Has the addition of Dante allowed Voyage Audio’s Ambisonic mic to realise its full potential?
There are times when an otherwise great product is held back by a single limitation. Voyage Audio’s Spatial Mic, which I reviewed in SOS October 2020, is a good example. This is a nice‑sounding second‑order Ambisonic mic at a price to rival most first‑order mics, and as it has built‑in preamplification and A‑D conversion, it does not require expensive matched preamps and converters. However, in a music‑recording context this second positive is also a negative. The Spatial Mic can connect either to a host computer over USB, or to an audio interface over ADAT Lightpipe. Both options mean it can only be used with extremely short cables, and make it very difficult to record with other microphones simultaneously.
I ended my review of the original Spatial Mic by wondering whether Voyage Audio might consider developing “a ‘pro’ version that could be powered and connected to an audio‑over‑IP network using an Ethernet cable”. And evidently I wasn’t the only person who felt that way, because that’s exactly what they’ve done. The Spatial Mic Dante is, well, a Spatial Mic that hooks up to a Dante network over Ethernet, presenting up to eight channels of audio at sample rates up to 192kHz. This is already an improvement over its predecessor, which topped out at 96kHz over USB and 48kHz over ADAT Lightpipe. A 48kHz‑only AES67 mode is also supported for connection to other audio‑over‑IP networks, though I did not test this.
The Spatial Mic Dante is similar in shape to the original but marginally larger, with a tough but low‑key matte black finish. This time around, however, there’s no headphone socket and no physical gain control. The assumption is that anyone using a Dante network will have a proper monitoring setup and access to a computer to adjust Spatial Mic parameters, which seems entirely reasonable. If the Dante version feels more substantial than the USB/ADAT version, that’s mainly down to the presence of a large metal heat sink, which is clearly needed, as the mic gets quite warm in use.
Mounting arrangements are carried over from the USB/ADAT version, meaning that the mic itself has a 1/4‑20 socket of the type used on camera tripods, which can be paired with the supplied ball‑and‑socket adaptor if you want to mate it to a mic stand. Given that this is a much more expensive and pro‑oriented product than the original, it might have been nice if Voyage Audio had included the optional Rycote InVision mount and a proper carry case.
The base of the mic houses a Neutrik NE8FBH‑C5 locking etherCON connector, which is also compatible with standard RJ45 plugs. Either side of this are two LEDs indicating the presence of power and network activity.
The Spatial Mic Dante is not quite a ‘plug and play’ device, and there are a few steps you need to take in order to get it working. In order to do anything at all with the mic, you’ll need to be able to deliver up to 4.8W to it using the Power over Ethernet (PoE) protocol. And whereas power delivery is an integral part of the USB and Thunderbolt protocols, it’s very much an optional extension of Ethernet. Many computers have Gigabit Ethernet sockets built in, and there are many USB and Thunderbolt adaptors that can add it to a machine that doesn’t; but you won’t get PoE support without an additional powered switch or PoE injector. These are readily available and affordable, and there are even battery‑powered models available, but take care to get one that fully supports the IEEE 802.3af specification, as the Spatial Mic Dante requires 48V rather than the 24V that some injectors deliver.
Naturally, you’ll also need cables, and bog‑standard Cat5 worked fine in my tests. One of the biggest advantages of the Dante version over the original Spatial Mic is that Ethernet supports enormously long cable runs, and anything that works for other Dante devices should be fine with the Spatial Mic Dante.
Finally, you’ll need to install some software. The Spatial Mic Dante has its own ‘control panel’ application called MicNetControl (see box). This, in a sense, makes the Spatial Mic Converter plug‑in somewhat optional, though I imagine all users will want to install that too. You’ll also need to visit the Audinate website to install the Dante Controller software; and, if the Spatial Mic Dante is your only Dante device, you’ll also need a licence for the Dante Virtual Soundcard, which starts at $49. Once all this is in place, you simply tick a few boxes within Dante Controller and select DVS as your input device, if necessary, whereupon you should see signal appearing in your DAW.
The internal DSP can generate virtual mics on the usual omni‑to‑figure‑8 spectrum, as is possible in first‑order Ambisonic mics, but if you want second‑order cardioid, MaxRe or In Phase outputs you’ll need to record the raw output and use the plug‑in.
As described in the ‘MicNetControl’ box (see below), the signal‑processing capabilities built into the Spatial Mic Dante permit a usable output to be derived directly from the mic. Where possible, though, it’s better to record the raw eight‑channel output and use the Spatial Mic Converter plug‑in to derive your chosen signal, not least because that seems to be the only way to take advantage of the additional directivity that second‑order Ambisonics makes possible. The internal DSP can generate virtual mics on the usual omni‑to‑figure‑8 spectrum, as is possible in first‑order Ambisonic mics, but if you want second‑order cardioid, MaxRe or In Phase outputs you’ll need to record the raw output and use the plug‑in to derive these (see my review of the original Spatial Mic for more detail). Likewise, the internal DSP can generate a first‑order B‑format output, but not a second‑order one.
Unlike the internal DSP, Spatial Mic Converter also offers a choice of two filter sets to be used in processing the eight‑channel raw signal. Voyage Audio say that “Type A filtering exhibits high spatial resolution, while Type B offers a more diffuse, flat response.” They sound surprisingly different from one another, with Type A being considerably brighter and more inclined to emphasise transients.
I wasn’t able to compare the Dante version of the Spatial Mic to the original, but it certainly sounded good to me. Self‑noise is theoretically a concern with a mic that derives its output from eight small‑diaphragm capsules, but the review model was whisper‑quiet, and the gain range of 35dB seems adequate to cope with most real‑world recording scenarios. I should point out that although the Spatial Mic Dante can generate a 32‑bit floating‑point output, this doesn’t offer any protection from clipping, as it does in the Rode NT1 5th Gen and other devices that use multiple converters in parallel. You might as well record the 24‑bit fixed‑point output and save yourself one byte in every four.
For the sake of variety, this time around I did my testing in Reaper and Logic Pro X rather than Pro Tools, and this unearthed a few quirks. When you insert the AAX version of Spatial Mic Converter in a Pro Tools mixer channel, you have to choose an output channel configuration. If you were deriving a stereo virtual mic array, for example, you’d choose the 7.1‑to‑stereo version of the plug‑in, and every subsequent plug‑in on that channel would see a stereo signal. In AU and VST hosts, by contrast, there’s just one version of Spatial Mic Converter and it always has a multi‑channel output. If you use it in Virtual Mic mode to synthesize a stereo array, the L and R channels within the surround output carry signal, but the rest are still present, albeit silent. If you want to downmix the channel back to stereo you’ll need to use something else to do it.
That’s all perfectly manageable within Reaper, but Logic throws some additional spanners into the works, because of Apple’s predilection for mucking about with the order of the channels within a surround signal. In order to get sensible results from Logic, you need not only to select the correct surround format for the Project and your input, but also to adjust the default input ordering in Settings / Audio / I/O Assignments. Voyage Audio provide a helpful guide on their website (https://voyage.audio/getting-started-with-logic-pro-and-spatial-mic/) but it might be better to simply include a Logic mode in the Spatial Audio Converter plug‑in that remaps things automatically.
Talking of which, I’m told that other plug‑in improvements are in the works already, including visualisation that will reveal where incident sound is coming from. This is already a feature of Rode’s Soundfield By Rode plug‑in, and hopefully should be even more useful in a second‑order Ambisonic mic with its superior ability to resolve directional information. Likewise, MicNetControl should enable firmware updates that can improve the built‑in processing still further.
In short, the Spatial Mic Dante is exactly what I and others have been asking for from a ‘pro’ version of the Spatial Mic. It offers the same, uniquely flexible virtual microphone functionality without being tethered to your laptop by a 2m cable. It can freely be combined with additional Spatial Mics and any other Dante‑enabled hardware in a configuration of your choosing. And although it’s more expensive than analogue second‑order Ambisonic mics, it doesn’t require multicore cables or matched preamps, has built‑in processing, supports cable runs that are practically unlimited, and can be configured with one click from the comfort of your keyboard. Voyage Audio have hit the nail squarely on the head.
A second‑order Ambisonic mic like the Spatial Mic has a coincident array of eight capsules. However, the raw output from these capsules is not in itself an Ambisonic signal but a precursor, usually referred to as A‑format. In order to generate a second‑order (nine‑channel) or first‑order (four‑channel) Ambisonic signal in the B‑format, these must be matrixed and filtered. Further processing is then required either to synthesize virtual microphones from the B‑format signal, or to map it onto a particular output format such as a 5.1 or 7.1 speaker array.
The original USB/ADAT Spatial Mic can only output the raw eight‑channel signal from the capsules, meaning that downstream processing is required to convert this to B‑format and then to a suitable output format. That’s what the Voyage Audio Spatial Mic Converter plug‑in does, and this will usually be the preferred option, but there are some circumstances where you might want to do things differently. For example, you may need to use the Spatial Mic Dante with a DAW that doesn’t support multi‑channel tracks, or you might want to route its output directly to another node in the Dante network without passing through the plug‑in, or perhaps you just want to record a simple mono or stereo signal without wasting drive space.
Enter the Spatial Mic Dante’s built‑in DSP, which can perform some of the same functions as are available in Spatial Mic Converter. This is set up using a standalone application called MicNetControl, which offers four processing modes. The simplest and default option is Unprocessed, which passes the raw eight‑channel signal to your DAW for matrixing and decoding later. In this mode, the only controls available are a Mute button and a simple Gain slider with a 35dB range. This is the only mode available at sample rates above 48kHz.
In AmbiX mode, the individual signals from the eight capsules are matrixed and filtered to generate a four‑channel, first‑order Ambisonic output. Surround mode, meanwhile, matrixes the raw signal to Ambisonics before mapping it onto a 5.1, 5.1.7 or 7.1 speaker array. Finally, Pattern mode synthesizes a stereo virtual microphone array of your choice.
If you’re looking specifically for a second‑order Ambisonic microphone, the main alternatives are the Core Sound Tetramic and the Brahma Studio 8, while first‑order options include the excellent Soundfield By Rode NT‑SF1 and the Sennheiser Ambeo. However, all of these are purely analogue devices, so as well as matrixing and decoding plug‑ins, they also require matched preamps and A‑D converters.
- The Dante format is perfect for the job, allowing the mic to be connected alongside other devices, by a single cable of practically unlimited length.
- Built‑in processing allows a usable signal to be derived without plug‑ins.
- Offers significantly better directional resolution than a first‑order Ambisonic mic.
- Additional hardware needed to deliver Power over Ethernet (PoE).
- At the price, it would be nice to have a shockmount and hard case included.
- There are hoops to jump through with Logic Pro X at present.
Voyage Audio have delivered a ‘professional’ version of their Spatial Mic that is an excellent showcase for the advantages of audio over IP.