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Allen & Heath SQ‑5

Digital Mixer
Published January 2019
By Mike Crofts

Allen & Heath SQ‑5

This compact yet powerful console puts Allen & Heath's touring-grade processing into a much more affordable package.

Allen & Heath describe the SQ series of mixers as the most powerful in their class, with 48 processing channels and a 96kHz mix core, all in a super-compact physical format. There are three models in the SQ line; all have similar mixing capabilities but the SQ-5, SQ-6 and SQ-7 have, respectively, 16, 24 and 32 channel faders, plus master. The series has recently benefitted from a major firmware upgrade to version 1.3, and a number of features have been added or enhanced (see box). The good people at Allen & Heath provided me with an SQ-5 to get hands-on with, but all three models are identical in terms of their channels-to-mix count and processing; the differences are in the local input/output provision, physical faders per layer, soft controls and console dimensions.

The internal hardware is the same on all versions, so they all have exactly the same signal path, and all are constructed in the usual Allen & Heath 'brick outhouse' style with rigid, well-finished metalwork and a solid feel to all the rotary controls, which are directly nutted to the surface — no wobbly pots on this console! I'll gladly admit that the look and feel of a mixing console is a major factor in deciding if I'd like to own one and, ergonomically speaking, the SQ-5 racked up a big score as soon as it emerged from the shipping box. It's basically black, with a steeply canted upper section where the touchscreen and dedicated 'strip' controls live, making for a generous rear panel with plenty of room for all the I/O.

I was fortunate to have this particular SQ-5 delivered by Keith Johnson, Product Manager for the SQ range (and also the Qu and ZED series), so I was able to ask him about the thinking behind the SQ-series mixers. Keith recounted the story of how Allen & Heath had become involved with small‑format digital mixers at an early stage with a product called the iCON, since when they have created the iLive series, the GLD, Qu, dLive and now the SQ.

As many will know, one of the reasons A&H gear has built up such a loyal user base is because they design and develop everything in-house, and therefore have complete control over every aspect from basic metalwork and PCB layouts to low-level FPGA programming and all DSP, GUI and stylistic design. This may be what you'd expect from any established maker, but one of the stand-out differences with Allen & Heath is their willingness to engage with and incorporate feedback from product users — and the close, in-house design approach is what makes this possible. I do say this from direct personal experience, and there's an example of how this works right here on the SQ itself: during Keith's visit to demonstrate the v1.3 firmware release I happened to comment on how the EQ screen was presented. Keith happened to agree, and a couple of weeks later the EQ display happened to incorporate my suggestion. How many manufacturers could or would do that?

Impact Assessment

One of the things I'm often asked to do in my reviews is a real-life, on-the-road practical test, so I like hearing about how products are developed and tested — not only to make them sound good and be user-friendly, but also how they are put through their paces to ensure reliability and a long service life. Here's what Keith Johnson told me about how they tested one vital element of a live digital desk, namely the motorised faders: "We worked very closely with the supplier and carried out a lot of our own research into materials, which resulted in faders that were still functioning correctly after 10 times the 'number of movements' of their original specification. The fader tracks are also mounted at 90 degrees to the control surface, which results in lower friction, faster movement, less noise — and means any ingress of dust and dirt falls straight through instead of turning into an abrasive powder for the tracks! We tested this by pouring in all sorts including dust, fine quartz sand, cigarette ash and Coke (the fizzy drink). We also carry out transport and extreme vibration testing, dropping from a height, throwing down the stairs and 'spilling' pints of beer over things." Now this sounds like my kind of workplace.

The three things that sell digital mixers (other than the price point) are the audio path, the so-called 'workflow' and the overall build quality, and it's clear that the SQ has drawn upon both the A&H family lineage and new technology in all areas. The audio path — in other words, everything from the mic preamps to the output stages — depends not only on the preamp design and conversion performance but also on the processing power available and how it is applied to reduce system latency and ensure coherence through the DSP stages. The workflow is how the operator interacts and gets the best from the mixer functions, and the whole lot has to be contained in a good-looking and long-lasting outer skin. It's worth looking in a bit of detail at the processing of the SQ, as there appears to be a lot of power under the hood.

