Managing Modeling Expectations

To get one thing out of the way upfront, this is not a shootout and there will be no winner. Neither is this meant to be an exhaustive review of each unit on all of its own merits – you’ve already got a long read in front of you and there exist many of these in written and video form as it is! Rather, the following is a comprehensive comparison of the Fractal Audio Systems AX8 and Line 6 Helix from a real world, bass-playing user’s point of view. My suspicion is that you will prefer one of these incredibly capable processors to the other depending on what value set you hold for modeling – i.e. whether you’re most concerned with amp models, usable factory presets without tweaking, wide effects options, ease of use, or a number of other factors. I found neither to be superior in a measurable way, but also found each to be capable in ways the other was not.

Fractal Audio’s and Line 6’s product offerings have matured greatly in recent years, with their respective AX8 (currently $1,099 direct) and Helix ($1,599 MAP) amp and effects modeling systems reflecting that growth, even during each product’s own lifecycle; both have enjoyed numerous firmware updates that have brought tons of added functionality and gear models, and the updates don’t seem to be slowing. Each company offers multiple products in their lineup to appeal for players with different needs. The AX8 is the “little brother” to Fractal Audio’s flagship Axe-Fx III (with a list price of $2,499), but if you want effects-only, they offer the FX8 for $999.99, list. Line 6 offers the more streamlined Helix LT (which comes in at the same price as the AX8), and for effects-only, they offer the HX Effects and HX Stomp (both at $599.99 list).

Fender Rumble 600×200

For this review, however, we are focusing on the two floor-based flagship models that do both amp and effect modeling – the AX8 and Helix. Little has been said about both from a bassist’s perspective. Allow me to rectify (pun intended) that situation!

But …Why?

Well, whether or not you like it, modeling of some part of your signal chain will very likely be an increasing dimension in your musical world. Existing amp sims like the venerable SansAmp completely aside, we at Bass Gear Magazine have noted the quickly growing trend towards inclusion of speaker cabinet “impulse responses” (digital, sonic fingerprints of a physical speaker cabinet’s performance and vibe) in popular pieces of gear, from Darkglass pedal DIs to Bergantino bass heads to DAW plugins. There are more powered cabinet options on the market than ever before and amplifiers are rapidly shrinking and becoming deemphasized; while class-D and SMPS power sections continue to grow in wattage and ability to impress. You’ve doubtlessly heard of large acts going totally amp-less on stage by now, which has some incredible benefits for reproducing and controlling live sound. But it’s not just for the big guys anymore. Welcome to the dawning era of fully virtual amplification and effect modeling for the everyman.

Fractal Audio Systems

As I mentioned earlier, I believe users will gravitate to one of these over the other depending on their individual “use case.” Allow me, then, to clarify my own “use case” for the reader. I’m generally more a fan of clear bass tone than a highly colored one, but as I’ve entered the glorious (but often sterile) world of in-ear monitoring and amp-less gigs altogether, I’m now more inclined to want some degree of speaker cab or amplifier coloration in my live tone – just as I prefer a mixed DI/mic’d recorded sound. I also really love effects. Having enjoyed owning effects pedals almost since I started playing in the mid ‘90s, I’ve alternated back and forth over the last 10 years between MIDI-controlled, laptop-hosted plugins for live effect use and an ever-evolving and growing physical pedalboard.

All-in-one effects processors face a tough challenge in impressing those who have drunk from the near-infinite well of a painstakingly curated collection of VSTs housed within a great host (I prefer Ableton), and have made me feel a little trapped and painted into a corner with their more limited in-built parameters and options. More than anything else, what I look for in something like this is expandability or malleability; if it doesn’t have something I need, can I create it in the native environment? I was very interested to see how my experience might differ with these all-in-one processors this time.

Bass / Guitar

But here’s potentially the biggest bassist-specific piece of this puzzle, as I see it, and the question that begs asking: are bass players as in love with their amps as guitarists tend to be? One of the arenas in which bassists and guitarists generally behave very differently is that of the almighty amplifier; more pointedly, how important amps are to what we think of as our own sound.

