If you have an iOS-based recording habit of any long-standing then you will probably be very familiar with the iOS music apps developed by Igor Vasiliev under his iMusicAlbum label. I’ve reviewed a number of these apps in the past – Audio Mastering, Master FX and Master Record – and they all are well worth owning.
Audio Mastering gave us the first stand-alone app for, well… audio mastering since you ask. It does a great job at a great price and can achieve some pretty remarkable results in the right hands. In contrast, Master FX is a multi-effects processor combining a range of processing options into a single app. Finally, Master Record provides you with some very useful tape emulation for when you need to add some analog-style warmth to a recording.
All three of these apps share many common elements in terms of the design of the user interface. This makes them easy to use and, even on the relatively modest screen real-estate available on an iPad, the controls are pretty intuitive despite there being a lot of features on offer.
Igor’s apps have earned a well-deserved reputation for their performance and audio quality and, if you like any of the current roster, I expect you are also going to like the newest edition to the list; AltiSpace. While we have some very good stand-alone reverb apps already available for iOS (AD 480, AUFX:Space and AudioReverb, for example), unless I’ve missed something, AltiSpace is the first stand-alone convolution-based reverb to become available (although Auria does have a convolution-based reverb built-in).
As I’ve commented before on the blog, good digital reverb can require a lot of CPU cycles. However, reverbs can come if different types (that is, the way by which the artificial reverb is generated is achieved in a different fashion). Perhaps the three most obvious categories of artificial reverb are analogue, algorithmic and convolution.
An example of the first might be the humble spring-based reverb found in a classic guitar amp. In a digital context, algorithmic reverbs use a mathematical process to simulate the different aspects of a reverb (early reflections, pre-delay, size of the space, length of the decay, etc.). However, a convolution reverb uses an audio sample from a real physical space (a small room, a church hall, a concrete bunker, etc.) and then, again through a mathematical process, applies the characteristics of that real space to your audio to simulate the effect being in that real space might have.
Reverb software that’s algorithm based tends to be fairly processer hungry (well, if it’s any good it does) but these tend to be the norm when it comes to reverbs built into DAW software anyway as they are still less CPU hungry than convolution based reverbs.
Over the last few years, as desktop computers have become more powerful and can cope with the processing required, convolution reverbs have become common and many of the top-end DAWs now include such a reverb alongside an algorithmic reverb (or two) within their default plugin collections (for example, Cubase includes the REVerence convolution reverb).
The processing demands of any high-quality digital reverb plug-in is one of the key reasons why it’s best to use reverb as a send effect (where you can share the reverb between multiple tracks) rather than as an insert effect (where it is applied to only one track).
Incidentally, if you want a more detailed description of these different reverb types, there is a very readable introduction in an article by Paul White over on the Sound On Sound magazine website that’s worth a quick read.
So, to see a stand-alone convolution reverb running on an iOS device is quite a thing given the (by modern desktop computer standards) rather modest processing grunt available. However, if it’s a trick that Igor can pull off, then the app could be very appealing as, while convolution can be processor hungry, it can also produce very realistic results.
The new (Alti)Space
AltiSpace therefore provides a convolution-based standalone reverb effect app for iOS. It requires iOS6.1 or above to run and will work with iPad, iPhone or iPod Touch. At least an iPad 3 or iPhone 5 (or better) is recommended particularly if you are using the app alongside other iOS music apps within Audiobus or an IAA host. The app is a c. 25 MB download so, unless your iOS device is full to bursting, almost any iOS musician ought to be able to find room for it.
And, if you are quick off the mark and an early adopter, there is a special introductory pricing available; you can get hold of AltiSpace for just UK£3.99. Honestly, as someone who lusted after the first convolution-based plugins when they appeared for desktop computers but simply couldn’t afford the investment, to now see a convolution-based reverb available for about the same price as a Latte Grande is kind of eye opening. I’m not sure what the price might revert to once the introductory offer is over, but even so, if AltiSpace can deliver even a respectable performance, this will still be quite some deal.
The audio samples used in a convolution reverb are generally referred to as impulse responses (IR files – derived from the fact that it is often an impulse of sound used to trigger the reverb response in the space and that is then captured for use in the reverb process). In fact, it is possible to capture an IR from almost any ‘space’, whether that space exists as a real space (such as a church hall) or as a virtual space (an algorithmic reverb).
