Yamaha S10X and S20X
For near field monitoring or for small scale PA work, these compact speakers pack a hefty punch.
To begin with the S10X (of which the S20X is a derivation), we find a micro monitor with a 4" driver, in a chunky plastic cab that has a surface similarity to a certain other oriental monitor that has been reviewed in recent months. As we'll see later on however, the real similarity is very different.
In common with the majority of Japanese micro monitors, the cabinet is ported. To do otherwise would be a nonsense, because with such a small driver, nothing must be wasted - and ported cabinets do give you 3dB extra to play with. According to the designer's choice, the bonus take the form of an extra half an octave's flat response, or as a 3dB increase in low end sensitivity, or else as 3dB's worth of extra LF power handling capability. Because big amplifiers aren't an issue in Rock 'n' Roll applications, Yamaha have opted for the latter approach. So, while the sensitivity and low end response of the S10X are nothing to get excited about, the driver's thermal ability to handle 300 watts of music won't be stymied by any cone bottoming.
At four inches, the driver itself has a one and a half inch voice coil, (50% larger than is usual); evidence that the 300 watt rating is certainly no idle boast! Furthermore, the magnet is surrounded by a mu-metal shield which is significant as the majority of monitors aren't magnetically shielded. This is particularly naughty in the case of small monitors, not just because of their tempting position, but also because the external magnetic field is stronger, the magnet being so much closer to the enclosures surfaces. So, when your head is turned, a muso puts a cassette on top of your little monitors whilst emptying out his/her pockets. Thirty seconds later he/she picks it up, and hands the cassette over. You coolly drop it in the machine, and, after a few minutes we have a) magnetised tape heads, and b) a tape minus top end. But this sort of accident is ruled out with these Yamaha monitors; the shield is so effective that even a steel screwdriver isn't attracted when actually in contact with the back of the driver.
The heart of the S10X is in the cone material. It's carbon-fibre doped, making it heavier than the ordinary paper pulp, but it's absolutely rigid (and therefore less prone to breaking up). However, the opportunity to eliminate discontinuities on the cone's surface has been missed. Although the lead-out wires and associated glue-blob occupy only some 8% of the total area, the break up modes they engender is out of all proportion to their size, and this naturally has an effect on the overall sound of the speakers.
For a four inch drive unit to reproduce any sort of bass at all, it has to move an unusually large distance relative to this diameter. To achieve this, the rubber surround at the edge of the diaphragm has a disproportionately high profile. On a four inch diameter unit this causes diffraction in the upper mid-range - and once again, the lack of attention to detail is ironic, when you consider that Yamaha's plastic-moulding designer has gone to the trouble of seeing that the driver itself is front mounted and seated flush in the enclosure. The reason is, of course to prevent diffraction! So, in fact they've got the expensive bit right (the mould), but a slight redesign of the drive unit, (lowering the roll-surround profile), wouldn't go amiss.
The 'crossover' is actually a bandpass filter that cuts back the extreme low and high frequencies. I'd be tempted to uprate the bass 'stopper' capacitor, and change it to a bi-polar (reversible) type if only to see if it then sounded even better on bass end, given that the bandpass filter as it stands is certainly a vital protective mechanism if any sort of PA work is envisaged. Otherwise, a dropped mic would probably make the cone shoot across the room.
The filter's assembly is agricultural 1920's style, but is undeniably road worthy, and also incorporates another shielding subtlety. The inductor is snug-wound on a ferrite boblin (shaped like a mini Antex solder-reel), which blocks off the path for magnetic flux, so preventing any coupling with surrounding objects, and is insensitive to receiving magnetic fields (eg more carelessly placed tapes), as well as magnetic coupling (eg proximate, unshielded audio or mains transformers, and inductors).
Compared with the S20X, the array of termination options is not so great. Firstly, there are spring terminals to accept bared wires. Secondly, there's a quarter inch 'A' gauge jack socket. Both are recessed just enough to protect the receptacle alone if the S10X's should drop off the back of the console onto a hard floor, yet both are speedily accessible. In fact two of us changed over the pair of S10X's to S20X's in only 6 seconds, using the spring terminals. The jacks would be quicker still of course, but less reliable and more prone to fall apart.
Because the drive unit's protective grill was flimsy and undamped (and therefore liable to vibrate), we left it off for the tests. It's fabricated from mild steel so it's quite springy, but it's missing the stout, substantial feel of the S10X as a whole. Two contrasting examples of mechanical proficiency include threaded bushes with lock washers for the driver mountings (which unfortunately weren't tightened fully!), and the 6 self tappers which hold the two halves of the enclosure together that take a rather significant time to undo.
A wad of fibreglass completes the interior. Given the improved midrange detail that's (in theory at least) available by paying out extra for a carbon fibre cone, the wadding material can be improved to advantage. To be specific, a sandwich incorporating materials other than glass-fibre wool helps quell reflections off the cabs' interior walls over a broader range of frequencies.
Accessories include the usual number of lookalike 'torture equipment', enabling us to clamp or screw the apparatus to mic stands, tables, racks walls or ceilings. Of these, the 'Free Angle Clamp' and wall mounted bracket include a ball and socket swivel head.
