CAB block

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The information on this page supplements the official manuals.

H cabs.png


Cabinet modeling: supported by which Fractal Audio products?

X/Y switching in the Cabinet block

The CAB block supports X/Y switching.

About Impulse Responses (IRs)

The Impulse Responses (IRs) page provides information about IRs, including resolution (Ultra-Res and others), difference between near-field and far-field, and more.

IR Capture lets you create IRs yourself with suitable hardware.

Disable and enable cabinet modeling

If you never use of cabinet modeling, turn it off in the Global menu. You'll have more CPU room.

You can also leave out the Cab block per preset. Or bypass it, but this will not decrease CPU usage.

Factory cabs (stock cabs)

Number of stock cabs per device:

All stock cabs are time-aligned, which means that you can mix them using a single Stereo cab or dual Cabs blocks.

Detailed list of all stock cabs

Fractal Audio:
"The factory IRs were hand-selected by me after auditioning thousands of OH and RW and other IRs. Some of the IRs are custom mixes of mine. My rule-of-thumb was to select as neutral sounding IRs as possible. However, what I like may be much different than what others like. Some people complain the Axe-Fx sounds too bright. Others say it's not bright enough. It's a no-win situation. This is why I've been harping on capturing IRs. It's personal preference. Producers probably spend more time perfecting mic placement than anything else when getting guitar tones to tape. An IR is the same thing, it's capturing the mic and placement." source

To get a list of the stock cabs used in presets, use FracTool.

Other free IRs

Some commercial manufacturers provide free IRs. There are also quite a few popular IRs available in the public domain. Some examples:

Matching amp and cab models

It’s a matter of personal preference which Cab you want to use with an Amp model. You can go for traditional combinations. Or be creative and innovative. The differences can be huge. Cab selection often has more impact on the tone than choosing a different amp model!

When comparing cabs, don't judge too quickly. Each time you select a cab, you may need to adjust the amp settings to dial in a tone.

Common combinations of amps and cabs are listed in the wiki and in Yeks Guide to the Fractal Audio Amp models.

Mono or stereo output from the Cab block

Keep an eye on the mono/stereo configuration. The Cab block will sum the incoming signal to mono, unless it's set to Stereo mode or when using two (panned) Cab blocks to handle the left and right sides.

When a Cab block in Stereo mode is followed by a mono effect, such as Drive, the resulting signal will be summed to mono.

Position of the Cab block on the grid

In the "real" analog world it makes a difference where you put effects: before or after the speaker cabinet. It's different with the Axe-Fx II and AX8.

Javajunkie: "You can place the effects loop anywhere in the chain (just add the fx loop block). Unless you are running a stereo cab or 2 mono cabs panned hard L/R, you may want to place stereo effects after the cab. The cab is a linear time invariant effect (unless you add drive) so effects like delay and reverb will sound the same before or after it. As Cliff and others have stated on numerous occasions LTI effects can be placed before and after each other and they will sound the same. Only when placed before or after non-LTI effects (drive, amps, et. al) it really matters. The one caveat there is that some effects are mono, placing effects before and after that makes a difference."

Fractal Audio:

Cabinet blocks in parallel rows sound louder than a single Cabinet block. Explanation. Bakerman: "It depends on how you're panning. Assuming a mono signal sent to cabs: Stereo cab w/ Pan L and Pan R fully left & right will be the same output level as 2 mono cabs w/ balance L & R. If pans/balances are centered the 2 mono cabs will be 6 dB louder. Balance elsewhere would be between 0 and 6 dB louder, and balance doesn't correspond 1:1 to pan L/R for the same placement. Balances will need to be further toward -50 or 50." source

User cab slots for external IRs

If you are looking for something different, try external IRs. The Axe-Fx II and AX8 provide user cab slots which can be filled with IRs, using Fractal-Bot, Cab-Lab, Axe-Edit or a MIDI librarian.

