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Nevaton BPT / Pfanzagl-Cardone technique Condenser Microphones
Old 19th March 2018
  #1
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Nevaton BPT / Pfanzagl-Cardone technique

This was brought up in another thread, but probably deserves its own!

I can't find any detailed information in English about Dr. Pfanzagl's technique, but it would appear that the Nevaton mic contains three capsules, all of them conventional circular 33mm large-diaphragm capsules with switchable polar patterns. Two of these are at a fixed(?) 90-degree mutual angle and can be set to either figure-8 or cardioid. The third points straight ahead (ie. in the middle of that 90-degree angle) and can be set to cardioid, figure-8 or omni.

As a fan of the Soundfield mic I am curious about this, but I'm also struggling slightly to see the point in it. The use of large-diaphragm capsules means that it has significantly better noise performance than the Soundfield, but I can't see any other advantages, and there are several obvious disadvantages:

* Although the stereo field can be adjusted in post-production to a certain extent by varying the level of the centre capsule, there is nothing like the flexibility that you get with a true B-format output. Certainly the direction of the mic is not steerable retrospectively as is the case with the Soundfield.

* Polar patterns have to be adjusted on the mic itself, rather than remotely.

* The capsules are physically further apart than in the Soundfield, so it will not have the same phase coherence.

* A Blumlein array using multi-pattern LD capsules is likely to be significantly further from the theoretical ideal than one using ribbon mics or true figure-8 condenser capsules.

* Although it's billed as a surround mic, it cannot represent height information.

Given that this mic is in roughly the same price bracket as the Soundfield, why would you choose it? What are the advantages of Dr Pfanzagl's technique, if any, over B-format recording?
Old 19th March 2018
  #2
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This is the English abstract from Mr. Pfanzagl's paper on his BPT concept.

„The Blumlein-Pfanzagl-Triple – Theory and Experiences in Practical Use”
Based on the well-known ‘Blumlein-Pair’, it is the aim of this project to find a compact microphone system – well suited for mobile applications – which delivers signals for the three front-channels of a 5.1 surround recording with appropriate channel separation.
Most of the commonly used 5.1 surround microphone systems are characterized by either relatively large capsule spacings (see OCT, various ‘Tree’-techniques, as well as the ‘Microphone curtain’, etc.), or relevant weight (see Schoeps ‘KFM- Kugelflaechenmikrofon’ or Holophone ‘H2-Pro’), which makes them non-ideal for easy-to-install or mobile applications (as camera-microphones or on the boom-pole).
The ‘Blumlein-Pfanzagl-Triple’ (BPT) microphone is proposed for the – ideally - localization-error free recording of small sound sources with complex (i.e.frequency dependent) radiation characteristics. In practical use it has turned out to be very well suited also for the recording of large sound sources (e.g. symphony orchestra), especially as a so-called ‘centerfill-microphone’ in combination with large-AB microphone systems.



Looking at the BPT microphone's pricetag, around 4.000 euro, it isn't something you decide to buy from one day to another without serious testing.
Old 19th March 2018
  #3
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It seems quite a niche product then!

I am still struggling to understand why you would buy one of these, when the Soundfield does all of those things and a lot more besides. Is it just that people prefer the sound of the capsules in the BPT?
Old 19th March 2018
  #4
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Quote:
Originally Posted by Peller View Post
It seems quite a niche product then!

I am still struggling to understand why you would buy one of these, when the Soundfield does all of those things and a lot more besides. Is it just that people prefer the sound of the capsules in the BPT?
What I miss in Pfanzagl's technical paper, Pfanzagle does not mention Soundfield and is not referring to any of the papers written by Gerzon.
Old 19th March 2018
  #5
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looks like a serious tool with serious specs/size/weight - and a serious price tag!

would be interesting to compare it with any soundfield mic: with the capsules that far apart, i'm having some doubts how well they combine - on the other hand, the direct output of all capsules without external gear (or dsp) is a nice feature.

(although it's obvious that the position of the mic was chosen for visual reasons in the venues shown in the videos, i'm getting the impression that the directivity cannot make up for the large distance from the mic to the orchestra: all i can tell is how the room/venue sounds up there. the need for reflection filter/absorber/diffusor seems obvious in this position too, but i wouldn't want to put up something alike near my main mics: i'd rather opt for different characteristics/patterns)

Last edited by deedeeyeah; 19th March 2018 at 11:26 PM.. Reason: typo
Old 30th March 2018
  #6
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Dear Peller,
Dear All,
I am glad to see some discussion going on concerning my BPT microphone principle and some very valid questions have been raised along the way.

