Transferring audio from one place to another is easy—until the question comes up of how to get lots of audio over a long distance, and do so reliably. For pro audio, Audio over Internet Protocol (AoIP) is the solution for distributing audio in stadiums, large houses of worship, multiple studios, broadcast, and the like. AoIP systems have the potential for high audio quality; they can run at a high bit rate, with low latency and no audio compression. However, whether that potential is realized depends on the AoIP protocol itself, and the system hardware.
Another consideration is redundancy, because for any kind of broadcasting or live sound work, reliability isn’t just desirable—it’s essential. Ease of collaboration and data-sharing is also an important AoIP attribute. For film scoring, where multiple studios and teams are often in play, networking promotes a collaborative workflow and shared resources. Professional recording is another field where not everything you want to work with is in the same place at the same time. The grand piano or drums might be recorded in Studio A, while the mix into which these will be incorporated is being fleshed out in a post room. In today’s big studios, there are more rooms, more people, and more potential congestion in getting audio from one place to another.
Although there are numerous technological advantages to AoIP, there’s also the “neatness” factor. In particular, public venues like houses of worship, conference rooms, hotels, and airports don’t want miles of copper cable running around. The svelte nature of Ethernet cables, and their ability to be hidden easily, is a huge advantage under these circumstances.
For audio networking, Dante is a popular, mature protocol (see the related article, What is Dante Audio Networking: A Basic Overview). As to the hardware—that’s where Focusrite comes in.
The company has established a stellar reputation in the world of pro audio, specifically with preamps and interfaces. With RedNet, they’ve combined that hardware experience with the Dante AoIP protocol.
The Big Picture
Zooming out a bit, all of Focusrite’s Dante-friendly Red gear works over the Layer 3 protocol of network communications. This is the so-called network layer that handles all the “busy work” of addressing and routing, so any data being transferred only needs to know its source and destination—the network layer itself is smart enough to get the data where it needs to go. Compared to Layer 2, which is subject to congestion, Layer 3 can grow to handle a system’s needs while retaining efficiency. Most of the infrastructure for buildings where you’d need a RedNet system already include Layer 3 networking, because businesses prioritize both a need for control and the ability to handle growth, which is where Layer 3 excels.
The issue that Focusrite’s line of RedNet gear addresses is that your mic pres, audio interfaces, and converters are inherently incompatible with Ethernet. Several companies provide adapters to link existing, non-Dante gear to Dante networks, but Focusrite designs Dante into the Red product line from the ground up (some of them also include Power-over-Ethernet, aka PoE—these have no need for power supplies or AC adapters).
It’s also important to understand that RedNet is modular. Just as you can add hard drives, audio interfaces, and the like to a computer, you can add modules to a Dante/RedNet system. Need a headphone amp somewhere? Sure. Do you have teams working in Studio A and Studio B who not only need to exchange files, but pass along audio being sent into Studio B’s interface to Studio A? No problem; simply add another interface to the system.
The Audio Interfaces
Focusrite’s three Red audio interfaces look similar; their main differences are on the back panel. While they have the Thunderbolt ports you expect to see on a high-quality audio interface, they add Ethernet connectors to provide 32 x32 Dante I/O. For example, one of the most common Dante applications is adding more mics to a system. The Red 8Pre’s front panel looks familiar (Fig. 1), with I/O selection, metering, headphone outs, and even a couple instrument inputs.
Turn around to the back panel, though, and in addition to Dante you have eight mic pre inputs on a DB-25 connector, 16 analog line ins and outs on DB-25 connectors, a pair of ADAT optical connectors, S/PDIF, dual Thunderbolt 2 ports, dual Mini DigiLink ports, word clock I/O, loop sync, and two analog monitor outputs to go to your control room.
Focusrite’s emphasis on DB-25 connectors makes sense. In addition to being wired to existing standards, they simplify cabling but also, save enough space that most RedNet modules fit in a single rack space. However some situations require a simpler solution, with XLR connectors so you can just plug in mics and go. For this, the lower-priced Red 4Pre has four mic ins on XLR connectors, and halves the analog line I/O to 8 channels.
Focusrite’s mic pres have always had a superb reputation. However, they too are part of RedNet because they can be controlled remotely (enable highpass filter, choose phantom power for individual mics, set gain, recall settings, and the like) over Thunderbolt using the RedNet Control software. In addition to mic preamp control, this software handles mapping physical I/O to drivers and Pro Tools|HD channels, monitoring, and “virtual patching” for external hardware inserts. Another advantage of all three interfaces is that because they include both DigiLink and Thunderbolt, they can switch between Pro Tools and another DAW that’s hooked into the Thunderbolt interface.
There’s even an option for Thunderbolt 3-based, cutting-edge Pro Tools studios. The Red 16Line is similar to the Red 8Pre, but handles mics via two XLR mic inputs (Fig. 2).
Figure 2: The Red 16Line’s rear panel is similar to other Red interfaces, but offers Thunderbolt 3 instead of Thunderbolt 2, and includes two mic ins on XLRs instead of using a the Red 8Pre’s DB-25 connector.
