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Figure 8 mic

Hi guys,

Not sure how it really happened, but I've never added a figure 8 capable mic to my locker. Still love my original At4033a and my original NT2 RODE . Now I've another RODE , NT2a. Looking forward to testing this as a room mic for acoustic guitar.

 

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Comments

Tony Carpenter Sun, 01/29/2017 - 00:09
I put the NT2a through the MOTU turned on its side for figure 8. Recorded my singing and the 12 string. I then layered that with my at4033a nearby directly at me sitting half down between my voice and guitar. The result is the fullest live sound I have yet achieved. I also reverse phased a copy of the NT2 capture per advice I had seen. Panned hard left right, lowered below the at4033a take. That provides the ambient take. It wasn't perfect because I can hear my breathing when not singing even at a foot and a half away. Less hot signal will sort that out I'm sure.

The point is though, after worrying about no longer having my Orion/RME and the RC500, I'm no longer concerned. The Traveller MK3 is doing a great job, for me.

pcrecord Sun, 01/29/2017 - 17:13
Makzimia, post: 447022, member: 48344 wrote: Hi guys,

Not sure how it really happened, but I've never added a figure 8 capable mic to my locker. Still love my original At4033a and my original NT2 Rode. Now I've another Rode, NT2a. Looking forward to testing this as a room mic for acoustic guitar.
I have a pair of KSM44 and pair of Fatheads. Figure 8 opens for great posibility. The side rejection is great...
When you try M/S or blumlein, it's kind of a revelation that not only the front of the mic has great content.

Boswell Mon, 01/30/2017 - 02:19
Makzimia, post: 447022, member: 48344 wrote: Not sure how it really happened, but I've never added a figure 8 capable mic to my locker. Still love my original At4033a and my original NT2 Rode. Now I've another Rode, NT2a. Looking forward to testing this as a room mic for acoustic guitar.
You should find that setting them up as an M-S pair gives you greater control of the sound and the width. With reference to your photo above, I would normally mount the S-microphone upside-down vertically above the M-microphone in order to minimise the vertical separation of the diaphragms. Leaving an appreciable gap between them opens you up to phasing artifacts on sounds that have a significant vertical component such as floor and ceiling reflections.

audiokid, post: 447050, member: 1 wrote: How about the new Rode ntr! I just heard about them and would love to add one to my locker. http://www.rode.com/microphones/ntr
The NTR looks a lovely microphone, and I, too, would love to get my hands on one to try.

Don't forget that you can't use a ribbon (velocity) microphone and a condenser (displacement) microphone as an M-S pair.

Tony Carpenter Mon, 01/30/2017 - 03:36
:oops: Thanks Bos, I hadn't tried it that way yet, I was just so excited to even try this. And honestly, it was just so much better even this way, than past attempts. When I did record the Minstrel and Marie the NT2 (not NT2a) was placed upside down on top of the Blue bottle I had at the time. I'm still learning more, nice to be able to tap greater minds on it :).

Oh and, as I suspected, that is in fact how Bob Sell, guy I saw way of doing it, does it... I just didn't go back and look at his video again...

Boswell Mon, 01/30/2017 - 05:07
Looks good.

The other thing I meant to say in my post above is that I try, whenever possible, to mount both microphones on the same stand rather than different stands. The idea is to minimise the separation distance between the mics being modulated by vibration or other movement. It's probably less important when set up in a studio with good, solid floors than on a live stage with musos clomping about, but it can bring about mechanical stability concerns with heavy microphones.

I often use a Beyer M160/M130 pair of ribbons for M-S recording. These are neat, featherweight units where there is no trouble using them with a spacer mount on a single-stand. On the occasions where I've put up a pair of NT2-As, whether in M-S or one of the stereo configurations, I always have to think carefully about the mechanical stability, and not hesitate to bring out the sandbags to weight the base of the stand.

Boswell Mon, 01/30/2017 - 11:25
audiokid, post: 447090, member: 1 wrote: Thank you for mentioning this, Bos. Can you please explain why?
A velocity microphone gives an electrical output proportional to how fast the diaphragm (ribbon) is moving through a field created by permament magnets. A displacement or pressure-sensitive microphone gives an output that is a function of the position of the diaphragm as it moves with the incident sound wave. If you draw a sinewave of pressure, then you see that the maximum pressure occurs at the peaks, whereas the maximum change of pressure (velocity) occurs as the wave goes through zero. These two are always 90 degrees out of phase with one another, at all frequencies. This means that if you put a ribbon microphone and a condenser microphone side-by-side in a sinewave sound field, the two outputs you get will be permanently 90 degrees out of phase as you sweep the frequency over the audio band.

