Tech Focus: Surround Microphones

By Dan Daily, Audio Editor, Sports Video Group

Part 1 — Next-Generation Audio Immersiveness Nears, or Not

More than a decade has passed since broadcast audio moved into the surround era. Today, it’s poised on the brink of next-generation audio (NGA) immersiveness. Yet the dedicated surround microphone remains a unique niche in pro audio in general and in sports broadcasting in particular: somewhat exotic, technically sophisticated, relatively expensive, alluringly complex yet seductively suggesting a simple solution to a complex problem.

Cost is a major factor, as is the architectural diversity of many sports venues, which complicates the predictable placement of mics. DPA, Sanken, and Holophone surround microphones can have unit prices of $5,000 or more, and SoundField’s DSF-B Digital Broadcast Package ranges into the low five figures, including its processor. However, manufacturers have also created simpler and lower-priced surround-mic products, such as Holophone’s Sports Mic and HD3, which sell for $1,000 and $2,000, respectively, a fraction of the $6,000 cost of its H2 Pro flagship model.

But there are also cultural differences: whereas surround mics are a small niche in the U.S., they’re a regular component of the broadcast-sports audio infrastructure in Europe. Karl Malone, director of sound design for all of NBC Sports, notes the overwhelming dominance of a single sport (soccer) there, the limited number of national broadcasters, and the architectural uniformity of its stadiums make it a good fit for permanently installed dedicated surround microphones.

“UK stadia generally follow a certain build structure, which places camera positions and announcers under an extended roof structure generally in the 130- to 160-ft. height range,” he explains. “The announcer position can either be hanging from that roof closer to the rear stadium wall or extended out as much as 30 ft., which, when you hang a surround microphone system, will give you lots of left-surround/right-surround crowd [sound] behind the microphone.”

In the U.S., by comparison, the variety of major-league sports, the diversity of their venues’ architectural designs, and the scattering of their broadcast rights among a half dozen major networks and a growing pool of regional sports networks, plus the relative independence of the freelance base of A1s and A2s here versus the staff-based personnel in Europe, work against a uniform approach to capturing surround elements.

Though acknowledging that the time required to properly position and test surround mics in live sports can be challenging, Malone points out that the huge variety and relentless scheduling of broadcast sports in the States, combined with the thinness with which networks’ field-ops assets are distributed, actually argues for more use of dedicated surround mics.

“When using a fixed array [of microphones to capture the surround field], the placement is crucial, and that can be difficult in a one-day set and shoot,” he says. “If there is time to mount the mic correctly, then [surround microphones are] a great tool in providing surround crowd ambience. The advantage of having a phase-coherent downmix makes the resulting signal clean of potential phase issues.”

That, he continues, would be even more apt in an immersive sound environment. “In any live Dolby Atmos or DTS:X mixing, having a stable 5.1 bed from a fixed surround mix would definitely give room for the engineer to build objects around it and above it, whilst all the time checking and maintaining the downmix for the stereo listener,” he says. “Perhaps the market will be reinvigorated when we start to hear the next-generation audio systems delivering even more-immersive productions.”

The Manufacturer’s Perspective
Manufacturers of surround microphones say the shift to immersive audio could very well jump-start the category. Jim Pace, president of Plus24, which distributes Sanken’s WMS-5 surround microphone in North America, says activity has been picking up first in cinema markets, where formats like Atmos and DTS:X already have significant traction, with episodic television increasingly using that type of mic, in anticipation of broadcast’s future transition to NGA.

“That’s the path that this will likely take to broadcast sports,” he says. “Immersive audio is going to be great for live sports because they’re emotional and immediate. Surround microphones are a good tool for capturing that.”

However, sales and rentals of dedicated surround microphones may actually have receded in recent years. Rod Allen, senior product manager at Bexel Global Broadcast Solutions, says he saw a spike in interest a few years ago but that has faded. He observes that the ability of A1s to remotely steer the capsules on SoundField’s DSF-B MKII microphone and its DSF-2 MKII microphone controller stirred interest for a while. More recently, he says, rentals for those types of applications have shifted to SoundField’s UPM-1 stereo-to-5.1 upmixer, which automatically generates a surround sound field.

“There’s a lot going on in the A1 booth, and a dedicated surround microphone might be one more thing that distracts them,” he speculates. “They’re concentrating on building a show, and it’s easier to deal with stereo sources and then upmix them with a simulator.”

Joe Prout, broadcast specialist at Dale Pro Audio, largely concurs, also citing U.S. broadcast culture, where freelancers may find themselves in unfamiliar remote units facing tight deadlines, unlike European A1s, who usually stay with the same unit for years at a time. As a result, he says, “our major broadcast-sports mixers and sound designers choose to go a different route … in terms of how they create their surround beds for their mixes.”

As surround sound moves from the 5.1 model into a much denser multichannel future, it may be an ironic anecdote that the tools to create it will remain rooted in the mono and stereo microphones that most domestic A1s deploy to create their surround fields. But the dedicated multicapsule surround microphone will always be on the shelf, within arm’s reach.

Part 2 — A Look at the Latest Products

Considering how crucial surround audio has become for broadcast sports, the number of specialty surround microphones has remained relatively static in recent years. But manufacturers say that the major networks are showing heightened interest lately. Here’s what they have to choose from, including Holophone’s new VR360, the first surround mic specifically intended for the immersive market.

