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IRT Cross vs A Format for sound-only ambience

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Hi there folks


Medium term lurker and first time poster here, hoping to gather some experience and input to supplement my research and tests (and confirm my biases haha).


I've been asked to record the night-time ambience during seabird breeding season, on islands that are an ongoing conservation project.  The intended usage is not 100% clear, but will include using the soundscape during events promoting the conservation project, and it may be part of a museum installation about the islands in the future.

I'm a music soundie by trade, in live sound and recording at the classical & arts end of the spectrum.  I've done only a bit of post sound for picture, and no location sound (but plenty of live recording).  I've been wanting to get into field recording for pleasure and raw material for a while, hence my lurking here.


My inclination is to try harder than stereo only, and capture this in a surround format.  Partly this is due to the sound-only immersive usage of the resulting material, and partly because I'm learning about surround and have recently upgraded my studio to a decent 5.1 system.  As a music guy inlcuding classical, I'm much more drawn to spaced microphone arrays from a sound aspect, but I appreciate the utility of a coincident setup, particuarly in a situation like this.


Budget is minimal (this is a volunteer effort).  After research, I've come down to two options:

1. Purchase Rycote BBG's + windjammers and deploy four of my Schoeps MK4's I already have in an IRT cross on hardware I already have. 

2. For only slightly more than the Rycote's, I could purchase a Rode NT-SF1 A format mic.  Exotic location mic hire options are pretty slim here.


I've used IRT cross once before recording room / ambience / audience for a surround electronica show.  I do like the spaciousness rendered, but haven't used the mix outside my studio.  I've been experimenting with downloaded NT-SF1 demo recordings, and the Rode plugin.  It seems to work really well, does all the tricks, but doesn't give me an expansive feeling with the rendered soundstage.  However, playback on a larger system in a larger space may be a different experience.  I also feel that the capsules are less great than what I am used to.


I'll use a hired SD MixPre recorder.  I'm assuming the CMC6/MK4 IRT cross setup will be a small world of inconvenience, and capture a more organic and detailed sound.  The NT-SF1 and it's included windstopper will be extremely convenient, and have a lot more downmix and upmix options for future useage.  It's possible that this recording may recurr to build up a small audio library of the recovering seabird life on the islands.


That's my scenario.  Any input into which option you would pick and why would be hugely appreciated (as well as any other angles).






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Hi Simon, 


ambisonics is good for VR applications on headphones, or when you want to rotate your soundscape. Just be aware that first order ambisonics on loudspeakers has some disadvantages, like phasing issues (because all speakers are simultaneously active and partially the sounds are opposite in phase), a sweet spot from the size of a tennis ball (hard to get your head inside) and that the localization is not super precise. All these issues disapear when increasing the order, but most affordable higher order ambisonic mics make some compromises on the capsules (due to the size that has to be small) and the sound. So a really good higher order ambisonic mike is still quite expensive. 


In this PDF you'll find some basics on ambience recording and alternatives to the IRT Cross:


https://www.hauptmikrofon.de/HW/Wittek Ambience 15102013.pdf 


I also think an IRT Cross is a good option for you,



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For the IRT cross option, I'm now trending towards either Cinela Leonard 20 with fur, or Schoeps W 20 R1, after digging up a bunch of Jeff Wexler's posts here.  My gut feeling is not to jump into Ambisonics at the low end and knowing very little.

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20 hours ago, SimonL said:

Thanks Ramallo!  Listening with interest!

Take a look a Harpex plugin, the Harpex upmix the FOA (First Order Ambisonic) to third order for more spacial accuracy.




Some of my audios in freesound are in B format (If you want to experiment with the Harpex demo)


Like any other coincident technique, is phase perfect 😁



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pillepalle, thanks very much for your perspective and the doc link.  That's the way I am now trending (IRT cross), but I really value other peoples input, including the counter perspective.  I have been really interested to be listening to some ambisonic examples (thanks ramallo) - I haven't yet trialled Harpex but I will.  My gut feeling is I definately want to get into ambisonics for the right project, but not at the low end with minimal knowledge.


It's been really interesting consideration though, despite appreciating full well the convenience of a coincident rig, I have a lot of baggage from my musical background where spaced arrays sound much more natural to me.  The nature of the gig (not professional or with picture), means I can afford to be a bit less risk averse.


Unfortunately the possibility to hire anything above basic location mic rigs is extrememly limited here.

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Hi Simon, interesting question for the group.


Like you, I am very fond of spaced mics, specifically spaced omnis. I also have friends in the conservation / environment industries and have talked over similar possibilities for sound so I think I have SOME idea where you're coming from.


The chances are extremely high that there is no 'end format' in anyone's mind here and moreover that it is somewhat expected that you yourself might come up with the several possibilities of presentation since you are the 'sound expert' - and they would be right, enjoy the chance and discuss it with them!


