Review – Stealth Limiter and Saturator X from IK Multimedia

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Two recent additions to the IK Multimedia T-RackS line are most worthy of your consideration.  Find out more in this double review.


by David Baer, July 2016


IKMultimedia’s T-Racks began life billed as a mastering solution.  It contained a number of discreet standard mastering effects units (EQs, compressors, et. al.) that could be hosted in a DAW or in the standalone T-RackS dual-channel host rig.  As a mastering solution, it has served well in that capacity.

Many of the original T-RackS modules also served well as track inserts in mixing situations.  Over time, IKM has added new T-RackS modules.  Today, the lines are a bit blurred as to whether a T-RackS module is intended primarily for mixing or mastering, but that’s fairly immaterial.

What is not immaterial, at least for some disgruntled shoppers, is the IKM Custom Shop mechanism used to sell these modules.  At lot of people seem to struggle to understand how to best use this.  And then there are Jam Points, rewarded for previous purchases.  And then there’s the occasional crazy-good-deal IKM group buy to keep potential customers even more up in the air as to when would be the best time to buy T-Racks gear.

Well, the pricing story will get possibly even more complicated given that T-RackS 5, the next major upgrade of T-RackS is rumored to be in the works and available as early as later this year.  What this means in terms of opportunities to pick up T-RackS modules at advantageous prices is anyone’s guess.

Nevertheless, two recent additions to the T-RackS line are superb and merit your attention, especially if you are already a fan of IKM’s VST effects.  We are going to look at two of these here, the Stealth Limiter and the Saturator X.  These have a list price of $130 USD and $80 USD respectively, but given the IKM way of selling things, don’t take those figures as gospel.  Deals – sometimes quite exceptional ones – do come along from time to time.

These modules are available as VST, RTAS, AAX (32 and 64-bit) for PC and Mac plus AU for Mac.  Presumably they work inside the T-RackS host standalone application, but I tested them only as hosted in Cubase 8.


Stealth Limiter

OK, I already said this was a superb piece of gear.  But it’s reasonable in a review like this to discuss just how badly most of us actually need another limiter.

For starters, how many limiters do you already have on hand?  There’s a good probability that there’s a completely serviceable one in your DAW (at least such is the case in both Cubase and SONAR, the two DAWs with which I have experience).  And maybe you’ve already acquired an extra-special third-party model.  For me that would be Fab Filter’s Pro-L because … well, they’re Fab Filter.  If you are a typical GAS victim, no doubt you’ve acquired a few extra limiters along this way due to discounted bundle purchases or group buys.

Next, think about the way in which you use a limiter.  Some producers/engineers use limiters on tracks in the capacity of very aggressive compressors.  Now, when it comes to compressors, I would argue that one needs a single really transparent unit, and just one is quite sufficient.  But additional “character” compressors, such as those modelled on vintage gear are also great to have at ones disposal.  A nice collection of compressors is generally a really good thing.  If you use limiters like compressors, then you may very well benefit from having some not-so-transparent limiters on hand as well to dirty up the sound just a tad.

But some of us only use limiters in one capacity: on the master bus.  In this case, first of all we desire absolutely no clipping.  We also often are using this master-bus limiter to increase or maximize loudness, making the clipping avoidance even more critical.  In almost all cases, when doing this kind of limiting, we want to avoid the process calling attention to itself.  In the end, if you already have a transparent, musical limiter, I would propose that you don’t really need another one.

Let us take this notion one step further.  If you are mixing something that is later to be mastered, it could be argued that you should not be using a limiter at all.  Application of limiting is in the domain of the mastering engineer.  Of course, you might keep a limiter on the master bus just as a safety valve to preserve your ears and/or speakers against unintended blasts.  But if you’re doing things right, that limiter should never actually kick in.  The mastering engineer needs sufficient headroom in the final mix if they are to work their magic.  And if it’s there for safety-sake alone, the quality and transparency of that plug-in really doesn’t matter.

So, do you really need another limiter?  Maybe not – but of course that doesn’t mean you won’t want one, and Stealth would satisfy your GAS just fine, or at least until the next fancy piece of gear appeared on the horizon.


Stealth Features


IKM markets Stealth as follows: It’s a versatile sonic ninja of a mixing and mastering tool that features an advanced inter-sample peak limiting algorithm that lets you turn up the loudness of your mixes while still maintaining a clean sound that’s full of dynamic range and sonic breathing room. T-RackS Stealth Limiter is your new go-to mastering peak limiter when you want impressive loudness without the damaging side effects of traditional processors.

