Seesaw installation by Alvin Lucier in Max/MSP

December 6, 2009

From December 21, 1983 though January 18, 1984 Alvin Lucier exhibited his ‘Seesaw’ sound installation in the Film and Video Room of the Whitney Museum of American Art in New York. The installation aimed at having the visitor experience sound waves as a physical presence.

In a small Max/MSP project I set out to recreate the experience.

The idea is to have two sine waves generated in a quiet room, one at a fixed frequency of 256Hz, the other sweeping between 255.8 and 256.2 Hz.

A spinning is noticed that accelerates to once every 5 seconds as the sweeping oscillator frequency drops from the reference 256 to 255.8 cycles per second. Movement is from the speaker with the highest frequency to the one with the lower. As the sweeping oscillator raises its frequency the sweeping reverses. For full experience the room must be free of reverb.

For now my patch requires manual operation of the sweeping oscillator. In the original installation the sweep down 0.2 cycles, up 0.4 cycles past unison and down to unison again would take 3 minutes. Automating this will be for version 2 of the patch.

The spectroscope window provides on screen visual feedback about the (slow) beats occurring.

 

Literature:

Alvin Lucier: Reflexions Reflexionen; Interviews, Scores, Writings 1965-1994; MusikTexte; Köln, 1995


Mid-Side recording and Microphone Sensitivity

November 1, 2009

Small technical backgrounder this time.

When recording stereo it is essential to have equal gain settings for the microphones at the risk of the stereo image shifting to either left or right. More gain on the right mic channel will shift the image to the right and the other way around. Equal gain settings are especially important in XY, ORTF or any other spaced or coincident microphone positioning.

With mid-side recording the gain setting for the mid and side channels allow you control the stereo spread. More gain on the side channel compared to mid will widen the stereo image. More gain on the mid channel will narrow the image. Ultimately, no gain on the side channel will leave you with a centered mono signal from the mid mic.

Reading gain or trim pot settings is easy enough but you usually end up with differences in signal strength if you don’t take into account microphone sensitivity even with an equal gain setting on your recorder or mixer. Unless you have a matched pair, microphones have different sensitivity characteristics.

A typical MS setup is the Sennheiser MKH60/ MKH30 microphone pair.

The MKH60 has a sensitivity of 40mV/Pa, the MKH30 has 25mV/Pa. With equal gain you will end up with a much stronger mid signal and consequently a narrow stereo image.

The calculation to compensate for sensitivity is as follows:

±dB = 20 x log(MmV/SmV)

where

MmV = sensitivity of the mid mic in mV/Pa
SmV = sensitivity of the side mic in mV/Pa

In our example we need 4.1dB more gain on the side channel compared to the mid channel to get equal signal strength on both of the recorded channels.

This is easy to realize on mixers such as the Sound Devices 302. With MS stereo linking set trim pots allow you to set gain for the mid and side channels separately. The input 2 fader controls the overall gain for the pair.


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