End formats could be (limited bandwidth) podcasts, full bandwidth stereo either on headphones or speakers, simple (quad) speaker arrays or OTT multiple speaker arrays. Or gadgets like VR headsets. So, without freaking your friends out with the differences or the 'possibilities', I would subtly try to ask what main end format is usual or expected, then take that as a starting point. (Maybe you've already done this re original question).


What I would be most interested in as a recordist is what scientific or documentary angle they're looking at to involve you in the first place ('cause I've been through this too in hypothetical stages but not yet gone beyond). It could be they are just looking for an exhibition situation to point (known) stuff out to the public or a client. They could however be looking for something which could be measured and analysed and archived.


It is the end formats probably which will answer your original question (or help you make your own decision) but the actual aim is the more interesting technical challenge! For a similar situation, not knowing either (end format / aim) up front, my gut reaction would be to go for:


a 'perfect' mono omni (... for scientific use in the future if not immediately envisioned)


plus an IRT


plus an ambisonic.



If I was limited to 8 tracks there I would possibly lose the Z of the WXYZ to allow a (coincident but better mic) omni to make up the channel.

One last but important thing - you work in music so I assume you are familiar with Mid - Side in recording and mixing? (I must have worked in some degree with MS every single day I worked on music stuff, far far more so than I had to in broadcast or film). It is important to understand since you have no direct ambisonic experience that ambisonics is an MS technique, so your existing knowledge of the various techniques, problems and benefits of MS also will be those of ambisonics ... so it might help you in working out if ambisonics may be the better or worse choice at least to pursue.


Good luck and have fun - wish I was doing this one!


Jez "I love spaced omnis ... hundreds of them!" Adamson

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The difficulty is to choose the right technique in a certain situation. Therefore you must know to the pro and cons of every technique and have a lot of experience. Beside that not everybody has all the equipment needed for certain tecniques. I think your approach is a good one. To start with the equipment you have at your disposal and find out their limitations. If you know what you don't like in your recordings you can try to find a technique that works better regarding that aspects. 


Everybody knows that there is no technique that fits it all. That's why I have mentioned some of the downsides of ambisonics. Reasons why first order ambisonics became popular again is not only due to the use in VR and binaural applicaitons, but also because it's simple to use (small single spot microphone that is relatively cheap) and gives a lot of flexibility in post also regarding the speaker setup. That's really attractive and a big advantage from the practical side. But there are good reasons why a lot of experienced people avoid ambisonics in most situations and it's good to know them. The more tools one has to his disposal the better it is, but as a starting point I wouldn't buy new equipment without having a good reason to do so. But if you think ambisonic is the way to go, go for it :)



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Hi Jez


Thanks for your fullsome response!  You are right that the only real idea of an end format is one that I am putting on myself.  I could make my mission much easier with a stereo MS rig thats for sure.  But I do have a new-found interest and studio capability in surround. Also, when I mentioned the S word to the "client", her eyes widened in excitement, before the conversation rapidly turned to something else!  SInce you have shown interest, the context is a group of very small islands in a "marine park" called the Hauraki Gulf.  Incredibly, only 3% of the Gulf is under marine protection, if you can believe it.  Three generations of the family that "owns" the island group have worked to make them predator (rat) free, with a corresponding explosion in seabirds and returning (giant) insects.  But the sealife around the islands is under intense pressure from recreational fishing plus other factors, and as everything is interlocked this has a huge knock-on to the viability of the bird populations.  The island's custodians do a large amount of outreach & educational events on marine protection, and are want to give audiences a taste of the cocophony of a successful seabird habitat - a sound that mosts New Zealanders would not of heard before.


I would love to do concurrent multiple formats as you suggest, but a limited budget means I have to commit to just one at this stage.  I've ordered 4 x Cinela Leo's w/ fur (I must say Philippe from Cinela was very responsive and helpful).  So IRT Cross it is, and I am sure the Leo's will have a life after this project as I've been wanting to do some field recording for pleasure, but a new CCM rig either spaced or coincident is out of reach for the moment. 


Contingency plans for bad weather are 1) we postpone (it won't be very fun camping there anyway), 2) I take some omni capsules too (less wind sensitivity) for a spaced pair, and/or 3) take a hired Sanken CSS5 in a Rycote.


Thanks for your encouragement, I appreciate it.


Fun fact:  the name of the island group is The Noises.   !!!


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pillepalle  - thanks very much again, I appreciate the input.  Certainly, the ease of use of a point source mic is seductive, double so after setting up my hardware for the IRT today, where it seems every piece of hardware has multiple points of rotation!  Also, there is an argument I guess for getting into ambisonics inexpensively, in order to learn and experiment.  The positives of a single ambisoncis mic and post flexibility are compelling, but my gut has gone for the IRT method & kit.  It's been pointed out to me that worrying about the most high end sound is fine in theory, in practice the least cumbersome and most practical rig will likely give a better result.  Were it a professional gig I would totally agree, but am giving myself a bit of extra latitude for this volunteer one.  Thanks for Wittek resource, fascinating read.

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