Processing Plant

The SQ mixers use the latest version of the 'XCVI' processing and mixing engine that was developed for the upmarket dLive range, and it uses a customised FPGA to do everything on a single chip, using virtual parallel processing cores. This approach has a number of advantages, including a very low latency of below 0.7ms all the way from analogue in to analogue out, and this figure doesn't change when any amount of channel processing is applied — an increasingly significant consideration when in-ear monitoring is used. The single-chip approach also means that phase coherence can be maintained throughout the entire signal path; all the DSP is running all the time, and the time travel between different processing blocks is negligible, so all signals remain time-aligned in the mixer core no matter what EQ, dynamics and so on you switch in or out. The result is clear and transparent audio, free from the 'smearing' problems that can arise (try using in-channel and aux bus processing at the same time on a budget digital mixer as a comparison). The other obvious advantage of having the processor running full-on all the time is that performance isn't affected at all by throwing all the available DSP into the mix. You can think of it as having every bit of DSP always running in the background, even if you have chosen not to listen to it for the time being!

The SQ has a very good noise spec, and the use of variable bit depth increases headroom when required. The output busses run at 96-bit, which theoretically allows in excess of 400dB of dynamic range, meaning practically unlimited headroom and no internal clipping worries when summing anything to the busses.


Because the SQ mixers run exactly the same channel processing blocks as found on the dLive consoles, the A&H DEEP plug‑ins can be brought into play. The DEEP suite includes accurate models of classic hardware units, and these are available as optional add-ons for the SQ. These plug‑ins are used in place of the standard channel processing (you simply recall them from the library), and because they are embedded directly in the channel they add no latency. Once 'unlocked', each plug‑in can be used on every single channel, and they don't take up any slots in the internal effects rack — a superb implementation in my view.

The (sort of) bad news is that you have to pay extra for them, but the good news is that they can be purchased individually, so you only pay for what you need rather than having to buy the whole suite. The best news is that they give you one for free! The free plug‑in is a 'tube stage' mic preamp, which has six tube topologies to choose from and is designed to add musical distortion, harmonics and compression to the existing super-clean input path. The current list of DEEP plug‑ins includes three graphic EQ types, four compressors, a peak limiter and of course the free tube stage. The DEEP plug‑ins are already installed in the SQ firmware, and when purchased you get a unique key to enable them, so there are no downloads or messing about with installation.

One final DEEP function is the SQ's twin 24-channel automated mic mixers (AMM): a gain-sharing algorithm that automatically raises or lowers levels across all the inputs assigned to the AMMs (you can even combine the two 24-channel AMMs to make one big 48-channel setup). Again, because it uses the DEEP processing for adjustment it adds no latency.


One of the main reasons for switching from analogue to digital mixing is that you can do away with all your outboard processor racks, and the SQ has eight virtual rack slots available. Slots 1 through 4 are fed from the four effects send busses, and all eight can be fed from or used as inserts in any input or mix channel. One feature that I particularly like is that there are eight dedicated stereo return channels for the effects, so that none of the 48 input channels have to be used up, and there's a parametric EQ on each of these returns. The returns can be routed to mixes as if they were normal input channels, and this makes setting up live foldback mixes a straightforward business.

The effects themselves are those used in other A&H mixer ranges, and include the expected 'industry classics'. They have good clear graphics (with front/rear panel views in many cases) and are straightforward to use if you have at least a basic understanding of their operation. I found that the relationship between screen selection and parameter adjustment using the single encoder was easy and fast, with just enough 'gearing' to minimise physical movement whilst dialling in accurate settings. The presets library contains everything you'd normally need to at least achieve a good starting point, and whatever fine adjustments you make can of course be saved in the user preset list for recall at a future date.