Let me first answer to why I had not mentioned the Soundfield microphone or papers by Michael Gerzon in my research report on „The Blumlein-Pfanzagl-Triple – Theory and Experiences in Practical Use” of which 'Adorno' was so kind to post the abstract.

This may indeed look rather ignorant from my side, but my research paper (written in German in 2010) was mainly intended for academic use inside the university / institute (IEM - Institute of Electronic Music and Acoustics, Graz, Austria) where I was working on my doctoral thesis at that time and not for a more widespread publication. My aim was to put the BPT microphone in the context to other (more similar) microphone techniques, like e.g. the one proposed in: Martin, G. (2005): “A New Microphone Technique For Five-Channel Recording”, Preprint 6427, 118th AES-Convention, Barcelona 2005

'Adorno' is right in respect to the fact that - in the case of setting the capsules of the BPT mic to omni/fig-8/fig8 - this arrangement bears some similarities with the Soundfield's B-format (with the obvious omission of the fig-8 pointing in the z-direction). While ideas have been there to add a fourth capsule to the BPT thus providing the 'missing' fig-8 for z, this arrangement would of course have its physical/acoustical limitations by (at least this fourth capsule) being shaded off by one of the others in such a co-incident (or - at least - co-axial) alignment, which is the primary reason why Gerzon went for the tetrahedron arrangement of four sub-cardioid capsules.

When it comes to deriving a (5.1) surround signal from the BPT microphone (via means of applying the principles of MS-technique), with its 33mm wide diaphragms the resulting signals certainly have their sonic limitations, since the capsules are not located at the same physical point in space.
Unfortunately, the same is true for the four capsules of the Soundfield microphone, the result of which, according to my experience, is a high degree of cancellation of diffuse sound in the resulting surround-signal (after leaving the outputs of the MkV Processor, in case of the old Soundfield mic).
Under certain circumstances, this rather ‘dry’ output signal of the Soundfield mic may be of Advantage in some situations, but one unfortunate side-effect (in my opinion) is that also the impression of ‘depth’ of the sound source (very relevant, in case one records an orchestra, for example) is very limited due to the partial cancellation of diffuse sound.

In a previous study by [Camerer, F. and Sodl, C. (2001A): “Classical Music in Radio and TV - a multichannel challenge”, The IRT/ORF Surround Listening Test, http://www.hauptmikrofon.de/stereo-3...und-techniques, 2001 (Date of research: Dec.. 2016)] , as well as in the study by [Hildebrandt, A. und Braun D. (2000): “Untersuchungen zum Centerkanal im 3/2 Stereo-Format”, Paper zur 21. Tonmeistertagung des VDT, ISBN 3-598-20362-4, S. 455ff (2000)] it has been shown that the FOA first-order-ambisonic Soundfield Microphone was sonically inferior to the other systems under test.
This is also the reason why I did not include the signals of the Soundfield microphone into the subjective listening test connected with a comparative recording of several 5.1 surround microphone systems (DECCA-surround, AB-PC, Schoeps-KFM, OCT) which I conducted more than10 years ago. (see Pfanzagl-Cardone, E. and Höldrich, R. (2008): “Frequency-dependent Signal-Correlation in Surround- and Stereo-Microphone Systems and the Blumlein-Pfanzagl-Triple (BPT)”, Preprint 7476, 124th AES Convention, Amsterdam 2008) a rather substantial convention-preprint of about 40 pages … )

In 2003 I have had the chance to test the Soundfield MkV myself and while it sounded great, when used with the MkV processor in pure 2-ch 'stereo' mode, I was VERY disappointed by the results which I was able to obtain in 5.1 surround operation mode.
Simply by listening to it, it became clear to me that the spatial resolution of the system as a whole (Soundfield mic and the MkV processor in conjunction) was not providing enough channel separation at low frequencies to result in a convincing "spatial impression" which I consider a very important aspect, especially for a 'surround' microphone which should surely excel in that respect in comparison with a pure 'stereo' microphone technique ... otherwise, why go through the hassle of the extra channels ?
(Rem.: I have done an analysis of the Soundfield mic's signals in the form of measuring the cross-correlation coefficient over frequency for the Soundfield's (processed) 5.1 surround signals, which proves my claim above)
I assume that also the new Sennheiser AMBEO VR microphone will not perform much better, as – to my understanding - it is again based on the same tetrahedron arrangement of sub-cardioids, as the Soundfield.


