Review: Sennheiser Esfera

Sennheiser’s Esfera surround sound system has certainly generated interest in the pro-audio industry, and won an IABM Design & Innovation Award at this year’s IBC too. Iain Betson immerses himself in its
sound-field to hear what everyone has been talking about.

A while ago I attended a training session on a much-respected broadcast industry audio desk and met others from different disciplines within the industry. An attendee from the OB sector remarked to me how pleased he was that one of his clients didn’t want surround sound in their sports coverage, since it would make his rigging of the venue much less complicated.

Well, the new Esfera product from Sennheiser may change his mind. Rather than five mics, the Esfera achieves 5.1 surround sound with only two microphones and associated cables. Surround sound with rigging ease then? Perhaps this may be true. I do know it is most definitely a case of getting more for less.

What You Can’t See 

How does the Esfera create 5.1 from just two microphones? In short, I am not entirely sure really! Both from searching the net and questioning Sennheiser when I saw a pre-production model at IBC 2013, I received a range of answers, from “it’s in the DSP” to “smoke and mirrors."

The Esfera SPB 8000 processor is designed to work with two specially-matched MKH microphones, arranged in a conventional X-Y pattern, thereby acting as a single point source from which to capture sound. The mics are housed in a basket windshield blimp (a fluffy comes as a supplied accessory too) and a couple of short XLR terminated cables thread their way through the pistol grip handle. This whole arrangement is called an SPM 8000.

The X-Y arranged microphone pair plugs into the Esfera processor via two XLR connectors and this is where all the smoke and mirrors stuff happens. The algorithms within the processor’s DSP recognise the physical and electrical responses of the MKH mics and how they are positioned relative to each other. Armed with this information, it is able to create a 5.1 surround sound-field and output this as three discrete AES signals. AES output one has the FL and FR signals, output two the centre and LFE, and number three the two surrounds, Ls and Rs.

What You Can See

The front and back panels of the processor are both simple in layout. On the front, from left to right, you will find a single rotary switch to adjust the two mic preamp gains, and three buttons for activating: 1. 48V phantom power; 2. the input signals as either analogue or digital format; and 3. a compressor.

In the centre of the front panel are eight meters that are useful for seeing what the Esfera is up to as they show the two input and six output levels. To the right of the meters you will find a series of LEDs indicating the selected sample rate – 44.1, 48, 88.2 and 96kHz – how the Esfera is synced – either from AES or word clock – and finally an LED telling you that the unit is powered.

Four push buttons on the right-hand side work in conjunction with the control software (more on that later) and allow direct access to the four surround configuration presets that can be set up and stored.

The back end is largely XLR based, with connections for the analogue inputs and three AES outputs. There are two BNC connectors that handle word clock input and loop-thru. The Ethernet connection uses a Neutrik Ethercon connector, which is good to see.

I have a personal gripe with manufacturers producing equipment aimed at the professional but using the cheap and horrible panel-mount version of this data connector, commonly found on IT kit. While the Ethercon still uses the RJ45 as its basis, at least the external shell offers it protection, a decent locking action and a more rugged quality.

Finally, there is a fused IEC mains inlet, rather than an external PSU.

The whole 1U-high package comes in a well-put-together, brushed aluminium fronted box; well, it is Sennheiser after all. 

Surround Control

With so few front-panel functions, control of the Esfera is done via a downloadable piece of software available on the Sennheiser website. If you want to see what it looks like, it can be downloaded from the following link:

I usually have a mental large pinch of salt handy whenever a manual glibly says “connect the device to a router and enter this IP address” as, more commonly, doing this results in a “no devices found” error message being displayed.

However, in this case, doing as the manual instructed resulted in the connection working first time, and perfectly too.

There are only two simple screens in the config software: a connection setup page and a compression/surround sound settings page. The screenshot below shows the surround settings page in more detail.

A University Examination

In order to give the Esfera a real-world test, I enlisted the help of John Crossley, senior lecturer in music production at the University of Derby’s Department of Performing Arts. I have known John since I wrote a piece on the Dante-based Focusrite RedNet system. The department was the recipient of the first RedNet system sold in the UK and, upon visiting John to see it, I was struck by the quality of the studio facilities at the university. So, I was aware that if the Esfera was going to be put through its paces, this was the place to do it.

As well as spending time testing the Esfera, John very kindly put his thoughts about it, and the findings of the tests he conducted, to paper.

