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Yamaha APX 900 and Compass CPX 900

Acoustic guitars with ART pickup system

Published in PM December 2007
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Reviews : Guitar: Acoustic
Successfully amplifying acoustic guitars on stage has always been a bit of a challenge, but now Yamaha's ART (Acoustic Resonance Transducer) pickup system may provide the solution.
Bob Thomas
As readers of some of my previous features may already be aware, I've been searching for the perfect acoustic guitar pickup and preamplifier setup since about 1972. Every time a new concept or a new bit of technology comes along aimed at the acoustic guitarist, I'm up at the front of the queue, waving my credit card at the salesman. In some respects, Yamaha guitars have been partnering me in that journey, starting with my first Yamaha acoustic — a 1969 red label Nippon Gakki FG180 (that eventually ended up sporting a DeArmond soundhole pickup) — through to the knockout APX 9N that I own today, which is outfitted with a highly practical and useable undersaddle pickup and internal microphone combination.
Yamaha is a company that doesn't rest on its laurels, and over the last three years, Yamaha engineers have developed the new Acoustic Resonance Transducer pickup system. This is designed to handle a wide dynamic range, while still being usable at high volumes, to give improved feedback rejection, provide a more natural and controllable tone, and improve the response of the guitar and pickup to the player.
The two guitars under review here, the APX 900 and the Compass CPX 900, are part of the recently revamped APX and Compass ranges of performance electro-acoustics, and are fitted with a top of the range three-way ART pickup configuration, partnered by the new System 57 preamp. Although these guitars have both been designed primarily for on-stage performance, there are significant differences between them in terms of sound and construction. As the ART pickup system is common to both guitars, I am going to compare and contrast the two guitars and unite them again around their pickups.
APX 900 and CPX 900
Manufactured in China, the Yamaha APX 900 and the CPX 900 guitars reviewed here are testaments to the extremely high quality standards that can be achieved when good design, good materials and a skilled workforce are all brought together under the watchful eye of a company that's renowned for its quality control. On both guitars, every single joint is totally without flaw, every piece of wood from the neck to the smallest brace is beautifully cut and shaped, and there isn't so much as a hint of stray glue anywhere in the body cavity.
The body shapes are very recognisably part of the Yamaha heritage. The APX 900 retains the familiar single-cutaway outline and its distinctive oval soundhole, which is emphasised by an abalone and plastic insert that takes the place of the traditional purfling rings. The Compass CPX body shape is in a somewhat more conventional single-cutaway, small jumbo configuration that, to my eyes, still manages to look distinctively Yamaha. The woods used are common to both guitars: solid spruce top, flamed maple backs and sides and a nato (eastern mahogany) neck. The fingerboard and bridge are, according to the specifications, made of striped ebony, which has an appearance that looks very much like rosewood to me. On this particular CPX 900, you can see that the top wood has been cut right on the quarter so that the medullary rays are clearly visible and give a beautiful 'silk' effect to the top, which also features a conventional abalone soundhole surround. The flame in the maple of the back and sides is also most visible on the CPX 900 and, in all, makes for a very attractive guitar indeed.
The headstocks also share the same outline, rosewood overlay and gold plated machine heads, underlining the family appearance — although the abalone inlays on the headstock and fingerboard differ completely. The APX 900 headstock inlay is a very attractive fern-like double scroll, which partners — somewhat incongruously, to my eye — the large 'CJ' split triangle inlays on the fingerboard. The CPX 900, being a member of Yamaha's Compass series, carries an abalone representation of a compass motif usually seen on antique maritime charts. In a styling quirk more literal than pleasingly aesthetic, North points left of centre towards an imagined magnetic North, rather than the true North, which, as everyone surely knows, lies at the centre of the end of the headstock. The CPX 900 fingerboard inlays are small abalone diamonds, with a unique 'diamond chevron' inlay marking the 12th fret.
Necks and bodies are fully bound with a creamy white binding, which, on both guitars, exhibits no trace of overspray from the beautifully applied finishes. The review APX 900 came in 'Crimsonburst', a distinctive dark cherry colour that darkens slowly towards the body edges. The CPX 900 came in a gorgeous brown 'Sunburst' that has, somewhere in its genes, the DNA of the legendary Fender two-tone Sunburst. These finishes are available on either guitar, as are the other two available options — Mocha Black and Ultramarine.
