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MKH 30 / 30 MS imaging Condenser Microphones
Old 22nd May 2016
  #1
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MKH 30 / 30 MS imaging

Hello all, just wanted to raise some issues I am having with MKH 30/30 MS imaging.

So, I have been following as much as I can read about Rolo 46's MKH 30/30 MS rig, and picked up a second MKH30 myself very recently, expanding into being able to employ a Blumlein pair or 30/30 MS array for certain situations that may require something more 'open' and/or where a bidirectional pickup may be desirable.

Before I describe the effects of what I am hearing, let me describe the tech specs:

Mounted vertically, aligned shoulder to shoulder, like Rolo 46's:
MKH30 M (+ facing forward)
MKH30 S (+ facing left of forward)

Sound devices 702 with MS decode in the box, M 55% : S 45% = L/R. The inputs are in the correct sockets for decoding, everything checked (I am using MS extensively, so the settings are very familiar)

But am I having issues? It seems my MKH 30/30 MS array is giving a pleasant stereo image, smooth and full field, but L/R localisation is very confusing. sounds such as balance check with a passing voice or claps from left or right seem surprisingly and prominently more centered than they should be. I hear each sound spread across both channels somehow, in much the same way that a stereo 'spatialiser' might behave. The image is pleasing but not accurately depicting the positions of sounds in the field. It seems like a very different kind of beast so far. Could I have the S's +/- facing the wrong direction for the decode? Are the nulls at 10 and 2, 4 and 8 o'clock worth more consideration? What else am I failing to consider here?

Any suggestions very much appreciated!

Thanks

adam
Old 22nd May 2016
  #2
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Quote:
Originally Posted by AdamAsnan View Post
What else am I failing to consider here?

Any suggestions very much appreciated!
Assuming that you decoded correctly, check also that your playback speakers or headphones are not wrongly wired with one channel having inverted polarity. That can cause woozy imaging.
Old 23rd May 2016
  #3
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Quote:
Originally Posted by Tom McC View Post
Assuming that you decoded correctly, check also that your playback speakers or headphones are not wrongly wired with one channel having inverted polarity. That can cause woozy imaging.
Yes, all checked, all in order.

I'm just thinking, is the the nature of this array utilised more to capture a diffuse (stereo) field at the compromise of distinct and accurate positioning? Or should I have both equally?

I will try to record discreet M/S and decode in post later, and see how this sounds
Old 23rd May 2016
  #4
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Quote:
Originally Posted by AdamAsnan View Post
Yes, all checked, all in order.

I'm just thinking, is the the nature of this array utilised more to capture a diffuse (stereo) field at the compromise of distinct and accurate positioning? Or should I have both equally?

I will try to record discreet M/S and decode in post later, and see how this sounds

The Problem you might be getting is that the reverse of the MS set-up using an MKH 30 will reverse the image and might be lending something (or not) too the image. Personally with MS I tend to use either a Cardioid or an Omni as they work well for me. Just a thought.
Old 23rd May 2016
  #5
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Have you linked the mic amps in the menu and selected MS decode ?
55/45 will give more mono and linking is essential for proper gain control, which should be 50/50 for correct spatialisation imho
The positive side of M (the side with gain and LF switches) must face fore and aft and the side S positive must face LH
They should be shoulder to shoulder, but at right angles to each othe ,polarity is essential
Check your cans monitor on the 702 ,you need A,B out, the recorder menu can give many variations, which can confuse in the dark of performance
Proper MKH30/30 MS will easily resolve a detailed soundstage and cohesive image ,including the inverted rear field remember.
Roger
Old 23rd May 2016
  #6
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Quote:
Originally Posted by Rolo 46 View Post
Have you linked the mic amps in the menu and selected MS decode ?
55/45 will give more mono and linking is essential for proper gain control, which should be 50/50 for correct spatialisation imho
The positive side of M (the side with gain and LF switches) must face fore and aft and the side S positive must face LH
They should be shoulder to shoulder, but at right angles to each othe ,polarity is essential
Check your cans monitor on the 702 ,you need A,B out, the recorder menu can give many variations, which can confuse in the dark of performance
Proper MKH30/30 MS will easily resolve a detailed soundstage and cohesive image ,including the inverted rear field remember.
Roger
All checked, all in order; pair are aligned correctly, decode in the box outputs L/R to cans and track (monitoring on device and loudspeakers in studio are consistent). Was firstly set to 50/50 as the two mics are matched, then pushed a little more forward to see if this made any substantial difference. I am noticing after listening back again, that there are 'pockets' of L/R localisation at around where I expect the nulls to be. anything hard left or right seems to be in both channels, or meandering softly between. Just to say also, that these tests were made outside in a open space, so reflections are not a factor.. I am really confused.

