SME 312S Tonearm

(from Hi-Fi World, October 2009 issue)


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Twelve Bore


Noel Keywood brings home some serious firepower from SME, in the shape of its 312S new twelve inch tonearm...


Whilst nine inch arms occupy the functional end of the market, twelve inchers look altogether more intriguing and purposeful. Perhaps that's why they seem to be making something of a comeback in today's vinyl revival, where appearance matters. Not to be caught napping, SME have launched an upgraded version of their long 312 arm, the magnesium alloy 312S, reviewed here. The SME312 I have lived with happily for the last twenty years or so, and finally I had to do what I have always least wanted to do, change my arm!

Why buy a twelve inch arm, especially when it costs £1,750? The rational answer is because it looks good! Like a Ferrari or a Triumph 675, an SME312 is an object of beauty that is finely honed to do its job immaculately well, and years away into the future you'll still enjoy owning and using it – as I do. Twelve inch arms not only look superb they are gorgeous to use and sound wonderful I can assure you. You've possibly read all about reduced tracking error and lower distortion, Baerwald's equations, increased mass and all that, but in practice it is mostly hot air, more of which later...


As well as looking good, with their beautiful design and gorgeous finish, SMEs feel good in the hand and the 312, as well as the 312S are second only to the remarkable SME V (and IV) in this respect (although I must say Regas feel good too, to be absolutely fair). I never quite took to the original 3012 because the lightweight tube rang, a tap on its tube with a screwdriver revealed. So the 3012, although visually appealing, never qualified in my mind as a likely inhabitant of Keywood towers. But SME's 312 arm is an altogether different animal I realised long ago,


The damping bath with adjustable paddle. It damps laterally, to cope with bouncy floors.

one I couldn't do without. The 312 has a rolled, tapered, stiff aluminium arm, unlike the 3012.


I am not going to start droning on about lower tracking distortion but I did find originally that using the SME312 arm when measuring pickup cartridge distortion gave me obviously better figures. A distortion figure of 0.8% or so, mainly second harmonic I should add, would fall to 0.5% or so from a CBS test disc, in line with what is to be expected from looking at Stephenson's modified Baerwald equations, a subject I worked through for Hi-Fi Answers in 1975 no less! So the SME312 and the geometrically similar 312S do give lower distortion than shorter nine inch arms – and that has to be good.


But I've never quite been certain that that fact alone accounted for the smooth sound that I've so appreciated over the years from my SME312. Now I suspect it is a contributory factor, a useful benefit but not the only benefit to be had from making an arm longer. If you've used nine inch Regas and SMEs like the legendary V you will  know they are hardly short of ability: think fast, clean and concise. A twelve inch tonearm is an altogether smoother and more svelte experience.


If you've never seen an SME in the flesh, then think finest Japanese camera quality, plus about ten percent. They're objects of engineering perfection. Like all SME products the 312S comes beautifully packed. It has more tiddly bits than the 312: you get screws, three special adjusting tools, two templates, two instruction books (one for the arm, the other for the damping trough) a small spanner, counterweight shims and now even a simple tracking force balance. Vinylistas will love it all, but others may balk and want their dealer to handle fitting and set-up. The arm itself is all black: the screws are black, the arm tube is black and so is the finger lift (which I choose to use).  Gold lines declare this is a 312S and a magnesium arm.


To be absolutely clear, the 312S like the 312 has a detachable headshell, to ease cartridge changing, but if you are looking for the ultimate and don't need to change cartridges regularly, the 512 is a better choice, assuming cost is of no consequence of course!

Our pictures show the arm  tube is tapered for strength and to suppress arm tube resonances. Tap it lightly with a small screwdriver and it responds with a dead 'clunk'. The arm tube needs to be non resonant if it is not to impose its own sound on the cartridge. The 312S is less resonant than its less expensive stablemate, the 312, our accelerometer tests revealed [see MEASURED PERFORMANCE] but still has a main arm tube resonant mode, albeit at a lower frequency than shorter arms, pushing it downward in frequency to the lower midrange - the other reason a 12in arm sounds different to others.


The lightweight magnesium headshell comes with an optional finger lift and clamps to the arm with a screw tightened collar. The screw passes through a depression in the arm tube to hold the collar in place and this means the headshell cannot be slid on or off the arm until the screw has been lifted out completely – and this I find is a fiddly and often difficult process. The headshell must be pushed back against pressure from the spring loaded arm contacts before the screw will easily lift out and I usually use tiny jewellers pliers to extract it. Then the small washer beneath the screw's head falls off, rolls across the floor and...