Dangerously speaking in broad generalities, I submit that a majority of guitarists consider their amplifiers to be much more integral pieces of their signal chain than do most bass players. Heresy? I can point to a few examples, such as the bass gear marketplace’s present abundance of “clear” and “transparent” amps to match full-range and near-flat response speaker cabinets. And of course the fact that, more often than not, bass players’ signals to FOH are commonly run only through a DI, rather than being mic’d as often as guitarists’ amps are in live scenarios. This can lead to a certain agnosticism on the part of bass players toward the perceived importance of having unique tonal character added by the components of their amplification systems.

This difference in amplifier reliance and typical usage is at the heart of the difficulties that companies like Fractal Audio and Line 6 face in marketing what they essentially see as amp modelers to bass players, and subsequently why there are comparatively so few bass-friendly models and patches to choose from out of the box. But modern bass players, along with the gear they use, are evolving into different ways of thinking and playing and will eventually come to hold a new set of expectations from their predecessors. From acceptance of de rigueur live sound standards to a growing interest in quickly accessing vastly different tones, modern bassists are slowly driving some of these market forces to innovate and provide novel solutions for a new generation of thumpers and pluckers.

Fractal Audio Systems

What’s in the Box??

Fractal Audio’s AX8 weighs in at 11.8 lbs, in a 16.4″ x 10.3″ x 3.1″ sturdy steel enclosure. It is the more diminutive of the two, foregoing the Line 6’s built in expression pedal and extra column of footswitches (the AX8 employs 11 switches arranged in 5 columns). Line 6’s Helix in turn is a stout 14.6 lbs of equally sturdy aluminum construction, in a considerably larger 22” x 11.85” x 3.58” form factor, and presents 12 footswitches (not counting the expression pedal’s toe switch) in 6 columns. While each can be seen as a pedalboard replacement with comparable footprint, neither of them can accurately be described as lightweight or portable in the way we’ve come to think about smaller class-D amp heads or 3-button effects processors; neither of these is going in your gig bag.

Both products rely upon two dual-core 450 MHz ADSP-21469s processors. AX8 has a fixed audio sample rate of 48 kHz, with Helix’s being user-selectable up to 96 kHz. I measured the AX8’s monochromatic black-on-green display at just under 3.5” diagonally; Helix’s color display spec is 6.2”. Both systems feature universal voltage switching internal power supplies, rugged and non-clicking footswitches, stereo XLR outs and S/PDIF outs. The AX8 provides a single ¼” input while Helix adds an additional ¼” aux input (also suitable for low-impedance sources like active basses), an XLR mic input with available 48v phantom power, and a Variax input. Regarding the Helix’s XLR in, with a well-planned parallel effects chain that’s separated by input, this would seem to be a great solution for the solo artist or singer/songwriter that would like to wring as much value out of one processor as possible, via the added bonus of simultaneous, yet separate, vocal or mic’d instrument effects. Helix also uniquely sports a headphone output with dedicated volume control on the front panel, S/PDIF in as well as out, and an AES/EBU out. Both units offer MIDI in and out/through, as well as USB connection, although the AX8 does not allow for audio over the USB connection – you cannot use it to pipe sound into your DAW via USB surprisingly, but it can accept and send MIDI commands via USB. Conversely, the Helix can be operated as an 8-in/8-out audio interface via its USB connection. One stereo pair of effects loops are provided on the AX8 to the Helix’s four mono loops.

Fractal Audio’s AX8 unit, differentiated from their effects-only FX8 platform, boasts a very cool dedicated rotary encoder knob section for the amplifier model in your current preset, for easy and quick adjustments of common amp settings right at your feet. Provided are controls for Drive, Presence, EQ, Gain, Master, and more. Each encoder is ringed by green LEDs that dynamically display that control’s setting along the virtual amp knob’s rotation – a fantastic feature not found on Line 6’s flagship. Helix’s answers to ease of setting changes and navigation come in the form of a multi-direction joystick for block selection and capacitive, touch-sensitive footswitches, as well as one-touch Home and Amp block buttons that take you right where you need to go when you need to get there in a hurry. Helix supports up to four simultaneous amp blocks, and pressing the AMP button (or touching a switch assigned to an amp) instantly jumps to and cycles through the tonestack knobs of any Amp+Cab, Amp, or Preamp blocks in a preset. Both boxes use a single row of (non-lit) multi-function rotary encoders to adjust parameters, to navigate through menus, and more. The function of these encoders changes depending on what’s currently selected.

