SPL Crimson Audio Interface Review


SPL Crimson Review: The SPL Crimson is an audio interface and monitor controller with brilliant sound quality and a whole host of features. It is certainly one to look out for.

Review Preface:

SPL Crimson Audio InterfaceWith an outboard product range featuring preamps, compressors, equalisers, custom channel strips, headphone amps, monitor controllers, and dedicated mastering processors, it is easy to see why German born ‘SPL’ (Sound Performance Lab) have analogue signal processing more than covered.

With such a heritage, it was actually only until recent that SPL decided to flex their muscles and bravely jump into the ‘digital signal processing’ market. The result of this bold decision was their first hybrid ‘six in / six out’ USB audio interface come monitor controller dubbed ‘Crimson’. As suggested Crimson can be integrated into your DAW workflow or can be used on its own in analogue mode to quickly plug in instruments and set up a simple monitor mix.


Initial inspection of the SPL’s outer packing yields a fairly standard retail package, upon opening you are greeted with your crimson suspended with polystyrene and wrapped in a protective polythene layer. The adequate internal packaging suggests that shipping should not immediately interfere with the with the product or cause irreversible damage to the internal components that could present itself later into ownership. Furthermore, included within the package is the crimson interface, an external 34v PSU, and finally an A4 sheet telling you where to download the drivers and manual. Unusually SPL have chosen to not include a type A USB 2.0 to Type B cable for environmental reasons.

Build Quality and Features:

The SPL Crimson is a desktop friendly interface that loves to live close to the edge so it has the full attention of your hand. This ergonomic ten degree tiled design increases workflow and has a sufficient size (13” x 8 ½ “) that it is easy to navigate without accidentally engaging other features. As a whole the SPL Crimson feels extremely sturdy due to the fact that the entire enclosure appears to be made from 1mm plate steel with a consistent matt black spray and red print screen details. The weight of this material is substantial and when this is paired with the four rubber feet the unit will not slip across your workstation top or cause damage. Although a small detail, I can report that the matt paint of the Crimson adequately resists ‘fingerprint graffiti’ and the decals appear strong and unlikely to tarnish following significant use.

The SPL Crimson is a USB 2.0 device and able to connect to your Windows (XP and above) or Mac (OS X ‘Tiger’ 10.4 and above) based system and inherently uses ASIO drivers without the need for any dedicated programmes to take care of routing options. An additional bonus is that if you own an iPad camera connection kit you can use Crimson as an iPad audio interface, but this is something that we will revisit later on in this review. Furthermore, as an advantage over some of the Crimsons competitors, SPL crafted this audio interface with a maximum sample rate of 192kHz and a maximum 24bit bitrate. This allows Crimson to be fully capable of recording and playing back high resolution files.

Looking at the top of the Crimson, also known as the faceplate, you will notice the grey opaque digital pushbuttons. These buttons light up various fixed colour LED modules that situated below and when engaged they have a nice springy resistance. The aluminium potentiometer caps appear to have a strange black slightly velvet coating paint that does feel a touch strange in the hands, although this is a matter of preference. Besides from this the Crimsons potentiometer actions are ‘unmetered’ to the fingers, although detailed reference is provided visually, but have a satisfying smooth quality with a medium degree of resistance. One reservation that I do have is that the master volume (DAW 1/2) has a recessed potentiometer cap that cuts through the steel chassis. With this information I would like to stress that although this is a desktop interface, you should be careful with your tea (as it can drip directly down onto the printed circuit board containing capacitors, integrated circuits, and resistors) – if in doubt, blame the tea boy. However, closer analysis of the internal potentiometers clarifies that premium components are being used. Other features on the faceplate include a plastic SPL badge adorned with chrome text details, and finally a trio of LED’s that form a rudimentary digital VU meter that is used to measure your four separate mic/line or instrument/line inputs. Located to the right of VU meters the Crimson has a ‘Power’, ‘Host’ (to signal when connected via USB), and Midi Input status’ for quick reference. Finally, on the lower part of the unit there are two independent headphone outputs and two high impedance instrument inputs.

Before moving on to more of the specific details of the Crimson I would like to clarify why SPL have chosen to use an external PSU with the Crimson. Building in an power supply unit into Crimson would have created two main problems, the first is that necessary PSU components would not fit into the convenient desktop Crimson sloping form factor, and the second is that building a PSU circuit into the product requires an advanced circuit that would have to be discreet to inhibit interference. This circuit would need to be isolated in a such a way that it does not add distortion or ultimately lead to a higher noise floor. Simply put, this is an expensive design to implement and would be fundamental to producing a high quality professional audio product. For this reason it is important to give credit to SPL for taking the design route of using an external Mean Well branded switching power supply although on the rear of the unit it says that you should not use any other adapter with the Crimson. Products that share a similar form factor, along with many products in this price range, all use this technique and is not something to be looked down upon. The end result is a superior and affordable product. However, the fact that SPL have opted to use a ‘higher than average’ input voltage of 34v allows for a lower signal to noise ratio and even better value for money.

