Belt-driven turntable with electronic speed control
Made by: Wirth Tonmaschinenbau GmbH, Altdorf, Germany Supplied by: Elite Audio Ltd, Fife
Telephone: 01334 570 666
Web: www.acoustic-solid.com; www.eliteaudiouk.com
Nestling in the foothills of the Swabian Jura, southern Germany, the tiny municipality of Altdorf is home to some very big turntables from the boutique Acoustic Solid brand
Review: Adam Smith Lab: Paul Miller
Weighing 22kg, with a good deal of this mass being platter, the Wood Round MPX is the latest turntable from German company Acoustic Solid and fits neatly into its seven-strong ‘Classic Line’, sitting above the Classic Wood but below the Wood Referenz. The deck’s appearance, with its three pillars, echoes the company’s top ‘Aluminium Line’ models and also differentiates it from the rectangular decks that make up the rest of the Classic Line.
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The turntable is offered in both ‘MPX’ and ‘Black’ versions, the difference being the outward finish of the plinth. For the MPX, the layers of plywood that make up the 100mm-thick base are left on show and varnished to a pleasing degree while the Black has a deep gloss black paint job.
At present, UK distributor Elite Audio is only offering the MPX version as part of two complete packages. The first costs £ and includes an Acoustic Solid WTB 370 tonearm – essentially a modified Rega RB220 – with an Ortofon Quintet Red MC cartridge. Alternatively, Acoustic Solid’s WTB 213 carbon tonearm may be specified, taking the price up to £.
The turntable’s plinth is probably the daintiest part of the assembly. It sits on three adjustable spiked feet that locate into three rack-protecting spike cups with felt undersides. A metal outrigger is bolted onto the plinth and this, in turn, supports the armboard. One bolt does the job, and not only does it hold it in position tightly, but this arrangement also means the armboard can be rotated to set optimum tracking angle for any arm used.
RIGHT: Top-down view highlights the deck’s three ‘legs’, outrigger for the Rega-sourced tonearm, separate motor pod [far right] and electronic speed controller [near left]. The latter is fed from a 32V DC (switch mode) PSU
The platter is machined from a solid billet of aluminium to a thickness of 60mm and tips the scales at 12.5kg. Leather and Perspex mats are supplied to top this off but, as per previous Acoustic Solid models I have reviewed, I found the deck to sound better with just the leather mat in place.
The platter is driven around its periphery by twin belts from the freestanding motor pod. Acoustic Solid describes the deck as ‘string drive’ but the belts are pliable and not unyielding as a true string drive would be. As a result, there is no fixed location for the motor – a set-up I’m not generally a fan of since it gives rise to the possibility of performance variation if belts are pulled too tight or left too loose. However, the Wood Round MPX appeared to be unusually immune to the positioning of the motor, so you won’t hear any complaints here!
The motor pod is a chunky affair with at least half of its internal filling consisting of metal to add weight. The motor itself is a 24V synchronous AC type made by Schneider Electric and is a pleasingly torquey item that starts the platter spinning surprisingly easily, despite it being barely larger than the pulley that sits atop its spindle on the outside.
ON THE BUTTON
The motor is driven from the control unit [see inset shot, p61] which takes a DC input and uses an 8-bit microcontroller to generate the necessary variable frequency supplies. Speed change is achieved at the touch of a button while incremental speed adjustment is brought about by using the controller’s up and down keys. This is handy because the deck’s speed has a tendency
to ‘wander’ [see PM’s Lab Report, p63]. I am used to increases in platter speeds with old idler-drive decks as the greases and oils warm up, but the Wood Round MPX often seemed to need a tweak of one ‘step’ in either direction every now and then.
The WTB 370 tonearm is based on the Rega RB220, which is the latest version of the UK company’s evergreen classic. In fact its lineage can be traced back to the original RB250. Acoustic Solid has modified it by substituting an aluminium counterweight and stub for the plastic original. This has been a common update throughout the life of the Rega arm variants and adds a touch of glamour as well as imparting a subtle improvement in sound quality.
To fit the arm, Rega’s non-adjustable and frankly fiddly three-point mount bolts into a beautifully machined tube. This fits into a collar on the deck, making set-up
‘The fine detail ensured strings were both vivid and lifelike’
easy while adding the ability to tweak VTA in way that is simple yet highly effective. Finally, the Ortofon Quintet Red MC is easily fitted as is setting the armboard mounting for correct tracking angle.
Packaging of all the elements that made up the deck was first class, but the superb quality imparted by both this and the deck itself was a little undermined by the series of A4 photocopied pages (in German only) that passed for a manual. Nothing else is currently downloadable online, so hopefully this is something distributor, Elite Audio, will look into.
© BRING IT ON…
I set the deck up on the twin-layer damped glass shelf of an Atacama Equinox rack and hooked it up to an Anatek MC-1 phono stage, Naim Supernait amp and PMC Twenty5.24 speakers [HFN May ’17].
ABOVE: Also available in gloss black, the polished plywood chassis is supported on adjustable spiked feet. The chromed platter has a combination leather and 5mm Perspex mat
Solid by name, solid in sound – I couldn’t help being amused at how the company’s name is so appropriate when it comes to describing the presentation of the Wood Round MPX. This is no thundering, out of control, bass monster by any means. Rather, it rewards with a quietly firm sense of authority and confidence. It’s a turntable that, when the going in the groove gets tough, seems to give you a wink to suggest: ‘Don’t worry – I’ve got this’.
Consequently, there is never any fear of upsetting it with any particular musical style. Soaring orchestral crescendo? No problem. Banging electronica? Great fun. The subtle whisper of an a cappella female vocal? Bring it on. The Wood Round MPX is very well balanced. And it’s a turntable as equally capable of hammering its message home when required, as it is sitting back and taking it easy.