DPA Microphones
The d:mension 5100 mobile surround microphone requires no external signal processing and can be mounted on a camera or microphone stand, suspended, or simply handheld via a handgrip. It features five miniature condenser transducers, which exhibit extremely low sensitivity to wind and mechanical noise, low distortion, highly consistent low-frequency response, and large dynamic range. Appropriate channel separation and directionality are achieved through a combination of DPA’s proprietary DiPMic (Directional Pressure Microphone) technology, which mounts interference tubes on the L/C/R omni capsules, and the use of acoustic baffles, which further preserve the accuracy of levels between the discrete analog output channels. The d:mension 5100’s three front microphones are time-coincident to eliminate comb filtering and ensure frequency consistency in downmixing stereo or mono. The rear microphones, which feature standard omnidirectional patterns, are optimally spaced both from each other and from the front array to simulate the most natural time-arrival differences. The LFE (.1) channel is derived from a L/R sum, which is then attenuated 10 dB in comparison with the signal from the main channels, in accordance with the 5.1 format. The 5.1 output of the 5100 runs through a multipin Lemo connector carrying all six channels electronically balanced, and an enclosed 5-meter (16-ft.), six-pair Mogami cable breaks out to six Neutrik XLR-M connectors. www.dpamicrophones.com

Holophone
The new VR 360 immersive-audio microphone is an eight-zone 360 microphone designed for capturing immersive 3D audio live for VR and 360 spherical camera systems. Pricing will be $2,495.

The H2Pro-5.1 terminates in six XLR microphone cable-ends (Left, Right, Center, Low Frequency, Left Surround, Right Surround) that co-relate to the industry standard 5.1 channels. Users have total control and flexibility over the incoming discrete surround-sound audio signals and may choose to use as many or as few channels as any surround project requires: channel assignments are discrete all the way from the recording and mixing process to final delivery.

The Holophone H2-PRO 7.1 is capable of recording up to 7.1 channels of discrete surround sound and terminates in eight XLR microphone cable-ends (Left, Right, Center, Low Frequency, Left Surround, Right Surround, Top, and Center Rear). These co-relate to the standard 5.1 channels and add a top channel for such formats as IMAX and a center-rear channel for extended surround formats, such as Dolby EX and DTS ES.

The cost-effective H3-D features five multidirectional, full-bandwidth microphone elements and a discrete LFE microphone in one integrated capsule. The unit offers LED verification of external phantom power and is compatible with all standard XLR mic inputs on recording consoles, external preamplifiers, and location recorders that provide phantom power.

The H4SuperMINI features both a Dolby ProLogic II encoded stereo output that can be used on any stereo recording device, from broadcast cameras to handheld recorders. In addition, the H4 SuperMINI also features three 3.5-mm stereo outputs for recording of the six individual microphones. The H4 also has built-in headphone monitoring, a zoom feature that will forward-bias the pickup pattern, a -12 dB pad, and an on-board center-channel microphone input that features phantom power supply. This allows the user to input any external microphone into the mix. Included with the H4 SuperMINI is a TA-6 to dual XLR output for a robust balanced signal. www.holophone.com

Sanken
The WMS-5 is a 5-channel surround microphone with its matrix electronics housed in a single body. Based on extensive M-S stereo research conducted in conjunction with broadcaster NHK, the WMS-5 delivers realistic surround sound with minimal setup time and is easily mounted on the camera, boom pole, or pistol grip. It delivers reliable, phase-coherent, 5-channel sound using five discrete output signals. The M capsule is used for both center (with shotgun directivity) and front left and right channels. The S signal is used for both front left and right and rear left surround and right surround channels. The rear M capsule handles left surround and right surround. All capsules are aligned vertically on the same axis for precise phase coherence. The WMS-5 weighs 8.3 oz. and is 9.25 in. long. www.plus24.net

SoundField
The DSF-B MKII Digital Broadcast Package provides everything required to capture audio in mono, stereo, 5.1, and now also with height surround-sound formats, such as 5.1+2, 5.1+4, and 7.1+2, as used in object-based surround sound. The DSF-B system offers a high degree of control over a wide range of microphone parameters from the audio-control room without the need for physical changes to the microphone. It consists of the DSF-2 MKII microphone — a multicapsule microphone and a 1RU digital microphone-control unit — and the DSF-3 MKII digital surround processor. The DSF-2 MKII microphone captures wholly phase-coherent multichannel audio, which can be folded down without the creation of unpleasant phase artifacts; this suits it for surround-sound broadcast applications where all 5.1-audio needs to be 100% downmix-compatible at all times. A crucial new function of the MKII is a wide range of integrated system self-tests with alarming and correction. They include the monitoring of all supplies (including those for the microphone) and monitoring of microphone-cable status, showing detected errors on the front-panel display and the SoundField remote app, while auto-correcting errors as necessary to allow the event or recording to continue. www.tslproducts.com

Sennheiser
The Esfera surround system consists of the SPM 8000 two-channel microphone unit and the SPB 8000 processing unit. The processing unit uses an algorithm matched to the microphones to generate a 5.1 surround signal with sampling rates of up to 96 kHz. An integrated compressor ensures a broadcast-friendly signal. For ease of operation, the processing unit uses four directly selectable presets. These can be modified via an Ethernet interface to adapt to local conditions, including the settings for the gain of the individual channels, front and surround focus, surround delay, rotation, filters and cutoff frequencies, compressor, makeup gain, output gain, limiter, and windshield compensation. www.en-us.sennheiser.com