Posts Tagged ‘recording’

Portable Audio Recorders

May 10, 2010

For a few years now we have seen a wealth of portable audio recorders appear in the market. Most record two tracks at 96 kHz, 24 bit and have integrated stereo microphones.

While the 96 kHz, 24 bit suggests high quality audio recordings it is the integrated microphones that spoil it all.  Unfortunately not many manufacturers document the specs of the microphones on their devices. Even elementary information like whether the mics are cardioid or omni is often lacking. Instead we are left with descriptions like “Internal Stereo Microphone”. No noise performance indications or frequency response information. Clearly a sign most of these devices are not positioned as devices for the professional sound recordist.

Luckily a few websites come to our rescue. Of note here are www.wingfieldaudio.com who provide excellent noise floor samples and www.avisoft.com who provide both noise floor samples for a few models and EIN data for a fairly complete range of portable recorders available in the market today.

In my experience an Equivalent Input Noise number of -120dBu, unweighted and at maximum gain setting is the minimum for the field recordist to be able to make decent recordings. Also, a frequency response of 40Hz through 20kHz is a minimum specification to be met.

On the noise spec that rules out popular recorders such as the M-Audio Micro Track II and the Edirol R-09HR. These might prove effective in high dBFS music recording environments but are pretty useless to record in quiet environments.

Two recorders in my view perform particularly well: the Sony PCM-M10 and the Sony PCM-D1.

The PCM-M10 has very quiet omnidirectional built in microphones. Omnidirectional microphones are less sensitive to handling noise (nice to have on a handheld device) and have extended low frequency response.

The PCM-D1 has Analog Devices pre-amps that are virtually noiseless. The microphones are cardioids mounted in an XY coincident pattern. While this would suggest a narrow stereo field Sony managed somehow to overcome this and give recordings made this device a wide stereo image. Might be a device that is hard to find these days as it seems to have been discontinued in some countries in favor of the PCM-D50.

The microphones on both recorders are high sensitivity so dealing with quiet environments is no problem. The D1 has better high-end response compared to the M10.

Samples of recordings I made:

PCM-M10: JanuarySleet.wav, ThunderandRain.wav

PCM-D1: QuietForestSpringEvening.aif, LakeSide2.wav

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North India Field Recording on SoundCloud

September 26, 2009

Just posted an excerpt of the field recordings I did in North India earlier this year. Using SoundCloud for the first time for this.

Recorded with a Sennheiser MKH8020/ MKH30 MS stereo microphone configuration to a Sound Devices 702 recorder. MS converted to AB stereo at the recorder stage.

SoundCloud uploads are transcoded to 128 kbps mp3 format for streaming. That’s still twice as good as MySpace.

Plug-ins for the field recordist

September 14, 2009

As anyone familiar with processing audio on a computer will testify there are hundreds of plug-ins available for any application. Searching the KVR site for an EQ for OS X based applications gives you a choice of 141 different plug-ins. For the Windows platform you will find 226. And that’s just for EQ.

Without any exception these plug-ins were engineered with music in mind and that makes life for the field recordist slightly more difficult. While the Abbey Road TG12413 compressor/ limiter plug-in is a brilliant piece of software that does wonders on a drum kit, few field recordists will find a use for it. Vintage style EQ plug-ins can bring excessive coloration to a recording. Many plug-in developers will advertise the ‘warmth’ their processors will bring to your recorded material but that does not interest me, and I suspect most field recordists,  at all. What I am looking for is audio processors that keep the recorded material intact. No added warmth required, not looking for increased presence or transients adjustment to obtain better attack.

My search for the ideal field recording plug-in pack is an on-going thing but here is the result so-far:

EQ: Waves Q10 Paragraphic equalizer, DDMF LP10 Mastering Equalizer

Dynamics: Flux Pure Compressor II, PSP Xenon Limiter

Channel strip: Waves Audio Track

Audio restoration: iZotope RX

Analysis: RNDigital Labs Inspector XL

‘What We Left Behind’ on iTunes

September 7, 2009

UK based band A Dancing Beggar are releasing their second album called ‘What We Left Behind’ on iTunes today. The album features samples of recordings of mine. A big thanks for that. I can only hope the recordings helped in the inspiration process.

Go check these guys out:

http://www.myspace.com/adancingbeggar

What We Left Behind

Mid/Side + Mid recording

April 29, 2008

No need to introduce the Mid/Side technique developed by Alan Blumlein as a means of obtaining a stereo recording.

While the the technique allows for an omnidirectional microphone to be used for the mid channel one most often sees a microphone with cardioid pick-up pattern being used. This is also the case in my own recordings. For field recordings this usually is a shotgun mic like the Sennheiser MKH60.

Not all cardioids are created equal however. Their frequency response differs greatly and by design cardioids do not pick up low frequencies very well. The same holds true for the figure eight mic used for the side channel. The excellent MKH60 and MKH30 have a frequency response of 50Hz to 20kHz and 40Hz to 20kHz respectively. Some microphones show a more or less important roll-off on the low end.

The relative lack of low frequency information which is the result of this frequency response can seriously influence the recording quality. Recordings might appear particularly thin. In some situations, e.g recording of bird calls, this might not be a problem. In other situations the recording is just not going to be realistic. A typical example is the recording of high waves rolling onto the beach. There is lot of low frequency information in the sound of waves hitting the beach.

To solve this I thought of extending the classic MS technique by adding a low pass filtered third mic. This third mic preferably has an omnidirectional pick-up pattern as an omni captures the low end much better then do cardioids.M/S+M recording

As I said, the trick is to low pass filter the signal. This can be achieved in post production or in the field by inserting a low pass filter such as the Schoeps LP 40 U in the signal chain before recording.  There is of course a requirement to have three input channels available. One for the mid mic, one for the side mic and one for the low pass filtered omni mic. I call this third channel the +M channel because it needs to be panned center in the mix.

In the field I mount a DPA 4060 just below the mid-side pair but since only low frequency information is retained I would think that it can be postitioned anywhere close to the main coincident mid-side mount. At low frequencies the time delay resulting from the distance between the mics becomes irrelevant.

One needs to take care not to turn up de volume trim on the +M channel too high. Low frequencies eat up the available dynamic range very quickly. The whole idea is to get a natural sound character.