The full set of analog specs are on Focusrite’s website; suffice it to say they’re impressive. In terms of digital specs, accommodated sample rates are 44.1, 48, 88.2, 96, 176.4, and 192 kHz, all with 24-bit resolution.
Expansion: The World of Audio over IP
If you add up the rear-panel I/O, it doesn’t equal the 64 x 64 channel count quoted for the Red 16Line or the Red 8Pre, or the 58 x 64 spec for the Red 4Pre. That’s because the additional I/O can come from anywhere else in a RedNet system, and while the interfaces are cool, Audio over IP is what gives RedNet its power because of the variety of signals you can interface (Fig. 3).
For example, suppose you need to make multiple AES/EBU (AES3) digital ins and outs part of RedNet. The RedNet D16R is a 16 x 16 AES3 interface, with DB-25 connectors wired to the AES59 spec. It includes a feature that underscores RedNet’s professional nature—redundancy for both the network and power supply. With a Focusrite USB interface in a home studio, tripping over the power cable and losing the interface momentarily may be inconvenient, but it’s not a deal-breaker. With commercial applications, any loss of signal or power can be a disaster. Nor can you afford to spend too much time sorting things out, so features like sample rate conversion on all inputs assist with the promise of “plug and play.”
Other units cover analog I/O; the RedNet A16R provides 16 channels of line-level audio I/O (using DB-25 connectors), and one set of AES/EBU I/O. For smaller applications, the RedNet A8R does the same with 8 channels. For extra functionality, the RedNet MP8R hooks 8 Focusrite preamps into Dante networks. Whether you need extra mics for the drum set being recorded in Studio A, or to handle a panel discussion in a conferencing setup, this solves a lot of problems. As with other RedNet units, there are quite a few extra features—like automatic gain compensation for a second set of transmitters to simplify live broadcast and live sound work, “hooks” for Yamaha CL and QL consoles to control gain and other parameters, pad, phase control, highpass filter, and remote signal metering.
Additional Audio-over-IP devices include the RedNet HD32R, with 32 x 23 I/O for Pro Tools | HD-based systems (HDX, HD Native, HD Native Thunderbolt, HD TDM). Rear-panel I/O is Dante, primary and expansion DigiLink connections, word clock, and loop sync. One of the most important features is that you can cascade up to six HD32R units in a Pro Tools | HDX system to accommodate 192 inputs and outputs (the maximum Pro Tools HDX can handle). You can also cascade up to three units for Pro Tools | HD.
RedNet handles MADI as well with the RedNet D64R, which features 64 x 64 MADI optical and coax I/O. Like the previous units, this has network and power supply redundancy.
The original RedNet line includes units like the RedNet-5 (32 x 32 bridge interface for Pro Tools | HD). Its functionality is similar to the HD32R; it’s less expensive, but takes 2 rack spaces (Fig. 4), and lacks the network and power supply redundancy of newer units. RedNet-1, another RedNet module housed in a 2U rack unit, is the simplest multichannel Dante option: eight channels of line-level, analog I/O.
Let’s Get Small
Not all RedNet components are as deep—two “tabletop” units round out the line. The RedNet X2P (Fig. 5) is a basic 2 x 2 analog interface for Dante, with stereo XLR output jacks, and stereo XLR “combo” jacks for the inputs (these accommodate 1/4″ instrument inputs as well as XLR mic and line). There’s also a convenient, front-panel headphone jack.
Of course, it boasts Focusrite mic pres, with phantom power, polarity switch, high-pass filter, and Focusrite’s proprietary “air” control (this is featured in the above units as well, and emulates the sound of Focusrite’s transformer-based mic preamps used in vintage gear). Because the X2P is power-over-ethernet, there’s no need for an AC adapter—the Dante connection provides power as well as clocking, data, and remote control. Meanwhile, the RedNet AM2 (Fig. 6) is the “I need a monitor output, now” unit with stereo analog outs, a headphone amp, and power-over-ethernet.
Finally, the RedNet PCIeR is a PCIe card that brings 128 x 128 I/O over Dante to Windows and Mac. Compatible with ASIO and Core Audio, it provides network redundancy, low latency, and works with Thunderbolt expansion chassis for computers that don’t have slots (Fig. 7).
It’s a Networked World…
Ultimately, so much of today’s world is about networks—anyone who’s used the internet knows that. It’s even worked itself into the vernacular, where people talk about “networking” with each other. Think of how many homes have home networks, and use routers and wi-fi extenders. It’s still a wired world, but also consider that the cost of copper wire has gone through the roof—the solutions that worked at the turn of the century are fading. Meanwhile, Ethernet has risen to a position of prominence that won’t be going away any time soon.
These kinds of networks will become only more prevalent in the years ahead. If you’re upgrading or installing a new system for commercial sound work, it’s crucial to take a look at networked audio and what it can deliver not just now, but in the future. Finally—the technology is proven, has become more affordable, and prioritizes reliability. It seemed like only yesterday that the Audio Engineering Society convention was abuzz with white papers about how networked audio was going to take over in the future…well, tomorrow is here.