Practical ORTF recording project

This project took me a bit by suprise, because my music tech teacher recommended me to do the recording for them. I agreed because it would give me some ambient recording experience, which I have never done before (at least, not seriously).

Recording would be done in a high noise-floor reverbrant music lodge (lots of traffic passing by). The look of the recording venue looked not too great, with the 7ft Steinway Grand piano very close to the brick wall behind and hardly any stage space. Musicians would be in close proximity and therefore reduce the stereo field.

The easiest technique would be the X-Y (crossed) pair cardiod mics, probably being AKG C1000s small-diaphragm condensers. Unfortunately, this teachnique has a narrow soundfield, and in the already narrow stereo field, it wouldn’t make it sound any better. In fact, we were in lack of a stereo bar.

After doing some research, I came across this technique called ORTF where cardiod mics are placed 17cm apart, with their capsules angled 110° apart. Any slight error in the placement could cause horrific phasing problems. Therefore, it would be necessary that a stereo bar be used. Sounded too troublesome, but more reasearch showed that ORTF yielded a better stereo field. So ORTF became my 1st preference.

I checked what choice of microphones I had access to, and I finally decided on taking a pair of AKG C414 B-ULS wide diaphragm condenser microphones as the main stereo pair. I also decided that spot miking could improve it, so I chose 2 AKG C3000S wide-diaphragm condensers (on hypercardiod) to spot the violin and cello. At first I was contemplating putting a spot (perhaps SM57) on the bass strings of the piano, but I decided that it would sound unnatural, and anyway the bass level of the grand piano sounded decent from my listening point. Frequency response was set to full (no filters) as I could filter what I needed later on.

The problem of aquiring a stereo bar was solved by my trombone teacher lending his stereo bar to me.

All this would be put through a Soundcraft Spirit Studio 16 track analogue mixer (I really needed preamps, but we didn’t have any suited for the job) into a M-Audio Delta 1010 Soundcard on a computer in a seperate control room. It would be recorded on to Cubase SX 2.01 .

I was originally planning to put some acoustic foam behind the piano on the wall, but later on we discovered that the trio was being filmed as well, and as the foam would look ugly, that idea had to be scraped.

Recording day arrived, and it took me about 1 1/2 to set up the equipment. The main stereo pair ended up about 3/4 metres away from the trio about 3 metres up, with spots coming in from behind the player’s shoulders, about a metre away from their instruments. The piano was dragged as far as it could be from the wall (which was about 30cm!) and was put on half-lid.

Timing for recording was timed around the school bell ringing, which made life a bit tough, but we got through the 1st movement without too much hassle. The 2nd and 3rd movements had to be redone (the trio was unsatisfied with their performance). Indeed, the high noise floor and sound leakage caused MAJOR problems in movement 4 when suddenly a police car zoomed by, it’s siren being picked up by the sensitive stereo pair. Unfortunately, we didn’t have time to redo it, so it remained.

Draft processing, mixing, and mastering was complete by the next day (done on Yamaha MSP5 near-field stereo monitors). Considering the lack of equipment and the state of the venue, initial results were decent. The stereo field was quite wide, and the sound coming from the stereo pair was such that only a bit of spots were added on, for definition. The excellent AKG 414s did their job well, as no equalization was applied. Of course, the control room couldn’t have worse acoustics, so I might be mistaken about that. Some problems included traffic rumbling here and there, the police siren, and the mid-lows were slightly muddy (probably because of the acoustics).

For a first time ambient project, I think things went quite well, and has been quite an experience. Just be sure to set up your ORTF properly and try different positions in the room to get a good sound.

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