Number of user cab slots:

The Axe-Fx II, AX8 and software editors display the names of the IRs in the user cab slots. The name is contained in the sysex data of the IR file. IRs can be renamed using the editor or Cab-Lab. The name is shown in italics when it's Ultra-Res.

To empty an user cab slot on the hardware, use the software editor or Cab-Lab. The Utility > Preset or Utility > Erase menu provides an easy way to delete ALL user cabs.


Scratch-Pads (the very last user cab slots) are "dummy" locations which can be used to load IRs but which are not saved to non-volatile memory. This allows auditioning IRs without overwriting any of the user slots.

Substituting an IR with a Tone Match block

When you use an external IR in a preset and want to share the preset, you need to share the preset as well as the IR. There are two ways around this:

It's NOT permitted to share commercial IRs (license violation).

Preset-Cab bundles

Read this: Preset-Cab bundles.

Recording 4 different CAB signals

This YouTube tutorial by G66 shows how to create 4 separate cabinet signals in the Axe-Fx II, which you can mix at will. It comes down to using two stereo CAB blocks, with one of the blocks connected to a FXL block to feed Output 2. In both CAB blocks the IRs are panned hard left and right. The stereo outputs 1 and 2 are connected to 4 separate channels on the mixers.

Cab-related parameters in the AMP block

The Amp block has a couple of parameters which are closely related to the Cab block. Check the SPKR tab in the Amp block.

See which cabs are being used in presets

FracTool polls the Axe-Fx II or AX8 and shows a list of the cabs that are used in presets. It also shows which user cabs are not being used in presets, so you can decide to delete these (or not).

Microphone modeling

Read this: Microphone modeling.

Cab block parameters

Input Select

This parameter lets you select the source signal that enters the Cab block. For example, if you wish to run two panned Cab blocks in an Axe-Fx II preset, you can use this parameter to force one side of the signal to go into one Cab, and the other side into the other cab, for stereo separation.

Room ambience

The Axe-Fx II provides room ambience parameters in the Cab block. This is a dedicated reverb effect, which works well when using headphones or IEM. Not supported on the AX8. It turns a mono signal into stereo.

Low Cut and High Cut Frequency

Most IRs have been captured "close-miked", and produce a lot of high and low end material. High Cut and Low Cut Frequency in the Cab block (low-pass and high-pass) allow you to EQ this, preventing boomy bass and harsh sounds. Equivalent to using EQ controls on a mixing board, to position the guitar sound in a mix. These are very important parameters. Default value of High Cut is 10 kHz (Quantum 7 and later).

Common settings are 80-150 Hz for high-pass (cut bass), and 5-10 kHz for low-pass (cut treble) but YMMV.

The “Filter Slope” parameter selects between first-order (6 dB/octave) or second-order (12 dB/octave) filters for Low Cut and High Cut.

Fractal Audio:
"Using Low Cut in the Cab block is akin to what you would do in the studio to carve out room for the bass player." source

Fractal Audio:


This parameter controls a sophisticated process that removes the “phasiness” from IRs and can yield a more “in the room” experience. This is especially helpful when using multiple IRs. Cab-Lab can apply De-Phase when mixing IRs together.

The processing required is extreme and the control can have some lag. No extra CPU usage or audio latency, however, is incurred.

Not supported on the AX8.

Fractal Audio:

Motor Drive

This parameter was present in the amp block as well, before Quantum 9. Quantum 9 replaced it with Speaker Compression. Motor Drive is still present in the Cab block (Axe-Fx II only). It models the effect of high power levels on the speaker.

Motor Drive was Revised in Quantum 7.0:

When using two Ultra-Res cabs in a preset, don't use Motor Drive with just one, because this will cause a hollow sound.

Fractal Audio:


The Air parameter mixes some of the "direct" signal entering the Cab block with the processed signal leaving the Cab block. This adds some "air" to the sound.

The Air Frequency parameter lets you adjust the cutoff frequency of the mixed signal. Increase the Frequency to its maximum value for a straight mix.