Also starting to wonder if this is a case of proximity? Would a close-up left or right be somehow confused in the imaging because of likelyhood of a kind of 'bleed' over to the reverse of the capsule? Distant sounds tend to have some truer localisation.. Height can be a factor here too?
Old 23rd May 2016
  #7
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Send us the file and pix of the array please
Roger
Old 23rd May 2016
  #8
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Quote:
Originally Posted by AdamAsnan View Post
I am noticing after listening back again, that there are 'pockets' of L/R localisation at around where I expect the nulls to be. anything hard left or right seems to be in both channels, or meandering softly between. Just to say also, that these tests were made outside in a open space, so reflections are not a factor.. I am really confused.
Assuming that you hadn't inadvertently done a double decode in the SD702 (re-check the warning in their manual), a remaining possibility for the poor experienced imaging could be an inappropriate seating arrangement of the performers on the podium:

Did you perchance have the performers located too widely across the stage - or have your mic array too close to the podium? A consequence can be that some unlucky, outermost sound sources then fall in the so-called ambiophonic region of the mic array. A single sound source emanating from the ambiophonic region will generate signals of conflicting polarity in the two capsules of the coincident array. This boils down to one playback loudspeaker cone pumping forward while its other channel sibling sucks backwards...with attendant complications to the imaging integrity.

To some extent, the 'out of phase' signals do yield a pleasant experience with enhanced image width, but the excitement often dampens on realizing that the image location is actually pretty fuzzy. And it can indeed even collapse into the centre. Moreover, different people can experience a different psychoacoustic result...some even mild nausea :-)

A fig8/fig8 MS array of 55/45 M:S equates mathematically to a 'narrow Blumlein pair' with the capsules splayed at included angle 77°, instead of the normal Blumlein 90°. The ambiophonic regions are thus those two sectors of angular width 77 degrees due hard left- and right of the array's main axis.

Perhaps you can re-visit any notes you made of the concert seating geometry?

FWIW, in an earlier GS thread I posted a pdf illustrating how the ambiophonic region dimension in MS varies with M type and weighting. But don't panic...an ambiophonic region ain't as dangerous as a Bermuda triangle. :-)
Old 24th May 2016
  #9
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His tests were made outside Tom..
I think he should try his 30s in crossed pair Blumlein and compare, sending us both files and pix for pathology on the mortuary slab that is GS!
Old 24th May 2016
  #10
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Thread Starter
Thanks gentlemen, I will make a new recording today comparing 30/30 MS (and same settings with an 8040 M) and Blumlein, calling the the angles. I do not have adequate wind shielding for a Bl. pair yet, so hope this works out.
Old 24th May 2016
  #11
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Quote:
Originally Posted by Rolo 46 View Post
His tests were made outside Tom..
Oops, I overlooked that. But the general principle remains pertinent nonetheless. Sounds arriving at the array from certain directions will inevitably image in a strange fashion.
"Ah canna change the Laws o' Physics, captain!"
Old 24th May 2016
  #12
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I used to mount Blumlein Crossed 30s in a Sennheiser 815 windscreen used vertically
Worked well
Plenty used on the Bay and BB List
Old 24th May 2016
  #13
Gear Nut
 

Thread Starter
Audio! Pictures!

Both M/S at 50/50% (= L/R), Blumlein linked L/R

In the process of making these tests, I am starting to get my ear around the kind of image it creates. I wish I let it roll for some longer to hear the diffuse/distant soundstage better.. anyway. Please tell me if this sounds about normal to you.

I know the Blumlein is mounted disgracefully, but it's best I could do in the moment, please bear in mind this is a pretty quick and general test for imaging.

