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XY Technique - Neumann KM184

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XY Technique - Neumann KM184

Postby gandsound » Tue Sep 10, 2019 3:23 pm

It seems like there are some misconceptions about where exactly the diaphragm is on the Neumann KM184. I’ve seen some photos with the center of the XY right at the edge of the capsules and others with the center point somewhere in the middle of the capsules. Any thoughts?
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Re: XY Technique - Neumann KM184

Postby Hugh Robjohns » Tue Sep 10, 2019 8:19 pm

It's really not going to make any significant difference to the stereo imaging whether you align the front faces or the bottom of the capsule's rear slots, but the actual diaphragm is about 5 or 6mm behind the front face.

Personally, I rarely find crossed (XY) cardioids a useful stereo array, but if I do use it I usually set it up with the capsules overlapping by about 5cm to introduce a small amount of interchannel time difference which I think improves the imaging and sense of depth.

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Re: XY Technique - Neumann KM184

Postby ConcertinaChap » Wed Sep 11, 2019 11:00 am

Hugh Robjohns wrote:but if I do use it I usually set it up with the capsules overlapping by about 5cm to introduce a small amount of interchannel time difference which I think improves the imaging and sense of depth.

I've never heard of that technique (nothing new there, then :) ). I'll give it a try sometime.

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Re: XY Technique - Neumann KM184

Postby Arpangel » Wed Sep 11, 2019 11:13 am

Hugh Robjohns wrote:It's really not going to make any significant difference to the stereo imaging whether you align the front faces or the bottom of the capsule's rear slots, but the actual diaphragm is about 5 or 6mm behind the front face.

Personally, I rarely find crossed (XY) cardioids a useful stereo array, but if I do use it I usually set it up with the capsules overlapping by about 5cm to introduce a small amount of interchannel time difference which I think improves the imaging and sense of depth.

H

Hugh, can I just chime in here and ask if the OP's question applies to an M&S pair? I always set my cardioid mic about half an inch back from the front of the figure 8, as that's how I've always seen it done, with my MKH's anyway, any comments on this?
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Re: XY Technique - Neumann KM184

Postby Hugh Robjohns » Wed Sep 11, 2019 11:16 am

It apparently comes from the practical wisdom of Tony Faulkner, and was reported upon by the late, great Michael Gerzon in Studio Sound magazine in 1986 -- which is where I learned about it and have used it ever since:

https://www.americanradiohistory.com/Ar ... 986-07.pdf

(Page 122 onwards)
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Re: XY Technique - Neumann KM184

Postby Wonks » Wed Sep 11, 2019 11:26 am

(That's page 132 of the pdf document, but printed page 122).
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Re: XY Technique - Neumann KM184

Postby Arpangel » Wed Sep 11, 2019 11:37 am

Hugh Robjohns wrote:It apparently comes from the practical wisdom of Tony Faulkner, and was reported upon by the late, great Michael Gerzon in Studio Sound magazine in 1986 -- which is where I learned about it and have used it ever since:

https://www.americanradiohistory.com/Ar ... 986-07.pdf

(Page 122 onwards)

I think this subject could be another thread, but regarding an M&S pair, moving the mid capsule back further than fig 8 could be a bit confusing, as the side mic is picking up sound mainly from room reflections and not direct, like the mid mic, so they don't rely on sounds reaching them at the same time anyway, but could it, like your XY pair, in any way alter or improve the stereo image?
Thanks for that link, extremely interesting, I have others from that site as well, a great resource.
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Re: XY Technique - Neumann KM184

Postby Hugh Robjohns » Wed Sep 11, 2019 11:42 am

Arpangel wrote:Hugh, can I just chime in here and ask if the OP's question applies to an M&S pair?

He specifically mentions XY cardioids, so I don't think so, no!

I always set my cardioid mic about half an inch back from the front of the figure 8, as that's how I've always seen it done, with my MKH's anyway, any comments on this?