Not supported on the AX8.

If you want to listen to just the Air'd part of the signal, set the Cab to an empty user cab, and turn up Air.


This is a "micro delay" for stereo applications. When running a Cab in Stereo mode, or when using two panned Cab blocks in parallel, delaying one side relative to the other can achieve interesting comb filter effects. A common practice in studio recording is to use multiple mics on a speaker at different distances to intentionally introduce comb filtering.

Fractal Audio:
"My secret to realistic cab sounds is Delay. Use two IRs in stereo or two cab blocks and put a small amount of delay on one (using the Delay parameter in the Cab block). I like around 0.06 ms. You may like more or less. Producers experiment with placing mics at different distances to enhance the recorded guitar tones. This is the same as using a small amount of delay. Adding a bit of delay introduces some comb filtering which creates notches and peaks in the response which, in turn, adds a sense of "space" to the tone. Try it." And: "If you have any cab packs try mixing the "Back" IR with one of the regular IRs. I use more delay when doing this, 0.1 ms or more. I lower the level on the back IR by a couple dB. This gives a nice "in the room" open-backed cab sound." source

GM Arts:
"This is about mixing 2 signals: one without delay, and the other with a very short delay. 0.06ms is way too short to be perceived as a repeat; the effect is filtering caused by mixing these two signals. To keep things simple, we’ll apply an equal mix of the same signal and another delayed by 0.06ms. An easy way to experiment with this in the Axe-FX is with a Flanger block, with depth and feedback set to zero, and mix set to 50%. Adjust the delay to 0.06ms (not 0.6ms) to hear the effect with a mono signal. This produces a notched frequency response with complete signal cancellation just above 8KHz, with the -3dB point one octave lower at just over 4KHz. The signal is restored over the next higher octave (8KHz to 16KHz), but bear in mind that most IRs will not have much response there anyway, so this effect is mostly a blocking filter over the range 4KHz to 8KHz. So if you have a cab IR that has some response over this range, it will be perceived as a loss of some treble response. For many, this will remove harshness in a way that’s difficult to achieve with other filters. Others may find this effect too much. You can soften this effect by decreasing the delay and/or changing the mix ratio. Decreasing the delay raises the frequency at which this cut occurs. For example, a 0.05ms delay blocks response over the octave 5kHz to 10kHz. Lowering the mix % decreases the depth of the notch. Similarly, applying a delay to a different IR than the un-delayed block will “jumble” and reduce the final response to some extent. If you increase the delay (typically from 1ms and above), you’ll hear the combing effects as multiple notches become low enough to hear in the range of “guitar frequencies”. This sounds like a flanger or chorus without modulation, which shouldn’t be a surprise given we’re experimenting with a Flanger block. So why does this delay sound produce a tone more amp-like? Most players prefer their amp tone off-axis, meaning that they’re avoiding the direct harsh sound directly in front of the speaker, where high-frequencies are beamed. This filter simulates that effect. It’s also similar to standing slightly off-axis when using multiple speakers. Sound travels at roughly one foot per millisecond, so there is a very short delay between sound from different transducers. As Cliff stated, it also emulates recording techniques with mics placed at different distances from the cab. How to calculate? To find the frequency where this rolls-off high frequencies at -3dB, it’s simply: Hz = 1000 / 4 /delay in ms. So for 0.06 ms: 1000 / 4 / 0.06 = 4167Hz. Complete cancellation occurs at double this frequency, 8333Hz, and builds back to -3dB a double this frequency again, 16666Hz. Bear in mind that with higher delays, there will be audible effects from additional notches above this calculated frequency." source

Preamp simulation

Read this: Cab preamp simulation.

Fractal Audio:

Speaker Size

Size Warping allows the user to change the relative size of the virtual speaker. This parameter appears only when the selected IR is non-Ultra-Res and the Cab block mode is set to Mono.

This parameter is not supported on the AX8.

Tutorials and more information

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