So - despite the undoubtedly congenial idea by Gerzon how to capture 3D-audio and also the mathematical 'elegance' behind the Soundfield / Ambisonic approach, the 'real-world' implementation has its clear limits. I have not done further research in that direction, but a more recent publication concerning recordings and listening comparisons with a HOA Higher-Order-Ambisonics system in the form of an Eigenmike with 32 capsules seem to point in the same direction: the Eigenmike was - unfortunately - judged inferior to the competitive systems, which used ITD cues as main principle for localization / spatial reproduction. (see: Howie, W., King, R., Martin, D. and Grond, F. (2017): “Subjective Evaluation of Orchestral Music Recording Techniques for Three-Dimensional Audio” preprint 9797, presented at the 142nd Convention 2017, Berlin)

However, having proposed the BPT microphone, I must - at least somehow - be a fan of 'coincident' microphone techniques, or - more precisely - the "Blumlein-pair", and there is a reason why ...

As already stated in [Streicher, R. and Dooley, W. (1985): “Basic Microphone Perspectives – A Review”, J. Audio Eng. Soc., Vol. 33, No.7/8, July/August 1985] the Blumlein-Pair is considered to be " ... very naturally sounding .. " by many sound-engineers as well as consumers, and this is certainly due to the very special overall polar pattern the system provides, which is characterized by (idealized) COMPLETE SIGNAL DE-CORRELATION over the entire frequency range between the L and R capsule-signals, which is a feature, which simply no other microphone system (with a ‘practical’ recording angle) can offer.

Why is this so important ?
Due to this 'behaviour', the Blumlein-Pair is able to deliver a highly realistic spatial impression which is clearly linked to high signal de-correlation in the low-frequency band below 500Hz, as various publications by David Griesinger (see http://www.davidgriesinger.com/ ), as well as other researchers in the field (see e.g. [Hidaka, T., Beranek L., and Okano, T. (1995): "Interaural cross-correlation, lateral fraction, and low- and high-frequency sound levels as measures of acoustical quality in concert halls", J. Acoust. Soc. Am. 98 (2), August (1995)] have pointed out.

This is the main reason why I prefer the - in comparison 'primitive' - Blumlein-technique over the much more sophisticated Ambisonic principle: because it simply provides the (sonically / spatial impression-wise) more convincing results ...
(But let me also say, that - if possible - I strongly recommend to use the Blumlein-pair or Blumlein-Pfanzagl-Triple in combination with large-AB omni 'outriggers', because then you get "best of both worlds": the very precise localization by which the Blumlein-pair of crossed fig-of-8's is characterized and the great 'spatial impression' (due to strong signal de-correlation in the low frequency band below 500Hz) which a 'large-AB' omni microphone pair will provide ...)

As a closing note: if 3D 'flexibility' is your main concern, the post-pro 'steering' abilities of the Soundfield-microphone will certainly beat the BPT, which - in comparison - is kind of 'old-school'. But if 'sound quality' is your main concern, then you should take your time and give the Nevaton-BPT a try.
You may want to check this out: YouTube (the first recording with the – back then brandnew – Nevaton BPT microphone)

Best regards, Edwin Pfanzagl-Cardone
Old 30th March 2018
  #7
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No DSP needed +optimzed absorptive panel for enhanced directivity (BPT mic)

Quote:
Originally Posted by deedeeyeah View Post
looks like a serious tool with serious specs/size/weight - and a serious price tag!

would be interesting to compare it with any soundfield mic: with the capsules that far apart, i'm having some doubts how well they combine - on the other hand, the direct output of all capsules without external gear (or dsp) is a nice feature.

(although it's obvious that the position of the mic was chosen for visual reasons in the venues shown in the videos, i'm getting the impression that the directivity cannot make up for the large distance from the mic to the orchestra: all i can tell is how the room/venue sounds up there. the need for reflection filter/absorber/diffusor seems obvious in this position too, but i wouldn't want to put up something alike near my main mics: i'd rather opt for different characteristics/patterns)
Dear deedeeyeah:
Yes, I agree - as you said:" the direct output of all capsules without external gear (or dsp) is a nice feature" ... we try to keep it 'as simple as possible' which is a great plus for on-location recording (you can have immediate control of what you are recording by simply listening via headphones)

Concerning your doubtful comment on directivity, I would suggest that you take a look /listen to the following BPT demo-video on Youtube:

Nevaton BPT Blumlein Pfanzagl Triple 3 capsule mic recording - YouTube

The distance-to-sound source indications (of more than 20meters [60feet] to the closest musical sound source) provided in this video is no hoax ! It has to be said though, that at the time of the recording, the whole stage area was covered with sand (for the horse-riding on stage …) and this most likely has brought the reverb time considerably down from its normal value of approx. 2sec …