The claim is that there is an algorithm that works under the hood to reduce levels below the volume ceiling moment-by-moment instead of applying traditional look-ahead envelope-based fast attack compression.  I’m not trying to be sarcastic by quoting at length from IKM promotional verbiage.  But I’m trying to emphasize that IKM claims there’s a secret sauce, about which they reveal little, that is the undisclosed basis of Stealth’s superior audio treatment.  Is it superior?  Maybe not superior, but certainly sensational – more on this shortly.  Let’s first explore the Stealth features.

The UI is quite straightforward.  There are two main knobs for maximum level output and input gain.  No controls are offered for attack/release and there is no option to set a look-ahead interval.  An option exists to automatically keep the processed and unprocessed sounds at the same volume.  Another option allows a very low cut filter to be enabled.  Oversampling rates can be selected from none, four-times and sixteen-times.  Dithering can be applied at the 16-bit or 24-bit boundary, but no actual truncation occurs, so this is probably better left to your DAW when exporting, which is the time at which the truncation does happen.  By avoiding the limiter dithering, you’re not going to forget and dither twice (not that anyone would be likely to notice).

The Mode selector is unique.  The Tight mode is billed as the most natural and the Balanced mode is for when a modest amount of dynamic compression is acceptable.  Harmonics 1 and 2 respectively add some tube and solid state color.  In my testing, I quite honestly could not hear differences between any of the modes, but perhaps younger ears than mine would be able to discern differences.

In comparison to other limiters, Stealth sounded as good as my gold-standard, Fab Filter Pro-L.  In fact, both sounded utterly transparent and the differences seemed quite subtle – so much so that I would not expect to do well if I had to differentiate in a blind test.  In this comparison, I left Pro-L at its default settings for attack, release and look-ahead.  These cannot be set in Stealth so there was no way to dial in equivalent behavior.

The other limiter I compared Stealth against was IKM’s earlier T-RackS limiter, the Brickwall Limiter.  While Brickwall Limiter was by no means any kind of slouch, Stealth did sound marginally better.  Again, attack and release in Brickwall Limiter were left at their default values.

I suppose it should be no surprise that limiters, assuming they are doing their job and actually steadily limiting and not in transition, should not sound all that different.  They should sound very alike once limiting has commenced, and, one could assume, should only produce substantial variances during release stages. To test how much difference there was, even if I was having trouble hearing it, I set up some standard null tests, the results of which can be seen to the right.

At the top, we have the input audio. For this I used the superbly mixed and oh-so-tastefully mastered “The Dream of the Blue Turtles” track from the Sting album of the same name.  As you can see, no attempt was made to make this audio a combatant in the loudness wars.  My testing used a 15dB increase in level to a maximum level of -0.5 dB.  Such way-over-the-top processing would be unpardonable were this not in the service of a quest for knowledge.  The limited output is shown the second subpanel.  The average RMS of this clip is approximately -5 dB and the peaks are at the requested -0.5 dB.

Below this we see four null tests.  In a null test, we run the input through two parallel plug-ins, flip the polarity of the output of one of them and mix the signals equally.  What remains is just that which is different in the processing between the two tracks.

The first null output shows the difference between the Tight and Balanced modes.  There clearly is a difference, but it is significantly lower than the output signal and, as such, it would be barely audible compared to the full limiter output.  In fact, the difference signal RMS average is -32 dB, or 27 dB less than the full limiter output.  A signal over 24 dB less than that of another would be audible in most situations, but if the two signals are similar, the lower level audio will be only barely audible.

Following this, we show the differences between the Stealth (Tight mode) and IKM Brickwall Limiter.  As expected, the differences here are a bit more pronounced (an average RMS of -14 dB in this case).  I actually could hear an audible, albeit not all that obvious, difference in my comparisons of these two limiters.  Again, the attack and release settings in this and the next test were left at the plug-in’s default values.

The real surprise for me was the third null test, comparing Stealth with Fab Filter Pro-L.  In listening comparisons, I found both of these to be absolutely transparent sounding, and thus could scarcely tell them apart when switching between them.  But the audio picture tells another story entirely – there is considerable difference that should have been more audible.

I was truly puzzled by the scientific measurement being so out of line with my subjective listening tests.  So, I reduced the input by 15 dB, thus insuring no compression/limiting was actually taking place.  While not loud, there were still audible differences between Stealth and Pro-L.  This was totally unexpected and I cannot suggest a possible explanation.  But in the end, the sound is what’s all-important, and both limiters delivered like thoroughbred champions.  So, I’ll let this one remain a mystery.