One of things this has allowed convolution reverb designers to do is capture IRs from a whole range of ‘classic’ digital reverbs units – the kinds of digital reverbs that (a) have gone down in recording history and (b) now cost several arms or legs to buy. Use an IR created from your favourite ever reverb treatment in the most expensive Lexicon reverb device ever created and you can have the sound of that particular reverb patch to use in your convolution reverb plugin whenever you want it.
And, in this first release of AltiSpace, that’s essentially what Igor has done. There are no IR responses from real spaces; instead the app provides more than 200 presets where all the IRs are derived from some of the most well known hardware digital reverbs ever created. As described in the app’s documentation, these include the lexicon 480L, 300 and PCM 60 amongst a number of others.
Having quizzed Igor on this particular element of the app’s feature list, he did suggest that there may be other IRs added as the app evolves and is updated. However, as you can also import your own IRs as audio files – and AltiSpace will then convert their format for use within the app – you can actually expand the collection of reverb types available very easily. And if you just do a quick search on Google for ‘reverb IR files’ you will soon discover a whole range of freebies to download. Having given this a try myself today, the process seems to work very well and I had no problems importing, and then using, a number of IR files I’d downloaded via the web.
The other key features to note here are that the app is launched with support for both Audiobus (although not, as yet, State Saving as far as I can see) and IAA. The latter is particularly important because it makes it much easier to use the app as a send-style effects within a suitable DAW host so you can share that processing load across several tracks. That is, therefore, how I did much of my own testing; using AltiSpace as a reverb send effect via IAA within Cubasis, although the app did also seem quite happy to work within Audiobus.
Staring into (Alti)Space
If you have used any of Igor’s other iOS audio effect apps then AltiSpace’s user interface will feel very familiar. The default styling is predominantly gray but, via the Settings options (accessed from the button located top-right), I switched to the ‘Audio Mastering Studio’ colour scheme as I found that more pleasing on the eye. Incidentally, the Settings page also gives you access to a number of other settings including the background audio toggle. It is also here that you can access any of your own imported audio files if you want to bring additional IRs into the app.
Do note also that all the screenshots shown here are taken from an iPad. In contrast to Igor’s other apps, AltiSpace does also run on an iPhone but, of course, the screen layouts are somewhat different to accommodate the smaller screen size.
On the iPad version, the vast majority of the controls are held within the single main display. This is split into a number of different zones. Along the top strip you can access the Settings and Help options as well as a number of your favourite presets for easy recall. The main list of presets is found in the panel located upper-right and, usefully, you can organise this panel to show the presets by groups (reverb types), device (based upon the source of the IR file) and an ‘all’ option. If you find a preset that you are using regularly, then you can place that into one of the top-strip slots by tapping the ‘Save’ button and then tapping the required slot; very neat.
Located in a panel bottom-right are the input and output meters and four faders controlling the input level, reverb mix, stereo spread of the reverb effect and modulation. If you are using the app as a send effect, then you will probably want to set the Reverb fader to 100% and control the level of reverb applied to any track via the host DAW’s send level controls. However, if using the app as a ‘live’ effect to be added to a recording as you are making it (for example, by using the app within the Audiobus Effects slot), then you can use the Reverb slider to control the overall balance of the wet/dry signal.
With a convolution reverb, what you essentially capture in the IR file is that character of the original acoustic space. The sound this creates will be influenced by the size of the space, the materials from which it is constructed, any sound absorbing objects within it and the distance from the nearest surface at which the IR was recorded. When used in a convolution reverb process, what you should get back – in theory anyway – is your audio recording with a reverb sound that makes it sound like it was performed within that original space.
Now, unless to have the opportunity to modify those reverb characteristics in some fashion (and many early convolution reverb plugins didn’t provide this) then that was exactly what you got and you couldn’t vary it. You couldn’t change the tonal character (often related to the nature of the surfaces in the space), the reverb length (often related to the overall size of the space) and the amount of pre-delay (the time between the actual sound and when you start to hear the reverb – and this relates to how close the sound source and/or listener are to a reflective surface within the space). Essentially, the IR file defined your reverb and, if you wanted a different set of reverb properties, you needed a different IR file even if those differences were quite small (for example, a reverb length of 1.0 seconds as opposed to 1.1 seconds).
