From Axe-Fx II Wiki
The information on this page supplements the official manuals.
Cabinet modeling: supported by which Fractal Audio products?
- Axe-Fx II: yes.
- AX8: yes.
- FX8: no.
About Impulse Responses (IRs)
- The Impulse Responses (IRs) page provides information about IRs and IR Capture.
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 here: Amp: all models and here.
Factory cabs (stock cabs)
- 3rd party IRs are included in the Axe-Fx II/AX8 firmware as stock cabs.
- All stock cabs are time-aligned, which means that you can mix them using a single Stereo cab or dual Cabs blocks.
- Number of stock cabs:
- Axe-Fx Mk I/II: 132.
- Axe-Fx II XL and XL+: 184.
- AX8: over 175.
- Detailed list of all stock cabs.
- Cliff: "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 see which stock cabs are being used in which presets, use FracTool.
X/Y switching in the Cabinet block
- The CAB block supports X/Y switching.
IR resolution modes
Mono or stereo output
- Keep an eye on the mono/stereo configuration. When placing the Cab block at the end of the grid, the output signal will be summed to mono, unless the Cab is set to Stereo mode or when using two panned Cab blocks.
- If the Cab block is set to Stereo mode, but it is followed by a mono effect such as Drive, the resulting signal will be summed to mono.
Position of the Cab block
- In the "real" analog world it makes a difference whether 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."
- 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
- Cliff's comments:
- "The difference in having the cabinet before or after the effects is usually subtle. It depends on how non-linear or time-variant the effect is. For effects like EQ, which are linear and time-invariant, it doesn't matter at all. For slightly time-variant effects like chorus and flanger the difference isn't very pronounced. For highly time-variant effects, like pitch shifting, the difference can be marked."
- "Linear means that the output is related to the input by a straight line: y = mx + b. Filters are example of linear systems. A cabinet IR is a filter. Distortion is an example of a nonlinear system. Linear systems are associative and commutative. Associative means that a * (b * c) = (a * b) * c. Commutative means that a + b = b + a or a * b = b * a. Therefore you can do cab -> eq (a * b) or eq -> cab (b * a). The cab block is "completely" linear if motor drive is non-zero but it is "wide sense stationary" so you can treat it as linear." source
- "The cab block is level-dependent if the Motor Drive is non-zero. So if you turn up/down the level out of the amp block you may need to compensate by doing the opposite with the Motor Drive." source
- "You gain nothing putting it before the cab and risk collapsing the stereo image if the cab is mono." source
- "Since a cabinet is linear (or mostly linear) the order is unimportant as linear systems are commutative (a+b = b+a). However if the cab block is mono your effects will collapse to mono if placed before." source
User cab slots for external IRs
- If you are looking for something different, try external IRs. The Axe-Fx II and AX8 have "user cab" slots for this purpose, in which you can load external IRs, using Fractal-Bot, Cab-Lab, Axe-Edit or a MIDI librarian.
- Number of user cab slots:
- Axe-Fx II Mark I and II: 100.
- Axe-Fx II XL and XL+: 1024.
- AX8: 512.
- The Axe-Fx II, AX8 and software editors will display the name 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 will be in italics if it's an Ultra-Res IR.
- 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 (Axe-Fx II only)
- 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:
- Note that it's not permitted to share commercial IRs (license violation).
- Axe-Edit and AX8-Edit let you save and import so-called Preset-Cab bundles. A bundle combines a preset and IR in a single file. Note: bundles should not include copyrighted IRs.
- The Amp block has a couple of parameters which are closely related to the Cab block. Check the SPKR tab.
How to discover which cabs are being used in presets
- FracTool is an utility by forum member AlGrenadine. It polls the Axe-Fx and shows which cabs are being used in each presets. It also shows which user cabs are not being used in presets, so you can decide to delete those (or not).
Microphones, microphone modeling, proximity
- Don't underestimate the impact of a mic type on the tone. For example, adding the R121 model (Royer 121, captured at 6", front) will add highs and lows to the tone. The 57 DYN (Shure SM57) works with almost everything and adds bite. Many studios and players like to combine the Royer 121 and Shure SM57.
- Mic modeling is not supported on the AX8, except for Proximity.
- Mic types:
- 57 DYN: based on the Shure SM57.
- 58 DYN: based on the Shure SM58.
- 421 DYN: based on the Sennheiser MD 421 II.
- 87A COND: based on the Shure Beta 87A.
- U87 COND: based on the Neumann U87.