The equations for resolving the outputs from an M-S captured field into L-R component signals implicitly rely on the phase responses of the M and S microphones being the same. They simply do not work if you use a pair of microphones that are always 90 degrees out of phase with one another.

As an example, if you were to take a correct M-S pair and put an acoustic sinewave source at 45 degrees left of centre, you would get outputs from the M and S microphones that were identical in both amplitude and phase. If you were now to move the sound source from that point through centre to 45 degrees right, you would see the M output increase in amplitude by sqrt(2) as it went through centre and then decrease to the original amplitude as you got to the 45 degrees right position. By contrast, the S output would reduce, go through zero and come up again 180 degrees out of phase (inverted) compared with the starting position.

rmburrow Mon, 01/30/2017 - 18:26
The attached pdf from Georg Neumann GmbH has its origins many years ago and directly explains the M-S sum and difference method. I don't believe there are any other copy right restrictions on it. I haven't used M-S much; I prefer the matrix transformer method. An op-amp matrix can be built for a lot less money than a transformer matrix. The schematic of the transformer matrix explains the derivation of the sum and difference components (and their reconstruction).
Attached files NeumannMidSide.pdf (572.2 KB) 

pcrecord Sat, 02/25/2017 - 14:58
Forget my ignorance or limited english understanding but figure of 8 microphones need to have dual diaphragm. One to capture the front and one the back sounds of the mic. So to be a figure of 8 mic the MKH30 must have 2 diaphragms. (of course in one capsule like they most do)
Ok unless you have MKH that are not figure of 8.. it changes my assumption.

So if I'm not wrong about this, using 2 MKH 30 don't qualify as M/S because the technic needs a cardioid and a figure of 8 and you use 2.
2 figure of 8 would qualify for blumlein technic which is also great for capturing, but are you using it from the side of the array ???


then M/S :

John Willett Sat, 02/25/2017 - 16:31
pcrecord, post: 447867, member: 46460 wrote: Forget my ignorance or limited english understanding but figure of 8 microphones need to have dual diaphragm. One to capture the front and one the back sounds of the mic. So to be a figure of 8 mic the MKH30 must have 2 diaphragms. (of course in one capsule like they most do)

Oh dear - I'm sorry - you are completely wrong.

A figure-8 microphone is a pure pressure-gradient device and only needs a single diaphragm.

The original figure-8 microphones were ribbons with a single ribbon diaphragm and the best condenser figure-8 microphones have just a single diaphragm.

Speak from the front and you get a good signal - speak from the rear and you also get a good signal, but polarity reversed - speak from the side and the sound pressure is equal both sides of the diaphragm and you get no signal - hence a figure-8 pattern.

This is the best figure-8 as the front and rear are captured in the same place.

A switchable-pattern microphone has two cardioid capsules. They have two separate diaphragms back to back.

If you add the two together you get an omni - if you only use the front you have cardioid - if you subtract the rear from the front you get a figure-8.

The best figure-8s have a single diaphragm: Sennheiser MKH 30, Neumann AK 20, Schoeps MK 8, etc.

But some manufacturers find it easier to stick two cardioid capsules back-to-back to make a figure-8 as they can use the same basic capsule as they use for a cardioid mic., but this method is not as good as having a single diaphragm.

If you look at the polar-pattern of the MKH 30 and compare it with any dual-diaphragm figure-8, you will see how much better it is, as having a single diaphragm is far more accurate - with separated diaphragms the high frequency polar response is not so good.

Probably the best dual-diaphragm figure-8 is the Microtech Gefell UMT 70S which, although it has two diaphragms, only has a single backplate - so the two diaphragms are closer together than microphones that use two cardioid capsules back-to-back.

The Gefell uses the Georg Neumann M7 capsule, which is the only dual-diaphragm capsule I know of that has a single backplate. These are more difficult to manufacture as front and rear responses have to be the same - it's easier to make separate cardioid capsules, match them as pairs and use matched capsules front and back - but this then has two backplates and teh diaphragms are further apart.

But the best method is a figure-8 with just a single diaphragm.

I hope this all makes sense to you and you understand now.

John Willett Sat, 02/25/2017 - 16:39
pcrecord, post: 447867, member: 46460 wrote:
So if I'm not wrong about this, using 2 MKH 30 don't qualify as M/S because the technic needs a cardioid and a figure of 8 and you use 2.
2 figure of 8 would qualify for blumlein technic which is also great for capturing, but are you using it from the side of the array ???