Regarding the build quality, he concurred with me in that it was impressive but, regarding the software, his experience echoed my earlier comment about easy configuration and pinches of salt.

Although the software was easy to use, he did encounter connectivity issues with the PC on which he was running it and had issues persuading it to connect to the Esfera. When the network switch in between was reconfigured, everything worked. So, although it was no fault of the software, this minor niggle meant the ‘plug and play’ setup was not as smooth as it could be.

Of the Esfera processor itself, John felt that for maximum connection flexibility it would have been ideal to have analogue outputs as well as AES.

To rig the Esfera in the studio he used a RedNet 3, the product in the Focusrite range that supports up to eight AES inputs and a word clock feed. Although all worked perfectly, having balanced audio outputs would have eased connection to the studio desk.

That said, I can see that trying to fit six XLR connectors onto the rear panel would be impossible, meaning a breakout lead from a multi-pin connector would be the only alternative. The result would then be increased complexity and, I guess, price.

“Testing, testing, one to ten”

The tests John and his students conducted were quite expansive. The initial test was akin to, if you recall, Track One on that Hi-Fi News audio test CD from a good few years back, in that one of the students walked around the array, counting from one to ten.

The impression gained from this test was of ‘rear-ness’ as he walked around the back. This seems at odds with the fact that, as the MKH microphones possess a cardioid pickup pattern, you would think that they would be biased more towards sounds from coming from the front. A case of the processor ‘smoke and mirrors’ working a little too much perhaps?

In the next test, a drum kit was set up in the facility’s live room and the SPM 8000 array was rigged on a stand about two metres away, and set to point at the middle of the kit. Playing the kit produced a nice natural sound from the Esfera, coupled with a good sense of space from the recording room.

I agreed with John when he said he could “sense” as well as hear the surround reflections from the Esfera. Perhaps you know that feeling too? You just can’t define what it is, but sometimes you can ‘feel’ a sound more than you hear it.

The next two tests conducted were to evaluate how well the system coped with a moving sound. To achieve this, while the kit was played, the SPM array was first rotated 360º on its horizontal axis and then, hand-held, walked 360º around the drum kit.

John said: “In both cases there was a clear sense of movement. The left to right space was very clear although, as the signal moved to the ‘rear’, it was slightly less identifiable as being behind the listener, but you did get a real sense of a shift in balance from front to rear.

“I wouldn’t say there were any ‘holes’ as the sound-field was quite uniform; it was more a case of a change in the definition of the sound as it moved to the rear.

“At times I definitely felt I was hearing something travelling around me which, considering the sound has been captured from a simple X-Y arrangement, is quite remarkable.

“Overall I was pretty impressed.”

In conclusion, John added: “To be able to generate a realistic 5.1 sound-field from a two-channel system so convincingly means I think the product definitely has potential. Being honest, in many cases, people listening in 5.1 just want to be able to hear a sense of ‘space’ and the Esfera easily achieves this too.

“Obviously, if you wanted to record a concert in 5.1 you would use multiple mics, but if rigging time/equipment etc was tight or if facilities wouldn’t allow, this would be a really useful tool.”

John’s last answer illustrates the perceptions of two sectors of the pro-audio industry when it comes to equipment cost. At a combined sum of around £10K for both the Esfera control unit and the SPM 8000 microphone array, I asked John if he felt this represented value for money when compared to a ‘conventional’ 5.1 microphone setup. His feeling was that it was pricey for the sector he knows well – the recording industry – but, interestingly, added “…but then again in the broadcast market this probably isn’t the case”.

With my professional experience being largely in the broadcast sector I can say that, while £10K for an audio-based piece of kit could be considered as being on the high side, when compared against video-based equipment it’s a drop in the sea (perhaps ‘ocean’ would be stretching it a little) But, when this price is offset against the costs incurred through the repeated rigging of a surround-sound system, using dedicated microphones in, say, a sports venue, and the fact that you could also put the two channels of the mic array down existing camera located microphone feeds, I think its price looks to be more acceptable.

I am sure my observations, along with John’s, would appeal to those industry colleagues I met on the training course. If the client’s remit changed and surround sound was demanded as part of the contract, they would be wise to consider the Sennheiser Esfera and its associated SPM 8000 microphone array as an acceptable counter to the extra rigging that would otherwise be required.

Sometimes, just sometimes, less is more.

Thanks must go to John Crossley, subject leader, popular music production, department of performing arts, University of Derby.