- E609 DYN: based on the Sennheiser e609 Silver.
- RE16 DYN: based on the Electro-Voice RE16.
- R121 COND: based on the Royer Labs R-121.
- D112 DYN: based on the AKG D112.
- 67 COND: based on the Neumann U67.
- NULL: this doesn't apply microphone coloring. But it enables the use of the PROXIMITY parameter.
- INVERT: this inverts the signal allowing for interesting effects in conjunction with the delay parameter.
- NONE: disables ALL mic processing in the CAB block, including PROXIMITY.
- The "NONE" and "NULL" types both disable mic coloring. A mic is still involved though, because the IRs themselves are always captured with microphones. Even when a neutral mic was used to capture the IR, such as an Earthworks mic. When capturing IRs, the mic is most often placed very close to the speaker, so the result is a close-mic'd tone. Still, selecting "NONE" is the best way to prevent adding additional EQ-ing to the tone.
- PROXIMITY: simulates the proximity of the modeled mic to the speaker. Higher numbers translate to the mic being closer to the speaker (nearfield). Lower numbers translate to the mic being further away from the source, with the lowest number providing far-field coloration. Proximity only works when a mic model is selected, including the NULL type. The Proximity Frequency parameter allows tuning the frequency range over which the proximity effect occurs.
- Cliff's comments:
- "The mic models are actually IRs. The mic IR is convolved with the speaker IR to create a composite final IR." source
- "The mic I've been most impressed with for recording guitar lately is the Beyer M160. I don't like SM57's alone for amps. They're too spikey and compressed but mixed with an M160 or R121 they add some nice sizzle." source
- "The M160 is an awesome guitar cab mic. All the IRs we got with the M160 came out really nice." source
- "Using a "neutral" IR with a simulated mic does not sound the same as an IR using that mic. It simply can't. Neutral mics like the Earthworks TC series are nearly omnidirectional. They operate by using a very small aperture as compared to traditional mics that have effective apertures orders of magnitude bigger." source
- "My typical workflow is to choose an R121 or M160 first as these have the best low end. Then I choose an IR from one of the other mic types to get the desired brilliance. This is usually an SM57 or 4047. I just don't like 906s or 414s but that's me. I leave the panning at default but that's just my preference." source
- "If I were to design a Cab block today I wouldn't even include a Mic parameter. I NEVER use Mic simulation anymore. I simply find an IR I like and EQ as desired." source
- "The mic options are mostly legacy. I never use them but if we took them out there would surely be much protestation." source
- "If you get a chance try a Shure KSM313, an AEA R84 and a Beyer M160. The KSM313 is now my preferred mic for guitar cabs. I like it better than the R121. I find the KSM313 a little more balanced. The R121 has a lot of bass and proximity effect and the high end can be a little dull." source
- There's useful about mics and mic positioning in the document Dialing in Your Tone by Red Wirez.
- Javajunkie: "Certain mics like the royer 121 have 2 sides (front, back). Each has a different sound.Back side of the R121 is a bit darker. The difference between the front in the back is only apparent at closer mic distances. Get out past 3 feet and the sound the same on either side."
- Additional information about microphones:
- U 67
- MD 421
- U 87
- D 112
- Beyer M160, Beyer M160
- Wicked Wiki thread.
Input Select parameter
- 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 parameter
- The Axe-Fx II provides room ambience parameters in the Cab block. This is a dedicated reverb effect, which also works well when using the unit with headphones or IEM. Not supported on the AX8.
- Enabling the cab's room reverb will turn a mono signal into stereo. So the left and right sides of the signal can be different because of this.
- See Audio topics.
Low Cut and High Cut parameters
- The Cab block provides low-pass and high-pass controls. These make it easy to tame boomy or harsh sounds. You can also use similar parameters in the Amp block, or apply eq-ing through a PEQ, GEQ or Filter block. Common settings are 80-150 Hz for high-pass (cutting bass), and 5-10 kHz for low-pass (cutting treble), YMMV.