Although the APX 900 has a slimline body where you might expect to find a slimline neck, it actually carries a comfortably chubby neck reminiscent of a 1959 Gibson Les Paul. The CPX 900, on the other hand, features a slimmer neck that reminds me somewhat of a 1964 Gibson ES345 that I once owned. Both the guitars were extremely comfortable and playable, thanks to good setups with well-finished frets and compensated saddles. Fender players in particular will find the 650mm scale length very familiar territory, and PRS and Gibson devotees will have to stretch a bit further than they are used to in the lower positions.
Acoustically, the two guitars couldn't be more different. The APX 900 has a tight, punchy sound, with a limited amount of body resonance. It does have a good deal of sustain and, as a result, seems a bit quieter than the CPX 900, which has much more character, volume and body in its tonality. As acoustic guitars, the APX is aimed more at a player coming from an electric guitar background, and the CPX would attract a player with more of an acoustic heritage. However, both the APX 900 and the CPX 900 are designed as performance electro-acoustics, whose natural home is on stage, plugged into PA and backline. So, the acoustic nature of each guitar is there, as I see it, to colour the sound and not necessarily to define the instrument.
ART and System 57 preamp
(From left to right) The treble-sub, two main and bass-sub pickups are situated on the underside of the bridge plate.
(From left to right) The treble-sub, two main and bass-sub pickups are situated on the underside of the bridge plate.
Back in the '70s, the recommended mounting for BarcusBerry's early piezo transducers for acoustic instruments was a couple of blobs of a then high-tech substance now known as Blu-Tack. The idea behind the Blu-Tack was to slightly decouple the pickup from the front of the guitar. In recent years, this type of mounting has largely been supplanted by superglue, although another survivor from the '70s, FRAP (Flat Response Acoustic Pickup), still uses a cushioned, double-sided adhesive tape to mount their pickups to a guitar's bridge plate. I've always mounted my handful of original Barcus-Berry pickups on Blu-Tack and it definitely does help to produce the natural sound that I look for. It's a technique that you might want to try sometime.
Over the last few years, while undersaddle piezo transducers have ruled the market, a small band of pioneers (and mad folk like me, who butcher Maplin piezo buzzers to get at the piezo elements) have used multiple circular transducers mounted on the bridge plate, in order to get a sound that contains more of the woodiness of the guitar, while still trying to retain a reasonable level of feedback rejection. The bridge plate, by the way, is a piece of maple (or sometimes rosewood) that reinforces the area of the top that the bridge sits on, to prevent splitting or deformation.
Yamaha's R&D engineers have taken these two mounting and positioning concepts a quantum leap further forward in developing the ART system pickups, and have wedded them to a totally unique preamp design.
The circular pickup elements of the three-way ART pickup system sit in the middle of individual multi-layer bases and are shielded by a copper hat (not unlike those worn by Bill and Ben of TV fame), which is connected to the earth side of the pickup connection in order to eliminate as much hum as possible. The two main ART pickups are placed on the underside of the bridge plate, towards the front edge of the bridge, wired together at the preamp connector and form the first of the three-ways of the system. Incidentally, these two pickups also make up the one-way ART system fitted to lesser models like the APX 700 and CPX 700 series. The bridge plate has, to me, also been dimensionally designed to optimise the performance of the pickups.
In the ART three-way configuration, there are two further pickups known as the sub pickups. The treble sub is placed on the treble edge of the bridge plate, with about 80 percent of its area lying in front of the bridge-pin line. It is also considerably smaller than the main pickups, which, together with its positioning, will tend to bias its output towards the treble frequencies. I would also guess, from looking at it, that the multi-layered base is constructed differently for this pickup. The corresponding bass-sub pickup is a size larger than the main pickups and sits on the base edge of the bridge plate, with 80 percent of its area lying behind the bridge pin line. Its larger size and rearward positioning will tend to favour the guitar's bass frequencies.
The multi-layer base is designed to achieve several goals. One aim is to slightly decouple the pickup from the guitar and thus reduce handling noise. This decoupling has also to balance the need for sensitivity in order to reproduce the dynamics of finger-picking and control, which needs to be exerted when the playing gets heavier in order to avoid the harshness prevalent in some systems. Another key aim of the decoupling is to reduce the likelihood of feedback by slightly isolating the pickup from body resonances.
One thing that I know from my own multi-element installations is that pickup positioning is critical to great sound. As Yamaha have extremely consistent manufacturing standards, this has enabled their designers to determine precisely the best placement for these four elements. This is the exact opposite of my case, where every instrument is hugely different, making pickup placement on my instruments a nightmare for my long-suffering genius luthier, Bill Puplett.
