Series IV Tonearm – Gramophone Magazine

It is quite extraordinary how. at a time when the whole of the audio world has been propelled into a quite new phase with the widespread adoption of digital techniques, the chase after perfection in more conventional analogue components has gone on unabated. Not only gone on, but in several areas seemingly even accelerated to surpass all previous attainments and in a few cases achieve truly remarkable levels. In the field of conventional LP record pressing, for example, one thinks of the Direct Metal Mastering process, now widely adopted and already almost taken for granted in terms of the quality which it can allow. In the analogue replay chain a number of first class components have seen the light of day turntables, cartridges and pick-up arms among them, but none that we British can be more proud of surely than the SME Series V tone-arm, which was reviewed by John Borwick in the September 1986 issue.

Superbly designed and made, the "V" offers a level of performance approached by very few and surpassed, surely, by no other competitors. Really the only negative aspect about it is its price: very audiophiles can even consider it, let alone afford for just one 'front end' component. To this would need to be added a turntable and cartridge of concomitant performance and more than likely price. Clearly those enthusiasts who can justify expenditure at this level belong to a pretty exclusive club, so the four-year research and development, programme which resulted in the Series V would have had a limited return had not SME had up their sleeve a somewhat simplified and much less expensive version to fill in the missing model number between it and the Series III.

At a first, or even a second, glance the Series IV and V look much the same apart from the fact that the new one is in a bright metal finish, contrasting with the V's satin black enamel. In fact many of the component items are common to the two models. I shall go into greater detail below but in essence the main differences are: (a) that whereas the V is dynamically balanced and the vertical tracking force applied by a spring, in the IV as in many previous SME designs, gravity is put to work and the downforce applied by setting the arm out of balance. (b) that the V has an optional fluid damping system which isn't supplied with the IV. (c) that the IV dispenses with one or two of the V's more refined setting up facilities. Really it is only to the first two of these areas that one might reasonably anticipate perceivable differences in the subjective performance. In all other respects the same component and build quality obtains and readers should refer to John Borwick's review of the V for in-depth descriptions.

Both of these pick-up arms were developed primarily to cater for the low to medium compliance (8-15cu. say) moving-coil cartridges which dominate the top end of the market these days. Previous SME designs had been designed in the first place to match higher compliance models, particularly moving-magnet types. as perhaps typified by the famous Shure range: in other words to cope with a broad range of compliances from about 15cu up to 50 or even 60cu. Up to and including the Series III, therefore, SME opted for increasingly low mass designs and were able to justify the use of relatively simple knife-edge bearings for movement in the vertical plane. Here, ball races are used throughout. Low compliance MCs place significantly greater demands on the pick-up arm if the ideals that (a) the arm be "perfectly unyielding in four out of six possible degrees of freedom" and (b) that in the two dimensions in which the record groove is modulated it should behave as a pure mass, are to be approached. It is in pursuing these objectives that the Series IV and V achieve such conspicuous success.

The main so-called tone-arm in both designs is a one-piece magnesium casting which incorporates the cartridge mounting platform at the front and the counterweight support cantilever at the rear. It is of circular cross-section, heavily tapered straight, and is internally damped. At the rear the counterweight is a tungsten-alloy block suspended on a damped two-point suspension within a metal housing and "underslung" to achieve the optimum centre of gravity. It is mounted close to the fulcrum to reduce inertia, only 19mm of movement being required to accommodate cartridges of between 5 and 16gm in weight. As with the Series V this counterweight can be moved to and fro by rotating a leadscrew thumb wheel and then locked in position by moving a clamp lever. Playing weight here is achieved by first balancing out the arm with the cartridge in situ and then adjusting the thumbhole accordingly, one full turn applying 0.5gm. Naturally, on an SME, this is extremely accurate.As has been noted above, many of the component parts of the Series IV are similar, if sometimes less rarefied, to those in the V. For example, bearings of ABEC-3 tolerance are used instead of ABEC-7. These special wide contact angle bearings are made for SME in Japan. The horizontal races are 10mm diameter with nine balls and those in the vertical plane 17mm with 10 balls

Both are widely spaced to resist tilt. The construction of the arm allows these bearings, so crucial to the final performance, to be adjusted before the unit itself is finally assembled. The horizontal bearing axis is directly in line with the playing surface, given a cartridge of average body height, and this is the ideal arrangement for minimizing wow with warped records. It is particularly important, too, with gravity-applied downforce designs such as the IV.