An info to those who might be hearing a slight phasy-ness in this recording on Youtube: as can be seen in one of the accompanying photos, at that time I was still using a rather cheaply built acoustic absorptive panel by a well known German manufacturer. As I found out later, this panel was not really ‘reflection free’ over the entire audio frequency range. After that, we started to build our own absorptive panels, (which - b.t.w. - weigh only about 400grams) and now this sonic problem has totally disappeared :-)

All the best, Edwin Pfanzagl-Cardone
Old 31st March 2018
  #8
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Dear Edwin,

Thank you so much for contributing to this thread in such detail. What you say is very interesting. I have made quite a few recordings with Soundfield mics, but never for a surround mix. (For me, the great thing about the Soundfield is the ability to derive any mono, stereo or surround array from the B-format signal after the fact.)

It's interesting that you say the Soundfield 'cancels' diffuse sound. I wonder if it's actually the case that other arrays such as your own introduce a greater element of time difference into the capture, because they are less coincident, and thus sound more spacious (in much the same way that a pair of spaced mics sounds more 'spacious' than a coincident stereo array)?

Do you not find that the quality of the Blumlein capture with the BPT is diminished by the use of large-diaphragm, switched pattern capsules? I imagine most of us would reach for 'pure' figure-8 mics for this purpose because of their better off-axis response and more accurate polar patterns.

I would certainly like to try the BPT out one day, it sounds very interesting.
Old 31st March 2018
  #9
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Quote:
Originally Posted by Peller View Post

It's interesting that you say the Soundfield 'cancels' diffuse sound. I wonder if it's actually the case that other arrays such as your own introduce a greater element of time difference into the capture, because they are less coincident, and thus sound more spacious (in much the same way that a pair of spaced mics sounds more 'spacious' than a coincident stereo array)?
I think you make a point. It is my own experience. Coincident stereo with two cardioid pattern small diaphragm microphones on top of each other (XY) gives a very "mono-ish" sound regarding the reverb picked up, but my AKG C426 microphone set to XY cardioid, with large diaphragm capsules on top of eachother - I estimate approx. 6-8 cm separated - results in a far less mono-ish sound regarding the reverb.
Old 1st April 2018
  #10
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Quote:
Originally Posted by futuresonic100 View Post
The distance-to-sound source indications (of more than 20meters [60feet] to the closest musical sound source) provided in this video is no hoax !
in my experience, a closer position always beats a tighter pattern (although i have to admit that i never tried main mics at such a large distance, mainly out of a preference for more direct and less room sound).

anyway, thx for sharing some thoughts on your mic - should one like a mic based on a blumlein pair (with a twist in this case), i'm having no doubt that anyone using it can get stellar results!

frohe hasenjagd...


p.s. i assisted jürg jecklin for years: he experimented with similar designs in the early/mid-eighties - if i remember right, he wasn't satisfied with results due to the lack of correlation from multi-mic arrays (for stereo production)

Last edited by deedeeyeah; 3rd April 2018 at 08:31 AM.. Reason: p.s. added
Old 2nd April 2018
  #11
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Quote:
Originally Posted by Peller View Post
Dear Edwin,

Thank you so much for contributing to this thread in such detail. What you say is very interesting. I have made quite a few recordings with Soundfield mics, but never for a surround mix. (For me, the great thing about the Soundfield is the ability to derive any mono, stereo or surround array from the B-format signal after the fact.)

It's interesting that you say the Soundfield 'cancels' diffuse sound. I wonder if it's actually the case that other arrays such as your own introduce a greater element of time difference into the capture, because they are less coincident, and thus sound more spacious (in much the same way that a pair of spaced mics sounds more 'spacious' than a coincident stereo array)?
OK - I understand. For what concerns the 'diffuse-sound cancellation effect' with the Soundfield mic: in order to try to let you see the differences between the Ambisonic and the BPT System from an 'acoustic measurement' point of view I will try to upload two graphs which display the cross-correlation coefficients over frequency (or: FCC - Frequency-dependent Cross-Correlation Coefficients) for both systems, used in a surround-configuration.

For better undestanding of the graphs I need to add that the BPT was used in "3.0-mode" (i.e. all the capsules in fig-8 pattern and their signals routed directly to the L-C-R front speakers), while the rear signals LS, RS were derived from a pair of spaced cardioids in the rear of the recording venue, which has to do only to do with the recording set-up which was used on that occasion.
For the Soundfield-mic all signals were derived by means of the MkV processor.

