Sound, Space & AMBEO
It’s 9.1, it’s binaural — just what exactly is Sennheiser’s AMBEO platform all about?
Sound and space become one”, announced Dr Andreas Sennheiser at the Global Press Conference for IFA 2017 in Berlin. “If the brain can’t differentiate between reality and reproduction, we are there.”
He was talking about AMBEO, Sennheiser’s “3D audio experience on headphones or loudspeakers”. The company has been putting increasing emphasis recently on AMBEO, but for what purpose, exactly? It’s clearly evolved since we first reported on it, when AMBEO was presented as a variation of multichannel audio, more for music than movies, and replayed on a 9.1-channel loudspeaker system. Sennheiser’s ‘tonmeister’ and sound engineer Gregor Zielinsky was pioneering such music recordings in 9.1, and he spent several years demoing and advocating this recording technique at expert meetings and (pro) audio conventions, culminating with open demonstrations at CES 2016 in Las Vegas, and elsewhere.
The 9.1-channel AMBEO system includes height elevation speakers, and in addition to the native music recordings the system could upscale from two-channel stereo. It found early application in event audio, installed for a travelling David Bowie exhibition in 2015 and currently for the Pink Floyd ‘Their Mortal Remains’ exhibition at London’s V+A Museum, which includes an AMBEO mix of Floyd’s ‘Live 8’ performance (a slightly awkward one-off reunion in 2005 between Roger Waters and the rest of the band). This adds one more multichannel format to the
Floyd’s long experimentation through quadrophonic ‘Dark Side’ to Hugo Zuccarelli’s Holophonics technology on ‘The Final Cut’ (slightly scandalous, see panel overleaf).
But the domestic market for multichannel audio is in notorious decline, and is heavily weighted towards movies, where Dolby Atmos, DTS:X and Auro-3D are already defining the new adaptive and/or object-based delivery of soundtracks, and occasionally music. And by CES 2016 Sennheiser was already shifting emphasis to “a strategic focus on 3D immersive audio”, seeing the rise of virtual reality and 360 video as key markets for a wider definition of immersive audio. These applications would seem to be the very antithesis of loudspeaker-based multichannel reproduction, requiring two-channel headphone delivery of an immersive environment, able to track or match video movement. And when the AMBEO logo was unveiled, it included the tagline ‘Capturing - Mixing - Processing - Listening’, highlighting Sennheiser’s ability to deliver at every point of the chain thanks to its combination of professional and consumer product lines — from microphones through to headphone delivery.
Today, then, Sennheiser splits AMBEO into three areas. “Pick your blueprint”, says its guide to AMBEO best practise. There is AMBEO for loudspeakers, “recording 3D music for 9.1 loudspeaker setups and beyond”. Secondly there is AMBEO for binaural, “for easy on-the-go headphone reproduction”. And thirdly AMBEO for Virtual Reality, “fully immersive sound – Sennheiser’s take on Ambisonics”. Binaural versus Ambisonics Binaural and Ambisonics are two quite different things. Binaural recordings are generally made with microphones placed in the ears of dummy heads to capture every nuance of what our ears truly receive, and are then replayed through headphones or earphones with the hope that the result convinces the brain that the sound is real and immersive. Software today can mix to binaural, and there is also a ‘quad binaural’ technique which requires four sets of binaural dummy heads. There have been periodic revivals of interest in binaural recording, and we are seeing this at present — Episode 4 of the current Doctor Who season was given a special binaural mix made available on ABC iView — head to 23:30 for some highly effective knock-knocking effects with clear ‘behind you’ directionality, showing off the binaural ability to deliver convincing positioning.
Binaural is, however, a fixed two-channel recording. Ambisonics aims for a channel-independent spherical sound field, which should be able to be adapted to any speaker layout — and, crucially for VR applications, which allows for dynamically manipulated binaural playback on headphones. And although various parts of the technology were originally patented and licensed out of the UK (Nimbus Records was a key licensee), the main patents are now expired, so that any company can develop the ideas.
Last year Sennheiser brought its microphone expertise into play to create the Sennheiser VR Mic, a beautiful object (pictured below left) with four identical condenser capsules in a tetrahedral cluster — it’s like a 360 camera for audio. It records to four separate channels at once, expanding the idea of an M-S microphone where the primary audio is recorded with a left-right soundfield for width; the VR Mic adds front-back and up-down to these. For professional recordings it would be likely to add separate spot microphones to highlight details or for clean dialogue pick-up, and for augmented reality, as Dr Andreas Sennheiser put it, “this is more than the real world — we need to blend it with the virtual world”.
The mixdown is, therefore, not trivial, and to deliver an effective twochannel result for headphones or VR goggles, binaural rendering software is required, including Head-Related Transfer Function processing to deliver the brain-convincing elements that come from true binaural positioning. Yet despite the complexities, the interest is high — accelerating global investment in VR and 360 video has seen Sennheiser sell more than 2000 of these microphones since its launch last November.
