Freebie of the Month – Roth-AIR from Rothmann

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Roth-AIR is a one-trick pony, but oh how brilliant this pony is at doing that one trick: adding upper-frequency-range excitement to a track or a mix.


by David Baer, Mar. 2017


This month’s freebie is another entry in the most recent KVR Developer’s challenge.  It did not win the competition but it certainly should have made most people’s finalist list.  It does one thing, but does it brilliantly – so much so that any mixing engineer would be perfectly justified on using it even in a high-budget production.

Many audio professionals have names for areas in the audio frequency range, and while there’s no uniform, standardized definition for these, the range of 3K (or maybe 4K) on up to the upper limit of human hearing is often said to be comprised of “presence”, “brilliance” and “air” in that order.  Roth-AIR’s mission is to add a bit of excitement to these areas of the spectrum.  It does this with a simple UI that needs little explanation.


The brief documentation Roth-AIR doesn’t precisely reveal the secret sauce employed to do the job, but there are a couple of things at work.  The main ingredient is some kind of saturation (possibly combined with wave-shaping).  Then there’s a compression component to the processing that can optionally be added to the result (or maybe it’s the compression that gets in on the wave-shaping action).

The large control, Air, is clearly the most important one.  But let’s get Frequency and Mix out of the way.  Mix is the usual Dry/Wet ratio control.  Roth-AIR affects the portion of the input signal from a selected frequency on up.  As you might expect, this frequency is specified with the Frequency control.  The image below shows the range of affected frequencies with frequency fully counterclockwise (green) and fully clockwise (white).  The input signal is pure pink noise and Mix is 100% wet.  As you can see, we’ve got as much of presence/brilliance/air ranges covered as we’d like.


The compression is pretty subtle and uses a low ratio.  We have no control over attack/release – only Threshold can be specified.  Gain affects the wet portion of the signal only, so you can think of that as make-up gain or just a wet-signal boost.  Fully clockwise gain gives you something in the neighborhood of 18 dB boost if my measurements were accurate.  You can turn off compression (it appears) by simply setting Threshold fully counterclockwise.

Lastly there’s the Air control.  This is the part that doesn’t completely make sense because low settings of this control seem to actually cut the signal in the targeted high-frequency area.  In the image below you can see three curves: Air fully counterclockwise, midway and fully clockwise (green, red and white curves respectively).  Once again, pink noise is the input signal and 100% wet is the Mix setting.


But all this is merely useful background.  With controls this simple, just set them to what sounds good and don’t worry about it.  Be assured that you can get some great-sounding results  Perhaps do be careful of use on vocals since the sibilance area of the spectrum is right where Roth-AIR operates.  In general, like a lot of audio manipulation, a great rule of thumb would be to increase your settings until the effect is clearly audible and back off to where it’s not in your face but something is lacking when your disable the plug-in.  A little of this sonic seasoning can be magic.  However, too much might sound good in the near term yet be detrimental for lengthier listening experiences.

But, really, a five-control plug-in is hardly rocket science.   Something this simple doesn’t even really need presets.  This one is dead easy to use and can sound fabulous.  My only wish would be for a low-pass filter to be available on the wet signal.  That way you could easily, for example, target just the presence range to be stimulated.  But as Roth-AIR is a great-sounding plug-in that’s also absolutely free, who am I to complain?

Roth-AIR is available for PC and Mac, 64-bit and 32-bit, VST and AU.  You can download from here:


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