User Interface & Experience

A floor-borne effects system to me, at an essential level, must be highly intuitive and configurable on its own – this is what really separates a rack-mounted or studio-intended system from one meant to live under your feet and be used and modified, if need be, on its own accord. After considering how to describe the differences in user experience between these two companies’ hardware solutions, a simple metaphor occurred through use of the computing technology we all use and have used in the past.

Interacting with and using Line 6’s Helix is somewhat akin to using a current Android or iOS smartphone or tablet; it largely uses an icon-based, intuitive graphic interface, displaying the signal chain plainly, not to mention the touch-sensitive footswitches that are handy for quickly selecting their assigned block for easy editing.

If Helix is like a modern mobile device, Fractal Audio’s AX8, with its monochromatic and slower-to-render display and more utilitarian (perhaps even militaristic) build, would be closer to the very stable, but outdated, Windows XP operating environment. Hey, it’s no frills – that is understood and intentionally stated in the company’s own materials and messaging – and that may well make it more stable under harsh, pro-user conditions. One could understandably be suspicious that an overly adorned book’s cover may be hiding much blander prose within, so neither of these assertions mean much on their own.

If you have previously read about the Helix elsewhere, you may have seen comments to the effect of being able to program and use every facet of the Helix’s offerings directly from the unit’s front panel itself, without need of the software; I’m attesting that this is not just hyperbole. After you’re comfortable with the Helix ecosystem, you can create whole presets, snapshots, routing and more directly on the hardware – and there’s even a deeper editing mode which allows you to stay standing or sitting and edit selected parameters with values you input via the expression pedal. Very cool.

Shifting focus to the AX8, while it’s more graphically simplistic display might be the less alluring of the two, it does offer visual representations and listing of all the deep editing functions its virtual software allows – and here’s where a decidedly stronger value point for this unit comes into play. The AX8 Edit software is to HX Edit what the Helix’s display screen is to the AX8’s. Again, familiarity with the Fractal Audio way of thinking and accomplishing tasks is necessary, but after that is gained, AX8 Edit is a very intuitive, incredibly fully featured, and dare I say “attractive” piece of programming. This is clearly the best path to customization and tweaks for this product, and it’s immediately obvious that Fractal has invested heavily in the development of the accompanying software. While both Helix Edit and AX8 Edit can accomplish any task their physical counterparts can, AX8 Edit makes it a much easier and more enjoyable experience.

Fractal Audio Systems


I can hear you out there, “But what about those TONEZ, bro??” Here’s an answer seemingly steeped in diplomacy, but in truth as well: in stark contrast to most of what I’ve read or heard one way or the other in countless reviews and video demos I’ve delved into, I’ll go on record saying neither unit sounds superior to the other. Expanding on that, the quality of audio and of the models from both units is fantastic. You won’t find fault with bit rate, noise floor, poor sampling frequency or any such formal metric; both Helix and AX8 are professionally usable and highly capable processors. Where players who have real first-hand experience with both systems will likely squabble and debate is in WHAT has been modeled, how it was done (i.e. type of mic used in the case of cabinets, any parameters or functions ignored in an effect’s model, switching and channel variables on amps), and how close to the real world piece of gear that model sounds.

And this brings up an interesting point: that of modelling veracity. I’ve discovered through this process that I actually don’t much care if a model of a particular piece of gear sounds just like I think I remember that piece of gear sounding (or can imagine it sounding as a part of my larger signal chain). I only care if it sounds good. In fact, I’ve learned that I prefer models to be more generic and offer lots of tweaking flexibility than to be based on a certain metal box that was once produced under a thousand real-world compromises – manufacturing cost, viability for the marketplace, size and weight notwithstanding.