To answer your second point.

The mid mic of an MS rig can be any polar-pattern you want - anything from omni to figure-8.

Cardioid is the most popular, but you can use any pattern you want.

The Dooley and Streicher paper I linked to above explains all this and shows the resulting stereo array using omni, cardioid and fig-8 as the mid mic.

And Blumlein himself used two figure-8 microphones in MS rather than crossed many times aas you can steer the image in MS (see Dooley and Streicher paper).

I hope this makes it clear.

I have recorded MS many times, though my preferred rig was the Sennheiser MKH 40/30 combination - this clips together easily and can be fitted into a single mic. clip and even used outdoors in a Rycote basket wndshield.

pcrecord Sat, 02/25/2017 - 18:39
John Willett, post: 447871, member: 47971 wrote: Oh dear - I'm sorry - you are completely wrong.

A figure-8 microphone is a pure pressure-gradient device and only needs a single diaphragm.

The original figure-8 microphones were ribbons with a single ribbon diaphragm and the best condenser figure-8 microphones have just a single diaphragm.

Speak from the front and you get a good signal - speak from the rear and you also get a good signal, but polarity reversed - speak from the side and the sound pressure is equal both sides of the diaphragm and you get no signal - hence a figure-8 pattern.

This is the best figure-8 as the front and rear are captured in the same place.

A switchable-pattern microphone has two cardioid capsules. They have two separate diaphragms back to back.

If you add the two together you get an omni - if you only use the front you have cardioid - if you subtract the rear from the front you get a figure-8.

The best figure-8s have a single diaphragm: Sennheiser MKH 30, Neumann AK 20, Schoeps MK 8, etc.

But some manufacturers find it easier to stick two cardioid capsules back-to-back to make a figure-8 as they can use the same basic capsule as they use for a cardioid mic., but this method is not as good as having a single diaphragm.

If you look at the polar-pattern of the MKH 30 and compare it with any dual-diaphragm figure-8, you will see how much better it is, as having a single diaphragm is far more accurate - with separated diaphragms the high frequency polar response is not so good.

Probably the best dual-diaphragm figure-8 is the Microtech Gefell UMT 70S which, although it has two diaphragms, only has a single backplate - so the two diaphragms are closer together than microphones that use two cardioid capsules back-to-back.

The Gefell uses the Georg Neumann M7 capsule, which is the only dual-diaphragm capsule I know of that has a single backplate. These are more difficult to manufacture as front and rear responses have to be the same - it's easier to make separate cardioid capsules, match them as pairs and use matched capsules front and back - but this then has two backplates and teh diaphragms are further apart.

But the best method is a figure-8 with just a single diaphragm.

I hope this all makes sense to you and you understand now.
Interesting ! All my multipatern mics have front and bac diafragm. But you're right, I didn't think about my ribbons...
Thanks for the precisions

pcrecord Sat, 02/25/2017 - 18:43
John Willett, post: 447872, member: 47971 wrote: To answer your second point.

The mid mic of an MS rig can be any polar-pattern you want - anything from omni to figure-8.

Cardioid is the most popular, but you can use any pattern you want.

The Dooley and Streicher paper I linked to above explains all this and shows the resulting stereo array using omni, cardioid and fig-8 as the mid mic.

And Blumlein himself used two figure-8 microphones in MS rather than crossed many times aas you can steer the image in MS (see Dooley and Streicher paper).

I hope this makes it clear.

I have recorded MS many times, though my preferred rig was the Sennheiser MKH 40/30 combination - this clips together easily and can be fitted into a single mic. clip and even used outdoors in a Rycote basket wndshield.
Also interesting.. Most info on M/S I find online calls for a cardioid and a figure of 8
Any idea, which MS configuration naturaly has the widest stereo spread results??

John Willett Sun, 02/26/2017 - 03:34
audiokid, post: 447878, member: 1 wrote: John Willett Thank you for your very informative post. You never mentioned Royer ribbons and what do you think of them?

When I think of ribbons, there are only a few companies I would consider - mainly AEA, Coles and Royer. Beyer also make good ribbons, but those are not figure-8s.

I do not personally use ribbons very much, but the above would be top of my list.

John Willett Sun, 02/26/2017 - 03:48
pcrecord, post: 447881, member: 46460 wrote: Interesting ! All my multipatern mics have front and bac diafragm. But you're right, I didn't think about my ribbons...
Thanks for the precisions

If you hold piece of paper taught between two hands - blow on the front and the paper bends away from you - blow from the back and it will also bend away from you (but wold bend towards somone the other side - hence the reverse polarity) - blow from the side and it will not move at all.

