with 27 Comments

Ever since I can remember I’ve been fascinated by recording the sounds of the natural world. We had no TV in our household until I was 13, so I grew up listening to the BBC’s weekly “Natural History Programme”. Without the visual impact of a TV documentary the programme depended heavily on recordings of the environments and wildlife being discussed. At that time I had a Sony mono cassette recorder and a £10 microphone from the local Radio Shack (or Tandy as it was then), so my own efforts at recording were pretty dire.

A couple of years ago I needed some equipment for a project that involved recording railway engines, and ended up with a Tascam HD-P2 CompactFlash recorder and an Audio-Technica AT825 X/Y stereo microphone. This setup worked fine for the railway project – with the mic mounted in a Rycote windshield/windjammer combo it can be boomed out the window of a train moving at 25mph with no appreciable wind noise. Any attempt at recording quieter natural sounds just ended being drowned out by clearly audible hissing, and I resigned myself to the fact that the equipment I would need to make any decent recordings was way beyond my budget.

A few months ago I discovered the excellent “naturerecordists” Yahoo group. Reading the postings there and doing some of my own research I began to realise that what I had was a perfectly adequate sound recorder that was being crippled by a microphone with high levels of self-noise. Further reading led me to a couple of (relatively) cheap mono microphones with very low self-noise, which can be used in pairs to create stereo recordings. One of these is the Audio-Technica AT3032 omnidirectional mic, as used by Curt Olsen. When I tried to purchase a pair of these I discovered that they are now discontinued and the replacement, the AT4022, is far more expensive.

The other affordable microphone people were talking about was the R?DE NT1-A. After listening to some of John Hartog‘s excellent recordings with these microphones, I went ahead and purchased a matched pair from DV247. Unlike the omnidirectional AT3032s which require some kind of barrier between the pair to achieve a stereo effect, the NT1-A is a cardioid microphone, so named because it is most sensitive to sounds coming from a roughly heart-shaped are in front of the capsule. This means that by placing the two microphones at the correct angle and spacing relative to each other, a stereo effect can be obtained with no barrier between them. There are various configurations, developed through years of testing – in the end I decided to use an ORTF array, with the microphone capsules spaced 17cm apart and with a 110 degree angle between them.

The next problem was shielding the microphones from wind and vibration, both frequent problems when trying to record very quiet sounds outside. R?DE supply a pretty decent shockmount with the microphone, but it’s designed with studio use in mind and it’s very hard to fit any kind of windshielding around. My first design, using the R?DE shockmounts on a stereo bar with a large, fleece-covered flowerpot over the top worked surprisingly well, but didn’t score very highly on portability and looked totally bizarre. Clearly I needed something more sophisticated, so I paid a couple of visits to B&Q, called up the bits and pieces of knowledge left over from A-Level design technology lessons, and the result is what you see below:

Stereo array with windshields in place

This is a great improvement on the flowerpot design – people might still stop and stare, but at least it looks professional (and most nature recording takes place as far away from other people as possible anyway!) Removing the fur (long pile toymaking fur on a mesh backing) shows the microphone suspension:

Microphone suspension

This is made from a length of 68mm diameter plastic drainpipe, roughly as long as the body of the microphone. Wrapped around this is a 25x25cm sheet of metal mesh, held in place with cable ties. The mesh has gaffer tape wrapped around the edges to cover up the razor-sharp points left behind when the metal is cut.

View of elastic microphone shock mount

The image above shows how the microphone is mounted within the pipe. The red bands are the ones Royal Mail use to hold together bundles of letters – our local postman scatters them around the area like confetti, so there’s always a good supply of spares! The band at the bottom of the microphone restricts side to side motion, while the one and the top (not visible in this picture) restricts forward and backward motion. This allows quite a lot of play in the microphones, and I know some of the other mounts I’ve seen use a more rigid system with additional bands, so I may have to make some modifications in the future to improve the shock mounting.