Case-in-point; although the Helix has a perfectly serviceable Mu-Tron envelope filter model that’s relatively faithful to the original stompbox, I like to have way more options when it comes to that type of effect and preferred the AX8’s approach to this effect category specifically, and others more generally. On the AX8, many effects are more comparable to highly configurable VST studio effects than are intended to mimic a classic piece of gear, with its inherent physical limitations. For the envelope filter I edited in AX8 Edit, I enjoyed being able to really closely approximate my favorite real-world filter (the 3 Leaf Wonderlove) by altering the curve of the envelope, the low and high-limit frequencies of the filter, an offset to better match my input volume with the desired filter behavior, drive level, and several other tonal ingredients. To be fair, many of these dimensions were also available and editable on the Helix’s 3 envelope models, but were perhaps easier to discover via the AX8 Edit software, initially.

I preferred the AX8’s in-house created FAS bass amp to models of other real-world amp offerings, which include of course the ubiquitous Ampeg SVT (which both the Fractal Audio and Line 6 units boast), as I felt it very closely approximated clean settings of my Genzler Amplification Magellan MG 800 head after some tweaking. In fact, what I found I wanted was a more or less transparent amp to occupy the preset’s amp block, allowing me to make use of the dedicated amp controls on the AX8’s panel. If there’s no amp loaded, those rotary controls do not function and can’t be mapped to anything else. I wanted to be able to boost drive for some grit of course, as well as to make EQ adjustments, and this amp model performed admirably. In fact, there are so many amp-specific variables you can adjust in any of the Fractal Audio’s amp blocks that, even for a gearhead like me, a person can quickly find themselves out of their depth! You’d never have access to this many options on a physical piece of gear.

Fractal Audio Systems

I found that I didn’t love any of the included cabinet models – ironically, none were “full-range” enough for me (but I didn’t want to go completely full-range, as in direct!). This was the case for me with the Helix, as well. However, both systems accept 3rd party IRs, and I was able to test a good number of aftermarket responses with help from my friend, initial Fractal Audio pusherman and modeling enthusiast, Ray Salamon.

On the Helix side, I honed in on their model of a Pearce bass amp; a make with which I was previously unacquainted. Again, more for its relatively neutral tonality when set to sound that way, while providing an amplifier to fill the amp designation within the preset and give me the ability quickly adjust amp EQ and drive settings. A major boon to the Helix’s workflow and processing arrangement is the possibility of multiple amp and cab modeling in the same preset; the AX8 allows only one of both types of blocks, although it should be noted that each block has switchable channels “X” and “Y,” allowing for two sets of sounds from within a single preset. It was easy to try out multiple amp and cab scenarios in parallel signal paths on the Helix, with the ability to adjust the send level of each leg of the signal’s Y-split and stereo balance from the junction points themselves along the audio path – an extremely useful and well-thought-out feature that is inherently available whenever you split the signal path, without invoking another block and its accompanying CPU usage to control those elements, as is necessary on the AX8.

When using that ever-present SVT model or other tube power amp-based models (several guitar amps included), while the AX8 certainly goes the extra mile in modeling depth and configurable options, both the Helix and AX8 produced thick and marbled results that to me were so realistic, I wasn’t able to discern recorded and played back tracks of these models from the real thing. The reason I state it that way is because, frankly, an amp model – or even a real amp connected only to an interface – is never going to “feel” the same in real time as plugging into a big speaker cabinet and experiencing all the sensation and psychoacoustics that are part of the experience of amplified real-world playing. You’re hearing it through headphones or studio monitors, at lower volume levels, etc. But I’m no stranger to recorded tube amp bass tones (full disclosure: I was once an Ampeg employee), and when I hear the tracks and looper audio that both Helix and AX8 are capable of producing with personally preferred settings, if I were to compare with a control track of the same bass recorded at the same time through a real SVT, I wouldn’t be able to tell you which were the “real thing” and which weren’t, truthfully. There’s so much variety in the way any real-world thing can be recorded for future playback, all of which have massive implications on the resulting tone, that each of the units’ tube models were for me fully believable after playing with some digital knobs.