This is the essence of a proper figure-8 mic.

A multi-pattern mic has to have two capsules - back-to-back cardioids - and the patterns are changed by adjusting the capsule polarisation voltage.

EG:
Front diaphragm: +60V / Rear diaphragm: +60V = Omni (both capsules added together)
Front diaphragm: +60V / Rear diaphragm: +30V = Hypo-cardoid (ie: wide cardioid) (both capsules added together but rear at half level)
Front diaphragm: +60V / Rear diaphragm: 0V = Cardioid (only front capsule used)
Front diaphragm: +60V / Rear diaphragm: -30V = Hyper-cardoid / super-cardioid) (rear capsule subtracted from the front at half level)
Front diaphragm: +60V / Rear diaphragm: -60V = Figure-8 (rear capsule subtracted from the front)

I hope this helps.

If you (or anyone) is in London this coming week, I will be giving a talk on microphones at Broadcast Video Expo (BVE) at Excel at 10:40 on Thursday.

John Willett Sun, 02/26/2017 - 03:54
pcrecord, post: 447882, member: 46460 wrote: Also interesting.. Most info on M/S I find online calls for a cardioid and a figure of 8
Any idea, which MS configuration naturaly has the widest stereo spread results??

The Dooley and Streicher paper explains all this.

The widest stereo spread is with an omni as the mid mic., this matrixes out as back-to-back cardioid mcrophones.

Using a cardioid as the mid matrixes out as crossed hyper-cardioids.

Using a hypo-cardioid (ie:wide cardioid) appoximates crossed cardioids

Using another figure-8 matrixes out as a Blumlein pair - but - varying the level of the side mic. will widen or barrow the image.

Look at the diagram at the top of page 4 of the Dooley and Streicher paper (link above) that will clearly show this.

I hope this helps.

DonnyThompson Sun, 02/26/2017 - 06:46
John Willett, post: 447891, member: 47971 wrote: I do not personally use ribbons very much, but the above would be top of my list.
I frequently use a ribbon/dynamic combination on guitar amps - they're my "go-to" array. Instant tone ( as long as it's a good amp to begin with).
I'll put the dynamic mic in tight ( 57/58/421/RE20/409...take your pick, you won't go wrong with any of these) and then use a ribbon backed-off from the amp by anywhere between 2 and 5 ft... sometimes on-axis, sometimes off.
If it's an open-backed combo amp, sometimes I'll place the ribbon behind the amp.
You just have to experiment a bit, to see what works best within the context of what you are working on at the time.

My most often-used and preferred mic combo for amps, was always an RE20/R121 - if these were available... (it depended on what the studio had in their locker)...
But, over the years, I've used several other dynamic and ribbon models for this array with great results, too. I've used cheaper mic combinations too - like a 58/Fathead, and a 57/MXL860, etc., and I've still been quite pleased by the tones that those various combinations have provided.

As a side note, ribbons are also good for room mics, too - drums in particular - because of their inherent top-end roll-off, so you don't get that "brashy" sound of the cymbals that condensers can so often give.
In this regard, they can be a nice alternative to condensers for this scenario... style depending, of course.
But, like any live recording set-up, the placement of the mic and the sound of the room itself figures into the end result quite a bit, too ... but, that's going to be the case for pretty much any mic. ;)

FWIW
-d.

Boswell Sun, 02/26/2017 - 08:21
John Willett, post: 447891, member: 47971 wrote: When I think of ribbons, there are only a few companies I would consider - mainly AEA, Coles and Royer. Beyer also make good ribbons, but those are not figure-8s.
The Beyer M130/M160 ribbon pair is one of the best known combinations for M-S recording.

John Willett Sat, 03/04/2017 - 03:42
John Willett, post: 447892, member: 47971 wrote:
If you (or anyone) is in London this coming week, I will be giving a talk on microphones at Broadcast Video Expo (BVE) at Excel at 10:40 on Thursday.

I gave this talk a couple of days ago - if anyone is interested, and could not make the talk itself, I uploaded the annotated handouts of the talk [[url=http://[/URL]="https://sound-link…"]HERE[/]="https://sound-link…"]HERE[/].

It's called "The Ins and Outs of Microphones" and goes through microphone types, polar-patterns, proximity effect, microphone distances and basic room acoustics in a simple manner.

I also gave this talk at the AES in Paris last year (under a different title - this is the improved version).

I hope you find it useful.
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