Detail of tripod mount

The final picture shows how the whole setup attaches to a Velbon tripod head. The central structure of the array is made three sections of lightweight aluminium angle bar. The sections are held together with butterfly nuts for easy removal. The central section is bolted to a piece of 6mm MDF sheet, cut to fit into the quick-release plate holder on the tripod. The only flaw with this design is that the left-hand microphone pod prevents full movement of the quick-release lever, but a few turns of the butterfly nut on that side creates enough space to move the lever and remove the array from the tripod. Ironically, the weather since I put the array together has been exceptionally calm for winter on the English coast, so I haven’t yet had a chance to try it out in a stiff breeze. I did make a recording of the frogs in our garden pond a few nights ago, which nicely demonstrates the stereo field and can be heard below:

Common Frog (Rana temporaria) calling in garden pond, Devon, UK:

[audio:http://awildear.co.uk/wp-content/uploads/2009/02/20090217_frogs.mp3]

27 Responses

  1. Vicki Powys
    | Reply

    Very innovative set up Tom! Lovely recording too. A funny tag line for Pterodaktyl – maybe ‘the way life used to be’? Good luck with your nature recording ventures!

  2. […] « Building a stereo microphone array for nature recording Mar 21 2009 […]

  3. David
    | Reply

    These recordings are very clear and quiet with a great stereo image. Also have not heard this frog before… Can’t wait to hear more.

  4. Taisto
    | Reply

    TOM!

    Have you tested several mics before stayed with RODE?

    One of my collegues tried these in studio and compared them to Behringer quality. Actually there is a question for me – the prices of RODE mics – and the knowledge that they produce them at the same factory as M-Audio etc in China.

    Best!

    Taisto Uuslail
    Helisen Stuudio O?
    helisen.blogspot.com
    ESTONIA

  5. Tom
    | Reply

    Taisto,

    The only microphone I’ve had any real experience with prior to the Rodes was my Audio-Technica AT825. I would love to try a pair of the AT3032 omnis but it’s impossible to get hold of them any more. The primary attraction of the NT1-As is their incredibly low self noise of 5dB – I would be amazed if any of the Behringer microphones can match that!

    My only concern with the NT1-As is that as studio microphones they were designed to be used in an indoor environment and may not stand up to high levels of humidity as well as a dedicated field microphone such as some of the Sennheiser MKH models (which cost 10 times as much…)

    In the UK a matched pair of NT1-As now retail for around ?295 (around ?50 more than I paid 2 months ago, due to the falling value of the UK pound against other currencies). I believe all Rode microphones are now made in their own facility in Australia, it was only the earlier models that were made using Chinese capsules (based on this article: http://www.soundonsound.com/sos/aug05/articles/rodevisit.htm)

    Hope this helps!

    Tom

  6. Taisto
    | Reply

    Thanks!

    Manifestation: MKH set for every enthusiast all over the world!

    Lord knows now, just be patient ;O)

    Taisto

  7. Taisto
    | Reply

    Hey!

    Some foley-makers say that with large-capsule mics it`s impossible to get any sound if windy weather.

    What you say about working with NT1-a-s in windy conditions? Even with the wind protection on?

    Taisto

  8. Tom
    | Reply

    Taisto,

    The NT1-As are certainly very sensitive to wind – anything above a light breeze tends to produce some noise. To some extent this can be controlled using the recorder’s low-cut filter, but they’re certainly not ideal for use in strong wind. You might find you get better results with them mounted in RODE blimps rather than my home-made setup. Of course, wind produces other noise, from rustling leaves, creaking branches and waves which tends to negate the low-noise advantage of a large-capsule condenser. If I could afford two sets of mics at the moment I’d use the NT1-A’s for still weather and something like a pair of AT4022s in a barrier array for windy days!

    Tom

  9. Taisto
    | Reply

    Have you ever tested AT4022-s? Compared to any other?

    Taisto

  10. Tom
    | Reply

    Have you ever tested AT4022-s? Compared to any other?

    Taisto

    No – we don’t have any audio shops in the area that have a decent range of microphones to try out, so I have to go solely on other people’s recommendations. You could try asking around on the naturerecordists group (http://tech.groups.yahoo.com/group/naturerecordists/) as I think some people on there use the AT4022.