At Your Surface

No matter what functionality or performance levels a digital mixer can achieve, it has to be driven by someone, and the surface design, layout and workflow are critical in terms of how usable it is under live conditions. Different users will want different features and layouts on the top panel, but I can't imagine many having problems with how the SQ is presented: the labelling is clear, and the layout of controls well spaced, with plenty of room around everything. The surface looks roughly symmetrical, with the touchscreen in the middle of the upper panel, and every control — be it a linear fader or turny knob — has a quality feel with a nice degree of resistance. The faders, as already mentioned, benefit from being side-mounted beneath the panel and therefore do not 'dig in' — a real annoyance with some designs — no matter where or how you press, push or drag them (within reason!). On the SQ-5 there are 16 channel faders and a dedicated master fader to the right, with the mix bus selection buttons in a long vertical strip on the extreme right and the fader layers and other functions to the left. These two sets of buttons — with soft-touch rubber caps, as on all the current A&H digital range — are all that's needed to mix live show levels once everything else is set up, and they give one-touch access to every mix send (all the auxes and the effects sends) by flipping the current fader layer into sends-on-faders mode for whatever mix you have selected. The only thing I'd like to see here is some kind of additional warning when the main house mix is not the current selection. True, the relevant mix button lights up (a nice bright blue), but perhaps something a bit more obvious (on the screen, or the scribble strip?) would be an idea to prevent me happily mixing one of the foldback returns and wondering why I can't hear much difference out front.

In general, the SQ workflow is simple, obvious and efficient, and avoids the need to dive deeply into menus. I reckon any 'new' engineer should be able to start mixing once they've figured out that the blue buttons access the mixes (sends on faders) and the green buttons access the channel processing screen and dedicated knobs!

Like most modern digital mixers, the SQ series can be controlled from an app — either locally, as a way of gaining an extra touchscreen, or remotely over WiFi. In the latter case, there are two apps available, for both Android and iOS. The SQ‑MixPad offers full control, while SQ4You is designed to allow personal monitor mixing.Like most modern digital mixers, the SQ series can be controlled from an app — either locally, as a way of gaining an extra touchscreen, or remotely over WiFi. In the latter case, there are two apps available, for both Android and iOS. The SQ‑MixPad offers full control, while SQ4You is designed to allow personal monitor mixing.

Screen Time

The large capacitive touchscreen is at the heart of making adjustments to all parameters, and rotary control knobs are used to control various functions. Any parameter (except for some that have dedicated knobs) that is selected by touching the screen lights up the encoder below to enable precise adjustment. In the case of switches, they simply respond to screen touch. The most commonly used channel parameters — preamp level, pan, high‑pass filter, EQ and dynamics — have individual knobs assigned to them and, as these are not used for anything else, you soon get to know where and what they are for quick access any time, providing they are active (illuminated). Many functions can be assigned to the bank of soft controls, which include both keys and rotaries that can be assigned independently (one of the few differences across the models is the number of soft rotaries). The soft keys have tri-colour LEDs to indicate different functions.

Setting up the SQ mixer is straightforward, and there are enough user options and preferences to suit most applications. Routing and patching operations are extensive and easy to accomplish; almost anything can be freely patched wherever you want it by using the touchscreen, and the layouts and options are all clearly presented to make this potentially confusing task a simple one. The flexibility offered by this level of routing access, together with the number of fader banks provided, makes the SQ a very versatile unit, and these options are sometimes only appreciated when something has to be re-patched mid-show (for example, remote inputs could be changed on stage and control channels quickly reassigned at the mixer).

The screen is impressive, with sharp, clear presentation and very well thought‑out graphics. Touch control is consistent and smooth across the whole area, and there are preference settings for whether you're sitting or standing behind the desk. There isn't room here to go into all the surface functions, but everything you'd expect is right there and it's all laid out in a pleasing and sensible way. If you have a look at the reference guide (downloadable from the Allen & Heath website) you can see a good layout diagram with all the controls explained. This isn't anything like getting your hands on the real thing, but it does give an idea of how much functionality has been packed into what looks like an uncluttered and efficient control surface.

Neat Tricks

One of my favourite features is the 'CH to All Mix' key, which is new to the SQ range. This is a momentary action key that, when pressed, shows all the sends from the currently selected channel as sends-on-faders (identified on the scribble strip). So you have the option of pressing a mix button to see what's going into a bus, or using 'CH to All Mix' to see exactly what's being sent to all busses (except the main LR mix) from a particular channel. I love this feature, and it certainly proved useful when I was using the SQ-5 on a live show.