Comparison of the graphs:
(Rem: mainly the signal pairings L/C and L/R are of interest for us at the moment)
For the Soundfield signal-correlation is very high (i.e. above 0.6) among all front channels and at the same time amazingly high throughout the entire frequency range (both for front and rear channels), which means that the "sterophonic width" (or ASW - apparent source width) will be rather poor.

On the other hand, with the BPT, signal correlation for the L/R pair drops off significantly at least for frequencies below 200Hz, which enables a high degree of spatial impression for the listener. (As can be seen also from the L/C graph, it will depend on the level with which the signal of the center-capsule gets mixed in to the L/R pair, as to how 'de-correlated' the overall signal will remain for low frequencies)

In any case, the BPT seems to offer better "signal separation" between the front channels, as for the Soundfield-Mic correlation in these channels never drops below 0.6, actually it remains well above 0.8 ...
(Rem: the acoustic measurements are taken from a 'real world' orchestra recording, and are therefore applied on sound-samples wich consist of a mix of direct AND diffuse sound. For a purely diffuse soundfield, the L/R BPT-mic signals would be pure Blumlein-pair style (90deg to each other) and therefore completely de-correlated, as can also be deducted from graphic 3 which I will refer to below.)

I also wanted to show you a third graphic ("Corr in Coincident Mic-Systems"), which is from a paper by Wittek [Wittek, H.(2006): “M/S Techniques for Stereo and Surround.“ Proceedings of the 24. Tonmeistertagung, 2006, http://www.hauptmikrofon.de/HW/TMT20...S_neutral.pdf] and shows signal decorrelation vs. physical opening angle between the capsules. From this it can be seen that while Blumlein-style fig-8 with 90deg opening angles provide completely de-correlated signals, the sub-cardioid used for the Soundfield-mic will never achieve correlation below 0.8 (even at 180deg orientation towards each other), when arranged in a coincident mode.
This result seems to be pretty much independent of any post processing, as my measurements of the Soundfield's MkV processors output signals (graphic 2) shows.

I guess the graphs provided show quite clearly that the BPT is not just a 'cheap' or 'simplified' version of trying to do a simliar thing as the Ambisonic / Soundfield mic does, but due to the conscious 'abstinence' from (MS-)processing the signals maintain their 'integrity' and we manage to achieve much better channel separation, which is to the clear benefit of spatial impression (and also to the 'naturalness' of the overall sound, as I would like to claim, even though of course I cannot prove this only with the graphics provided here ...)
Old 2nd April 2018
  #12
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[QUOTE=futuresonic100;13234994]OK - I understand. For what concerns the 'diffuse-sound cancellation effect' with the Soundfield mic:
QUOTE]

Sorry, it seems adding the three graphic has now worked right away.
I am trying to attach them now - apologies for the inconvenience -

Edwin Pfanzagl-Cardone
Old 2nd April 2018
  #13
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Quote:
Originally Posted by Adorno View Post
I think you make a point. It is my own experience. Coincident stereo with two cardioid pattern small diaphragm microphones on top of each other (XY) gives a very "mono-ish" sound regarding the reverb picked up, but my AKG C426 microphone set to XY cardioid, with large diaphragm capsules on top of eachother - I estimate approx. 6-8 cm separated - results in a far less mono-ish sound regarding the reverb.
Dear Adorno,

Yes, I would agree that the greater capsule separation (in combination with the different mic pattern: XY cardioids vs XY. fig-8's) will probably also have its share in responsibility for the lesser degree of diffuse-sound cancellation in comparison to the Soundfield's subcardioids.

I am trying to attach the 3 graphic here, which I have already promised in my reply to Peller, as they also apply to this side-discussion
Attached Thumbnails
Nevaton BPT / Pfanzagl-Cardone technique-soundfield-paired-fcc.jpg   Nevaton BPT / Pfanzagl-Cardone technique-8_21-bpt-corr-paired-31-band.jpg   Nevaton BPT / Pfanzagl-Cardone technique-9_9-corr-coincident-mic-systems.jpg  
Old 2nd April 2018
  #14
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OK - second attempt in trying to attach the graphics
Attached Thumbnails
Nevaton BPT / Pfanzagl-Cardone technique-8_21-bpt-corr-paired-31-band.jpg   Nevaton BPT / Pfanzagl-Cardone technique-soundfield-paired-fcc.jpg   Nevaton BPT / Pfanzagl-Cardone technique-9_9-corr-coincident-mic-systems.jpg  
Old 2nd April 2018
  #15
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BPT-mic: true ribbon fig-8 vs. switched pattern large-diaphragm capsules

Quote:
Originally Posted by Peller View Post
Dear Edwin,

Do you not find that the quality of the Blumlein capture with the BPT is diminished by the use of large-diaphragm, switched pattern capsules? I imagine most of us would reach for 'pure' figure-8 mics for this purpose because of their better off-axis response and more accurate polar patterns.