Away with your dummy head Mr Neumann; Sennheiser’s AMBEO Smart Headset means we can now use our own.” Neumann KU 100 dummy head, image: EJ Possel
AMBEO Smart Headset: a review The $3000+ VR microphone is, however, hardly a thing for the more casual video maker or recording fan. Sennheiser’s latest delivery, however, proves quite the marvel in that regard. We have been playing with a sample of the AMBEO Smart Headset, presented to us at the IFA GPC by Dr Andreas himself, and we love the results — though we might note that we had been less impressed with the short headset demonstrations being given in the Sennheiser booth at CES 2017 back in January.
The concept is simple enough — earbuds with microphones on the outside, able to record native binaural two-channel from as near as damn-it the binaural dummy head position. Dr Andreas noted the experience of Sennheiser and sister company Neumann in this regard — the Sennheiser MKE 2002 “head stereo microphone” in 1974 and Neumann’s KU 100 dummy head in 1992. The new AMBEO Smart Headset brings the technology firmly into the the 21st century — for starters it’s built for Apple devices only, its cable terminating in an Apple Lightning connector, and apparently only working with OS 10.3.1 and above. The
two omni-directional microphones are covered with unobtrusive silver grilles on the earpieces which hook over your ears, descending to a 7cm lozenge which contains “a premium A/D converter, mic preamp and SoftLimit from Apogee” — Apogee gets a ‘powered by Apogee’ credit on the back, and its reward seems to be that for audioonly recordings, you’ll need to buy the Apogee MetaRecorder app (pictured left; no great ask at $7.99; the free version will record only 60 seconds at a time).
But the Smart Headset also records without need for further purchase to the iPhone’s own Camera app when video recording, and this delivers results so spectacularly superior to the iPhone’s own microphone that it takes only moments to be convinced. The rich binaural soundfield avoids the usual ‘headphone’ sound of a plane between left, right and front/top of head — instead it is truly immersive. While the bulk of the sound does pan to hard left and right (the zones of maximum sensitivity for the microphones) there is enough surrounding detail to fill a real atmosphere of believability.
There are new recording rules to be learned — don’t point the iPhone without also pointing your head; most people naturally pan a phone moving just their arm or hand, whereas to track sound accurately with video, you need to pan with your whole body. And if, like us, you find earbuds need constant little pushes to lodge them deep enough in your ear for full bass response, well, here you’ll be pushing on the microphones and so causing big rustling noises.
Another oddity (perhaps to be corrected later, as these were an early sample) — you don’t hear what you’re recording until you play it back; they don’t play audio through the buds while you record, leaving you in a strangely silent world, passively isolated by the earbuds. We thought this was possibly to avoid feedback between the earbuds and the mikes, but with the Apogee app you can turn on ‘Input monitor’ in settings to hear the sound live, and without apparent problems. Also with the Apogee app you can choose your recording quality up to 24-bit/96kHz, whereas recording video to the iPhone’s Camera app seemed to offer only 128k AAC, making the results of recordings we made to video all the more remarkable.
Our 24-bit audio recordings via Apogee were sensational. We sat in a hall for a music concert and recorded the lot; again, you have to learn to keep still and face the music, but the sense of atmosphere and hall acoustic were thrilling. And with nothing to monitor — by virtue of the Apogee SoftLimit system there is no level control either into iPhone video or the Apogee app — we checked the recordings and they were kept about 6dB away from clipping, so there’s a fair bit of headroom left for trouble (or added to the noisefloor, depending on your point of view). Importantly there was no sense of ‘pumping’ from auto gain control, and the great plus of this is that there’s no need to keep a constant eye on level, and very little chance of buggering up your audio.
We assume Sennheiser will deliver non-Apple versions in due course — perhaps USB-C, perhaps analogue minijack (but perhaps not, given the processing and output here are all currently digital). The price — not yet announced but with hints putting it in the A$500-700 range — is not insignificant for your average punter keen just for a play, but for anyone serious about creating immersive recordings for video, Sennheiser has delivered a semi-professional binaural recording tool for a remarkable price. Away with your dummy head Mr Neumann; Sennheiser’s AMBEO Smart Headset means we can now use our own.
CES 2017: visitors queued for a mere minute of AMBEO. Insets: Dr Andreas Sennheiser presents AMBEO to the IFA Global Press Conference; our Editor listens in using the AMBEO Smart Headset.
Music by Pink Floyd, sound by AMBEO: The Pink Floyd Exhibition ‘Their Mortal Remains’ is running at the V&A in London, with an AMBEO 9.1 presentation of their 2005 Live 8 performance.
ABOVE: The new Sennheiser AMBEO Smart Headset, specific to Apple iOS devices as it uses a Lightning plug to connect. It records direct to video soundtracks in the Apple Camera app, or audio only to Apogee’s MetaRecorder.
TOP: Poster for ‘The Massed Gadgets of Auximines’. Designed by Hipgnosis in 1969. Given by Pink Floyd Music Publishing. © Victoria and Albert Museum, London BELOW: Azimuth Co-ordinator used by Pink Floyd; V+A Museum, London, Image Andreas Praefcke