The S20X occupies a slightly larger cabinet, and features a pair of drivers, each physically identical to the single S10X unit. The pair are wired in parallel, with the following potential benefits:
1. A 6dB (doubling) of power handling capacity.
2. A halving of impedance.
3. A potential doubling in bass-end output (or extension), and
4. An overall increase in sensitivity, typically 3dB.
At a nominal 6 ohms the S10X impedance is already on the low side. But don't panic, it's actually a minimum figure, and Yamaha have also clearly wound the S20X wire coils for double the impedance (12 ohms), so that the end result of the paralleled pair is the same, (ie. 6 ohms). The ultimate two driver trade-off is destructive interference and other phase/time anomalies that arise whenever discrete drivers carry exactly the same signal. This is a consequence of the impossibility of putting two drivers in the same space at the same time. Even with the dual concentric principle, you can't fit two full range units in the same chassis! Judging by the frequency response curves, the S20X has a marginally smoother midband response compared to the S10X, but of course, this is a static measurement carried out using tones, and says nothing about the energy distribution in a real room and this is where potential interaction between the two drivers would become apparent. Meanwhile, the critical frequency relates to their spacing. For 5", this is around 2.7kHz, the apex of the midband, and as anticipated, there's a suckout at 2.7kHz, and another at 1350Hz, exactly half this frequency, neither of which are manifest in the S10X (see response curves).
Interior details differ in that the crossover parts are heftier, but once again, Rock 'n' Roll durability isn't under dispute. Also, as hinted earlier, the S20X has some extra termination options. Firstly there's a second, paralleled jack socket which is useful for daisy-chaining units in tandem for PA work. Secondly, by removing one or other of the existing jacks, you'll find a machined fitting for both male and female chassis mounted XLRs. Even the otherwise redundant jack screws can be recycled, to secure the XLRs. This should be enough to keep everybody happy!
Our evaluation began as usual against the backdrop of tri-amped Turbosound TMS4 main-monitors, but for the first time, we've extended the listening tests for the purposes of cross-checking to include the local 24 track studio called 'The Chapel', thanks to muso Bram Tchaikovsky and engineers Andy Dransfield and Rick Woolgar. For the record, their main monitors are designed by Andy Munro as part of their Turnkey control-room package, with a pair of Tannoys and Turbosound TMS2s standing by. More to the point, their micro-monitors are Visonik 7000s, a model they'd arrived at after rejecting all the US and oriental made alternatives they'd tested previously.
Because the S10X closely resembles another micro-monitor in its salient details (driver size, enclosure shape and volume vent area and depth), the making of directly switched A/B comparisons proved irresistible. In the event, the only immediately obvious difference was that the S10X had a more level response, but also a lighter bass end. However, A/B listening displays only those differences between units made apparent by the instantaneous spectral content. In short, if there's no great 6kHz content in the music when you switch, you won't easily be able to discern any response deviations at this frequency. So thorough testing should be done without short cuts, and involves several days' evaluation against the backdrop of full-range main monitors.
The complete listening tests, beginning with S10X revealed a new standard in space, separation and detail. A good, stable centre image is to be expected from micro-monitors with a single point source driver, but much of the ambience at large in the signal, that which creates the sense of space, is at a much lower level, and is swamped out by the breakup modes in ordinary paper cones. The benefit of the S10X's carbon-fibre cone is to greatly reduce the level of spurious resonances in the midband, the result being the revelation of unsuspected midrange detail. This benefits the assessment of finickity vocal and guitar sounds, or indeed any instrument, when used to create intricate sounds or ones which are all too obviously 'fuzzed over' by most small speakers, making judgement hard work.
The bass end was definitely on the sparse side, perhaps more so than other monitors of the S10Xs size, but after acclimatising to this, the only obvious spikey colouration was limited to a mild transgression at about 6kHz. This tends to emphasise any sibilance. At high levels, (above 100 watts), the dominant hotspot was again around 5-8kHz and whilst the unit performed without any sign of distress and the cone proved impossible to bottom, the absence of bass, plus hotspot rendered these units less pleasant to listen to, though no more so than certain others. In essence, they're definitely capable of handling a lot of power, but should be issued, like the majority of other mini-speakers, with an aural health warning for when they're wound up above 100 watts and put to PA use. Also, don't imagine that because S10X's are small, that they'll enable you to make do with a small amp; sensitivity is on the low side, at 87dB for 1W at 1M, meaning that 100 watts will be needed to generate a 104dB monitoring SPL at four feet (1.3M) and allowing for thermal compression. For our tests we used a Bose Studiocraft (200W into 8 ohms), whilst at 'The Chapel', a Quad 405-II (100W into 8 ohms) sufficed.
The changeover to S20X was immediately apparent as the bass space filled out, and the tonal balance became more natural, yet without losing any of the points scored for detail by the S10X. This means you don't have to work so hard at listening and makes it more relaxing. This in turn heightens perception. An unexpected surprise, the bass extension also comes with a marked improvement in the solidity and depth of the imaging, separating out for example, the layers in a complex DX7 bass line. Also, resolution in the low midrange was streets ahead of a single 4" driver; important for percussion and bass.
Another happy surprise was that the anticipated phase cancellation and associated suckouts failed to materialise, or at least weren't evident unless you listened carefully for them. Regarding power, the S10X could be driven harder and was less unpleasant than the S10X when taken up to twice the power, (300 watts), even though the dominant hotspot remained in the low table treble.
Finding the S20X an improvement over their existing monitors, and relieved that no tissue paper was called for (hint to those of you who have used certain earlier Yamaha monitors...), Rick and Andy went on to engineer a number by Four Million Telephones on the S20X. They noted that the sound related better to their main monitors in comparison both to the S10X, and their existing units, in that there was less difference in perspective, they were easy to listen to for long periods, and were especially adept at handling vocals and guitar.
At £138 per pair, the S10X seems expensive for a micro-monitor, and S20X more so at £220 per pair. But any such thoughts can be put down to a misconception that small monitors are necessarily cheap, on account of their minimal materials content. In fact, a good speaker involves a certain, minimum outlay. Moreover, the midband resolution of these Yamaha units invites detailed comparisons with larger and considerably more expensive creations, like Celestion's SL6. On this basis, we can expect both models to become popular monitors, and to form part of a new standard for the second half of the eighties.
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Review by Ben Duncan
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