Another super-neat feature is the channel signal LED. Instead of having it simply glow a bit when an input signal is applied at some pre-determined level, the clever people at A&H have used a single LED to provide 'Chromatic Channel Metering', where much more information about the channel signal can be displayed. It shows different colours and brightness levels according to the signal strength, has a range of -72dB to +18dB, and the colour, intensity and threshold levels can all be configured on the Channel Meters page. This would be particularly useful to show very low mic signals, to give the engineer confidence that a mic is actually live when it's not being used — the -72dB threshold means that you'd see the LED light up well before you'd hear anything.

Making A Scene

Scene store and recall is all but essential nowadays when mixing a complex live show, and I certainly don't want to return to the analogue days of juggling subgroups and mute groups when doing musical theatre! The SQ is very well equipped and uses a 'scenes within show' architecture, where one Show is loaded on the mixer at any one time (stored and recalled using external media), and each Show can contain up to 300 Scenes, each representing a complete mixer snapshot. There's lots of control available through Scene‑safe management, and when I tried this function I was impressed with the lightning-fast speed of the switching.

Recording Options

These days, some sort of dedicated on‑board recording capability is to be expected, and the SQ doesn't disappoint. One of the most popular features of the Qu mixer range has been Qu-Drive (I know a couple of local theatre techs who have bought these desks mainly because of this feature), and like those consoles, the SQ can record and playback 16 channels directly to/from a USB device — but now at 96kHz. There is also a USB Type B socket that provides 32‑in/out audio interface functionality, and the SQ's MIDI channels also work over this connection, giving control options as well as audio.

Wedded WiFi

There are two useful wireless control apps available for iOS and Android devices. The SQ-MixPad app is for (pretty much) full engineer control of the SQ, including patching and assignment settings, while the nattily-named SQ4You is a personal monitoring app for performers. It's a lot more capable than some I've seen, and offers pretty comprehensive control of any aux mix. Personal monitor control can be a bit of a mixed blessing, depending on the situation, but I find it a big help when managing an orchestra pit, especially if the show is running for a few days and the band can get properly settled in. If these are a major part of your setup, check them out on the A&H website for more info on what they can do.

In addition to the local analogue I/O and integral SLink socket, you can expand the I/O either with a second SLink interface, or Dante or Waves expansion cards.In addition to the local analogue I/O and integral SLink socket, you can expand the I/O either with a second SLink interface, or Dante or Waves expansion cards.

Expand & Simplify

No matter what your initial requirement, there almost always comes a time when more inputs or outputs will be needed, and the SQ is provided with an SLink port capable of running three different protocols. This means that the SQ can be used with digital stageboxes previously used with the Qu, GLD (AR/AB units) and dLive consoles (DX), and offers full 128‑in/out gigaACE channels at 96kHz. An important point to note is that the port handles all sample rate conversion — up and down — so the SQ will happily run with other A&H 48kHz systems, enabling existing systems to be upgraded piece by piece. Perhaps the most interesting thing about all this is that an SQ mixer using DX expansion boxes or directly connecting to a gigaACE card will have exactly the same sound quality as a dLive system. Allen & Heath have had engineers carry out extensive comparisons with the two, and the SQ has even been used as a matrix mixer for dLive systems.

In addition to the SLink port, there's an expansion slot with three option cards currently available: a 96kHz Dante expansion (64‑in/out, and can also run at 48kHz); a 96kHz Waves card (64‑in/out, also at 96 or 48 kHz); and a second SLink card that runs independently, allowing 48 and 96 kHz rates to be used at the same time. With this sort of I/O capability, the 48-channel SQ can be installed in a situation where access to many more potential sources may be needed; marry this up to the flexible patching and scene memory and you have a small mixer capable of taking on a very big stage!

Live Notes

I managed to get the SQ-5 out on a couple of live‑sound jobs, and although I chickened out of using it for a full-on theatre gig (only on the basis that I wasn't quite familiar enough to risk it), I found it extremely easy to use, and a very pleasant surface to sit behind. The controls are nicely placed and the light-up knobs and clear colour-coded scribble strip are a delight to work with. Perhaps the best part was during the soundchecks, when I was easily able to set my EQ and dynamics to create a safe and controllable mix. I did use a couple of the DEEP plug‑ins too, and wished I had more time to spend playing around in this department — they really are very good and offer so many great options for detailing the sound.

