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Line 6 Variax Acoustic 700

Modelling Guitar
Published September 2004
By Paul White

Line 6 Variax Acoustic 700Photo: Mike Cameron

Extending the modelling approach they pioneered with the original Variax, Line 6 have now taken a shot at reproducing the sounds of different miked acoustic guitars. Almost completely immune to feedback, the Variax Acoustic will clearly be a hit in some live applications, but does it sound good enough to record?

Few people will need reminding that Line 6 were the company who brought guitar modelling into the mainstream market with their Pod, even though, to my knowledge, Roland were the first to test the waters in this area with their more complex V-Guitar systems. There was a lot of speculation about areas into which the company might diversify once it had grown sufficiently, and grow it certainly did, but rather than trying to cover all aspects of the music market as some companies do, Line 6 stuck to the guitar market, moving first into amplifiers and guitar effects, then most recently into producing their own guitars that use integral modelling technology to emulate a number of classic instruments. Once again, Roland offered guitar and pickup modelling, but the Line 6 approach is very different. Instead of creating a special pickup to be bolted to your guitar, Line 6 provide a range of guitars of their own, with everything built into the guitar body and operated by simple, guitarist-friendly controls. The necessary piezo pickups are built into the bridge, one for each string, and the end result is very simple to use, which counts for a lot when you're on stage with no time to mess around.

The first of these Variax models was based on a solid-body guitar (which is visually distinctive because of its lack of visible pickups) and most of the sonic emulations were either of solid-body or semi-acoustic models, though there were also 12-string, banjo, and sitar models and the odd acoustic guitar. Soon a version with a tremolo followed, but at Winter NAMM in 2004 we had a sneak preview of the Variax Acoustic, the production version of which is reviewed here.

Acoustic Guitar Modelling

Like the electric models, the Acoustic Variax 700 is a complete guitar, rather than a system relying on add-on pickups. It is a shallow-body instrument with the look and feel of a steel-strung acoustic guitar, but it's designed to have less natural body resonance so as to help avoid feedback problems in live performance. The design brief was to produce an instrument that not only offered a choice of sounds, but that could also be recorded or DI'd into a PA system to produce better results than a conventional acoustic guitar fitted with pickups. Indeed, the aim seems to have been to get as close to the miked sound of the real thing as possible.

The DSP engine room of the Variax Acoustic is hidden beneath a plate in the back of the guitar.The DSP engine room of the Variax Acoustic is hidden beneath a plate in the back of the guitar.Photo: Mike CameronThe guitar has an attractive natural-finish cedar top with a fixed mahogany neck and a more-or-less-solid mahogany body which has chambers machined into it rather than using a conventional acoustic construction. Looking through the soundhole shows that the cavity beneath it isn't much bigger than the soundhole itself. I can't say what other cavities there are without sawing the guitar in half, and I don't think Line 6 would appreciate that! A headstock reminiscent of the solid-body model houses acoustic-style tuning machines, and a cutaway provides good access to the upper frets of the 24-fret, 25.5-inch-scale neck, which has a 17-inch radius fingerboard and cross-shaped marker inlays. The setup of the guitar was fairly good straight out of the box, though, as is so often the case with new guitars, the nut slots could do with being cut deeper to really optimise the action.

Variax Acoustic 700 comes with its own DI/power-supply box, which provides both quarter-inch jack and balanced XLR outputs that can be fed into an acoustic guitar combo, a PA mixer, or a recording system. The guitar may also be powered by onboard batteries or directly from a Line 6 Vetta II amplifier (or other Line 6 products that have a Variax socket). A custom, heavy-duty gig bag is included.

As with the solid-body models, the string sound is picked up via a piezo pickup beneath each bridge saddle, after which it is subjected to a modelling process to make it sound like one of a number of classic instruments that can be selected by the user. The modelling process even includes a Mic Position slider, so that you can adjust the guitar tone by moving the virtual mic closer to or further from the soundhole. Because acoustic guitars are often compressed during recording, a simple onboard compressor is also included and, because of the proclivity of acoustic guitar players for using odd open tunings, a selection of these are available which use pitch-shifting technology to allow the player to switch tunings without retuning the instrument. Custom tunings can also be set up by the user and the same pitch-shifting technology is used to generate the twelve-string sound, where the top two strings are correctly tuned in unison and the remaining four in octaves.

Connecting Up

The output socket can feed an amp directly if you're running the guitar from batteries. Alternatively you can power the guitar from the included footpedal/PSU by connecting to it using a TRS cable, or from a Vetta amp by connecting to it using the Ethernet-style socket (hidden by its dust cover in this picture).The output socket can feed an amp directly if you're running the guitar from batteries. Alternatively you can power the guitar from the included footpedal/PSU by connecting to it using a TRS cable, or from a Vetta amp by connecting to it using the Ethernet-style socket (hidden by its dust cover in this picture).Photo: Mike CameronWhile the easiest way to use the Variax Acoustic is to connect it directly to a mixer or amplifier using a standard guitar cable, this means running the guitar from batteries, and a set of alkaline batteries only lasts 10-12 hours. There's also the facility to use a standard 9V battery in emergencies, but this will only run the guitar for an hour or two — maybe just enough to get you through the night. A cheaper way to run is to use the included XPS power-supply/DI box, which connects to the guitar via a TRS jack twin-core cable. A standard mono guitar cable then connects the XPS to your amp or mixer. The box also has an XLR output that provides a balanced feed at +4dBu line level, and the unit can also function as either an A/B selector (for sending different sounds to different amps via the jack and XLR output connectors) or as a standby switch.