Thanks!
Attached Thumbnails
MKH 30 / 30 MS imaging-dscf5137.jpg   MKH 30 / 30 MS imaging-dscf5138.jpg   MKH 30 / 30 MS imaging-dscf5139.jpg   MKH 30 / 30 MS imaging-dscf5143.jpg  
Attached Files

30-30 MS decoded (320).mp3 (3.94 MB, 1878 views)

30-30 Blumlein (320).mp3 (2.70 MB, 1821 views)

8040-30 MS decoded (320).mp3 (2.69 MB, 1849 views)

Old 24th May 2016
  #14
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Imageing wrong on MS and Blumlein pairs
Check your mic polarities again
Roger
Old 24th May 2016
  #15
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Thread Starter
Quote:
Originally Posted by Rolo 46 View Post
Imageing wrong on MS and Blumlein pairs
Check your mic polarities again
Roger
OK, so this is a step forward; can you see the pictures? + is fore on M, + is LH on S. Decoding in the box and discreet MS give me the same results.

Bl. pair admittedly requires more research/practice, although accordingly to everything I've read, +'s outward of each other at 90 degrees.

Just bypassed the connbox and same results..

Last edited by AdamAsnan; 24th May 2016 at 05:50 PM..
Old 26th May 2016
  #16
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Its the level variations that are worrying, and also the SQ achieved
I mark the M front + phase of my 30 with a red dot and the S front + phase with a green dot for identification
Red ship leaves port, ie Red is left
Try and perfect the mounts and with windscreening for the exterior, record them flat, the 30s should have more punch than your samples, coincidence is important
When you are voice testing, address the mic from that quadrant, this may be giving the level fluctuations similar to off mic
Check the two 30s for phase, just in case of a fault,fade two up and press mono, to check uniformity
Dont rush it.
Roger
Old 26th May 2016
  #17
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Roland's Avatar
Quote:
Originally Posted by AdamAsnan View Post
OK, so this is a step forward; can you see the pictures? + is fore on M, + is LH on S. Decoding in the box and discreet MS give me the same results.

Bl. pair admittedly requires more research/practice, although accordingly to everything I've read, +'s outward of each other at 90 degrees.

Just bypassed the connbox and same results..
I agree totally with Roger, this is definitely wrong. The sound level on the Left is severely quieter than the right and when you get to the 3-4 o'clock position it is out of phase. I can't look at it on a scope as this is just my junk office computer that I have on the internet.

I suspect, one of three things. Either you have a microphone lead wired reverse. One of the microphones has been inadvertently (or deliberately for some strange reason) wired reverse polarity, or something is physically wrong with your 702, bad contact, switch reversed, component down. If the same thing is happening with your 8040 then it's not the mic, either a lead or the 702. I see from your picture that you look like you have a "custom" loom wired to your MS set-up, I would carefully check that you haven't mistakenly wired one hot - cold, by accident, easily done.
Old 26th May 2016
  #18
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Roland's Avatar
Should have listened to the third file as well. This sounds generally correct, so it means the wire and the 702 are correctly functioning. You are doing something wrong with your MKH30 or you have a fault with it.
Old 26th May 2016
  #19
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A couple of other points having looked at the pictures more closely. The mid mic (I'm taking it that is the one furthest away from the stand), is reversed, you can see this from the picture, also it is usually the form to mount one capsule above the other to avoid shading, (this would be most noticeable at HF, exactly where you don't want it). Your samples are not the best example of a test as the birds appear to be mostly on the right and I would have looked for ambient sounds to come mostly from the front for the purpose of your test to remove distractions, perhaps do it inside? Good luck.
Old 26th May 2016
  #20
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Thread Starter
OK, thanks. I am at a loss for an explanation. I am quite certain I am not mis-orientating the 30s, so perhaps it's a phase issue with one mic, perhaps the pin outs. Could it be a mod?

But, if so, wouldn't a rotation of the mic to it's polar opposite resolve the image?

I will try to mono phase cancel test now

Just to note also, that imaging with 8040/30 with both 30s is consistent.
Old 26th May 2016
  #21
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Thread Starter
Quote:
Originally Posted by Rolo 46 View Post
Its the level variations that are worrying..
Check the two 30s for phase, just in case of a fault,fade two up and press mono, to check uniformity
Roger
So, no cancellation to my ear. I can check the phase individually with an analyser too, a while.

I did notice that one of them is outputting a approx 3 db less than the other. But this may not effect the image in MS?
Old 26th May 2016
  #22
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Roland's Avatar
Quote:
Originally Posted by AdamAsnan View Post
OK, thanks. I am at a loss for an explanation. I am quite certain I am not mis-orientating the 30s, so perhaps it's a phase issue with one mic, perhaps the pin outs. Could it be a mod?
Not from the pictures you have supplied.

