5
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Re: more than one mic for the Z1U.

Two mics are usually better than one, IF... two people are speaking, for instance two lavs, table mics or booms. In post, these two (or more) dialog sources would be mixed accordingly and typically panned to the CENTER...NOT LEFT and RIGHT. A 'stereo' mic (or stereo pair) is normally only used for ambient and/or S/FX..
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Old November 30th, 2014, 10:52 AM   #6
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Re: more than one mic for the Z1U.

John, just to be clear, are you making videos of trains, or are you making training videos?

The camera is certainly capable of recording two channels of audio. Depending on what you do in post, these can result in two tracks that will play back in stereo, or they can be mixed to one mono channel.

If you are making videos of trains and you want a somewhat realistic stereo playback of the sound of the train as it goes past, then I agree with Mr. Massengill's suggestion about single-point or coincident pair mics. Phasing is an important consideration, especially for potential TV playback, because there are still some old TVs out there with mono audio. Five-foot mic spacing is very wide and will most likely cause phasing problems. Personally, I think a coincident pair would give you a bit more flexibility (as compared with a single-point stereo mic), because if you are shooting at a great distance from the train, you could adjust the pickup angle if that helps with the final result. By all means browse around on the internet for into about "X-Y" mic usage.

If you are making training videos as some members seem to have assumed, and you are recording dialog, then yes, one mic for each person, and mix them down to mono in post.
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Old November 30th, 2014, 01:51 PM   #7
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Re: more than one mic for the Z1U.

Good point Greg,
I just assumed a "training" video w/ dialog, as in 'train employees'.
Yes indeed, a stereo mic or stereo pair of mics would be warranted.

.. Though I used a left-center-right mic array to record a large 1948 steam locomotive train pass-by (in 1997 as I recall) with gear I had at the time. Two 57s, @ 120 degrees, AT4041 in center, FP32> Casio portable D
https://www.freesound.org/people/knufds/sounds/78778/
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Old November 30th, 2014, 02:37 PM   #8
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Re: more than one mic for the Z1U.

OK, to clear up any misunderstanding, I am talking about TRAINS.... you know... those things that are thousands of tons and are about a mile or two long, and have anything up to 4 or 6 locomotives ... lol. I would estimate I am about 50 yds away at the closest point. The TV replay is on my own, fairly new 40in TV, although I have posted some vid clips to my Flikr account.

When I purchased the Z1U, it came with a shotgun mic that is unbranded, no markings on it at all to indicate left or right channels.

I fiddled with stereo sound a bit yrs ago when 7" tapes were popular and used mic separation to some success, but imagine what I am doing now is another game altogether.

I have yet to decide which mics to get but am leaning towards Rode.

Maybe 2 mono mics might be the way to go.

There is no thought of thought of edit in post.

Last edited by John Mahoney; November 30th, 2014 at 02:40 PM. Reason: More info.
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Old November 30th, 2014, 05:33 PM   #9
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Re: more than one mic for the Z1U.

John,

As you will find out (if you google a bit) there are many different mic configurations that can result in a "stereo" recording. There is also "binaural" which is a very special form of recording, for playback on headphones ... the realism is scary on headphones, but can sound nearly mono when played over speakers.

If you are posting some of these videos online, and have no control over the playback systems, then mono compatibility (and therefore phase coherence) should not be disregarded.

Two mono mics will give you a stereo image only if spaced significantly apart when recording. But that will result in phase problems. I would not recommend this choice. I would suggest two good cardioid mics. Start with the capsules as close to coincident as possible, angled about 120º apart (60º on either side of the center axis) and see how that sounds. If the capsules are truly coincident, there will be no phasing problems. If you like, separate them by a few inches and see if that improves the image at all.

Just for kicks I did some math. If you are 50 yards away, with a point sound source 45º off axis, and the mics are spaced 5 feet apart (perpendicular to the axis), the two paths will be 151.78 feet and 148.24 feet. The difference, 3.54 feet, represents 1/2 wavelength at 155 Hz so you would theoretically have cancellation of any component (of the train sound) at 155 Hz. And you would have comb filtering at frequencies above that. Just looking at those numbers, I'd think the mono sum of those two channels would be less than optimum.

Of course a train with multiple engines has a very complex frequency signature, so I don't know how objectionable this would be in practice. It would be easy enough (aside from obtaining the train) to conduct a test, switching between mono and stereo when you play back the audio.

A small spacing between mics will give you a bit more stereo image, but at the expense of mono compatibility. Just be sure the mics whose capsule is located farthest to the left is aimed at the left side of the scene. Don't confuse yourself if you start with coincident and then pull the mics apart by a few inches. You do not want the capsule on the right aimed at the left side of the scene ... if you do that, the timing relationship and the level relationship will be fighting each other. For any given sound source, in any given location, the capsule that receives the loudest sound should also receive the sound (slightly) before the other capsule.

It would be interesting to hear some of your tests!
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Old November 30th, 2014, 06:41 PM   #10
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Re: more than one mic for the Z1U.

Hi Greg. I am not sure if the shotgun I have was mounted on the cam "upside down" but what sound I had surely seemed first to come from the right side then the left, on playback, when in fact the opposite should have been the case. That's why I'm looking to get 2 mics.I guess I could replay a clip when first I get it to see if the mic is orientated correctly, them mark it somehow to ensure i get it sorted out after that.

On another aspect of this idea, 5 ft is the max I could separate the mics, based on the length of the XLR extension cables I have.
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Old November 30th, 2014, 07:33 PM   #11
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Re: more than one mic for the Z1U.

Hi John,

Without knowing anything about your present shotgun, I really can't say anything concrete. But if the mic is a simple cylindrical design, mounted in a round holder, it could of course be upside down, causing the channels to be reversed.