On the logistical side, I really liked how Helix offers almost completely customizable footswitching action, having a leg up on AX8, here. All footswitches on the AX8 can be custom-assigned to any single function in each preset, while two per preset can be programmed macro controls that can perform multiple functions at once. On the Helix, any footswitch can perform up eight functions at once. To further explain, say that I decide I want to press one switch to simultaneously turn on my distortion block, a compressor, reverb, and octave-up harmony (perhaps even switching the harmonist block from octave-down to octave-up if needed), but I don’t want to change to a different preset to do this, because I want to retain one-to-one, stompbox style on/off capabilities in a pedalboard-like fashion. I can accomplish this with both Helix and AX8 in different ways. However, with Helix I can setup many of these macros, in contrast with the maximum of two that AX8 allows.

Admittedly, this sort of functionality is largely what Scenes (AX8) and Snapshots (Helix) are meant for – but the experienced user will discover some potential frustrations going that route if, like me, they like for their footswitches to be a representation of a pedalboard layout, using one Scene or Snapshot in a global way most of the time; if you forget that a Scene or Snapshot you plan to switch to doesn’t have a certain block-on or -off to match its current state prior to switching, you may get the macro action you want, but an unintended on/off block state oversight can really crash the party. Especially if it’s a very noticeable change, such as a strongly voiced amp or cab being defeated or added in as you switch over.

Fractal Audio Systems

I’m also a huge fan of AX8’s Block Library, and I’m a little awestruck that Helix doesn’t offer a similar inventory of user-defined individual effect and amp settings (am I missing something?). When using the AX8, you will invariably play around with all the options they generously give you for each block, which you can then conveniently save as an effect/amp level preset (i.e., not a whole “patch,” just your favorite settings for a block saved and recallable by stored name). So when you get that Darkglass just right and want to put that into a new preset, you can call up your own edited and saved version of it, ready to go. Near as I can tell, Helix doesn’t have an obvious way of doing this, so if you remove an edited block to try something else out in your preset, or if you’re building a new one and want to use only one of the block’s from a previously perfected preset, you have to start from scratch. I feel like I almost must be missing something here with Helix. Kudos to Fractal Audio for this feature, which also provides access to an edited block library for a list of available settings.

Neither system is likely to ferry a bassist to sonic nirvana right out of the box. Both will require you to find individual components you prefer from the sometimes cacophonous factory presets, mess with and tweak them, then start building your own presets out of the inventory of components you like … then do that several more times, discovering other blocks and models that get you closer to oneness with the universe; rinse and repeat. It’s this process that I find often separates those who eventually end up happy with modeling and with processors and who throw in the towel, and playing heavily into that is how easily a user is able to grasp the ins and outs of editing and the operational environment to stick with it long enough for that sweet sonic payout.

Processing It All

There’s so much to be said about both of these modelers, there may be no end. And that, in and of itself, may be the greatest argument for both systems – that the conversation and comparison can go on almost indefinitely with pros and cons on one side being disputed one-for-one against a differing set of pros and cons on the other, ad infinitum. My finding is that a bass player who has the patience and level of interest required to make an effects processor work for them is going to be very happy with either the Fractal Audio AX8 or Line 6 Helix. They don’t use all the same bass amplifier models. They don’t have the same cabs (but accept 3rd party IRs). What they both DO is sound good! I can say with confidence that either can be made to sound great, no matter your tonal preferences, due to the near-infinite tweakability and modification to models and presets allowed for. Chances are, if you run into a wall trying to get a certain sound, or are bummed out by the lack of a factory programmed sound you wanted, there’s another path to that aural glory that you will discover; perhaps by means of a combination, routing, or parallel chain you hadn’t thought of before. Which option you choose will probably come down to which cognitively makes more sense to you at first touch (informing your subsequent desire to stick with it), as well as your own highly individualized use case (e.g. whether or not you absolutely must have a headphone output or LED-ringed encoders), or something much more mundane, such as dimensional requirements.