Fortunately, most convolution reverbs – AltiSpace included – now provided you with the ability to tweak the basic properties of the reverb character in a number of ways. In AltiSpace those controls are provided by the two larger panels located left/center of the display with the upper panel allowing you to tailor the EQ of the reverb while the lower panel allows you to adjust the amplitude envelope.
Both these panels are very well designed and, like most of Igor’s apps, provide the user with just enough control to get the job done but without drowning you in unnecessary details. In the upper panel you get three bands of EQ. This includes a low-cut and high-cut filter where you can vary the cutoff points to suit. These can be set very easily by tapping and dragging and you get good visual feedback as you do so. The middle band is fully parametric. Toggle buttons at the top of the panel allow you to place the EQ either pre the reverb processing (on the input) or post (on the output).
The Solo button solos just the EQ so you can hear what the EQ is doing to the audio while the Mute button bypasses the EQ module. As audio reaches AltiSpace’s input, you also get a real-time spectrum display in the EQ panel. The Rev, In and Out buttons allow you to together this spectrum between showing just the spectrum of the reverb, the audio input or the audio output. Most users might not touch these options but they are useful to have if you are looking for some visual feedback on what the EQ processing is doing to your sound.
The lower panel allows you to adjust the amplitude of the reverb. The spectrum shown in this window shows the density of the reverb and how that changes over time. This is information that is, essentially, ‘captured’ within the IR and is fixed for that IR. The visual image is useful because it shows you the overall length of the reverb in seconds and gives you an impression of how quickly the reverb reaches its peak intensity (essentially the pre-delay).
However, you can change these characteristics by dragging three envelope nodes around within the panel. This allows you to change the time it takes for the reverb to reach peak intensity and the overall length of the reverb. Note that you can only shorten the length of the reverb tail – you can’t extend the reverb length beyond the length of that captured in the original IR. Even so, the potential here to tailor the pre-delay and reverb length is considerable – it works brilliantly and provides lots of flexibility.
The Envelope panel also includes Solo and Mute buttons but, perhaps the most fun is the Reverse button that, as its name suggests, reverses the direction of the IR. If you want to hear your reverb built up to a peak slowly and then quickly fade away – great as a special effect – then this is the one to press :-)
Journey into Alti(Space)
While I did give AltiSpace a try via Audiobus, for me, the obvious way I would use the app is as a send effect for adding reverb to multiple tracks at the same time. For this option, using the app via IAA makes more sense so that’s how I did most of my own testing; using AltiSpace as an IAA send effect app within Cubasis.
To the user, despite being based upon convolution rather than algorithmic processing, in use, AltiSpace is very similar to operating any well-specified reverb effect plugin. Having set the app up as a send effect within Cubasis and adjusted the send level from the required track (or tracks), you then simply pick a suitable preset as a starting point (from the top strip or via the preset panel located top-right). You can then use the EQ and Envelope panels to fine-tune the sound of the reverb.
Those presets are, however, both large in number and wonderfully varied. While I quite like the occasional ‘special FX’ reverb (such as you can create with Crystalline) and there are some contexts in which a ‘I’m in a huge cave’ reverb is called for, for the majority of my own music recording projects, I tend to keep my use of reverb as subtle as possible. I want it there, but I don’t want too much of it as I find it just makes things more difficult to mix if lots of reverb is filling up the space. As such, I’ve always been a bit of a fan of ‘ambience’ style reverb presets and AltiSpace has a good crop of these. Indeed, some of these are taken from what many long-standing (and much better qualified than me) recording engineers consider the best source of ambience reverb sounds; Lexicon’s various hardware reverbs such as the L480.
Working my way through these ambience presets was a real pleasure. While you can make them obvious, you can also make them super subtle; the reverb is there but it is not overly obvious. With vocals in particular, I love these kinds of treatments as it leaves you plenty of space to apply other vocal effects where required without competing with the reverb yet it also avoids the sound being completely dry.
That said, if your own tastes in reverb – or the task in hand – require something more obvious and spacious, then AltiSpace has you covered. There are plenty of churches or halls or stages to pick from amongst the presets and, if you want to then tame things down a little, tweaking the reverb envelope makes that very easy to do.
