Acoustic Solid Wood Round MPX Turntable Lab Report

Lab Report

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


Wow and flutter re. 3150Hz tone at 5cm/sec (plotted ±150Hz, 5Hz per minor division)


Cumulative tonearm resonant decay spectrum, illustrating various bearing, pillar and 'tube' vibration modes spanning 100Hz-10kHz over 40msec

Turntable speed error at 33.33rpm 33.25rpm (–0.25%)
Time to audible stabilisation 8 seconds
Peak Wow/Flutter 0.20% / 0.25%
Rumble (silent groove, DIN B wtd) –70.9dB (–71.8dB with clamp)
Rumble (through bearing, DIN B wtd) –69.1dB
Hum & Noise (unwtd, rel. to 5cm/sec) –58.1dB
Power Consumption 2-4W
Dimensions (WHD) / Weight 310x190x310mm / 22kg
Price £5950 (with WTB 370 arm and Ortofon MM)

Wirth Tonmaschinenbau GmbH
Altdorf, Germany
Supplied by: Elite Audio Ltd, Fife
01334 570 666