Obviously, this very much depends on the specific mics you're using, and the physical locations of the diaphragms in each mic.

With the Sennheiser MKH mics, the diaphragm in the MKH30 fig-8 is in sideways-on in the middle of the grille, so to align an MKH 40 or 50 (cardioid or hypercardioid) with that, the front of the grill would indeed be about 20-30mm back from the front of the MKH30, as shown below.

Image

... But this wouldn't be the case if you were using a ribbon fig-8, or even a dual-diaphragm multipattern LDC, or example...

Mid-Side is a coincident technique, so the diaphragms of the two mics should, theoretically, be aligned vertically, one directly above the other. However, that's not always practical so if there needs to be an offset to make mounting the mics easier, the stereo imaging is more stable if the diaphragm of the Side mic is fractionally behind the diaphragm of the Mid mic. So that the Side mic captures sounds fractions of a millisecond after the Mid mic.

If the Side mic is too far forward from the Mid mic, it captures sound first and so the leading transients in the stereo image start off 'out-of-phase' which creates the impression of an unstable image.

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Re: XY Technique - Neumann KM184

Postby Hugh Robjohns » Wed Sep 11, 2019 11:42 am

Wonks wrote:(That's page 132 of the pdf document, but printed page 122).

Thanks Wonks -- I was quoting from the paper mag I was reading in my library... :lol:
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Re: XY Technique - Neumann KM184

Postby Hugh Robjohns » Wed Sep 11, 2019 11:50 am

Arpangel wrote:...regarding an M&S pair, moving the mid capsule back further than fig 8 could be a bit confusing...

Absolutely! As I was saying...

...the side mic is picking up sound mainly from room reflections and not direct...

Not True! Any sound source which is anywhere off the centre-line will be picked up directly by both mics. This is an essential requirement to create the stereo imaging! The Side mic picks up a lot of room reflections as well, of course, but it's there primarily to capture direct sound from anything that's not directly front and centre!

...they don't rely on sounds reaching them at the same time anyway

Sorry... that's completely wrong. The stereo imaging results from the mathematical addition of the outputs from both mics, both of which capture the direct sound at exactly the same time, the amplitude (and polarity) of their contributions being entirely dependent on the angle of sound incidence and the polar patterns of the two mics.

Thanks for that link, extremely interesting, I have others from that site as well, a great resource.

There are so many fantastically interesting articles throughout the 1970s and early 1980s, especially from Gerzon about stereo, binaural, and ambisonics... Really well-written technical articles. It was a very fertile time in the audio/music production industry, and the education level was still relatively high... :shock:

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Re: XY Technique - Neumann KM184

Postby Arpangel » Wed Sep 11, 2019 12:17 pm

That's how I always set-up my M&S pair, with the mid mic about 20mm back. I do it because that's how I remember Mike Skeet doing it, but as you can see, there are huge gaps in my knowledge!
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Re: XY Technique - Neumann KM184

Postby Tomás Mulcahy » Wed Sep 11, 2019 6:44 pm

Hugh Robjohns wrote:https://www.americanradiohistory.com/Archive-Studio-Sound/80s/Studio-Sound-1986-07.pdf
Oh wow. What a resource. Thanks!

Great explanation of stereo shuffling. I finally get it. I'm off now to mangle everything in a DAW :D
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Re: XY Technique - Neumann KM184

Postby The Elf » Wed Sep 11, 2019 9:38 pm

And I'll be reading that interview with Peter Gabriel! ;)
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Re: XY Technique - Neumann KM184

Postby Mike Stranks » Thu Sep 12, 2019 9:50 am

... and a quick :clap: and :thumbup: to Mr Faulkner and all his works...

... second only to the esteemed Dr Robjohns in my estimation of people who know good stuff about how to record on location... :)
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Re: XY Technique - Neumann KM184

Postby Aural Reject » Thu Sep 12, 2019 9:52 am

I'll be digesting some of the serious stuff later....but the adverts.... :D :beamup:
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