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Allen & Heath Qu-SB

iPad-controlled Digital Mixer
Published March 2017
By Mike Crofts

Allen & Heath Qu-SB

The stagebox-cum-mixer format has proven popular over the last couple of years, and now Cornwall’s finest have joined the party!

The latest addition to the popular and ever-expanding Qu range of products is the Qu-SB, which Cornish mixer veterans Allen & Heath describe as hosting the mix engine of the Qu-32 in a compact, rackmountable format. All of the Qu-32’s DSP, including all the processing of the largest model in the Qu range, is indeed at the heart of the Qu-SB, and all the family traditions are present in this diminutive product, albeit accessed via a different interface — the Qu-Pad app. I like scalability and compatibility between products within a model range, and the Qu approach fits this concept very nicely.

If you haven’t yet explored the world of app-controlled rack mixers, the best way of describing the Qu-SB is that it looks like the rear panel of a ‘conventional’ digital mixer, in that it presents all the input and output connectors necessary to interface with stage sources and the sound system, and the unit contains all the necessary processing to deliver a full mixer functionality — you just don’t have a ‘top panel’ hardware control surface. In the case of the Qu-SB there are 16 local mic preamps and these first 16 channels are accessed via XLR (mic) and TRS (line) input connectors; a further 16 mix channels can be added by connecting an external A&H AudioRack, via an Ethernet cable, to the dSnake port. There’s a stereo TRS input labelled ‘ST1’ which can be used for local line inputs, for example backing tracks or walk-in music, and if you count the four effects returns that takes the total available channel count to 37.

The Qu-SB is very well-endowed with output busses, and the front panel provides XLR outputs for the left/right main mix plus another 10 mix outs, the first four of which are mono and the remainder grouped as stereo pairs, ie. 5/6 to 9/10. There are two stereo matrix busses, the first has front-panel TRS outputs and the second can only be accessed via an additional AudioRack connected via the dSnake port (the same is true of the stereo groups and parallel mix outputs). Finally there’s a local headphone output which is used for monitoring any individual channel or mix bus within the mixer using the P/AFL buttons within the Qu-Pad control app.

Physically, the Qu-SB integrates comfortably into the Qu range and the labelling and colour coding is consistent with the larger products. As with every Allen & Heath product I’ve ever come across the build quality and finish is very good indeed and the Qu-SB has a very solid feel about it. The unit is nominally 4U in that it is designed to fit into a shallow 4U rack case, but it can also be left free-standing and its distinctive angled-front design looks particularly at home in a studio or mobile desktop recording environment — it reminded me of those classic stand-alone units you used to find in broadcast studios. If you want to mount the Qu-SB in a case then rack ears are available, and it’s not only a simple process but also convenient; the substantial rubber feet on the underneath don’t have to be removed (a small point but one which I really like as there’s no chance of losing them). The design of the case also means that there is a guaranteed ventilation space below the unit when racked, and the ultra-shallow depth provides extra space at the rear for the mains cable to be neatly stowed in transit. When mounted in a rack case the front panel retains its upward angle which does improve visibility and access for making connections, although if it’s mounted right at the front of the sleeve then the bottom of the unit will protrude slightly.

The front panel is clearly and neatly laid out with plenty of space around the connectors, and thank goodness the Qu-SB has avoided the use of those latching XLR sockets — you know, the ones with little metal tabs designed to rip your fingernails off and occasionally jam...

If You’re Appy & You Know It

The Qu-SB is designed to be controlled by an iPad running the Qu-Pad app, available for free download, and a considerable amount of A&H design and development expertise has clearly gone into making this control system as smooth and stable as it can be. Although the engine room of the Qu-SB is the mix processor within the unit itself, all the user control functions are performed using the Qu-Pad app, and the app is therefore what chiefly influences both the look and feel of this mixer. This does mean that the Qu-SB cannot be operated without an iPad running Qu-Pad — for example, it won’t work with a laptop or an Android device, and it can only be controlled over Wi-Fi using an external router. I must admit that with my own digital mix setups I tend to use Wi-Fi for setting up and soundchecking but always prefer the comfort of having an Ethernet cable connected for the live performance — the Qu-SB doesn’t allow this and so you have to trust not only the system quality (no problem with this) but also the external router and environment which is supplied by you or the venue. The user guide does recommend the use of a dual-band router with auto-switching (an excellent idea and something I’d regard as essential in many/most venues) and gives advice about positioning and so on.

Despite my reservations about using Wi-Fi in a live context I have to say that I didn’t experience any problems at all using my travelling Netgear router mounted about two feet above audience head height and a mix position about 15m away at the back of the venue. Of course, many potential users of the Qu-SB may well just control it from the stage anyway, which minimises potential wireless issues, but issues with interference or lost connections may only become apparent over a longer period of continued use, if at all — and knowing A&H they will have invested a lot of time and effort into the testing of every aspect of this product. I should mention here that the Qu-SB also works with the Qu-You personal monitor control app, and this free app is for iPad, iPhone, iPod Touch and also for Android devices.

A final point to mention is that the Qu-SB and Qu-Pad apps must be at the same firmware version; for example the v1.8 app will not work with v1.9 mixer firmware, and Allen & Heath recommend disabling auto-update on the iPad to prevent a potential and unsolicited mismatch.

In terms of analogue I/O, the Qu-SB offers 16 mic/line inputs, 10 aux outputs, plus the stereo mix output and a stereo matrix bus. These can be greatly expanded via the dSnake Ethernet port.In terms of analogue I/O, the Qu-SB offers 16 mic/line inputs, 10 aux outputs, plus the stereo mix output and a stereo matrix bus. These can be greatly expanded via the dSnake Ethernet port.