- The “Filter Slope” parameter (Quantum 2.0 and later) can be used to select between first-order (6 dB/octave) or second-order (12 dB/octave) filters for the Low Cut and High Cut filters. Prior to Quantum 2.0 these were fixed at 6 dB/oct." source
- In firmware Quantum 7.00 and later High Cut defaults to 10 kHz:
- "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
- Cliff's comments:
- ""LOWCUT FREQ" in the cab block sets sets the -3dB point of a highpass filter at the output of the cab block." source
- "If at the min/max the filters are off." source
- "People often talk about applying low cuts and high cuts. This is because the cabinet models used in modelers are almost always (with a couple exceptions) based on near-field samples of guitar cabinets. IOW, the mic is pushed up against the grill cloth. This just happens to be the way that record producers/engineers mic a cabinet in the studio and the way guitar cabs are mic'd on stage. This is done primarily for isolation reasons. The downside of this approach is that the resulting tone will have a lot more lows and highs than when listening to the amp+cab "in the room". What the mic "hears" when pushed up against the grill cloth is not the same thing that we hear standing 10 feet away. The most common technique to deal with this is to simply cut out the lows and highs using blocking filters, e.g. highpass and lowpass filters. Producers routinely do this when mixing as excessive amounts of lows and highs will cause the guitar tracks to get "lost in the mix". Live sound engineers often do the same thing. The Cabinet block has blocking filters built in for just this very reason. You can also use a couple dedicated filter blocks or a parametric EQ block. For now let's use the Cabinet block. My personal settings are Low Cut around 80 Hz and High Cut around 7500 Hz and Filter Slope set to 12 dB/octave but these are just a starting point. Far-field IRs are available but they are rare due to the difficulty in obtaining them. They require a large facility and special techniques making the process impractical in most cases. So, until an abundant source of far-field IRs are available we need to think like a producer/engineer who is dealing with the mic pushed up against the grill cloth. This means shaping the tone with EQ to remove unwanted frequencies." source
- This parameter controls a sophisticated process that removes the “phasiness” from IRs and can yield a more “in the room” experience. Note that 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.
- Cliff's comments:
- "Close-mic'd speakers can sound "phasey" because you are in the near field. When sampling the near field of any source the frequency response and beam pattern is rough. This occurs due to multiple spherical waves arriving at various phase angles. These multiple waves come from the various modes of the speaker, internal cabinet reflections and from other speakers in the cabinet. In the far field the response is more uniform because the wavefronts get flatter and the phase angles converge. The De-Phase parameter removes some of the phasiness due to multiple wave arrival using a complex FFT technique." source
- "The higher the setting the more "character" you remove. De-Phase removes some of the character but that's precisely what you want to do as a cab has less character in the far field." source
- (Why is De-Phase necessary?) "You don't listen to a guitar speaker with your ear against the grill cloth." source
- "It's so simple that even experts in the field don't realize why it works." source
- De-Phase is implemented in Cab-Lab as "smoothing" (though not quite as pronounced).
Motor Drive parameter
- The Air parameter mixes some of the signal going into the Cab block with the signal leaving the Cab block.
- Not supported on the AX8.
- 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.
- 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 stereo mode, or two cab blocks in parallel, delaying one cabinet 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.
- Cliff: "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 parameter
- Preamp simulation recreates the sound of overdriven channel strips, preamps, tapes, etc. The Drive parameter controls the gain of the simulation. The Sat parameter controls the ratio of even/odd harmonics. The Preamp Mode parameter allows selecting between Economy and High Quality modes. In High Quality mode oversampling is employed to prevent aliasing but this requires more CPUusage.
- Not supported on the AX8.
- Cliff's comments:
- "The VU meter shows the level into the pre. Select a pre Type and turn up the Drive. As the VU approaches the 0 dB marker you will begin to overdrive the pre." source
- "Probably not something you would use for clean sounds. A common technique for rock music is to push the pres, console, tape, etc. to varying degrees to get compression and "sparkle". The trick is getting just the right amount. Too much and it sounds raspy and nasty." source
- "0 on the VU meter indicates onset of clipping. It's not the same as your plug-ins in that regard. The problem with plug-ins is that you don't know where the onset of clipping is since the headroom isn't specified. Our way is superior since 0 dB indicates the point where things are clipping. The other way you have no idea where things start clipping. So 0 dB on the Axe-Fx is NOT equivalent to 0 dB on a typical plug-in." source
- "I've done a lot of testing with isolation cabs. The big thing that happens is that the mic distorts, especially when using an SM57. This adds some crispness to the high end and some compression. I've found that I can duplicate that effect very closely by using the FET I preamp type in the Cab block and turning the Drive up until the desired compression is achieved. I set Sat to zero." source
Speaker Size parameter
- Cabinet Size Warping allows the user to change the relative size of the speaker.
- This parameter is available only when the selected IR is non-Ultra-Res and the Cab block mode is mono.
- This parameter is not supported on the AX8.