The excellent base clamping system is also common to both arms and was described in detail by JB in his review. One difference on the IV is that the arm height has to be adjusted by hand rather than via a "VTA screw". Thus it is not possible to make fine adjustments to the vertical tracking angle whilst a record is playing with this model. but that is really the only inconvenience and it is a small one at that. As before two clamp bolts on the base release the arm for adjustment in both horizontal and vertical planes. spring applied friction loading retaining the chosen settings until the bolts are finally tightened.Height is adjusted manually, then, but the sideways movement required to achieve correct horizontal alignment is via a rack and pinion system enclosed in the base "slideways" as before.

Height is adjusted manually, then, but the sideways movement required to achieve correct horizontal alignment is via a rack and pinion system enclosed in the base "slideways" as before. Once again, extremely precise setting-up is possible with the alignment protractor supplied, guidelines on the armtube itself facilitating the vertical adjustment while the horizontal setting is far more straightforward than with almost all rival designs.

Anti-skate, or bias, compensation is provided by a tension spring and filament arrangement as in the V, the calibrations on the dial corresponding with the playing weight selected. Below decks the IV also has the same damped swivelling output socket, this clever idea allowing the arm lead to find its own best position without compromising the spring settings of suspended subchassis turntables. Whereas the V is supplied with sets of both stainless steef and aluminium cartridge-fixing screws the IV comes with just the aluminium set. A finger lift is supplied with the arm and this is held in place by the cartridge-fixing screws. Its use is thus optional and the purist might choose to leave it off, although it is doubtful whether the difference will be audible. 1 much prefer to have the control it affords when cueing. Linear crystal oxygenfree copper litz-wire cartridge leads are fitted (in the V they are silver) and a generous 1.2m length LC-OFC balanced audio lead replaces the van den Hul D-501 supplied with the V.

Performance

As we have come to expect from SME, the instruction booklet is a model of clarity and good sense, its 20 pages providing a clear, unambiguous regime for obtaining the best performance. The mounting template supplied with the IV will be familiar to those who have fitted previous SME arms (the one provided with the V is more elaborate) and involves carefully marking the armboard with a long pin or needle to find the centre point for the oblong cut-out. Small errors here are fortunately immaterial, however, since they can be absorbed by the fore and aft adjustment provided on the arm base itself. All aspects of the setting up procedure are straightforward and readily accomplished.

Subjectively the Series IV is unquestionably a state of the art device, to use the jargon phrase, with an almost uncanny ability to separate out all the various goings-on-musical strands, textures, ambience details, etc. in a quality recording. I have owned and used a number of high quality pick-up arms over the years but none has provided me with this kind of resolution. Sceptics might question the degree to which such enthusiasm might be put down to infatuation with the product itself, for it is well known that in terms of finish alone, SME have no peers. But whilst owning to a deep admiration for the aesthetics of this product, I would still insist that the kind of subtle detail that it can convey, given appropriately chosen ancillary equipment, provides a degree of involvement with what is going on in a score which, with an analogue system, I have only experienced to a comparable extent when listening to master tapes under studio conditions. From a rock-solid bass to the most delicate cymbal 'zing' at the top end, the IV gives the impression of being totally neutral, seemingly adding no coloration of its own. Dynamic contrasts, too, are revealed to a frequently revelatory extent, where with less able designs everything is held within a more constrained envelope. And last but not least, record surface noise, the bane of so many people's hi-fi lives, is considerably less intrusive believe it or not!

To sum up

The SME Series IV offers the audio purist a level of performance surpassed, probably, only by its very much more expensive bigger brother. For the enthusiast with a treasured and substantial LP collection who is looking to spend, say, £1,500 on a turntable/arm/cartridge combination with which to exploit it, the Series IV leaves him with just two more choices to make.
IVOR HUMPHRIES. See more of SME's products: http://www.gramophone.co.uk