I would certainly like to try the BPT out one day, it sounds very interesting.
Dear Peller,

The question you pose is very valid. Indeed, I would be very curious to compare the overall sound and sonic behaviour of a true ribbon fig-8 BPT arrangement with our large-diaphragm, switched pattern capsules. However, for the added benefit of being able to switch the top capsule to omni for the purpose of obtaining a full 5.1 surround-signal from just one microphone (like with the Josephson C700S) it was clear to me from the start that I would want to go for a switched pattern capsule design ...

In case you are curious to try out the BPT, I can offer to help in getting you in touch with the European Distributor. Where are you located ?
Old 2nd April 2018
  #16
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Thank You Mr. Pfanzagl for your extensive explanation !

You note above the Soundfield system deploys sub-cardioid capsules. This confuses me. I saw at the Wikipedia site the same is noted. I have read many papers concerning Gerzon's experiments and there has never been a notation made of the use of sub-cardioids. In those days sub-cardioids were not even available, that's why Volker Straus invented his Straus-Paket. Gerzon in fact only used Calrec 600 series cardioid microphones, and to make the seperation between L, R, front and rear channels stronger hypercardioids were simulated by using a common mode reduction circuit to reduce the common mode (i.e. omnidirectional) component of the four cardioid signals.

I am a bit surprised about the results of your measurements. Have you actually used a Soundfield microphone for your measurements or have you simulated a Soundfield microphone, and are you referring to a sub-cardioid directional pattern? Have you used software to create the B-format or the box Soundfield provides with the microphones?

Adorno
Old 3rd April 2018
  #17
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I've been experimenting with something similar. Don't have results I can share yet. I am using a Lewitt LCT640TS which allows me to pick any microphone pattern after the fact. I've been setting it straight ahead and pairing with a Shure KSM 44a in figure 8 pattern placed as close as possible and sideways. Recording three channels of info I can blend them to any horizontal direction or pattern after the recording is done. It works pretty well for 5 channel surround. Typically I simulate the double MS type of pattern. Add an omni channel for the low end, and a cardioid straight ahead. Initial results are encouraging. I've done a little with a second KSM44 pointed vertically, but haven't really got that to work in a worthwhile manner yet.

My favorite stereo pattern is the Blumlein, but doing double Blumlein MS hasn't quite worked out either so far. Anyway, a less expensive way to try such a thing out.

The Lewitt btw is fantastic even for your more conventional uses. Probably going to have to get a second one to replace the KSM44A (which is a darned nice mic itself).

Maybe worth reminding everyone, all basic microphone patterns are the result of omni and figure 8 mixed in various ratios.

Last edited by esldude; 3rd April 2018 at 06:42 AM..
Old 3rd April 2018
  #18
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Edwin, thanks again for such a clear explanation. So the difference in the correlation is a factor of the native polar pattern of the capsules -- as in, there is intrinsically much less correlation between figure-8 mics at 90 degrees than there is between subcardioids in a tetrahedron. That makes a lot of sense.

Adorno, I have always understood that the Soundfield uses subcardioid capsules. Presumably these were originally commissioned specially from Calrec.
Old 3rd April 2018
  #19
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In comparing Soundfield technique to other methods I would strongly recommend using the
Soundfield DSF-1. The DSF-1 digital preamp-processor is much better than the earlier analog
Mk V. It is quieter and has better phase accuracy. To my ear the Mk V was inferior to
quality highend SDC’s but the DSF-1 is not a compromise. ( I sold my Mk V and now have a DSF-1). Also in comparing the Soundfield
to other methods it is important to know what
decoding software is being used. Harpex B offers
some additional control (including “Envelopment”) that other software does not.
Old 3rd April 2018
  #20
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Quote:
Originally Posted by Peller View Post
Adorno, I have always understood that the Soundfield uses subcardioid capsules. Presumably these were originally commissioned specially from Calrec.
Your answer made me very curious, so I started a search and I found it in the description of Soundfield, so we assume that is correct. Of course it works with sub-cardioids, substracting the common-mode will generate all the other patterns. In fact to get a total hemispheric coverage the amount of capsules is probably too low with the use of only cardioid patterns, therefore AKG has a patent on a polyhedron microphone with many more capsules, and SF compromised with the use of sub-cardioids, but still the de-correlation values Pfanzagl measured I find bothersome. I just wonder if Pfanzagl's measurement is done with the SF-microphone quite far from the source with a lot of indirect sound. The more diffuse the soundfield is, the less convincing coincident systems sound.
Old 3rd April 2018
  #21
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Quote:
Originally Posted by Adorno View Post
Thank You Mr. Pfanzagl for your extensive explanation !

