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Double M/S with Neumann rsm 191 + km140


knod

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Hi, this is my first post in this forum :) 

I'm interested in recording some surround ambiences and I was researching the techniques, that I can record with my equipment.

Has anyone any experience rigging rsm191 and neumann km140 for a double m/s surround recording. Are there any holes or phase problems?

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It's difficult to tell, I'm afraid: will you be trying to use the Schoeps DMS plug-in to get your results? I'm not sure how it will behave with that combination of microphones. Apart from differences in frequency response, it seems that the RSM191 has a quoted sensitivity 23mV/pa compared to the KM140 which is 15mV/pa, which is quite big difference, so you'll probably have to ramp up the level a bit. You'll also need to locate the position of the bi-directional element of the RSM and get the KM140 capsule as close to it as possible. I assume you're using a remote cable with the KM140, so that it's just the active capsule attached to the RSM?

John

 

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hi Knod,

I particularly love the stereo image of the 191, for choirs, solo voices, strings, small orchestras and any situation with acoustic signals arriving from various spots. It is also very good for ambience recording. Not so much for piano though.

I also did use a double MS array with the KM140 on some occasions. I must admit I never had a chance to listen to the decoded signals in a real surround studio situation but I assume it should work out well, especially if you manage to adust the gain of the KM 140 properly after some testing.  The rig itself is easy to mount, provided you have the thin active cable for the KM 140. You can see the membranes of the side mics of the 191 and should get the 140's membrane to the same plane.

The rear MS array will behave differently from the front part, because the 191 uses a interference tube ("short shotgun") as a mid.

Afaik the side mics of the 191 is not a figure of eight but is formed of two indepent cardiod capsules. It's signals are joint inside the matrix to behave like a single figure of eight and you can use that resulting signal for double MS also. The 191 side mics offer a dramatically attenuated low end compared to the mid capsule, but in conjunction with MS decoding the resulting signal provides an exceptionally vivid spatial image with all the details clearly to spot.

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Hey, thanks for the replies. 

I also love the stereo image of the rsm, Axel and I'm in love with the detail of this mic : )

 

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I'm afraid: will you be trying to use the Schoeps DMS plug-in to get your results?

My first thought is to use the Schoeps plugin but I want to try to emulate the plugin with a simple 5.1 DAW mixer setup. Maybe I am missing some math here, but I think I can solve it with simple tools!

I'm thinking that the sensitivity missmatch will lead to more noise to the rear, but with good-noiseless field preamps I think this wouldn't be much of a problem (to match the sensitivity with gian boost on the km). I still need to buy one good field recorder! 

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The rig itself is easy to mount, provided you have the thin active cable for the KM 140. You can see the membranes of the side mics of the 191 and should get the 140's membrane to the same plane.

Indeed I can see the 3 capsules of the rsm and it's easy to bring the ak40 capsule in the same Y and Z point of the axis.

I don't own an LC 3 cable,  and as I wait to find one on eBay (I find it somewhat expensive to buy it new) I was planning to test this rig with the body on top of the grilles of the rsm, plugged with a thin right angle xlr kortwich style. All these inside a rycote kit #3. 

Will the km100 body refract the sound? 

I Also find more stable to tie the km140 on 2 points on the rsm body than in one. Is  there any clamp in the market that I can use like these? http://www.bhphotovideo.com/c/product/770035-REG/Rycote_48488_Back_to_Back_Clips_for_Microphones.html I think those can't fit on the rsm fat body!

 

 

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23 minutes ago, knod said:

My first thought is to use the Schoeps plugin but I want to try to emulate the plugin with a simple 5.1 DAW mixer setup. Maybe I am missing some math here, but I think I can solve it with simple tools.

What you'll end up with, assuming you're using the separate mid and side outputs from the 191 is three tracks: one forward facing mid mic, one rear facing mid mic and one side mic. I think you'll need to decode each M/S pair separately and then reverse the direction of the rear-facing pair and send it to the rear channels. I guess the centre channel is just the mid signal from the RSM panned centre and the .1, if you're interested in it (and unless you're recording earthquakes or thunder or anything else that produces extreme LF, you can leave it empty) you could LPF a mono mix of all signals and send that to the .1 output.

Or something like that. Make a test recording and see what you get. The Schoeps plug-in is free, by the way...

Let us know what happens.

John

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 I think you'll need to decode each M/S pair separately and then reverse the direction of the rear-facing pair and send it to the rear channels.

That's my initial thought about it! I'm not sure about the double usage and the sum of the S signal. Maybe it will need 3dB attenuation on each side (front-rear) to reach the total 6 dB gain that a sum will result. I will A B with the plugin of course anyway.

Hopefully this weekend I'll post some thoughts on the results, or the results themselves 

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