However, these comments apply to the deck with only the leather mat in place. The Perspex mat made the midrange shouty and added a coarseness to the treble that did the sound no favours. I dispensed with it for reviewing purposes.
This sense of sonic solidity was accompanied by a decent level of bass, but this was far from being all quantity and no quality. The bass line from Maxi Priest’s ‘Suzie – You Are’ from his Maxi LP
HOME SPUN VINYL
Acoustic Solid was founded in 1997 by Karl Wirth who began building high-mass turntables in a garage belonging to his parents. Karl designed his first deck using mechanical engineering principles he had learned as a production manager
at an automotive firm, and as word spread he soon found himself making turntables for friends. Demand increased so swiftly that in 1999 the search for a proper manufacturing facility began and in 2001 the company relocated to Altdorf, with international distribution commencing in 2002. By 2006 production had ramped up to such a degree that further expansion and new machinery was required, the company purchasing its first CNC machine four years later with a second arriving in 2011. The factory in Altdorf was then expanded further and the company resides there to this day.
ABOVE: Dual-belt drive brings the platter up to speed within 8secs while the leather/ Perspex mat and LP weight combo are very effective at quelling low-level vibrations [see Lab Report, adjacent]. Motor connects to the speed controller via a flying lead
[10 Records DIX64] was deep and powerful yet skipped along with a lightness of touch that seemed at odds with the large lump of metal spinning in front of me. Each bass note was clearly defined and started and stopped with precision.
Further up the frequency range, the Wood Round MPX maintained its aura of quiet confidence by deftly capturing the fine detail of both instruments and vocalists. This meant that strings, in particular, were vivid and gloriously lifelike. Spinning ‘Fell Down Hard’ from Kathryn Williams’ album Little Black Numbers [Snowstorm STORM008LP] demonstrated this perfectly. The acoustic guitar was expertly defined while the backing cellos sounded both rich and fulsome.
The Wood Round MPX also made a fine job of placing Ms Williams right in the centre of the action, though I was aware of a lack of projection. Rather than push her vocal into the room, the deck positioned it behind the plane of the loudspeakers. There was still a good sense of depth, but the overall effect was like standing up in an auditorium then moving half a dozen rows backwards.
This was the case with other recordings during my time with the deck, which eventually saw me swapping the supplied arm for an Inspire X100 (another hot-rodded Rega design). This pulled things forward by a good amount leading me to conclude that while the WTB 370 is a fine budget tonearm, it was the weak link here.
With the WTB 370 back on board, though, it was hard not to be impressed by other aspects of the combination’s performance. At the top end, the arm’s neutrality and the slight sparkle offered by the Ortofon Quintet Red added up to bags of detail presented crisply and tidily. The gently strummed electric guitar that begins ‘So Real’ from Jeff Buckley’s Grace LP [Simply Vinyl SVLP 0077] had a menacing intent to it and Buckley’s vocals themselves were gloriously heartfelt. And when the track moved up a gear, the Wood Round MPX exhibited no sense of strain or compression, rising to the challenge of the particularly explosive cymbal strike that appears later in the track with ease.
Finally, I have to offer one last paean of praise for the Wood Round MPX. It’s been a while since I have heard a turntable so quiet between tracks with one of the lowest levels of general vinyl surface noise I have encountered in a long time. This only served to ensure recordings sounded even more dynamic and it speaks volumes for the high quality of the drive system and bearing.
Acoustic Solid has done it again with the Wood Round MPX turntable. The plinth layout adds a dash of style while the engineering ‘under the bonnet’ is top drawer. The package with the WTB 370 arm and Ortofon Quintet cartridge is sonically very well judged yet the turntable itself will give even more if treated to an arm upgrade when the mood or funds arrive. Solid by name, it’s a solid choice too.
ACOUSTIC SOLID WOOD RND. MPX
Described as a ‘string-drive’ by Acoustic Solid, its 60mm-thick chromed alloy platter is in fact driven via two continuous silicone rubber belts. Unlike a thread drive, these circular-section belts are extremely flexible, allowing the separate motor pod to be parked in a wide variety of positions. With other decks having this arrangement, the precise motor position and belt tension typically has an impact on wow and flutter. Here, however, placing the motor in over 15 different positions around the deck, the belts from slack to taut, the peak W&F remained stubbornly high at 0.45% (best case) with a significant near-DC drift evident [see Graph 1, below]. Acoustic Solid is using an AC synchronous motor here, governed by a ‘microprocessor controlled PSU’, but this degree of low-rate speed drift (still inaudible to many listeners) is more common with DC motor solutions.
While speed stability is disappointing, Acoustic Solid’s ceramic bearing is first-rate, offering a low -69dB rumble (direct), reducing still further to -70.9dB through-the-groove and -71.8dB with the record weight in place. That alloy/leather/ Perspex sandwich seems genuinely effective! Furthermore its WTB 370 arm, with alloy counterweight and thread, looks to benefit from a somewhat cleaner and more distinct series of resonances than Rega’s donor. The main tube mode occurs at 100Hz [left hand edge of Graph 2] with harmonics and twisting modes clearly defined at 195Hz and 300Hz. The high-Q mode at 550Hz, and minor harmonics, seem to be linked to the headshell but are all swiftly damped. As with the Rega RB220, its excellent bearing tolerance ensures there’s no perceptible play while friction is <20mg in both horizontal and vertical planes. PM
ABOVE: Wow and flutter re. 3150Hz tone at 5cm/sec (plotted ±150Hz, 5Hz per minor division)
ABOVE: Cumulative tonearm resonant decay spectrum, illustrating various bearing, pillar and ‘tube’ vibration modes spanning 100Hz-10kHz over 40msec