iConvolver review – compact convolution reverb app for iOS from ART Teknika

Download from iTunes App StoreiConvolver logo 1There is a nice discussion (Friday night argument over a beer or three) to be had about the ‘most important processors’ required when it comes to the mixing stage of a project. In terms of getting your basic mix together, with each element of the performance balanced, it is difficult to look beyond EQ and dynamics control (compression, limiting, etc.). However, there is a good case for ‘ambience’ or ‘spatial’ placement being next in the pecking order and a core part of that may well revolve around reverb.

Not that many years ago, this used to be the week spot in the ‘in the box’ approach. Software reverbs in the form of plugins were… well, not very good. This was anyone’s fault… just the state of play when the calculations required to emulate the reverb process require some quite complex maths and a lot of CPU cycles. However, computers have since caught up, algorithms have improved, and software reverbs can sound very good indeed thank you very much.

Including, of course, convolution reverbs. These are based upon different principles to a more ‘traditional’ algorithmic reverb in that they employ something a little closer to physical modelling and, as such, are even more CPU intensive (all other things being equal) than algorithmic reverbs. They are also capable of more realistic results and, while ‘real’ sounding reverb might not always be exactly what’s required when mixing contemporary pop or dance music, if you need your sounds to seem like they are sitting in a real space, convolution reverb is a good way to go.

iConvolver - a compact convolution-based reverb for iOS.

iConvolver – a compact convolution-based reverb for iOS.

With higher CPU demands, you would have thought that a convolution-based reverb was a more challenging proposition for iOS music app developers. But, despite that – and much to my own amazement it has to be said – we have seen some very credible convolution-based reverbs appear on the App Store. Indeed, the first such example – AltiSpace from Igor Vasiliev – has become a pretty sophisticated beast and is one of the 16 ‘core set’ apps I recently listed as part of my ‘less is more’ recording app collection.

Even more amazingly, AltiSpace is not our only convolution option and an addition choice for iOS musicians hit the App Store a couple of weeks ago; iConvolver from ART Teknika. Incidentally, while iConvolver was their first release, the second has now also arrived; M/S Proc is a mid-side processor and I’ll work up a review of that in the next couple of days.

So, if you are still looking to add a convolution reverb to your iOS effects rack, is iConvolver a likely contender?

What’s involved with iConvoler?

iConvolver is a universal app, requires iOS7.0 or later to run but, as indicated in the app’s blurb on the App Store, a 64-bit iOS device is recommended; yes, convolution does still chew through CPU cycles. The app is an 87MB download and has a special launch price of UK£2.99/US$3.99 for a limited time only. This is 50% off what will become the standard price.

The app can be used stand-alone (as a ‘live’ reverb effect) but includes both Audiobus and IAA support from the off so, for recording duties, you could easily use it within your usual iOS music making workflow as, for example, an insert or send effect in your DAW/sequencer.

As with all convolution reverbs, iConvolver requires impulse response (IR) files taken from real acoustic spaces to do its reverb magic. The app comes supplied with over 100 of these covering a range of both small and large acoustic spaces. However, if you know what you are doing on this front, you can also load your own suitable IR files (there are sources of these available on the web if you do a quick search) so you could easily expand on the reverb ‘types’ built into the app.

There are a few 'set and forget' type settings to be found within the app but, otherwise, all the controls are found in a single main screen.

There are a few ‘set and forget’ type settings to be found within the app but, otherwise, all the controls are found in a single main screen.

There is a Settings page where you can configure the app’s key global parameters. These include a Buffer Size option but, if running the app within a host (for example, as I did within Cubasis for most of my testing) then, most likely, the host will control this anyway.

Reverb made simple

When it comes to the controls offered by iConvolver, ART Teknika have, I think, struck quite an interesting balance. On the iPad, pretty much everything is contained within a single screen and, even on a smaller iPhone screen, things don’t get too cramped as the 8 main faders are split between two tabbed screens in the lower half of the display.

This main screen is split into two areas. At the top we have the input and output level meters and, filling most of this portion of the screen, a visual representation of the currently loaded IR file. Tapping the Load button (located next to the global On/Off button that can be used to bypass the effect) gets you access to the IR files included with the app and these are usefully organised into sub-folders based upon the type of ‘space’ they are derived from. These include short (small rooms), medium (plate-based) and long (hall-style spaces) as well as some spring-style reverbs and some effects-style treatments. In short, there is a bit of everything and, for routine recording and/or music mixing duties, there is plenty of choice.

The upper portion of the display provides you with a graphical representation of the currently loaded IR file.

The upper portion of the display provides you with a graphical representation of the currently loaded IR file.

Within this upper portion of the display you can also grab the two ‘handles’ and adjust the length of the reverb and its fade time. This is useful if you have a longer IR that you like the sound of but want a shorter reverb decay. This works well enough although you don’t hear changes made in real-time; you have to adjust the parameters and then confirm the changes by tapping the ‘OK’ button that appears.

You can adjust the length and decay of the reverb's amplitude envelope to adjust the time element of the ambience generated.

You can adjust the length and decay of the reverb’s amplitude envelope to adjust the time element of the ambience generated.

The lower half of the screen provides 8 faders to adjust other key parameters. These include Input and Output levels, Wet and Dry levels and a WetBal fader that further adjusts the balance between the wet and dry signals (although you can do that just with the individual Wet and Dry faders if you wish). In terms of tweaking the character of the reverb, the remaining three controls are perhaps most important. Here you get a high-pass filter, low-pass filter and PreDelay. The two filters are very effective for tweaking the tone of your reverb – rolling off any low-end rumble (usually not useful in musical contexts) and taming any high-end ringing (so you can warm up the reverb sound).

The pre-delay allows you to ‘separate’ the reverb slightly from the original dry sound. The time value represents the delay between the original sound and when the first reverb from that sound is heard; in effect, it defines the virtual distance from the original sound source and the first reflective surface it hits to start creating reverb. This can help you maintain the clarity of the original dry signal but still apply a sense of ambience. Rather usefully, you get Reset, Bypass or Mute buttons for each of these 8 faders for a little extra control and to facilitate A/B comparisons.

The main faders provide just enough control to adjust the level and tonal character of the reverb sound.

The main faders provide just enough control to adjust the level and tonal character of the reverb sound.

Placed in space

From a technical perspective, I had no issues using iConvolver in my own testing. It worked well in Audiobus and, where I did the majority of my testing, as a send effect via IAA within Cubasis. It also worked happily within AUM via IAA.

In terms of the sound, the results were also generally good. I particularly liked the small and larger ‘room’ style IRs. Convolution reverbs do have the capability to sound very ‘real’ and iConvolver does a remarkable job here when you consider just how little the app costs. Some of the spring-style IRs were – to my taste at least – a little less useful, but I’m sure others will find plenty of applications for them and there were also some pretty cool ‘special FX’ treatments including a couple of the slap-back and reverse IRs.

Iconvolver ships with around 100 IR files to get you started and these are organised into useful categories.

iConvolver ships with around 100 IR files to get you started and these are organised into useful categories.

I did find the EQ controls to be pretty much essential, although this is something I’d say about most reverbs, and iConvolver’s high- and low-pass filters are very easy to use when it comes to dialling in a bit of tonal control. Anyway, I’d have no problems finding a spot for iConvolver in my own iOS recording projects…. it is more than up to the task and easy to use to boot.

iConvolver was capable of some very good sounds when used within Cubasis via IAA as a send effect.

iConvolver was capable of some very good sounds when used within Cubasis via IAA as a send effect.

This last point is also interesting at a technical level as I suspect this is a UI that could actually survive the transition to the AU format under iOS (which can restrict the screen real-estate available to developers) without too much difficulty. While reverb is perhaps not something that you would always need multiple instances of anyway, having that option (perhaps a different reverb for your drums, other instruments ands vocals?) does provide extra flexibility, providing your hardware is up to the task of running multiple instances of a convolution reverb in the first place.

Reverb wars

And talking of CPU loadings, iConvoler is a reasonably demanding app. In fairness to ART Teknika, they do state this quite clearly in the App Store description. On my iPad Pro, with a fairly modest test project running within Cubasis, my CPU meter jumped by perhaps 20% when I loaded iConvoler and did move around a little about that figure. This is perhaps something that you might need to manage in a more complex project via some track freezing, etc.

The obvious comparison for me was against AltiSpace... and while AltiSpace perhaps offers greater control, sonically, iConvolver wasn't out of its depth.

The obvious comparison for me was against AltiSpace… and while AltiSpace perhaps offers greater control, sonically, iConvolver wasn’t out of its depth.

Exploring iConvoler alongside my usual iOS convolution reverb of choice – AltiSpace – was quite interesting. Sound-wise, iConvolver could generally get very close to what AltiSpace was doing and the quality of the sound between the two apps perhaps depended as much on the nature of the IR being used in each case. AltiSpace undoubtedly offers more options for tweaking the nature of your reverb – more comprehensive EQ adjustment for example – and, a little to my surprise, also resulted in a somewhat lower CPU hit, but iConvoler certainly wasn’t out of its depth in comparison; this is a very solid and, with the right IR, very ‘real’ sounding reverb.

iConvolver also performed well when used within AUM.

iConvolver also performed well when used within AUM.

In summary

If you already own AltiSpace (currently UK£4.99/US$6.99) then perhaps you might feel you don’t need iConvolver as well. However, if you are looking for a first convolution-based reverb, or perhaps a second one to sit alongside something like AltiSpace, then, at the UK£2.99/US$3.99 launch price, this is most certainly a good deal.

What many users might appreciate is the combination of the very ‘real’ convolution-based sound and the fairly streamlined control set. iConvolver offers just enough control to give you flexibility but without taking any time at all to really get to grips with. And while it does chew through a decent number of CPU cycles, providing you have fairly up-to-date iOS hardware, it could most certainly serve as your high-end reverb source for the critical elements of your mix (such as vocals).

I didn’t explore the importing of addititonal IR files but I suspect that expanding the selection provided (which is already good) would be something on the agenda for any future updates….   This first release of iConvolver is a good one and, if you have space for a convolution-based reverb in your app collection, iConvolver would make a perfectly good selection. Here’s hoping that the new M/S Proc app from the same team makes just as a good a debut :-)

iConvolver – Impulse Response Reverb


M/S Proc – Mid/Side Level & EQ


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