  11. Taisto
    | Reply

    Wee!

    I tested NT1 mics during last three days. The old and grey version. Today I tried to record how “grass-frogs” are having sex. very quiet and sincere! I compared them to Neumann KM184-s. Not a big sounding difference. I rigged NT1-s into DPA WindPac`s shockmount without big work and finally covered with warm scarf – no problems with big wind blowing at all.

    Looking forward to order NT2-A-s.

    Something interesting: http://www.busmanaudio.com/bscs_l.html

    Good sounds!

    • Tom
      | Reply

      Taisto,

      I rigged NT1-s into DPA WindPac`s shockmount without big work and finally covered with warm scarf – no problems with big wind blowing at all.

      Did you manage to mount both NT1s into a single WindPac? That would make a very handy setup, much more portable than mine. WindPacs are pretty expensive though I believe.

      The BSCS-L microphone looks very clever – not sure how good it would be for recording quiet wildlife though with 16dB of self-noise… maybe for noisy birds and frogs!

  12. Taisto
    | Reply

    Exactly – I rigged them both into WindPac suspension. It makes them into quite narrow stereo set – distance between capsules are ca 8cm, angle 90 degrees. But I`m satisfied with the room.

    I?m afraid that NT2-A-s are too heavy for WindPac. Waiting already delivery from Thomann.de… And then I start to invent handy mounting. Thank you for inspiration!

    Best!

    Taisto

  13. Tom
    | Reply

    Taisto,

    Not sure if you’ve seen this site, but if you’re thinking about using the NT2-As as an M/S rig, it might come in handy:

    http://www.uwm.edu/~type/audio-reports/MS_Mount_Rodes/WebSite_MS_Mount_Rodes.html

  14. Taisto
    | Reply

    Thanks, yes I have met this site.

    Anyway, your version looks more proper design.

    Let`s invent!

    I make certainly some photos when succeed.

    Taisto

  15. Jonathan
    | Reply

    Hi Tom,

    Like your design. Could I trouble you for a few more details on it?
    I too have bought the Rode NT1-A matched pair. They are extremely impressive.
    I used to do a lot of SFX recording for various libraries with a portadat and a Sennheiser 30/40 MS setup in a Rycote suspension.
    I sold that kit years ago now but now am looking to do some more. It’s amazing to me that some very good and expensive mics havequite high inherent noise floors. I work in music and voiceovers for radio/tv – mainly using a Neuman u87 for vo work. Lovely sounding mic and fine working close but it has far too much noise for anything else.

    NT1-As are a bit of a find – for the money quite amazing. At the moment I am using them through a Fireface 400 interface and a MacBook Pro – which sounds great as the Fireface has excellent preamps but it’s not particularly mobile! However it’s workable and like you did to start I have the NTs on a stereo bar in their Rode mounts.

    But I shall have to pay a visit to B&Q I suspect. So in your picture you have cut the length of the drainpipe to that of the body of the NTs – and then cut out a forward facing section – leaving a strut to the top and bottom rings as it were? Some holes in the rings for the bands? Then wrapped that in the mesh? Sorry it that’s all obvious!

    Nice work – cheers for now.

    Jonathan

    • Tom
      | Reply

      Jonathan,

      Yes, the noise floor of the NT1-As is fairly spectacular. I often notice on 30/40 M/S recordings that the self-noise is high enough to be intrusive in a quiet environment. You still can’t beat that set-up for portability though!

      I did originally plan to have the microphones completely inside the pipe with a cut-out section, however I was worried that there might be cavity resonance effects between the capsule and the inner wall of the pipe. In the end I cut the pipe to the length of the microphone body, excluding the mesh capsule shield. Once the microphone is mounted the XLR socket on the bottom is roughly level with the bottom of the pipe, and the capsule pokes out the top. The mesh wrapped around the outside of the pipe then provides the rest of the height needed to support the fur windshield.

      The bands are doubled up for strength and passed through holes on drilled in either side of the pipe, then looped around offcut pieces of cable tie to hold them in place. The only flaw in this is that when a band breaks the outer mesh will have to be removed to replace it… but Royal Mail obviously chooses well because this hasn’t happened yet.