The arm is balanced by a large, rigidly clamped counterweight that is adjusted along the axis of the arm tube to set tracking force. When set, the weight is locked into place using a special screwdriver supplied. SME provide a set heavy shims that fit into the counterweight carrier to accommodate cartridges weighing from 7gms to 19gms they state, but our Goldring 1012GX weighs just 6.2gms and balances, as well as accepting 1.8gms VTF by moving the counterweight forward. Grado, Goldring and Nagaoka cartridges all have lightweight bodies and the 312S will accommodate them. Quality moving coils usually weigh more; the Ortofon Cadenza Blue I used weighs 10.4gms for example. Whilst the counterweight would balance this as supplied, it was some distance from the hub so I added weights to bring it closer, reducing the arm's moment of inertia and also structural vibration by a small but useful amount. This improves sound quality by lessening midband resonance effects.

Carrying out numerous adjustments highlighted another long standing weakness in SMEs, a simple arm rest with no lock.  Absence of a lock to hold the arm in place whilst working on it forced me to twist a piece of single core wire around tube and rest to bind them together securely to prevent the arm flying out of the rest. The review process is different and more demanding than ordinary usage I must admit, but owners who buy this arm are likely to change headshells and cartridges and need a way to lock the arm whilst doing so, to avoid stylus demolition.


The 312S slides on SME's locking base system, to adjust tracking  and arm height. It's a neat system but demands an elongated cutout in the plinth that's more difficult to cut than the simple, circular hole required by other arms, another reason it can be a good idea to get the arm fitted by a dealer. The sense of this will become even more apparent when you see the size of plinth a twelve inch arm needs; my Martin Bastin plinth is a monster weighing 42lbs. and needs its own table.


The SME312S comes with a damping trough attached, which was a surprise as I haven't fiddled with paddles and damping fluid for a long, long time. The trough has a cover and a paddle that screws up or down, to adjust the amount of damping applied.  The trough system only damps lateral arm motion; it does not affect behaviour over warps; SME told me it was to cope with bouncy floors. Our measurements show even with full damping and a slightly over filled trough the degree of damping applied is quite light, but it is there [see MEASURED PERFORMANCE].


SME now supply a silver litz wired signal cable terminated with gold plated phono plugs. They can supply a fully balanced cable with XLR connectors as an alternative, for those with an Aqvox phono stage.


The 312S keeps the broad, open soundstage and deliciously sleek sound free from the zest of shorter arms, that I have become so used to from my 312. I suppose you could poke fun and call it an "armchair and slippers" presentation against the more boisterous results from some arms, but this is going a bit far. I call it simple, clean and very refined, a sound so free of artifice it doesn't draw attention to itself, instead letting the music flow through unaltered.


The 312S in use with Ortofon Cadenza Blue cartridge, and Garrard 401 on a Martin Bastin plinth.

The 312S improves on the 312 in many subtle ways. From the off I noticed it was even quieter to use than my old 312, and that both electrically and mechanically it was deadly silent. Let me explain; not only has my 312 had a hard working life as a review tool for pickup cartridges, it had fully balanced cables attached that I had to make up some time ago for an Aqvox phono stage review. These were terminated by XLR to phono adaptors so I could use everyday phono stages including my one of choice used within this review, an Icon Audio PS3. The 312S comes with new, better cabling than before and it was deathly silent against my 312, as was the arm structure. With my usual World Audio Design 300B amplifier I was greeted by total silence from the loudspeakers, until the arm hit the playing surface – and then I realised that I had set volume too high to compensate for the silence.


Not unexpectedly the 312S sounded altogether tidier in its image construction, adding body and weight to singers and instruments, as well as greater dynamic thrust. Spoken verse in 'Clay Jug' had Jackie Leven sounding larger centre stage, his deep voice fading away into the silence of the studio behind. Instruments had more push to them too. This only became irritating with a newly remastered 200gm version of 'Teaser and the Firecat', simply because the album has been rebalanced badly, bringing to prominence poor quality, boomy bass. With 'Tuesday's Dead' this was more apparent through the 312S than the 312, making the track an even more painful listen! However, following is a bass-free 'Morning Has Broken' and here the 312S showed its mettle, sitting Cat Stevens up on centre stage in the smoothest, most fully embodied form I have ever heard. Here, all the strengths of the 312S came together I feel: nothing could quite match the silky clean rendition, quite uncoloured and seemingly free from – well – that residual greyness to whites that all shirts suffer if they are not washed in Persil!


Rear view, showing counterweight adjustment and lock screws, damping bath at right and skating force adjustment at left.

