From Stereo to Spherical: Why Ambisonics Needs Better Microphones
Traditional stereo recording captures sound along a single horizontal axis, but spatial audio experiences demand a full 360 degree recording of the soundfield. Ambisonics microphone recording, particularly with spherical arrays, enables engineers to reconstruct entire acoustic environments for immersive playback, precise acoustic measurements, and complex soundfield analysis. mh acoustics’ Eigenmike family has long been a reference platform in higher-order ambisonics, offering dense arrays of capsules mounted on a rigid sphere to encode full three-dimensional information. However, higher-order ambisonics is extremely sensitive to noise, dynamic range, and capsule matching; any deviation in magnitude or phase between microphones can degrade beamforming accuracy and spatial resolution. This has pushed developers to look beyond conventional electret condensers and capacitive MEMS devices. The latest evolution, the Eigenmike em64d, addresses these constraints by integrating next-generation optical MEMS microphone technology, bringing studio-grade performance and array-friendly consistency into a compact, production-ready spatial audio capture system.
Inside the Eigenmike em64d: Sixth-Order Ambisonics with Optical MEMS
The Eigenmike em64d is a sixth-order ambisonics microphone array built around 64 sensiBel SBM100B optical MEMS microphones distributed on an 84 mm diameter rigid sphere. This preserved geometry from the earlier em64 model allows continuity in workflows while significantly upgrading the sensor core. The array delivers a 20 Hz to 20 kHz frequency response, a 48 kHz sampling rate, and a spatial aliasing cutoff above 12 kHz, enabling detailed 360 degree recording ready for higher-order processing. On top of the hardware, the em64d includes a complete software environment, such as the EigenStudio application and EigenUnit plug-ins, to handle multichannel capture, advanced beamforming, and ambisonics decoding. For spatial audio professionals, this integration means that the array functions as a turnkey platform: from on-location ambisonics microphone recording to post-production spatial audio rendering, the em64d offers a tightly coupled hardware–software toolchain optimized for immersive soundfield work.
How Optical MEMS Microphones Deliver Studio-Grade Performance
sensiBel’s SBM100B is not a conventional MEMS microphone; it relies on optical sensing rather than a capacitive backplate structure. Inside each device, a vertical-cavity surface-emitting laser, diffractive optical element, and photodetector form a miniature interferometer that measures diaphragm movement via changes in optical path length. Eliminating the backplate allows up to 20 times greater membrane excursion compared with traditional capacitive MEMS, overcoming long-standing limits in noise and dynamic range. The SBM100B achieves an 80 dB signal-to-noise ratio, a 146 dB SPL acoustic overload point, and a 132 dB dynamic range, matching the acoustic performance of handheld professional condenser microphones that are 50–100 times larger in volume. For ambisonics arrays such as the Eigenmike em64d, this combination of low self-noise, high headroom, and tight unit-to-unit matching is critical: it preserves fine spatial cues, supports robust beamforming at higher orders, and maintains clarity across both whisper-quiet and extremely loud soundscapes.
Precision Spatial Audio Capture for Measurements and Immersive Production
By pairing a dense 64-channel spherical array with optical MEMS performance, the Eigenmike em64d enables spatial audio capture that meets both scientific and creative demands. Researchers gain a measurement instrument capable of high-accuracy acoustic characterization, complex soundfield analysis, and advanced beamforming with sixth-order hypercardioid patterns. For content creators, the same platform becomes a powerful ambisonics microphone recording system for immersive music, film, VR, and game audio. Its full-bandwidth, high dynamic range response allows sound designers to record intricate 3D environments—from quiet indoor ambiences to dynamic urban and natural soundscapes—without sacrificing fidelity. The precision of the array’s channels ensures stable localization and smooth movement of virtual sources when decoded to binaural or multichannel formats. In practical terms, this means more believable 360 degree recording, better translation to head-tracked listening, and a closer match between the original acoustic scene and the rendered spatial experience for audiences.
Manufacturing Advantages Bring High-Order Ambisonics to More Professionals
Beyond audio quality, sensiBel’s optical MEMS technology offers important production benefits that influence the accessibility of professional ambisonics tools. The SBM100B leverages surface-mount packaging and reflow-compatible assembly, simplifying integration compared with hand-selected electret condenser capsules. For mh acoustics, this translates into faster builds, shorter lead times, and reduced manufacturing complexity while maintaining the tight matching required for high-order arrays. At a system level, the shift to optical MEMS yields an 8 dB improvement in signal-to-noise ratio and a 16 dB gain in acoustic overload point over the previous electret-based Eigenmike design. Combined with digital interfaces such as PDM, I²S, and multichannel TDM options in the broader SBM100B family, the technology is well suited for future ambisonics microphone recording systems and other spatial audio capture devices. As production scales, more studios, researchers, and immersive content creators can adopt professional-grade 360 degree recording solutions without compromising on precision or reliability.