For my own personal use – and not to be confused with a prescriptive statement – I’ve found that Line 6’s Helix Floor system offers slightly greater value for me. The Helix attracts me to it more strongly than the AX8 does, which makes me more likely to use and play with it in real time, adjusting parameters as I go. It may not plumb the depths of amp-modeling physics as deeply as Fractal Audio’s gear is so well-known for doing, but again, for my own scenario and as a bassist who prefers a somewhat “modern” tone in the first place, I derive greater value from the more pliable user interface and feature set presented by Helix. No doubt, factoring into this conclusion is my previous experience and mild frustration with PC-based, MIDI-controlled virtual plugin setups, which always left me pining for a better all-in-one floor unit that can provide the VST hosting environment itself, without the use of an additional laptop. This last piece echoing my experience with Fractal Audio’s AX8, which felt like I needed a laptop for intuitive editing. Obviously, each has its strengths, and both processors offer awesome attributes that the other makes less accessible, or fails to provide. But I am incredibly satisfied with both the Line 6 Helix and Fractal Audio AX8 and look enthusiastically to an expanding horizon of this caliber of pro/prosumer gear being more readily available. It’s a good time to be a bassist, musician, and gear head! 

Fractal Audio Systems AX8 Specifications

Company:Fractal Audio Systems
Warranty: 1 year, limited
Price: $1,099 (Direct)
Acquired from: Fractal Audio Systems
Dates: Fall-Winter, 2018
Locales: Seattle, Washington and surrounding region
Test gear: Genzler MG-800 and two BA12-3s, MTD 635-24, MTD 535-24, Focusrite 18i8, Sennheiser studio headphones, live venue sound systems
Dimensions: 16.4" x 10.3" x 3.1"
Weight: 11.8 lbs
Construction:Steel chassis, aluminum end caps
I/O:(1) ¼” in
(4) external controller ins
(1) 5-pin MIDI in
(1) stereo pair L/R XLR outs
(1) stereo pair L/R ¼” outs
(1) stereo pair L/R effects send or auxiliary output
(1) stereo pair L/R effects return or auxiliary input
* All ¼” outputs feature Humbuster™ ground loop protection
(1) SPDIF out
(1) USB out
(1) 5-pin MIDI out/through
(1) IEC power in, universal voltage switching
Models Included:Amps: 263 (discrete count closer to 160 when you consider that multiple inputs/channels/mods of the same amps are included on the list; 6 bass models)

Effects: 198 types in 23 categories, many iterations of several provided

Speaker Cabs: 130+ (6 bass models with mic variations of several, 3rd party IRs accepted)

Mics: N/A

More details can be found at the manufacturer’s website:

Line 6 Helix Specifications

Company:Line 6
Warranty: 1 year base, 2 years extended with product registration
Price: $1,599 (MAP)
Acquired from: Line 6
Dates: Fall-Winter, 2018
Locales: Seattle, Washington and surrounding region
Test gear: Genzler MG-800 and two BA12-3s, MTD 635-24, MTD 535-24, Focusrite 18i8, Sennheiser studio headphones, live venue sound systems
Dimensions: 22” x 11.85” x 3.58”
Weight: 14.6 lbs
Construction:Brushed aluminum chassis
I/O:(2) ¼” ins; high-Z Guitar and low-Z AUX
(1) XLR in; phantom power available
(1) Variax in
(3) external controller ins
(1) SPDIF in
(1) 5-pin MIDI in
(1) ¼” amp relay switch out
(1) stereo pair L/R XLR outs, stereo pair L/R ¼” outs
(1) ¼” headphone out; independent volume control
(4) stereo pairs L/R effects sends and returns
(1) SPDIF out
(1) USB out
(1) AES/EBU/L6 Link digital outs
(1) 5-pin MIDI out/through
(1) IEC power in, universal voltage switching
Models Included:Amps: 77 (includes same amp model with up to 3 different channels or settings, discrete count lower; 9 bass models)

Effects: 200 (not counting Line 6’s archival library from previous products, added in latest firmware revisions)

Speaker Cabs: 37 (7 bass models, 3rd party IRs accepted)

Mics: 16

More details can be found at the manufacturer’s website: