RF-1 review – Numerical Audio add an AU reverb to their iOS music app catalogue

Download from iTunes App Storerf-1-logo-1As I mentioned a few days ago, Numerical Audio – led by Kai Aras – have released a new iOS music app. The app, called RF-1, is a follow-up to the RP-1  that I reviewed here of the Music App Blog when it was first launched a few months ago. RP-1 provides a compact, but well-featured, delay effect and is capable of both conventional and more creative treatments. As well s a modest price (just UK£4.49/US$5.99) and stand-alone, Audiobus and IAA support, RP-1 also included both Ableton Link (tempo sync your delays via Link) and Audio Units (AU) support. The latter means that you can, of course, run multiple instances of the app within a suitable AU host such as MultitrackStudioCubasis, Modstep or AUM.

The new RF-1 is the perfect complement; it provides reverb treatments to sit alongside the delay options provided by RP-1. RF-1 arrives with a similar compact format, and a similar set of iOS music tech features – yes, including AU support – and exactly the same pricing. Both apps are universal and both require iOS9.0 or later.

RF-1 - Numerical Audio add a reverb app to sit alongside the RP-1 delay.

RF-1 – Numerical Audio add a reverb app to sit alongside the RP-1 delay.

We have some very good reverb apps already available for iOS – AltiSpace, AD 480, AudioReverb and DDMF Envelope to name a few – and most of the leading DAW/sequencers also ship with a ‘stock’ reverb effect. However, reverb is an effect where you often can hear quite marked differences of character between different software emulations and, in the case of the above listed examples, not different in terms of ‘some good, some bad’…  just sonically different and, therefore, each suited to different circumstances. Like with EQ, compression and delay, having a few reverb options to choose between is a nice place to be when it comes to mixing your latest iOS music project.

So, in that context, is RF-1 worth adding to your iOS music app collection?

Watch this space…

As with RP-1, the UI design for RF-1 strikes a really nice balance between being straightforward and easy to use while also giving you plenty of control over the reverb effect you are trying to create. The reverb is algorithmic in nature (as opposed to the convolution process used in something like AltiSpace) but, all other things being equal (and they never are), it should mean that RF-1 should produce too much of a CPU hit.

The app ships with a number of presets... but it is very easy to create your own given the compact control set.

The app ships with a number of presets… but it is very easy to create your own given the compact control set.

Inside the reverb engine, there are five basic reverb algorithms provided – hall, plate, ensembleverb, tremoloverb and vintageverb – and, as these labels might suggest, they span conventional treatments and more creative treatments. If you are looking for more conventional sounds then the hall and plate are great for things like spacious guitars or vocals, while ensembleverb and tremoloverb are slightly further ‘out there’ (although not so far out there as to be in Turnado territory, for example).

Of course, some potential users might already be thinking ‘no room algorithm?’ or something along similar lines. However, while a dedicated room or chamber style algorithm is something that it might be nice to see, the available control set really does make it very easy to both re-size and re-colour the reverb sound; if you start with one of the more conventional algorithms then you can generate reverb styles that go from very small and subtle (almost just a hint of ambience) right up to a large concert hall or cathedral style sound; RF-1 can pretty much span this full range.

In the full-screen version of the app (via Audiobus or IAA for example) you get input and output meters/controls. However, the AU UI is a little more compact and those in/out features are left up to you to manage via whatever AU host you are using (which is absolutely fine and now an issue in practice).

The AU support is great to see and I had no problems using the app via that route.

The AU support is great to see and I had no problems using the app via that route.

In both modes though, the key controls on the reverb sound itself are divided into two panels; Space and Color (or Colour depending upon which brand of English you prefer). Having picked a reverb algorithm type from the selection panel located top-centre, the Space controls then allow you to customise the size of that space in various ways.

So, the Size knob does exactly what you would expect but you can also set the Decay (how long the reverb lasts). Predelay (the delay between the original sound and the onset of the reverb which sort of models how close the nearest reflective surface is to the original sound), Diffusion (almost like the density of the reverb), Width (the stereo spread of the reverb) and the Damping (overlapping with the Color section a bit as it controls how quickly the high-end of the reverb fades and, in part, simulates the nature of the reflective surfaces being modelled) controls round out this section of the UI. The bottom line here is that there is plenty of control options for your reverb size and you can go plenty big or super small with ease.

The control set manages to combine flexibility with easy of use; the sign of a good design.

The control set manages to combine flexibility with easy of use; the sign of a good design.

The Color section provides a range of options for changing the tonal characterises of the reverb. Bass and Treble do what you might expect so, if you want to lose the boomy bottom end, and dial off some top-end to create a warm reverb, then that’s easy to do…  and other combination of course. The Crossover setting adjusts the frequency at which these two tone controls interact with each other. The two mod controls provide a bit of ‘movement’ in the character of the reverb (the app has an internal LFO) while, finally, the Mix control adjusts the wet/dry balance. You might not need this if using RF-1 as a send-return effect in your DAW/sequencer but it would be useful in other sorts of routing situations.

Where am I?

Having given RF-1 a bit of a workout on a number of different sound sources – vocals, guitars, brass, strings, drums, etc., I have to say I was pretty impressed with the results. If anything, I think the supplied presets – which perhaps tend to focus on the bigger and more creative styles of reverb – perhaps undersell just how flexible the app is. Like with many reverbs, I found it quite easy to get sounds out of it that didn’t really suit drums (although for more subtle treatments, it worked a treat) but, otherwise, I thought is sounded very good indeed…  and way better that UK£4.49/US$5.99 has any right to sound.

Yay! Multiple instances of the AU plugin within AUM :-)

Yay! Multiple instances of the AU plugin within AUM :-)

Thankfully, you can, of course, save your own presets very easily so I was soon crafting a few smaller spaces to place my sounds within. Given the cost of adding a few extra presets is pretty minimal, maybe this is something Kai might consider for the first update?

The app also worked very well within Audiobus.

The app also worked very well within Audiobus.

Alongside the very useable sound, like RP-1, RF-1 also performed very well from a technical perspective. Whether used via Audiobus, IAA or AU, I had no issues whatsoever. In both Cubasis and AUM (as you would be able to in other AU hosts), I was able to load multiple instances of RF-1, dial in different treatments, and apply them to different elements of my mix.

... and within Cubasis :-)

… and within Cubasis :-)

The AU plugin format is so much easier to work with in a DAW/sequencer context…  I, for one, can’t wait for AU to grab a firmer hold. That said, I can see why we currently have more audio effects apps that are AU compatible as opposed to virtual instruments. RF-1 has a UI that is simple enough to work in the smaller sub-window most AU hosts offer and, until there is more flexibility in this regard (AUM already allows you to re-size the AU window) then it’s easy to see why some more complex synths (for example) might be difficult to re-imagine in the AU format. I’ll keep hoping though….

In summary

As with RP-1, there is little not to like about RF-1 and it’s great to see (a) a developer who is obviously so active and (b) keen to embrace the AU format. And, as it is also priced at just UK£4.49/US$5.99, for keen iOS music app fans who use reverb treatments on a regular basis, this is pretty much a no-brainer.

Both RF-1 and RP-1 are no fuss to use, sounds great and very affordable. If you have not done so already, you can read the full RP-1 review here but, if you are happy to exchange the price of a coffee and a cake for a new reverb for your iOS music app collection, then RF-1 comes highly recommended. I wonder what’s next of Numerical’s ‘to do’ list?

RF-1 reverb

RP-1 delay

Download from iTunes App Store


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    1. Nathan Brazil says:

      RF-1 is a worthy addition to anyone’s FX collection. Lovely interface, easy to use and yet able to produce much variation. As you suggested, it has its own tonal qualities which sound different, in a good way, to other reverb apps. Factory presets are a bit OTT, but easy to dial back a notch or two. RF-1 also shows how developers who really want to can launch a product with the required connectivity.

    2. Nathan Brazil says:

      Tried to leave a comment earlier, but that vanished into the darkness of the Interweb . Anyway, I bought this because RP-1 was such a treat to use. I must say that I’m equally impressed with RF-1. I already have a number of reverb apps, but each one has its own distinctive tone and quality. RF-1’s presets are a little OTT, but easy enough to turn down a bit. As an AU app it’s superb. Now all we need is the inevitable RC-1 (chorus and phase app).

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