How was your shotgun connected electrically? Two XLR connectors? Is there any marking, or any color coding, on the mic or on the connectors? Often (but not always) right channel is designated by the color red, which might just be a small red dot somewhere on the mic. Blue is sometimes used to designate left channel.

If the mic has red and blue dots, orient the mic so the red dot is on your right, when you are behind the camera in operating position, and facing toward the scene you're shooting. If one connector has a red marking, plug that into channel 2. Then set up the camera on a tripod, either in a very large room, or outdoors (so you will not be confused by sound reflections). Walk across the width of the scene, just five or six feet in front of the camera. When you play back the video, check audibly for correct channel assignment.

If the playback is correct, be sure the right side of the mic (when viewed from behind the camera) has some sort of red mark, and the left side has some sort of blue mark. Mark the connector in jack 1 as left (blue) and the one in jack 2 as right (red).

Of course if the channel assignment is reversed, then either flip the mic, or swap connectors, and then mark as above.

You again mention a maximum of five feet of separation. I will again advise against recording that way in the long run. Sure, you can do a test like that. But that much spacing will surely cause some phasing problems if the track is ever played back on a mono system. You will get a much safer recording using cardioid mics, either as a coincident pair or spaced just an inch or two; or with a single-point stereo mic.

You mention 1/4 inch stereo tape. I started back in that era, too. Back then people were much less cognizant of phase issues than they are today. Some people recorded with mics that were 15 or 20 feet apart. That can produce a recording that clearly has two different channels. But there were mono compatibility issues, and when played back in mono the recordings simetimes sounded dull, and the stereo "image" was probably not as realistic as recording with closer mic spacing or a coincident pair. So I urge you to move into the 21st century and go for close mic spacing as a starting point. (True, some very sophisticated mic arrays are possible, but as a basic starting point I really think close spacing is best.)
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Old November 30th, 2014, 08:27 PM   #12
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Re: more than one mic for the Z1U.

John,
Lots of excellent advice already here, and I'm not trying to question any of it, but are you sure you need stereo in the first place? I film lots of trains, especially the kind you describe, and I find myself following the locomotives as they pass, then panning back around and filming the rest, then following the end/ rear locomotives as they pass. In this scenario stereo is really not needed, as with the mic onboard you are capturing the audio from the same place your camera is pointing. On the other hand, if you were setting up mics in a fixed position to capture the whole train as it passes, then you would hear the train approach on one channel and leave on the other. But is that how you plan to capture your video also, i.e. camera fixed in one spot? If not then the stereo effect might in fact spoil your video.

Last edited by Scott Hiddelston; November 30th, 2014 at 08:29 PM. Reason: clarity
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Old December 1st, 2014, 01:33 AM   #13
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Re: more than one mic for the Z1U.

Here is something else to think about.... Do you have a fixed stereo mic and let the movement go through the mic angle or do you pan the stereo mic with the camera?

Let me explain.
Fixed mic thoughts....Think of looking through a house window with a fire truck passing, you can hear it (eg) off to the left it then passes through the view and continues toward the right. And if the 'window' is a TV screen it will convey movement.

Paned / moved stereo mic..... Think you're standing in the street hearing a fire truck off to the left, you turn your head (the sound is now centre) and as the truck passes you move your head to the right with the sound 'centre'.

Which is correct I don't know..... I have used both techniques in TV outside broadcasting productions.
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Old December 1st, 2014, 04:13 AM   #14
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Re: more than one mic for the Z1U.

Thanks, Fellas, for your input. The theory of audio was a bit above my head, but gleaned some knowledge.
Scott. You brought me back on track as that is exactly how I tape my trains. I think the fascination of stereo sound track came from a clip I made a while back. The loaded grain train was about 3/4 of the distance up the grade but I could not see the train. It had 2 DELs on it and the sound of them in 8th notch was something to hear. Due to the topography there, sound was echoing from the various ridges in the area. The strange part was the train was still out of sight to my left, yet awesome sound was coming from my right, echoed off those ridges. This plus the the beat frequency sound made some great audio.Yet that sound did not show up on the tape, damnit..
I think I just put the idea of stereo mice to bed.

Greg, there is only one XLR connecter on the mic. There are no marks, coloured or otherwise on the mic, anywhere. It's a total cleanskin.
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Old December 1st, 2014, 06:37 AM   #15
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Re: more than one mic for the Z1U.

John, if your mic has only one XLR connector, it is almost certainly a single-channel mono mic, rather than a single-point stereo mic. (There are a very few stereo mics that use a single 3-pin XLR connector; they are unbalanced and would not work correctly with this camera, and you would most likely get no audio whatsoever. We can safely say you don't have that type of mic.) So of course your present recordings are mono. Personally, I can't think of any situation, recording natural sound or music, where mono sounds as good as stereo. (Dialog should be mono, but trains are not dialog.) So I still think a pair of good mics would give you a much more convincing recording.

Your present "mystery mic" might be worth all of $20. and might have no useful low frequency response. So in addition to recording only mono, that might explain why you're not hearing the beats in your recording.

Even assuming you use a pair of good mics, as far as recording the low frequency beats, be sure you have the "MIC NR" deactivated, the MIC GAIN set to manual, the AGC deactivated, and the WIND filters turned off. All those settings could cause problems with the low frequency beats between the engines.

As far as audio perspective, I think it would be interesting to set up a stereo pair of cardioid mics on a separate mic stand, a few feet from the camera position, so that the mics don't move when you pan the camera. That should give you a good representation of what you hear when standing at the camera, yet the sound image will not move around if you do pan to follow the engines. And if you record with a coincident pair of mics (or spaced just one or two inches apart), you can always mix down to mono later with no ill effects.
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