Personally, what I do think is different between a convolution and algorthimic reverb – and, like everything is the world of the art that is audio recording, this is a matter of opinion – is the naturalness of processing when listening to exposed sounds. While this does, of course, depend upon just how good your convolution or algorithmic reverb are (good algorthim will beat bad convolution obviously), when you listen to a simple mix, there is a quality to a decent convolution reverb that somehow just makes it more ‘real’.
AltiSpace seems to pull that particular trick off very well; applied to a simple vocal/acoustic guitar mix, for example, whatever preset you apply, and however you tweak it, the sound has a real sense of being ‘in’ that space. In short, AltiSpace does sound very good indeed. That it is running on an iPad (or iPhone) is both remarkable and, to an extent, immaterial; at UK£3.99 (the launch price), this is unbelievably good value for the money.
Make your own (Ati)Space
While there is a very good selection of supplied presets – including some great ‘special effects’ options – as mentioned earlier, you can also expand your options by importing your own IR files into AltiSpace. I downloaded a bunch of freebie IR files from the Voxengo website (although there are plenty of other places you can also find them online).
Having then copied these files (they are in a WAV file format) to AltiSpace via iTunes file sharing (other routes are supported also), it was then very easy to use the ‘convert’ process in AltiSpace and begin using these within the app as presets. I suspect Igor will add further IR files to the base app as updates appear but it is great to be able to source your own if you feel the need.
Hungry for (Alti)Space
Of course, given my comments earlier about how intensive convolution reverbs can be in terms of processing needs, I was interested to see just how much grunt AltiSpace required. I’ve yet to find a way of really measuring the overall load being placed on an iOS device that I’m really confident about trusting. Cubasis’ own CPU meter doesn’t really help here as it only really measures what Cubasis itself is doing.
However, running the Status app (which gives you a measure of the overall CPU load on your iPad) alongside a simple, four audio track Cubasis project, showed the load was 7% without AltiSpace but around 17% with it added and in use. In contrast, replacing AltiSpace with the AUFX:Space reverb got the CPU load running at around 12% while AudioReverb produced a figure of around 16%. I’ve no idea how accurate or representative these figures really are and I certainly wasn’t pushing my iPar Air anywhere near its limits in running these tests but they do suggest that AltiSpace is placing a slightly higher load on the system that some of the other reverb apps out there. Even so, if you are running on more recent iOS hardware, this is not an unbearable load by any stretch of the imagination…. and it does sound very good indeed.
The only other observation to make is that, initially, I did experience some technical issues during testing on my iPad Air. I would occasionally get thrown back to the Home screen or AltiSpace would lose contact with Cubasis. However, having contacted Igor about this, he did say that there was a known issue that applied just to the iPad Air and that an update was already with Apple. That update arrived just as I was putting the final touches to the review and I’m happy to say that it improved thing on this front immediately. As with any new app, you might expect there to be some teething troubles in early versions but it is great to see a developer who is so obviously responsive to these.
I’m very impressed with AltiSpace. Like all of Igor Vasiliev’s iOS music apps, this is a very well executed piece of software and strikes a brilliant balance between ease of use, depth of control and excellent sound quality. To repeat what I said earlier, to find a convolution reverb available for UK£3.99 (catch it quick at this launch price) is just remarkable. The fact that is actually sounds very good at this price is even more remarkable.
Reverb is one of the key audio effects that you can use when getting a mix to ‘gell’ and, the better the quality of that reverb, the better the mix will sound. As every reverb processor (app or desktop or hardware) will offer something different in terms of sound, having a few different reverbs to hand is never a bad thing. And, if you can spare the CPU cycles, using a couple of different reverbs for different elements of your mix can give you very useful creative options. In a busy mix – and on an older iPad – you might not always have those CPU cycles available. However, if you do, then the quality of what AltiSpace does is well worth expending them on.
It’s always a subjective call with any of these sorts of comments but, for me, this is now the most ‘real’ stand-alone reverb app we currently have for iOS and, while I’m still going to be turning to a number of my current ‘go to’ iOS reverbs on a regular basis, when I really want to add something just that bit classier, AltiSpace will be the first thing that I now try. This is another top-notch app from Igor Vasiliev….
AltiSpace – Convolution Reverb