I think it would be quite difficult to get any of the basics wrong when using the SQ, as the controls are so obvious, and the inexperienced user should get a lot of help from the 'intelligent' controls, which are disabled when not needed. If you follow the rule of 'If it ain't lit up, don't turn it,' you can't go far wrong. The super-compact design is another big plus for the SQ (and particularly the SQ-5) as it really doesn't take up much table space, especially when you consider its huge mix capability. For live use, the surface can be extended by using a tablet running the SQ-MixPad app, and there's a special mounting bracket available from A&H for positioning the tablet above the main unit. The SQ-5 was also very easy to carry around, and mine was in a neat A&H soft bag that fitted well and seemed to offer enough protection for normal lug‑about duties.


When an established producer of digital consoles introduces a new series within their existing range, it's understandable that people want to compare and position it alongside its family relatives. I think it is fair to say that the SQ currently fills a gap between the popular Qu series and the well-respected but significantly more expensive GLD consoles. The SQ has been brought in at a very affordable price, and incorporates bang up-to-date technology; but what's as important is that this technology has been cleverly and thoughtfully applied, thanks to a design approach that's focussed on making the workflow as efficient as it can be. Everything about the SQ's feature set and the way it's made accessible to the user definitely has a flavour of 'no stone unturned' about it.

There's a lot — an awful lot — about the SQ series that I haven't had time or space to mention in this brief review so, as ever, do visit the Allen & Heath website and download all the information or, even better, get your hands on a real live specimen. To sum up the SQ, it takes processing technology from the dLive range, uses workflow elements from the solid, proven Qu range, and will surely establish its own reputation as a powerful, fast and flexible live console that is likely to be at the top of many an engineer's wish list.  


There's a number of competing products available right now, which all share many of the same features. Obvious alternatives include the Soundcraft Si series, Yamaha TF range, the Behringer X32 and Midas M32 consoles, and the PreSonus StudioLive Series III.

Firmware Update

During the course of this review, Allen & Heath updated the SQ series to firmware version 1.3. Here's a summary of what was included:

  • Support for SLink and Waves cards added.
  • Support for DX164-W (16‑in/4‑out stagebox) added.
  • New processors: DEEP 16T, 16VU, Mighty, Opto and Peak Limiter 76 compressors; Proportional, DiGi and Hybrid graphic EQs.
  • New Listen Bus with patchable outputs (fed by P/AFL bus, this allows level control and stereo/mono output patching options).
  • Master fader 'Listen Level' mode (permanently assigns the master fader to control the level of the Listen Bus).
  • Reset Mix Settings (quick starting points for standard or monitor modes).
  • Tie Line patching mode (routes all available input sources to all available output destinations without using processing channels).
  • Input Patch Libraries (quickly switch between different setups or for virtual soundchecks).
  • External in to P/AFL (for patching comms lines to FOH/monitor).
  • User permissions (10 customisable user profiles for logging into the desk or control apps).
  • Compressor 'Ducker Mode' added.
  • Extra soft rotary options including absolute and relative MIDI, assignable soft rotary key functions, plus the addition of displayed values and info display using the View key.
  • Touch‑and‑drag control of parametric EQ.
  • SQ-MixPad app additions (user permissions, I/O patching, effects parameter and signal generator control).

Compare & Contrast

This table shows the differences between the SQ models, as well as some features that are common to all.

SQ-5 SQ-6 SQ-7 All Models
16+1 faders 24+1 faders 32+1 faders Talkback mic/line input
16 mic/line ins 24 mic/line ins 32 mic/line ins 3 stereo/6 mono line ins
12 XLR line outs 14 XLR line outs 16 XLR line outs 2 TRS line outs
8 assignable soft keys 16 assignable soft keys 16 assignable soft keys Stereo AES out
19-inch rack ears (optional) 4 assignable rotaries 6 fader layers
Published January 2019