I have to admit to feeling very smug at this point because as I mentioned in my Ortofon Cadenza review (August 2009 issue) the Blue is an amazing device and whilst it worked well in the 312, in which it was reviewed, the 312S squeezed even more from it. Coupled with the Icon Audio PS3 phono stage; another 'must'; the three items worked together superbly. What the 312S has is the easy clarity and relaxingly natural presentation of the 312, with improved midband dynamics and a stunning degree of electrical and mechanical silence. It allows a cartridge to work better and spinning 'Down on The Corner' from Willy and The Poor Boys had cow bell spring from far right as the track kicks off, followed by Fogerty's gravelly voice centre stage, his shout into the microphone stronger than ever. As guitar kicked in with real power behind it, this 1970 recording displayed dynamic contrasts to shame CD. But then, this is what modern vinyl playing equipment can do when it is highly developed.


Spinning Alison Goldfrap's 45rpm, 12in single 'Ride A White Horse' had the 312S staying tight and composed at low frequencies, as did very heavily cut 'Led Zeppelin Dirty Funker Remixes'. This is Garrard 401 territory, with metronomic heavy bass pounding from the loudspeakers, the 312S and Ortofon unphased by absurdly large low frequency cuts able to snap the elastic of belt drives.


The SME312S is a great twelve inch tonearm. It is a delightfully smooth and clear sounding platform for any quality cartridge, especially today's top moving coils. A deep, silent soundstage studded by bold images from a cartridge firmly supported are its striking features. SME's renown standards of engineering and finish add to the overall impression, making for an arm that is aurally and visually a delight to own.


Our vibration analysis of the magnesium 312S, made with a Bruel & Kjaer accelerometer, shows a basic modal peak at 200Hz, a relatively low frequency as arms go due to the structure’s extra mass. This shifts colouration down the audio band, away from the middle frequencies where shorter, lighter and stiffer arms resonate, an unappreciated feature of 12in arms. Light stiff tubes resonate in the 400-1,200Hz region, where the ear is more sensitive. Our analysis clearly shows that the standard 312 arm has a narrow but high 0.3g peak at 800Hz that’s far less evident on the 312S and it is cleaner in general around 1kHz, its main advantage over the 312. Surprisingly, in spite of the use of magnesium the main arm resonance at 200Hz remains unchanged in frequency and level from the standard 312, suggesting the basic resonant properties of the structure have changed little. For the purposes of comparison both analyses were made with our usual Goldring 1012GX test mule, an MM cartridge with two-part body due its removable stylus.


A third analysis was made with the cartridge used in the review’s listening tests, an Ortofon Cadenza Blue. This is an MC with a solid, non-resonant one-piece metal body. At 10.4gms it is heavy so to bring the counterweight closer to the bearing hub extra weights were added to it. The analysis shows the all-round stiffer structure behaves better in the midband and treble, although interestingly the same basic arm vibrational modes are still present. The main arm tube mode has moved down a little in frequency to just below 200Hz due to the extra cartridge and counterweight mass. By current standards the Ortofon cartridge in the 312S arm is affected (coloured) little by midband and treble vibrations so their mutual performance reaches high standards. The stubborn presence of the 200Hz modal peak is less impressive but at 0.15g it is less than the 0.3g or so of many arms. The 9in SME V one-piece magnesium arm exhibits no such vibrational modes, and for those who want better than the 312S with its removable headshell, SME now offer the one-piece 512, an SME V stretched to 12in!


Finally, the affect of the damping bath was also measured using a 3Hz-40Hz lateral modulation gliding tone from a Feickert Analogue test disc. Our analysis shows (background) no damping at all, and full damping applied with the paddle screwed right in. The arm / cartridge resonance peak at 7Hz was reduced from 9dB to 6dB, so damping is light but has effect (at an ambient temperature of 25 degrees C). Re-measurement of arm vibrational modes with our accelerometer showed this form of damping has no affect upon the behaviour of the structure.


Summarising, the 312S is an improvement upon the standard 312 arm, having a cleaner midband. The arm’s first main resonant bending mode remains unchanged however, at a low 200Hz. The arm is massy (heavy) compared to 9in types, but since cartridge weight constitutes 40% or so of the final effective mass figure for arm+cartridge, this isn’t overly consequential. With a good, modern MC cartridge the 312S performs well by today’s standards, having a very clean midband, if not as well as the best one-piece designs with non-removable headshells. However, it generates lower tracking distortion than shorter arms. NK

SME 312S


SME 312S + Cadenza Blue


SME 312


SME 312S damping


verdict five globes

Beautifully engineered twelve inch arm that is a delight to use and delivers  a great sound.

SME 312S 12in ARM £1,750

SME Ltd.

+44(0)1903 814321


- smooth and serene sound

- stability, focus and detail

- exquisite feel


- fiddly headshell removal

- no arm lock

- difficult to install



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