A further RJ45 connector is fitted to the guitar body and allows the guitar to be connected directly to those Line 6 amps and other products that have a dedicated Variax input. Via a standard Ethernet cable, such amplifiers can also provide power directly to the guitar. I believe the same socket can also be used to install Variax software updates.

The Models

With an instrument like this, which seems to be designed predominantly with live performance in mind, simplicity of use is paramount. To switch between the various guitar models, a rotary knob is built into the top edge of the body, and short versions of the instrument names are printed onto the knob so that it's easy to see what you've selected. After selection, the sound can be modified or additional functions activated by means of just three sliders.

In all, there are 16 instrument models: the majority are steel-strung acoustics, including resonator guitars, plus there's a nylon-string classical model and a few rather more obscure instruments thrown in for good measure. As with all the other Line 6 modelling products, the Variax Acoustic 700 is the result of extensive listening tests using selected acoustic instruments. According to their web site, the models Line 6 used for their research were: 1941 Martin 517, 1946 Martin 00018, 1960 Martin D28, 1954 Gibson J45, 1951 Gibson SJ200, 1933 Selmer Maccaferri, 1951 D'Angelico New Yorker, 1958 Manuel Velazquez classical guitar, 1973 Guild F412, 1935 Stella Auditorium 12-string, 1939 National Reso-Phonic Style 'O', 1937 Dobro Model 27, Gibson Mastertone banjo, Mandola, Japanese shamisen, and Indian sitar. The models were based on the sounds of these instruments, though as always there's a disclaimer that informs the users that there is no connection between any of these companies and Line 6, and that all trademarks are respected. Unfortunately, no manual was provided with the review sample, so all the information had to be gleaned from the Line 6 web site.

The included PSU pedal powers the guitar via a TRS cable, and provides an unbalanced guitar feed on a further jack socket. There's also an XLR socket which offers a balanced DI signal.The included PSU pedal powers the guitar via a TRS cable, and provides an unbalanced guitar feed on a further jack socket. There's also an XLR socket which offers a balanced DI signal.Photo: Mike CameronA number of products are already on the market that use modelling to improve the DI sound from existing acoustic guitars fitted with piezo or magnetic pickup systems, some of which sound very good indeed. Pickup systems tend to change the sound of the instrument, as they don't capture the full contribution of the body resonance, but, provided that you know what kind of signal the pickup is producing, modelling can be used to re-synthesize the missing body resonance and also to EQ the overall sound to better match what a microphone would hear. For the results to be anything more than an approximation, you'd need to have measurements made on your own instrument both from the pickup and via a microphone, so that a corrective EQ curve could be set up (using many frequency bands). Body resonance models based on other instruments can then be modelled to give your instrument a greater range of sounds, again provided that the resonance characteristics of your own instrument are known so that the modelling process creates only the difference between your guitar and the sound you're aiming for.

Most add-on systems assume a generic model for the guitar being used, so the modelled results can only be approximate, though I believe that one manufacturer already offers a customisation facility to those prepared to pay for it. Clearly, the benefit of the Line 6 approach is that every Variax Acoustic 700 guitar will sound ostensibly the same (via its pickups) so the modelled results can be predicted and optimised with much greater accuracy and consistency than if you used your own guitar. Furthermore, because the body doesn't resonate to nearly the same extent as a real acoustic guitar, feedback problems are virtually eliminated.

Variax On-body Controls

Moving the volume slider towards the model-selection knob turns it up. The Mic Position slider is closest to the front of the guitar, and it moves the imaginary mic closer to the soundhole as you move the physical slider towards the soundhole. This even works for those modelled instruments that don't have a soundhole. In effect, when the slider is moved towards the Model Select knob, the strings and overall brightness are emphasized, whereas moving towards the soundhole emphasises lower frequencies. The slider closest to the back of the guitar changes the amount of compression — all the compression parameters are optimised for acoustic guitar, leaving you just to set how much compression you want to use. Moving the slider toward the Model Select knob adds more compression.

The three sliders to the right of the Model Select knob control the position of the 'virtual' mic (top), the output volume (centre), and the amount of compression (bottom).The three sliders to the right of the Model Select knob control the position of the 'virtual' mic (top), the output volume (centre), and the amount of compression (bottom).Photo: Mike CameronAlthough it looks simple enough, the Model Select knob actually performs different functions, the most obvious of which is switching between instrument models. A little illumination is provided by a green LED, so you can select sounds on a dark stage with some degree of certainty. The same knob also selects the Alternate Tunings function, as it incorporates a push switch for changing its mode, whereupon the LED changes from green to red. A different alternative tuning is preset for each guitar model, and tunings include drop 'D', open chord, and dropped octaves on the lower strings. However, your guitar must be conventionally tuned for these to work properly, as all the shifted pitches are referenced to standard guitar tuning.