...

I am a bit surprised about the results of your measurements. Have you actually used a Soundfield microphone for your measurements or have you simulated a Soundfield microphone, and are you referring to a sub-cardioid directional pattern? Have you used software to create the B-format or the box Soundfield provides with the microphones?

Adorno
Dear Adorno,
As the question concerning the sub-cardioids in the Soundfield has been cleared in the meantime, I will just answer to the more specific question above:

Yes, I have used an original Soundfield back in 2003 in conjunction with the MkV processor. So the correlation-data graphics provided by me above are sort of state-of-the-art of that model back then. It may be that with software-decoders nowadays one might achieve better 'channel separation', but the sub-cardioid capsule characteristic apparently has remained an integral part of the Soundfield specification, as it can still be found with the ST450 model which is still being sold: [ http://cdn.soundfield.com/assets/dow...-%20manual.pdf ] (see page 5 of the manual)

However - as already mentioned in one of my previous posts - also with applying higher order ambisonics (like in the Eigenmike 32, with appropriate software) the listener impression was somehow a 'lack of depth' of the Sound-source. Citing from the already mentioned study by Howie et al (2017), pg. 7: " ... For example the {study by Camerer and Sodl} observed a lack of depth and adequate spatial impression for the Soundfield MKV, a 1st order ambisonics recording system. These observations are echoed in the current study, with the Eigenmike performing poorly for Scene Depth, Environmental Envelopment and Sound Source Envelopment. Sperical HOA microphones, although a convenient alternative to largely spaced microphone arrays, may not yet be suited to professional 3D music recording, espcially given the monitoring difficulties ..." (rem: this last remark is refering to the fact that you need a special software to synthesize a meaningful binaural signal from the 32 signals of the Eigenmike, just for monitoring ...) ...

In the graphic attached "Technique 3" refers to the Eigenmike, while technique 1 and 2 are using largely spaced microphone arrays.

Now I am not a specialist for Ambisonics, but I think one of the basic reasons behind this behavious lies in the very princple of the Eigenmike: even with higher-order ambisonics, the 'spatial resolution' deteriorates as frequency decreases:
From [Eargle, 2004 "The Microphone Book", Second Ed. pg.263],
refering to an Eigenmike with 24 capsules, hence 3-order ambisonics:
" ... In a typical application involving an array intended for soundfield reconstruction, third order patterns would be maintained above about 1.5kHz. At progressively lower frequencies the directivity would be reduced to second-order and finally, below 700Hz, to first order."
As I have tried to point out in my previous posts, a high amount of signal de-correlation at frequencies below 500Hz is very vital for good spatial reproduction and I am afraid this (still) is the weak point in real-world microphone designs of the Soundfield/Ambisonics type.
Attached Thumbnails
Nevaton BPT / Pfanzagl-Cardone technique-11_77-howie_results-3techniques-22-2_new.jpg  
Old 3rd April 2018
  #22
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But in situations where the low-frequency decorrelation is so crucial, would you not just use a spaced array instead? Or, alternatively, use an ambisonic mic for frequencies above 500Hz and a spaced pair of omnis for the bass?
Old 3rd April 2018
  #23
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Plush's Avatar
Where do I go to hear some really good recordings done with this Nevaton mic?

What I have heard before is not great and seems very distant sounding.
(the one where the horses are on stage)

Please direct me since I find the concept to be good.
Old 4th April 2018
  #24
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Quote:
Originally Posted by Peller View Post
But in situations where the low-frequency decorrelation is so crucial, would you not just use a spaced array instead? Or, alternatively, use an ambisonic mic for frequencies above 500Hz and a spaced pair of omnis for the bass?
Well, of course there are usually many different ways, how to achive things ...
For me, a spaced array (providing good spatial Impression) would have a capsule spacing of at least 4m, for which some people would claim that you already get a "hole in the middle" effect. Therefore you would need to fill that hole (lack of sound-source 'center' information) with some kind of 'center-fill' microphone.
What you suggest - using the Ambisonic mic for the highs and a spaced pair of omnis for the lows - would certainly work, in my opinion.

The same is true for using the combination of the BPT-mic with two (omni) outriggers, which is my favourite constellation for medium- to large-size sound sources. The BPT gives you localisation accuracy, while the large AB gives you solid spatial impression. However, I use all of these microphones "full range" (no LPF or HPF applied) and they usually combine very well with no localisation distortion or other artifacts one may not like ...

Attached a graphic of a stage-music recording which I did (with Blumlein-Pair, not BPT, and outriggers) a few years ago - :-)
Old 4th April 2018
  #25
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BPT vs. Ambisonic + omni outriggers

It seems I'm not too lucky in attaching graphics ...
sometimes it works, sometimes it doesn't

Here I try again .. the one I have promised above :-)
Attached Thumbnails
Nevaton BPT / Pfanzagl-Cardone technique-4.38-blumlein-ab-ensemble-recording.jpg  
Old 4th April 2018
  #26
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Quote:
Originally Posted by Plush View Post
Where do I go to hear some really good recordings done with this Nevaton mic?

What I have heard before is not great and seems very distant sounding.
(the one where the horses are on stage)

Please direct me since I find the concept to be good.
Dear Plush,

If you go to the NEVATON Website, there is a section with a few examples:

NEVATON BPT – AUDIO&VIDEO

If you listen to the third example on the page (Medley) from 0:50sec onwards you will hear an excerpt from an 'Octet' recording and then a section from a string quartet (both done with just one NEVATON BPT, in a main-microphone position, no spot-mic added). After that there is a small excerpt of a CD-mix from an opera aria with BPT+omni outriggers as main system.

(Rem.: for the first part of the Medley [up to 0:50] a rather distant BPT system was used, far out in the hall and - unfortunately - the 'old' (slightly reflective acoustic panel) - which results in some 'phasyness' in the overall sound ... the other recordings of the Medley also used a panel, but the new version - therefore no phasyness ...)
Old 4th April 2018
  #27
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Quote:
Originally Posted by futuresonic100 View Post
there is a section with a few examples
The examples sound well engineered, but this time too close for the brightness
of the mic. A problem with arrays with so many variables is that it's harder to
decide where to put them, as opposed to working with a simpler array.
Old 4th April 2018
  #28
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Plush's Avatar
I enjoyed the string quartet recording the most. The Octet with singer was also very well presented.

I cannot agree that the microphone sounds overly bright or that the placement was too close.

I liked the comparison done at Tonzauber by Georg. There, the BPT sounded very close to the AKG C12. Laudable!

I think that my interest in Nevaton is helped by hearing this. I would probably acquire some Nevaton mics but not sure I require this array.
Old 6th April 2018
  #29
Here for the gear
Quote:
Originally Posted by Plush View Post
I enjoyed the string quartet recording the most. The Octet with singer was also very well presented.

I cannot agree that the microphone sounds overly bright or that the placement was too close.

I liked the comparison done at Tonzauber by Georg. There, the BPT sounded very close to the AKG C12. Laudable!
Dear Plush,

As the 'father' of this microphone and the sound-engineer who recorded the samples I am very happy about your positive feedback ...

Through all my posts above I hope I have been able to 'position' the BPT among possible 'competitors' in the following way:

In comparison to the Soundfield/Ambisonic principle, the BPT is not as flexible in terms of 3D-audio and post-production, but due to the better signal de-correlation at low frequencies and signal-integrity (no signal-processing of any kind [not even MS] is needed) for me the BPT delivers a more convincing spatial impression and sounds more 'natural'.

For use in a (5.1) surround application: in comparison with the Josephson C700S the BPT offers more flexibility, as the first one offers only (omni, fig-8, fig-8), while for the BPT all three capsules can be switched also to different polar patterns (with the lower two capsules preferably in dual fig-8, i.e. 'Blumlein-Pair' mode) which allows for a larger variety of applications.
Especially the BPT 3.0-mode (all three capsules in fig.-8 mode = Blumlein-Pair + Center fig8) is something new to the trade and has proved to be very practical, especially if the microphone has to be positioned far to the sound-source, for whatever reason.
For best channel separation of signals in a (5.1 or 6.1) surround context I recommend to use 2 BPT microphones in a 'Back-to-back' configuration (with absorptive panels inbetween), thus providing a total of six 'direct' signals for L, C, R (front BPT) and LS, Center- Surr, RS (Rear BPT), as can be seen in the photos attached which I shot last week on the occasion of an 'audience' atmo recording session at a small municipal theatre :-)
Old 6th April 2018
  #30
Here for the gear
two BPT mics in 'back-to-back' mode (for 6.1 surround)

well, the photos ...
Attached Thumbnails
Nevaton BPT / Pfanzagl-Cardone technique-20180328_105525.jpg   Nevaton BPT / Pfanzagl-Cardone technique-20180328_105757.jpg   Nevaton BPT / Pfanzagl-Cardone technique-20180328_114307.jpg  
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