      If you want any more details or pictures of a specific part of the set-up let me know, and I’ll get you some photos next time I have the fur off.

      Cheers,

      Tom

  16. Jonathan
    | Reply

    Hi – sorry for the late reply! Thanks so much for getting back to me.
    Totally agree about the 30/40 noise floor – the NTs are quite outstanding.

    Thanks for the info – I need to have a go really at building it and see how I get on. That is unless you fancy naming a price to build one – I’m happy to pay a proper price for your time and the bits.

    Thanks again.

    Jonathan

    • Tom
      | Reply

      Jonathan,

      I’m not really sure the design is refined enough yet that I’d want to take anyone’s cash to build one for them… maybe when I’ve improved on the windshield design a bit, but there’s a long way to go before I start competing with Rycote!

      If you decide to have a go at building your own I’d be more than happy to run through the specific materials, dimensions etc. that I used – everything can be picked up at one of the larger B&Q stores, and you don’t need any special tools beyond a basic electric drill.

      Cheers,

      Tom

  17. Peter Hill
    | Reply

    Hi Tom
    Glad that you are enjoying your NT1-A’s for nature recording.
    I have been using 2 NT1-A’s for a year now recording environmental ambiance recordings and am very happy with them (In Australia). I use the Rode Blimp to house each on of them – I am sure it works very similar to your setup. I use a Edirol R44 for the recorder and find that the mic pre amps work well for me. I use Sound Forge 9 to edit the clips and need to normalise and run a noise reduction plugin as there is often some form of background noise that can intrude. The critical thing with environmental recordings is to do it when there is very little wind, and limited background noise and then you are guarrenteed a good clip to work with. I have tested a number of other mics, but come back to the NT1-A’s as they are so quiet and have a great sound. I have recently added two more NT1-A’s to my setup and do 4 track recordings which I render to AC-3 surround sound. It truely adds another dimention and a big smile to my face when I take time out in my surround sound audio room. You should try it – it takes the experience to another level. I will be setting up my web page again and will post you a link to the sample files if you are interested, Cheers Peter

    • Tom
      | Reply

      Peter,

      Yes, if you put the two NT1-As in a pair of vertically mounted Rode or Rycote blimps you’ll end up with a rather more effective (in terms of wind reduction) version of what I built. How do you mount the NT1-A inside the blimp though? Most of the mountings available are designed for narrow-bodied mics like the Sennheiser ME or MKH series, not hefty studio mics like the NT1-A!

      I’d love to try surround recording, but alas my budget won’t stretch to another 2 NT1-As and a 4-channel recorder at the moment. I’d love to hear some of your work though, so please do post a link.

      Cheers,

      Tom

  18. […] here to see Tom Williams nice guide that I followed. I must say that I’m kind of proud that I […]

  19. Magnus
    | Reply

    Hi Tom,
    Thanks for a fantastic guide!

    I built a rig for my NT1-A’s this weekend and put up some pictures that can be found on my blog:

    http://inovember.wordpress.com/2010/10/04/diy-stereo-rig-for-nt1-as/

  20. Andreas
    | Reply

    Hi Guys. Thanks for your cool responses here. Since i own 2 blimps, i created a nice combination with the SM6 Shockmount and my Røde Blimps. The only thing i find is, it it relatively sensitive to mechanical-vibration. how do you guys handle this ? check out my blog and my wind Test recordings in very strong conditions. regards Andreas

    http://www.klang-manufaktur.de/rode-nt1a-ortf-wind-test

    • Tom
      | Reply

      Hi Andreas,

      I watched the video of your high wind test. The Rode blimps seem to do a very good job, much better than my home-made windshields.. The problem with the NT1A in windy weather is that they have such large diaphragms (2.54cm) that they are very sensitive to any vibration of their support structure, even if the wind doesn’t reach them directly. You could try using a thinner elastic in the SM6 shockmounts to see if that transmits less vibration, but probably the best thing you can do is try and position the mics in the most sheltered position possible!

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