Reddich, UK—Toward the end of 2018, Luminex announced that SSE Audio Group had acquired so many of its GigaCore 26i network switches that it had become “one of the largest providers of Milan AVB-compliant networking solutions.” The switches were first deployed on a Christmastime UK arena tour by Madness on SSE’s drive system to its L-Acoustics P.A. rig.
AVB itself has been used by a variety of production providers in recent times on tours by the likes of Dierks Bentley, Metallica and Arcade Fire, and at the Roskilde Festival in Denmark, but with the availability of the new GigaCore 26i switches, Milan AVB appears to be moving closer to reality.
The Milan AVB specification is a subset of the larger open source Ethernet AVB protocol, which has been adopted for automotive, consumer and industrial applications, not just pro AV. To focus on the specific requirements of pro AV, a group of manufacturers within the Avnu Alliance—the consortium that promotes AVB and certifies compliant products—has been working to define the Milan specification. Those companies include AudioScience, Avid, Biamp, d&b audiotechnik, L-Acoustics, Luminex and Meyer Sound, among others.
“On the one hand, there are things that might be required for Avnu certification across all industries. We do not want to spend the time being compliant with something that maybe only automotive cares about,” explains Derk Hagedorn, senior product marketing manager, Avid live sound and studio consoles and controllers. On the flip side, he says, “There is something that we do want, and that we are agreeing on, that is going to work a certain way, and that we are compliant with—and that a car manufacturer isn’t going to care about and isn’t going to implement.”
A compliance program is in place, as is a preliminary Milan-capable certification, says Ryan John, Avid’s live sound principal product designer and product manager, who is on the Milan development team. “There will be an icon and certification, so users can just look for the Milan icon, at which point they should know that their devices can speak to one another.
Related: At InfoComm: AVB Advances with Milan Protocol, June 7, 2018
“I imagine that in software, we will also find a way to indicate that a device is Milan-compliant, since anything AVB could theoretically show up in an AVDECC controller. But I don’t think that has been included in the spec,” adds John.
“The real meat of it is that everyone can support the same stream formats. Devices that are just talkers can use any one of many options, but all listener devices must be able to support all of the options. This ultimately means that any device that can take an AVB audio input would be able to then listen to any Milan device,” John says.
In a news item on SSE’s website, hire manager Miles Hillyard stated, “With Milan on the horizon, SSE has taken the opportunity to stay ahead with technology and widen its arsenal by investing in AVB-enabled systems.” For the Madness tour, SSE added a pair of L-Acoustics P1 processors (one of the first Milan-compliant products to be introduced, at InfoComm 2018) to the drive rack, together with a Luminex switch. Two additional GigaCore 26i switches were added to the stage left and right amp racks.
From SSE Audio Group: Milan AVB Implemented for Madness by SSE Hire
“The initial signal path in the new system is AES from console to P1 processor, where it is converted to AVB,” explains SSE assistant technical manager Keith Sujeeun, who built and configured the system. “Once converted, the signal remains as AVB right through to the L-Acoustics LA12X amplifier inputs. Locally, signals are run over Cat 6 cabling, while the long run from FOH to stage is fiber optic.”
For those concerned about redundancy, “We use a pair of fibers between the FOH and stage left switches, which form an RSTP loop, and an additional pair of Cat 6 cables between the stage left and stage right switches, which form an additional loop,” says Simon Gladstone, SSE’s technical manager. “This allows the network to reconfigure in the event of a cable failure without manual intervention, which may not be possible during a performance.”
RSTP, or Rapid Spanning Tree Protocol, is a popular redundancy solution in critical aerospace and energy networks. “The nature of RSTP means that there can be some time to rebuild the network, especially when AVB streams are present and may also need rebuilding, so this is where the analog failover comes into play,” says Gladstone. “We are happy for the system to failover to analog in the event of a problem, and in the case of a cable failure, we can move back to AVB at the end of a song, once the network has healed itself.”
Touring system engineers may be understandably wary of commercial-off-the-shelf switches, but Gladstone notes that GigaCore was specifically built for the entertainment industry. “This means that our existing audio guys don’t need to become network engineers to program the switches. Making just a few configuration changes in the Luminex web GUI makes it very plug-and-play. The user only needs to enable AVB on the ports that require it and alter some basic redundancy settings.”
Related: Milan Gains Momentum in Pro AV, by Steve Harvey, Feb. 22, 2019
SSE has been using a digital drive setup for more than eight years, initially adopting Dante because it was native to the Dolby Lake Processor. That removed the numerous conversion steps demanded by the previous analog drive system. Yet even Dante, Optocore and others introduce a certain degree of degradation, Gladstone says.
“There is no doubt for me that taking a digital signal and buffering it, reclocking it through an AES transmitter, putting it through an AES receiver, converting it to Dante/Optocore or any similar protocol, then reclocking it and rebuffering it again to get it out of the transport system and back into the AES domain, rebuffering it and reclocking again to bring it into the land of ones and zeros for the amp to interpret—degrades the signal. Nowhere near as much as our analog system, but there is nevertheless a certain amount of degradation,” he says.
“Now we have AVB system processors and AVB amplifiers available, which don’t require any additional conversions to transport the audio between them. Milan AVB can take this one step further because we now have leading loudspeaker manufacturers not only choosing AVB as their preferred digital network protocol, but also joining forces and coming together to define the many different AVB ‘standards’ available to ensure interoperability. Once again, that enables us to remove another part of the transport system from the equation.”
Luminex • www.luminex.be
SSE Audio Group • www.sseaudiogroup.com