To set up your own custom tuning, you can retune any of the strings up by as much as seven semitones or down by as much as an octave to create your own alternate tuning. To get into this mode, you have to press the Select knob twice, rather like double-clicking a mouse button. Once in this mode, you select the string you want to tune using the compressor slider. A nice touch is that the selected string is louder than all the others, making it easy to know which one is currently active for editing. The Mic Position slider then selects the degree of shift for each string in turn. Once all the strings have been set, you can go back to the normal playing mode using your new alternate tuning.

Of course you need to have a way to save your customised instruments, and the way this works is that you have to overwrite a factory patch after modifying it — there are no user memory slots. Once all the tweaks have been made, you hold down the Model Select knob until the LED stays solidly lit. Your patch is then saved.

So How Does It Sound?

When I first plugged the Variax Acoustic into my studio monitoring system and played, I was somewhat disappointed, as I thought the sound was rather hard and unyielding, almost like a guitar that had been miked far too close or had been recorded using a contact mic on the body. However, the direct sound from the strings can be confusing when heard in conjunction with the modelled sound, so I recorded a few bars of guitar using each of the classic acoustic sounds and then listened to them played back without me twanging along. The impression was slightly better, but not much. Then it occurred to me that the modelling didn't include any room ambience, so what I was hearing was more like an acoustic guitar recorded in an anechoic chamber, so I patched in Emagic Space Designer and added some natural room ambience. Immediately the result improved significantly, though I still got the impression that the dynamics of the instrument weren't quite right and the sustain characteristics didn't match the real thing. What's more, adding more Variax compression didn't improve the sound in the way I expected it to.

Line 6 Variax Acoustic 700Photo: Mike CameronAs an experiment, I turned off the Variax compressor, and instead used Logic's own plug-in compressor with an attack time of 3ms and with Peak rather than RMS sensing. No more than 6dB gain reduction was applied on signal peaks. The improvement this time was very noticeable, with the sustain improving and the sound becoming more even and less honky — ever since hearing the banjo preset, I felt I could hear a hint of banjo in all the other presets too! Switching back to the Variax compressor confirmed that I couldn't achieve the same result using that. Although this test was very subjective, I couldn't help feel that the raw Variax sounds were rather harsh without the Emagic compressor.

Putting this into perspective, the sound of the Variax Acoustic is still more authentic than simply using an acoustic with a piezo bridge pickup, and the resistance to acoustic feedback is undeniable, but unless you add your own compression and reverb/ambience, you probably won't want to record with it. Checking out the other models showed the resonator guitars to be pretty convincing, and though the banjo probably wouldn't stand up to close scrutiny, it would certainly pass muster in a mix. The same goes for the sitar and shamisen — you're unlikely to hear Ravi Shankar playing a Variax, but if you want to add a bit of George Harrison nostalgia to a track, it should work fine.

I was impressed with the quality of pitch-shifting used to generate the 12-string and custom tuning sounds — the fact that each string is a single-note source has obviously enabled the algorithms to be optimised — and the ability to move the 'virtual' mic position is interesting as it enables you to get closer to the sound you want before resorting to EQ. The custom tunings can feel odd if you aren't monitoring loudly enough to hide the acoustic sound of the guitar, but that's also true of any other guitar system that achieves retuning using pitch-shifting.

Variax Verdict

Inevitably some compromises have to be made to keep the operating system simple, but I'd like to be able to apply any preset alternative tuning to any instrument, and I'd also like to be able to save more user tunings and patches without having to overwrite the factory sounds. Also, given that some reverb or artificial ambience is needed to make the sound breathe, it would have been useful to include this — most of the stand-alone acoustic guitar modelling preamps do. Indeed, if you don't need accurate modelling and aren't troubled by acoustic feedback, the subjective results obtainable from these external preamps used with a conventional guitar (fitted with suitable pickups) sound more musically acceptable to my ears than the untreated Variax sound.

The Variax Acoustic may need a little tweaking to get the best out of it, but currently it provides the only practical way to get an acoustic guitar sound live at high volumes without feedback, and of course you can switch between sounds very quickly. While I wouldn't use the instrument for recording solo parts, it works well in a mix provided that you add some external compression rather than relying on the onboard compressor, and I really like the resonator-guitar and mandola presets. Live, it should be no problem as part of a band, though some players may not feel comfortable using it for solo performances.

As with all firsts, there is bound to be room for improvement, but because the instrument is software upgradable this doesn't necessarily mean waiting for the next model. The Variax Acoustic 700 is a very clever piece of technology that meets a real need — a bit of fine-tuning is a small price to pay for freedom from feedback and the ability to switch guitars on a whim.

Published September 2004