SPL CRIMSON 3 INTERFACE & MONITOR CONTOLLER

SPL’s Crimson analogue-heavy interface is decidedly unfashionable, but contains precisely what the modern recordist needs.
Review: Preshan John
Three versions in and I can’t help but feel the SPL Crimson still looks like it belongs in a different era. It’s decidedly unfashionable. While a cockpit-like dashboard of lights and knobs was once the norm, modern interface design has thrown away much of the hands on controls and tucked it all away in the box. The Crimson stands alone in that regard. It’s big, has tons of buttons and knobs, and there’s no PC-control malarkey here. Let me introduce you to the most analogue-y digital desktop interface you’re likely to encounter.
Founded in Germany in 1983, SPL (Sound Performance Lab) is renown for high-end analogue audio processing gear — names like Transient Designer, Vitalizer, Passeq, and Phonitor may ring a bell. So when SPL makes an interface, you can expect its circuitry to be superior to a run-of-the-mill, Chinese op-amp-loaded plastic box. 
True to form, SPL has avoided IC-based preamp design, preferring to trust its analogue prowess and design a pair of discrete microphone preamplifiers. Both preamps have 60dB of gain on tap and the frequency response up to 200kHz means it’s canine and dolphin-friendly. 
INS & OUTS
The SPL Crimson 3 is a 16-input interface, but not all of those are recordable. One of Crimson’s touchstones is that it also functions as an analogue monitor controller. It means some of those 16 inputs never see your DAW, but are plumbed directly into the monitoring path. Those include three stereo input pairs on 1/4-inch TRS, RCA and 3.5mm mini-jack connections. Then there’s the stereo digital S/PDIF I/O, the input of which is recordable.
That’s eight inputs down, leaving eight, according to SPL’s count. However, the remaining eight analogue inputs can’t be used simultaneously. There are two instrument inputs on the front panel, a pair of mic inputs on the rear, and four 1/4-inch line inputs, but you can only record four at any one time.
On the output side, two pairs of speakers can be connected — one via XLR, the other via 1/4-inch TRS (with trim pots for calibration) — and you can switch between them with the A to B button. 
Crimson 3 is a USB 2.0 interface that can run in class compliant mode for plug ’n’ play operation on a Mac or when using it with an iOS device. It’s also the best route for low latency audio. Alternatively, you can download SPL’s bit accurate driver for Mac or PC, which increases latency but also ups the possible sample rate to 192kHz.
While SPL records its lowest measured roundtrip latency as 6.49ms (96k, 32 sample buffer), we had varying real world results. Practically speaking, when recording at 48k with a 32-sample buffer, the latency was noticeable in Studio One, but barely there when recording in Bitwig. You could happily record vocals while recording through plug-ins in that DAW. Of course, the Crimson is built on a foundation of impeccable analogue monitoring, so you can simply choose to direct monitor your inputs signals, or blend in any amount of your DAW return signal with the Monitor Mix knob.
BACK ON TRACK
I really like the old-school analogue feeling of recording with the Crimson 3. The knobs don’t have any play and are coated in a grippy rubberised finish. The buttons are big and have a reassuring press action, though most click audibly in your cans. There’s acres of space on the top panel, clear legending, and every function — setting gains, routing inputs, monitoring sources — requires pushing real buttons and spinning real knobs. I found the whole approach really refreshing — not to mention, fast — given most of these functions in today’s interfaces are controlled remotely via software.
One quirk to the legending is that the back panel has two sets of names; one right way up, and the other ‘upside-down’. Super handy when you’re peering over the top of the interface to plug in a cable. 
Once you’ve plugged in an input source, you have to enable the input number pair with a button press. By default, inputs are panned hard left and right when monitoring (i.e. Mic 1 is left, Mic 2 is right, etc.). Activating the Mono button places everything down the middle.
With so many switches, it’s a bit of letdown that there’s no power switch. You have to turn it off at the wall, or unplug the power pack to power down.
The preamps sounded classy with a clarity and firmness to them that’s a bit SSL-ish. A relatively gentle 80Hz high-pass filter and 48V phantom power are available for each mic input. The gain range of 60dB means the pot can often end up in its upper limits, but the good news is there’s virtually no noise even when it’s hard up at maximum. Visual monitoring comes by way of three LEDs for each analogue input — green for signal, yellow for -6dB (equivalent to +9dBu) and red when you’re clipping (+15dBu). It’s two more than you might typically get but you’ll still want to rely on external metering for transient-heavy sources.

MIX OF MONITORING
There’s plenty on Crimson 3 to ensure your artist receives an optimum, no latency headphone mix. There’s a gaggle of dip switches on the Crimson’s underside. Flipping them around will change the architecture of the unit, and setting the fifth switch to On engages Artist mode. In the normal mode, any routing is mirrored in your headphone and main outputs. In Artist Mode, it will automatically route DAW 1|2 to your main pair, and allow you to create a separate mix for your artist that is available in Phones 2 and Speakers B. You can send them DAW 1|2 or DAW 3|4 outputs and use the Monitor Mix knob to dial in the right balance between that and the input signal. 
Crimson 3 also has a built-in talkback microphone, a nice touch for any desktop interface. Talkback gain is set by way of a tiny pot in between the instrument inputs and it’s automatically routed into Phones 2 and Speakers B when Artist Mode is engaged. Pressing Talkback dims the artist mix.
You’ll find a similar pot, labelled Crossfeed, jutting out to its right. It’s a feature peculiar to SPL’s Phonitor products. When the Phonitor Matrix button is engaged, Crossfeed controls how much of your headphones’ left channel is fed into the right, and vice versa. This technique results in a less exaggerated stereo image that more accurately mimics the sound of speakers in a room. It’s not a fancy DSP-based spatial simulator — like Waves Nx or the discontinued Focusrite VRM — but it’s a nice option to have if you mix primarily on headphones. 
Because the monitoring section of the interface is entirely analogue, much of the I/O is operational and routable without needing to plug in a computer. It means Crimson can act as a mini analogue mixer. In a pinch, you could take it on stage, hook up a couple of mics, instruments and line sources, then send it off to the respective outputs using just the onboard routing buttons. Super handy. 
THAT I/O THOUGH
If you could put icing on the Crimson cake, it would be more digital I/O expansion options like ADAT or MADI. Digital I/O is becoming somewhat of a staple these days — an increasing number of desktop interfaces have an ADAT input — and the Crimson’s only option of the two-channel S/PDIF protocol feels limited. 
I respect SPL for its decision to keep the Crimson 3 miles away from any kind of software reliance. Tracking and mixing with this interface will take you back to the simple joys of routing without requiring a mouse. Plus, doing away with software updates and DSP will mean it’s more reliable. 
It is larger than the average interface, but if you have the real estate and count an analogue monitor controller as a must-have, then this is a great option. Especially for dedicated mix engineers, or professional scenarios that only require a handful of inputs: like a VO booth, or vocal producer.