FSPL Crimson Backurther to the above, if we now move to the rear of the Crimson it is notable that they have printed the input and output labels in two configurations so that it is legible if the user is looking at the rear from the top; a feature that will save time and frustration. One of the other main features of the SPL Crimson is that it uses two discreet proprietary SSL microphone preamps that operate between 10Hz – 200kHz. As an afterthought it may be important to identify that inputs one and two use unbranded third party XLR/TRS combo ports and that if you intend to record four line instruments at the same time you will surrender your rights to use these in combination. These microphone inputs can be controlled on faceplate with a phantom power (48v) input for condenser microphones, feature a high variable gain (+8dB to 60dB range) for use with tricky ribbon microphones, and finally the option to introduce a fixed sloping high pass filter (6dB an octave) for frequencies below 80Hz. 80Hz seems to be an agreeable filter limit to limit sub-frequencies and other ground born noise transferred without the use of a microphone shock mount. Other traditional interface features conclude with two high impedance instrument inputs, S/PDIF inputs and output for two additional digital input and outputs, and a MIDI input and output.

Now we enter some of the more interesting features of the SPL Crimson. A nice feature is that the Crimson allows you to connect two separate pairs of monitors by using the male XLR outputs from ‘Speaker A’ and two balanced TRS jack outputs with independent trim function to pair the gain correctly. Whether an average consumer will have access to two separate pairs of monitors is debatable due to the cost, but either way this is a good feature to have for checking mixes on two pairs of speakers and gaging translation. Furthermore users can run a 3.5mm jack, RCA pairs, and ¼” jacks from their music players or other laptops to play along with using the monitor controller without a USB connection. With this feature it is important to remember that the Crimson will ultimately be crippled by the input source and quality of analogue cables.

Saying all of the above is all well and good, but the main problem with the SPL Crimson is that it has limited inputs and outputs. In comparison to the Crimsons direct competitors it is fundamentally lacking output routing options and digital input expansion. It is understandable that the Crimson has two separate dedicated outputs for two pairs of studio monitors, although I would have much preferred if there was, like almost every other interface in this price bracket, two or four dedicated line outputs for use with outboard processors. Branding the only two free outputs as ‘Speakers B’ is misleading to young producers or engineers as unless they follow the routing procedures as found on the SPL website, they will possibly assume that their only role can be for a separate pair of speakers. Furthermore, while the Crimson sports an acceptable number of analogue inputs, it feels crippled by not offering an ADAT input or basic output clock source. Instead of offering a dual channel S/PDIF input I would have much preferred if this was removed and replaced by an ADAT input. Other final missing features would be a physical on and off button and a sum to mono button.

Sound Quality and Performance:

Due to numerous matrix options as a monitor controller and USB audio interface I found that comfortably mastering the full capabilities of the Crimson took a number of hours of trial and error. My best advice is to download the manual and make sure that you read it because you may end up believing that your new interface is an enigma. Now this has been mentioned this confusion shall now be pushed to one side.

With Crimson, SPL has created a great hybrid interface that allows an artist to quickly create a rudimentary four channel monitor mix (via channel 1, 2, 3, and 4) without all the confusion of a digital matrix or having to set up a session in a DAW (Digital Audio Workstation). With this four channel monitor mix you have access to two microphone preamps and two line inputs, or you can swap one or two of the XLR mic preamps for additional line inputs. The overall consensus is that this is a cleaver and quick way of applying an idea without the hassle of computer audio and allows guitarists and other line output instruments to be played silently if used with headphones. Thanks to the fact that SPL have included two independent headphone outputs this means that both a guitarist and a bassist can play together silently. Likewise, they can use the 3.5mm or RCA input to play along to a backing track. Basically the SPL Crimson takes the term ‘bedroom musician’ to a whole new level and adds an outstanding advantage over other ‘typical’ interfaces. Continuing upon that final point I would like to highlight that as this is an interface that works with iPads this brings production to the musicians with a great deal of flexibility and options.

Possibly one of Crimsons most cleaver features comes in the form of ‘Artist Mode’. When this mode is active the engineer has the option to hear a completely different monitor output to that of the musician. This happens because now all ‘in the box’ audio routed to stereo DAW 1/2 channels will be audible though ‘Speakers A’ and ‘Headphones 1’ outputs whereas all audio routed to the stereo DAW 3/4 outputs, such as via a bus, will be heard across ‘Speakers B’ and ‘Headphones 2’. For those fortunate to have a separate control and live room the Crimson has a talkback feature that allows the microphone connected to input one to be used to remotely speak to the musician’ like in a professional studio. Just as a general note though I would like to make it known that we have tested the Crimsons headphone amps and have found that they have enough power to adequately drive a pair of 250ohm professional audio headphones with ease and the performance comes close, if not matches, to the rear monitor output.

Now, in terms of microphone preamp and D2A performance, I can report that the SPL Crimson preforms favourably and is fully capable of driving dynamic, condenser, and even ribbon microphones with ease with 60dB of gain, although when pushed to their upper limited there is noticeable top end distortion (to be expected). Besides from this, the overall sonic signature of the preamps is certainly musical, ever so slightly warm with a slight low-mid presence, features a slight top end clearing that is free of harshness or distortion (unless pushed with high gain), and feels fluid and never disjointed, finally the sound recorded by the Crimson appears to be just so that it accepts equalisation well. From this analysis it is clear that the Crimson borrows some characteristics from SPL’s premium preamps and sets a very respectable standard.

In terms of the audio output performance, or D2A, the Crimson does a wonderful job of presenting an highly agreeable linear performance with a certain edge of sparkle that doesn’t at all detract away from producing a mix that will translate well on multiple systems. Similarly I have found the sound to be smooth and present a rich stereo field that makes all aspects of music production a joy.

Review Conclusion:

With exceptional function and sound quality, the SPL Crimson is an innovative monitor controller and audio interface that punches well above its weight. The Pro Audio Web Blog awards the SPL Crimson with a four and a half star rating.

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