Ambisonic vs SASS vs Iso-Binaural vs MS – Microphone rig comparison
There are a range of approaches to making audiophile, stereo recordings of natural soundscapes. Some of these technologies have been around for many decades, while others are more recently developed.
Last year, Doug Quin and Andrew Skeoch had the opportunity to put four state-of-the-art rigs to a side-by-side test.
Each array uses top-end microphones, deployed in the following configurations:
MS (mid/side): Pair of Sennheiser MKH 30 + MKH 40 in Røde blimp. This has been an industry standard option in film and TV for many years. (DQ)
Ambisonic: Soundfield SP200 Ambisonic, upright in Røde blimp. Ambisonic is a new technology offering multi-channel recording from a single microphone, with the ability to simulate various array patterns when decoded in post. (DQ)
SASS: pair Sennheiser MKH 20s in original Crown SASS head. The SASS has been described as quasi-binaural array. While the original Crown units are no longer available, many sound recordists have made DIY versions. (AS)
Iso-Binaural: Pair Sennheiser MKH 8020s, ~20cm apart, oriented 180º with convex baffles. This is also a quasi-binaural array, capturing a spherical soundfield with a light and versatile rig. It is a custom DIY design – info here. (AS)
The four rigs were set up side by side, in a small gully among wet sclerophyll forest, on the Lower Gellibrand River, Otway Ranges. Axes were aligned, and all recordings made to Sound Devices 7 series recorders at 24bit, DQ at 48kHz, AS at 44.1kHz. DQ’s raw levels were quite low. The MS rig was close to the ground (see pic)
As the ambisonic microphone can be rendered into almost any configuration, DQ created several different renders as examples of what it can do, using Harpex proprietary software. Screen shots of the software settings below for reference. The MS rig has been decoded to stereo wide.
In preparing edits, DQ’s files were down-sampled to 44.1 and everything to 16bit. Levels are subjective; all files have been normalised referencing the noise floor. This means some of the ‘noisier’ mics have been attenuated slightly to balance, thus reducing peak birdsong levels.
Hi-res files may be downloaded from soundcloud for better comparison. Headphones are recommended to hear spatialisation and localisation rendering.
Comments:
Each microphone array offers a subtly different stereo spatialisation. The SASS and Iso-binaural arrays capture true sound arrival time information, and hence create quite an immersive sense of space. While the single point configuration of MS and Ambisonic leads to audible limitations in this regard, these microphones offer more flexibility in the studio.
Localisation of sounds is similarly influenced. The bird that flies past the microphones at around 1.30 offers a good opportunity to compare this.
Tonality also varies, and here it is the microphone technology that is possibly more significant, with some capturing more delicacy and body of sound than others. Noise floors are also notably different. Of note may be the difference between the various older MKH series of Sennheiser microphones and the new MKH8020 (omnis).
(This comparison has been included on the Audiowings CD, edition #40, June 2019 – a stand-alone CD sans journal.)
Ambisonic rendered to omni capsule pair
Ambisonic rendered to ORTF configuration
Ambisonic rendered to cardioid pair in XY configuration at 180º
Ambisonic rendered to cardioid pair in standard XY configuration