The side-mounted System 57 preamps of the APX 900 and CPX 900 boast a handsome brushed gold finish, an onboard chromatic tuner, three-band EQ, master volume and individual gain controls for the bass and treble sub pickups. The integral tuner, which doesn't require that the guitar be plugged in to operate, is accurate and extremely easy to use. Power to the preamp and tuner is supplied by a PP3 battery, which sits in a battery box mounted just around the corner from the preamp on the top bout. Wires from the pickups enter the preamp via three mini jacks, one carrying the two main pickups and one each for the treble and bass subs.
With the EQ controls set flat and the sub pickups turned off, the main pickups give a pretty good account of themselves, with a lively dynamic sound that seems to me to be rolling off a bit in the treble and bass regions of the sound spectrum to leave a mid-forward sound. This basic sound characteristic emphasises again the performance aspect of both guitars' design parameters, as mid-range really helps to cut through the mix in a live situation. If you use the Bass and Treble faders of the onboard three-band EQ, you get the expected result — more treble, more bass and the need to play around a bit with the mid-range level in order to get a balanced sound. Using the System 57 preamp's Sub-pickup level controls to add bass and treble is a whole different ball game. It is really hard to describe, but the feeling that I get is of an organic lift in the respective levels. The effect is totally unlike anything I've ever heard before and somehow feels more natural than making EQ changes, possibly because of the reduction in the phase anomalies that are a by-product of all EQ circuits.
These two Sub controls could also make you rethink your approach to your live sound. Because you now have a way of 'naturally' getting a sound with more bass or treble, you can think about using these controls creatively by balancing them against the EQ faders to tailor your sound precisely to the way that you play and by making subtle, but really effective, changes to compensate for (or to enhance) things like changes in pick attack and percussion.
In use, I much preferred the sound of the CPX 900, as it is the more 'acoustic-sounding' of the two. That's not to say that the APX 900 was bad. In fact, it had a very useable sound and was loads of fun to play, but it just didn't quite float my boat in the same way as the CPX 900 did. I spent a lot of time delving into the capabilities of the CPX's ART pickups and the System 57 preamp, and I was considerably impressed. The sound was excellent, feedback rejection was good (and could be considerably improved by fitting the supplied soundhole cover) and the amount of variation that could be obtained from various combinations of sub control and EQ was seemingly endless. I didn't come across a sound 'problem' that I couldn't solve. Over the course of a couple of days, I found myself developing a favourite setting on the CPX 900, which was 50 percent bass sub, about 25 percent treble sub, with a little bit of mid-cut on the EQ faders. That combination produced, to my ears, a great acoustic sound that I'd be quite happy to gig with.
The position and smaller size of the treble-sub (left) mean that its output will tend to lean towards treble frequencies.
The position and smaller size of the treble-sub (left) mean that its output will tend to lean towards treble frequencies.
The APX 900 and Compass CPX 900 guitars are well designed and beautifully built and totally fulfil their brief as electro-acoustic guitars for stage performance. Building on heritage and experience gained from earlier APX and CPX models, and combining this with the new three-way Acoustic Resonance Transducer and System 57 preamp, Yamaha's designers have produced two guitars that set new standards of performance at this price point. I'll be sorry to see the CPX 900 go back. The ART system is a unique and very impressive approach to the challenge of successfully amplifying acoustic guitars on stage and it will be interesting to watch how it develops in the future.  0

Published in PM December 2007
Yamaha APX 900 and CPX 900 £685
The ART system, partnered with the System 57 preamp, produces great results, and if you're in the market right now for a stage acoustic in this price range, the APX 900 and CPX 900 should be at the top of your audition list.
Yamaha-Kemble Music Ltd.
+44 (0)870 4445575
Tech Spec
APX 900
Cutaway electro-acoustic.
Solid spruce top, flamed maple back and sides.
Ebony fingerboard and bridge.
Ivory body and fretboard binding.
650mm scale length.
22 frets.
Die-cast gold tuning machines.
System 57 (ART), three-way/piezo pickup with three-band EQ, volume and tuner controls.
CPX 900
Mini jumbo electro-acoustic.
Solid spruce top and flamed maple back and sides.
Ebony fingerboard and bridge.
Ivory body and fingerboard binding.
650mm scale length.
Die-cast gold tuning machines.
System 57 (ART), three-way/piezo pickup with three-band EQ, volume and tuner controls.