The final test is between the Stealth Tight and Harmonics 2 modes.  Here I can at least confidently state that the difference in these two modes truly will be absolutely inaudible even to the best of ears.  Perhaps different audio would have produced different results, but Harmonics 2 did not do much at all in this case.


Is Stealth for You?

If Loudeter, the Greek goddess of compression, paid me a visit and said “I am taking all thy limiters, save Stealth – hereafter thou may only use Stealth” (everybody knows that Greek deities talk like they were in the King James Bible, right?) – if this were to happen, I actually wouldn’t get all that bent out of shape.  I quite love Stealth and it could absolutely be my go-to limiter.

If you already own a top-of-the-line, transparent and musical limiter, you might want to consider passing since what you already have may be all that you ever will need.  But if you don’t own something top-of-the-line and you’re looking to remedy that situation, Stealth should absolutely go on your short list.  It is amazingly transparent – exactly what anyone should hope for in a limiter.

More information here:

IKM has a great policy on demo audition downloads – you get a full fourteen days, which should be more than adequate time to make an informed decision.

… and, OK, I confess that made up that bit about there being a Greek goddess of compression.  [We apologize to our readers – Ed]


Saturator X


Prior to Saturator X, IKM had nothing in the way of harmonic distortion inducing software, unless you consider the guitar-centric Amplitube to qualify in that category.  So, a plug-in like Saturator X was long overdue.  Long story short: it was worth the wait.  This is an excellent piece of gear, and although I’ve already got a number of first-rate saturation/distortion plug-ins, Saturation X brings enough new to the party that it’s a most welcome addition.

The operation could hardly be simpler.  For the main controls, we have a saturation type selector (more momentarily), Gain (which influences both amplification and the amount of saturation) and Output.  Gain and Output can be inversely linked by clicking on an icon picturing two chain links.  In practice, this is quite convenient up until the final fine-tuning stage when you’ll probably want to turn it off.

The big “eye” is a stereo level meter – it shows input levels only and really is not all that useful from a practical standpoint – but does look pretty cool.  To the right, we have an optional limiter and a two-times oversampling option (because heavens forbid that we get distortion in the process of introducing distortion into mix).

The main story here is the variety of distortion types on offer.  In all cases, a little bit of gain can result in nice, but subtle, warmth – great for both mixing and mastering.  Higher gain settings in all modes can result in very audible distortion.  Since there is no wet/dry mix control, Gain and Mode control the nature of the sound.  How much gain is needed to make things obvious depends upon the selected mode.

Tape 1 is for mimicking the character and high-frequency compression of analog tape.  Tape 2 is a more lo-fi version of the same.

Master +6dB and Master +12dB both introduce a soft saturation curve, with the +12dB simply being more prominent.

Tube – Push Pull and Tube – Class A emulate tube saturation.  For Push Pull, odd harmonics are said to predominate while Class A favors both even and odd harmonics.  Solid State – Push Pull and Solid State – Class A are more of the same, but this time with solid state being emulated.  No rules here for best fit.  Set by ear and don’t overthink it.

Lastly we have two transformer settings: Transformer – Iron and Transformer – Steel.  I don’t recall ever seeing this as an option in a saturation plug-in.  It’s quite lovely in small amounts and in larger amounts sounds unlike anything to which I can readily compare it.  Iron is said to favor even harmonics and Steel both even and odd.  These saturation types can withstand a bit higher gain than the others before the grunge builds up to unpleasant levels.


Is Saturator X for You?

With all these options, there’s a danger of spending rather too much time tweaking the gain and type settings to perfection.  But if you are just looking to add a pleasant but subtle warmth to your track or mix, you’re just going to turn down the gain to the point where the distortion is not noticeable to all but the most intent listener.  Like I said, don’t overthink it.  Just have fun.  This plug-in certainly offers the opportunity for that to happen.

If the Greek god of saturation, Hydroaestus, paid me a visit [OK that’s enough.  Just stop it! – Ed]

… um, what I was going to say was that, unlike a single first-rate limiter being all many of us need, one can easily benefit from having several different saturation effects.  I would not trade my beloved Fab Filter Saturn for anything.  When I want some vintage-fairy-dust-type saturation, there are a number of Nomad Factory and other IKM T-TrackS plug-ins that are go-to options.  But I’m more than happy to welcome Saturator X into my toolkit.  It brings a few new possibilities that weren’t there before.  This one is definitely a keeper in my opinion.  It’s fairly priced at the retail price.  If a crazy-no-brainer group-buy opportunity comes along (and probability is high that one eventually will), you’ll want to especially consider picking up this gem.

Find out more here:


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