It took me a little while to find my way around the app in order to carry out all the normal mixer functions, and I did have to spend a few moments figuring out how to jump around the various views to get to the page I needed. Whilst much of the app is intuitive without the need to continually refer to the manual there are a few areas where a bit more familiarisation time really pays off. Going back to the ‘manual’ I mentioned, the Qu-Pad app has a first-class help section right there on the screen, accessed via the setup menu, that provides clear, logical and beautifully laid-out pages of ‘how to’ complemented with full-colour screenshots — really impressive.

The full functionality and workflow of the Qu-SB is presented within the help section of the app and I’d recommend downloading Qu-Pad from the App Store and running it in demo mode and then reading all the way through the help section.

Driving Lesson

There are far too many aspects to the Qu-SB to cover in this brief review (check out the automatic mixing function, for example), and it would take some time to become properly familiar with all that the Qu-SB can do. However, I wanted to use it as a basic live mixer for a band gig, and having found my way around the main mix screens I felt ready to go. The Qu-Pad layout is logical and clear but doesn’t allow too much customisation of its screen layout. For example, each screen shows eight strips plus a master fader and you can’t change the displayed strip width to cram more onto a single screen — once I’m all set up I’d prefer to have a 16-fader view for looking at and controlling all my levels without having to slide left and right. The screen display is super-clear and very easy to read, with all the required channel information available by simply tapping the channel name box above the fader. Every function available on the screen worked smoothly and consistently, with more than enough accuracy when selecting various parameters to adjust; the EQ screen is particularly impressive, with excellent and precise fingertip control, and some parameters can also be highlighted and adjusted using an on-screen linear slider. A number of icons across the top (always displayed) will bring up various screens including setup, home (which is more-or-less an ‘about’ screen), scene list and in/out patching — but the main operational view is the one called ‘processing’ and this is where the live mixing work is done.

The parametric EQ control is a particular highlight of the accompanying Qu-Pad app.The parametric EQ control is a particular highlight of the accompanying Qu-Pad app.

The faders are laid out across the lower half of the screen and the usual functions are contained within them — mute, channel on/off, pan and P/AFL, all your standard mixer buttons. The upper part of the screen displays the channel processing in more detail, and tabs at the left select the input controls, dynamics and EQ screens. Interestingly, each channel has a ducking facility which is potentially very handy when using the Qu-SB in an AV or conferencing environment.

Depending on which screen is in focus, hitting the round ‘library’ button brings up a list of appropriate presets that are recalled and applied by a single button press. The ‘send to’ buttons are arranged in a vertical strip down the right side of the screen, and this is where you can flip between different mix busses, including the main left/right mix, the 10 auxiliary busses, groups and effects sends; hitting any one of these buttons puts whatever channels are currently displayed into a sends-on-faders mode for the chosen mix, and hitting the button a second time (or hitting the L/R button) returns to the main L/R mix.

Down the left side is where you can choose which processing channels are on the current fader layer (ie. inputs, mixes, DCAs, mute groups), or choose to display one of three custom layers — the provision of three user-defined custom fader banks is an excellent feature as this gets around the limit of eight faders on screen. Using DCAs or groups it’s possible to condense the overall mix view so that overall level control can be achieved unless more detailed individual channel adjustments are necessary.

Processing

The four built-in effects processors are very good, with great graphic interfaces, and provide two levels of user control — the main parameters can be controlled from the basic screen but an advanced set of parameters can also be accessed and put to good use by the more experienced user. The reset default is two reverbs, a delay and an ADT, but the effects are all configurable and can be patched as returns into the mix or used as inserts on channels or mix busses.

Setting up DCAs and mute groups is straightforward, although I did discover that if a channel is a member of a mute group it appears that its main channel mute button doesn’t over-ride the group mute state — it doesn’t light up either as there’s a separate indicator to show that the channel is muted within a group. This is a safe way of operating but it means that, for example, if all your stage mics are muted in a group you can’t just unmute one of them for a quick announcement by hitting its mute button.

Used in a live context, I was completely happy with the performance and workflow of the Qu-SB, and although I didn’t explore much of its potential I think it’s a flexible product which would lend itself very nicely to quite a few of my live-sound gigs.

The best way I can describe the Qu-SB mixing functionality is ‘comprehensive’. It has everything you’d normally find on a full-featured hardware surface and once you get used to the Qu-Pad app there’s a way of doing practically anything you want! To explore the capabilities in more depth have a look at the Qu range user manuals and specific Qu-SB guide online, and run the Qu-Pad app in demo mode on your iPad — you’ll quickly get a good idea of what this little beast is capable of. In terms of the sound quality the Qu-SB has the audio qualities you’d expect from a pro-spec mixer, and the smoothness of the EQ and dynamics processing makes them a joy to work with. If you’ve listened to or worked with any of the Qu range then you already know what to expect.

On The Record

One notable Qu-series feature is the ability to record multitrack audio directly from the USB ports on the mixer. A Mac or Windows PC connected to the USB ‘B’ port enables bi-directional streaming of 32 audio channels and sending of MIDI data — the necessary ASIO/WDM driver for streaming to a PC can be downloaded from the A&H web site. The other method of direct recording doesn’t even require a computer; stereo or up to 18 tracks of multi-channel audio can be recorded direct to a USB storage device plugged into the front-panel Qu-Drive port, which is an ideal ultra-convenient way to capture live performances. The recording capability of the Qu-SB isn’t just an attractive add-on, it means that this device can act as the heart of a studio or mobile recording setup, complete with monitoring facilities. There’s a lot more information in the A&H Qu Knowledgebase, accessible via the Allen & Heath web site — look for an article called ‘Understanding Qu-Drive and USB’ if you want to investigate further.

Published March 2017

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