I'm assuming the first two pics are the MS? In that case you have the R side (the side with the low frequency filter and pad, not the Sennheiser logo as it should be) facing forward and the L side facing the L in the MS.

Quote:
But, if so, wouldn't a rotation of the mic to it's polar opposite resolve the image?
Yes, but as I said the mic is reversed to start with

Quote:
I will try to mono phase cancel test now
If you do that, the side mic should totally cancel just leaving the mid, however, this will be facing backwards.

Quote:
Just to note also, that imaging with 8040/30 with both 30s is consistent.
Not in the audio samples you posted. The 30/8040 pair is working correctly, though I am not sure if the balance is as good as it could be.

If the last pair is the Blumlein, the microphone not being perpendicular to the axis of the other mic will have a severe effect as the nulls on fig 8 mics is severe, one of the reasons that they can make good spot microphones.

Good luck!

As a post note, I made one error, in that the Mid mic is correct, it's the side mic that is reversed. The trouble with Blumlein is that you get image creep for anything that goes outside of the 90 deg pattern of the microphone front angle, causing it to sound odd. One of the main reasons that either a Cardioid or Omni Mid microphone generally work better in MS too.

Last edited by Roland; 26th May 2016 at 01:23 PM.. Reason: Accuracy.
Old 26th May 2016
  #23
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Thread Starter
OK.. to quote Rolo 46:

Quote:
Originally Posted by Rolo 46 View Post
The positive side of M (the side with gain and LF switches) must face fore and aft and the side S positive must face LH
They should be shoulder to shoulder, but at right angles to each other
Is this not exactly what I have done?

I should say the the ground was uneven and so I couldn't quite get exactly 1 metre away from the mic at all times. The gong was also struck with casual intensity. I am most concerned with reconciling the image first. Should I be hearing the rear left quadrant in the right side and vise versa, or is this the primary issue? I am going to conduct some more tests by re-wiring the +/- in the XLR
Old 26th May 2016
  #24
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Thread Starter
Quote:
Originally Posted by AdamAsnan View Post
re-wiring the +/- in the XLR
wait.. this is just as good as reversing +/- direction of the mic itself..
Old 26th May 2016
  #25
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Roland's Avatar
Quote:
Originally Posted by AdamAsnan View Post
wait.. this is just as good as reversing +/- direction of the mic itself..
In your first two pics the side mic is facing right, not left so you are summing out of phase. That is why your image is reversed. Also, if I remember correctly, using two fig 8 mic's at the same level is mathematically the same as blumlien, hence the image creep and the reversal on the rear. Decent ms is always better with an omni or cardioid mid.
Old 26th May 2016
  #26
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Can I please request the briefest of hijacks to ask a simple MS question ?

If I'm standing behind a low stand mounted sideways-aimed (but vertically oriented) Neumann U89 LD mic, as if it were a camera (which I'm intending to be the Side mic),with a cardioid mid mic mounted atop of it facing straight ahead.... which direction should the + (or front) side of the Neumann be facing...left or right ?

Sorry about this brief diversion...back to the matter at hand with MKH30's
Old 26th May 2016
  #27
left. but if you get it wrong, it's easy to fix in post!

Quote:
Originally Posted by studer58 View Post
Can I please request the briefest of hijacks to ask a simple MS question ?

If I'm standing behind a low stand mounted sideways-aimed (but vertically oriented) Neumann U89 LD mic, as if it were a camera (which I'm intending to be the Side mic),with a cardioid mid mic mounted atop of it facing straight ahead.... which direction should the + (or front) side of the Neumann be facing...left or right ?

Sorry about this brief diversion...back to the matter at hand with MKH30's
Old 26th May 2016
  #28
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Quote:
Originally Posted by avillalta View Post
left. but if you get it wrong, it's easy to fix in post!
Thank you ! Now....back to normal transmission
Old 26th May 2016
  #29
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Exclamation

Quote:
Originally Posted by Roland View Post
Decent ms is always better with an omni or cardioid mid.
The attached is a screen grab from Dooley and Streicher's MS paper (downloadable from the AEA website) showing what happens with MS at various side levels with an omni, cardioid and fig.8 mid.

.
Attached Thumbnails
MKH 30 / 30 MS imaging-screen-shot-2016-05-26-20.51.19.jpg  
Old 26th May 2016
  #30
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Quote:
Originally Posted by Roland View Post
Decent ms is always better with an omni or cardioid mid.
Please explain?
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