B&O Beogram 4002 Turntable Lab Report

Lab Report

Unlike other B&O decks of the era, the 4002 did not include an illuminated strobe to assist in the fine-tuning of its speed. However, with the little adjustment dials (visible in our pictures at either end of the black strip above the function keys) set to their default position, the 4002's absolute accuracy was a mere +0.1% adrift. This is a fine result for a vintage deck equipped with an original Matsushita DC motor unit. And it's here we see the biggest difference with the older 4000 model [HFN Jun '14] whose wow and flutter clocked in at 0.12% (peak-wtd) – a mix of ±3Hz low-rate and ±45Hz high-rate components traded here for a significantly lower 0.2% peak wow and a peak flutter of ~0.05% centred around a cluster of sidebands at ±20Hz [see Graph 1]. The latter also appear on the unwtd rumble spectrum [not shown here], along with modes at 62Hz and 128Hz, but the lighter platter still helps the 4002 best the 4000's rumble by ~1dB at –68.3dB (DIN B-wtd). A through-bearing figure couldn't be obtained as the optical wand fouled the rumble-coupler.

The short, parallel-tracking tonearm may offer a very low 5g effective mass (compatible with the ~25cu compliance of the MMC20EN fixed-coil/moving-iron pick-up tracking at a mere 1.2g) but, as we saw in the Beogram 4000, its square-section tube still has a relatively low 120Hz main bending mode. This low-Q mode is broadly distributed across the bass spectrum [see CSD waterfall, Graph 2] but is accompanied by higher-Q harmonics and torsional modes at 280Hz, 360Hz and 460Hz. The elegance of the structure is reflected in the relative cleanliness of this waterfall spectrum, betraying a single, low amplitude, mid/high frequency mode at 1.1kHz. 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 33.35rpm (+0.1%)
Time to audible stabilisation 3sec (time to cue, ~10sec)
Peak Wow/Flutter 0.02% / 0.05%
Rumble (silent groove, DIN B wtd) –68.3dB
Rumble (through bearing, DIN B wtd) See lab report
Hum & Noise (unwtd, rel. to 5cm/sec) –60.2dB
Power Consumption 17W
Dimensions (WHD) / Weight 490x100x381mm / 12kg