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Author Topic: M/S Question  (Read 7583 times)

Strummer

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M/S Question
« on: May 24, 2009, 10:26:59 am »

Sorry if this is a stupid question. I've searched Google and PSW with no luck.

I've been working with m/s for acoustic guitar, recording the figure 8 to a track, the mid to a track, then adding and flipping phase on the added side track. I've found placement of the mid mic is critical, or it winds up partially canceling one of the sides and messing up the stereo image. I'd like to be able to hear what I'm doing while I set up and track rather than experiment by recording, then adding, flipping, playing back etc.

I have an RNP which the manual says I can use a balanced output and the insert as unbalanced, so this means I can track that channel into two panned tracks for the sides, one flipped on the mixer, correct?

My question is, the send on the insert is tip, return is ring, and sleeve is 0. Do I need to lift the sleeve on both ends of a TRS cable, or can I just use a TS? Will it damage anything if the return and sleeve are shorted on either end? Will either of these methods even work?

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marcel

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Re: M/S Question
« Reply #1 on: May 24, 2009, 02:01:18 pm »

Are you simply asking how to do a hardware (analogue) mult of the signal?  If you have at least 1 available bus or aux and 1 more available channel on your mixer, you can route the incoming S signal to a channel, send or assign to the aux or bus, and then return the output of your aux or bus to another channel's line input.

You could do this with a send in the DAW as well, basically in the same fashion.

I hope this helps with what you're asking.
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Best, Marcel

mr jason

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Re: M/S Question
« Reply #2 on: May 24, 2009, 03:13:17 pm »

Or, use the Direct Output, if you have them on your mixer channels, and flip the phase, or use an inline phase/polarity inverter thingy. No need to use up an Aux send then.

Strummer

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Re: M/S Question
« Reply #3 on: May 24, 2009, 05:24:06 pm »

I appreciate the replies, but I wasn't complete in my question.

My RNP goes directly into my converter box, I don't have a hardware mixer. I can do routing in the DAW, it's as simple as routing the input into two mono channels and flipping the phase of one, while panning them appropriately.

I was just wondering about the insert of the RNP into a second input to the converter, here's the text from the manual:

"Each channel on the RNP8380 has an unbalanced send/receive jack that allow you to connect an RNC1773 using a single Tip-Ring-Sleeve (TRS) cable (per channel). With proper cabling, you could also use this feature to balance any other unbalanced piece of gear. In addition, with the right external configuration, the RNP can provide a separate +22dBu unbalanced output and a +28dBu balanced output simultaneously to allow nifty things like separate M/S decoding while tracking the M/S signal without decoding."

I'm trying to understand what it means by "right external configuration", since it mentions the insert as a starting point, or am I reading this wrong?



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0dbfs

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Re: M/S Question
« Reply #4 on: May 24, 2009, 05:53:24 pm »

If the unit has a button that turn the insert "on" that usually puts the signal at the 'insert return" into the signal path. The insert-send should always have the preamp signal on it.

If this is true, you could use a pin-three-hot-TRS (inverted polarity) to feed one side (the inverted-side) of the "side" to your converter and the insert send to feed the other "side" to the other converter.

From your manual reference I believe that there would be a level mismatch between the two sides though. You could adjust that in the DAW.

You could also make a Y cable for the balanced out of the RNP which has one of the legs pins 2/3 swapped and feed each to a separate DAW input along with the mid mic. That way you record three tracks side-, side+, and mid... And the levels for the side's would be the same.

Cheers,
j
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Jonathan Burtner
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Hallams

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Re: M/S Question
« Reply #5 on: May 24, 2009, 11:40:31 pm »

From your description, it sounds like something is NQR with your m/s setup. You can set up the m/s in your DAW for monitoring. I use logic and simply pan the original fig 8 to the left,then send a post fade bus to an aux, pan the aux (or bus) right,open up the gain plug and invert the phase. I set the level of this fader to unity or "0". Then as you adjust the level of the original fig 8 track the amount of side info is adjusted in relation to your mid signal which is of course paned center.
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Chris Hallam.
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Strummer

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Re: M/S Question
« Reply #6 on: May 25, 2009, 09:27:17 am »

Thanks to all of you for the info and suggestions.

I found a block diagram of the RNP and it's clear to me now how the insert works. The send and return are behind everything in the pre except the phase switch and XLR balanced out. The send is always live, the return is shorted to the send until a plug is inserted.

It appears much simpler to route and flip in the DAW, and I don't see any advantage to making a special cable to use up another converter input.

I'm going to work more on the mid mic placement, distance to the instrument, etc and see what I can figure out. I've done m/s four times, twice it was great, twice I had the mid mic phase issue, and I thought the mic was in the same relative place to the sides mic, but placement relative to the guitar could have been different.

Thanks again all of you.

