Review: Fractal Audio Systems Cab-Lab 3

Shape your guitar tone with speaker impulse responses
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When I reviewed an early model of the Fractal Audio Systems Axe-Fx in 2008, I was so impressed with its amplifier emulation and effects processing capabilities that I predicted it would become the gold standard for products of its type, which it did. The Axe-Fx II XL is currently the centerpiece of my personal guitar rig.

Fractal Audio Systems Cab-Lab 3 plug-in lets you combine impulseresponses of speaker cabinets in order to alter the tone of your guitar recordings, for creative reasons or simply to fit them into a mix. Cab-Lab was originally developed exclusively for use with the Axe-Fx, and that’s still the case for the standalone version of Cab-Lab 3. But there is also a plug-in version of Cab-Lab 3, compatible with any DAW or other application that hosts 64- bit AU or 32- or 64-bit VST plugs. (An AAX version is in development.) While it, too, can be useful to Axe-Fx owners who are into recording, the plug-in brings Cab-Lab 3 to a wider world. The user interfaces for both versions are nearly identical, as is their functionality, though naturally, some functions are only active in one or the other. While this review focuses on the plug-in version, I’ll begin with a look at the standalone Cab-Lab 3 app, partially as a way to explain its raison d’être.

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One of the Axe-Fx’s core features is the use of Impulse Response (IR) technology to reproduce the sound of speaker cabinets. To use two or more cabinet IRs, however, it was necessary to have more than one Cab Block in my signal chain (signal chains comprise multiple Blocks linked together), and each Block consumed valuable DSP. So, if you wanted to simulate, say, the sound of several cabs (or the same cab miked in different ways) blended together, your signal chain and DSP usage could quickly become unwieldy.

The standalone version of Cab-Lab 3 removes this limitation by enabling you to mix the sounds of up to eight different speaker cab IRs into a single IR, which may then be loaded into a single Cab Block. Additionally, the app lets you monitor IR mixes in real time (using the Axe-Fx as an audio interface) and transfer newly created IRs directly to the hardware unit. The standalone app also includes tools for renaming, converting, and batch processing IRs, as well as providing remote control of the Axe-Fx’s IR Capture process (used for recording IRs). Testing these functions using my Axe-Fx II XL yielded excellent results.


Now, on to the plug-in, bearing in mind that its UI and mixing functions are almost identical to those of the standalone app. That UI is arranged in three sections. The Mixer includes eight faders with associated Mute and Solo buttons, and meters that indicate relative mix levels in dB. (Mixes are normalized to ensure consistent output levels.) In addition to clicking and dragging the faders, you can adjust levels in 0.1 or 1.0 increments using the Up and Down arrows on your keyboard or a scroll wheel. IRs may be further tweaked by accessing a fly-out panel containing highpass and lowpass filters, phase-inversion, a Delay control providing up to one millisecond of time alignment or offset, and a choice of two Processing modes. Adventurous souls may also change the mixer routing from parallel to serial (though caution is advised).

The Cab-Lab 3 GUI allows you to see the frequency of your selected impulse response, as well as load a reference IR. The Mixer Slot section lets you select and load up to eight files. Supported file types include .syx (used for standard-resolution IRs), .Ir (used for UltraRes IRs, which we’ll get to momentarily), and .wav (mono audio recordings of impulse responses)— in any combination.

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The Save+Export section, where newly created IRs may be named and saved, includes a Mix Output Plot that represents individual or mixed IR waveform in either frequency or time domains, and a Reference IR Processing option for removing power-amp coloration from IRs. IR choices and mixer settings may also be saved collectively as Sessions.

There are two types of cabinet IRs: Standard and UltraRes, the latter being a sort of proprietary super IR. While no IRs are included with Cab-Lab 3, numerous Cab Packs are available from Fractal and several third-party developers. These include multiple cabinet types, combined with a choice of microphone options, mic-positions, and so forth. Cab Packs range in price from $24 to $99.

I experimented with IRs from six Cab Packs, which reproduced the characteristics of Fender, Marshall, Vox, Orange, and other vintage cabinets, as well as cabs by boutique manufacturers such as Dumble and Two Rock. Microphone choices included models by Neumann, Shure, Sennheiser, Beyerdynamic, AKG, Royer, and RCA. The speaker choices and microphone-placement options were too abundant to list.


The most obvious use for the plug-in is to expand your speaker cabinet options when using amp-modeling software, though it is equally effective on guitar tracks recorded sans cab using a direct out from an amp, a load/DI box, or any hardware amp simulator (such as an Axe-Fx).

For my tests I recorded cab-less tracks into MOTU Digital Performer 8 using my Axe-Fx II XL and various software amp models within the IK Multimedia AmpliTube 3 and Native Instruments Guitar Rig 5 plug-ins. Then, I routed those sounds through Cab-Lab 3 as a channel insert. (Visit to hear audio examples.)

The ability to select and blend so many diverse cab IRs, as well as combine the results with myriad amp types was, frankly, a little overwhelming. But I did arrive at some fantastic tones, ranging from classic to bizarre. Sometimes something as simple as changing a microphone type or position was all it took to make a track sit much better in a mix.

My only reservation in recommending Cab- Lab 3 is that it’s so deep. There’s a high likelihood that users with Tonal Exploration Disorder may dive in and never resurface.

A super-powerful tool that plays well with others and provides myriad tone-crafting possibilities.

May induce severe option anxiety.

$49 plug-in or standalone version; $79 bundle

Barry Cleveland is a San Francisco -based journalist, guitarist, composer, recording artist, and audio engineer. Visit