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Fibes

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Re: M/S Question
« Reply #7 on: May 26, 2009, 05:17:05 pm »

In true M/S if your S gets closer than say 10db down from the M you will hear a shift to the + side.
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Fibes
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Strummer

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Re: M/S Question
« Reply #8 on: May 26, 2009, 05:29:12 pm »

Fibes wrote on Tue, 26 May 2009 17:17

In true M/S if your S gets closer than say 10db down from the M you will hear a shift to the + side.


When tracked or on playback with faders? Or both?

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Harland

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Re: M/S Question
« Reply #9 on: May 26, 2009, 07:21:36 pm »

Fibes wrote on Tue, 26 May 2009 17:17

In true M/S if your S gets closer than say 10db down from the M you will hear a shift to the + side.


Can you explain that more, I don't get what you mean.
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Fibes

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Re: M/S Question
« Reply #10 on: May 27, 2009, 09:28:30 am »

Harland wrote on Tue, 26 May 2009 19:21

Fibes wrote on Tue, 26 May 2009 17:17

In true M/S if your S gets closer than say 10db down from the M you will hear a shift to the + side.


Can you explain that more, I don't get what you mean.


The S signal can't be as prominant, it's filler if you will... Even properly tracked, decoded and inplemented M/S is going to lean toward the positive polartity side of the S channels at some relative amplitude. I find that if the s channels are more than 10 decibels down from the M channel you are usually good. The closer you get to equal amplitude, the more likely a shift to the positive S side will occur.

Since the advent of the DAW copying and flipping one S channel works better than most old matrixes but i still prefer to track into the DAW actually listening to what is going on, so i split and flip on the way in.
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Fibes
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Strummer

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Re: M/S Question
« Reply #11 on: May 27, 2009, 09:39:03 am »

So you set record levels equal between mid and side, and lower the faders of the sides to setup and monitor?



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Harland

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Re: M/S Question
« Reply #12 on: May 27, 2009, 01:56:05 pm »

Fibes wrote on Wed, 27 May 2009 09:28

Harland wrote on Tue, 26 May 2009 19:21

Fibes wrote on Tue, 26 May 2009 17:17

In true M/S if your S gets closer than say 10db down from the M you will hear a shift to the + side.


Can you explain that more, I don't get what you mean.


The S signal can't be as prominant, it's filler if you will... Even properly tracked, decoded and inplemented M/S is going to lean toward the positive polartity side of the S channels at some relative amplitude. I find that if the s channels are more than 10 decibels down from the M channel you are usually good. The closer you get to equal amplitude, the more likely a shift to the positive S side will occur.

Since the advent of the DAW copying and flipping one S channel works better than most old matrixes but i still prefer to track into the DAW actually listening to what is going on, so i split and flip on the way in.



What is "a shift to the positive S side"? And why does this occur?
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Fibes

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Re: M/S Question
« Reply #13 on: June 02, 2009, 09:34:04 pm »

Harland wrote on Wed, 27 May 2009 13:56

Fibes wrote on Wed, 27 May 2009 09:28

Harland wrote on Tue, 26 May 2009 19:21

Fibes wrote on Tue, 26 May 2009 17:17

In true M/S if your S gets closer than say 10db down from the M you will hear a shift to the + side.


Can you explain that more, I don't get what you mean.


The S signal can't be as prominant, it's filler if you will... Even properly tracked, decoded and inplemented M/S is going to lean toward the positive polartity side of the S channels at some relative amplitude. I find that if the s channels are more than 10 decibels down from the M channel you are usually good. The closer you get to equal amplitude, the more likely a shift to the positive S side will occur.

Since the advent of the DAW copying and flipping one S channel works better than most old matrixes but i still prefer to track into the DAW actually listening to what is going on, so i split and flip on the way in.



What is "a shift to the positive S side"? And why does this occur?



The positive S side will start to sound louder because it is interacting with the positive M. I'm not the scientific type but on many nearfiled (as opposed to diffuse field) M/S recordings the S+ still adds to the positive M and the image will begin to shift because the + is adding and the - is beginning to take away some. The sides typically won't effect the M in this way until they are closer than 10db down from the M. More than 10db down always makes my head hurt anyways. If you want tat much hard side action M/S is probably the wrong choice.


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Fibes
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jimmyjazz

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Re: M/S Question
« Reply #14 on: July 15, 2009, 10:48:51 pm »

Strummer wrote on Sun, 24 May 2009 09:26

I've been working with m/s for acoustic guitar, recording the figure 8 to a track, the mid to a track, then adding and flipping phase on the added side track.


Just to be sure . . . your 3rd track is a phase-inverted copy of your figure-8 track, right?  Your use of the word "adding" makes me wonder if you are somehow combining the original figure-8 and mid tracks when you generate the 3rd track to be phase inverted, which would result in all kinds of suck.  To clarify, the correct way to do M/S is (using your track layout):

Track 1:  figure-8
Track 2:  mid
Track 3:  figure-8 (phase-inverted)

I have never found M/S to be terribly "sensitive" to the positioning of the mid mic, other than the need to get both capsules (mid & figure-8) as close as possible.
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