Yamaha NS

With speakers of this vintage – even a pair in such immaculate condition as these – there is always a question mark regarding ageing effects. So when I plotted the forward frequency responses of this pair of NS-1000Ms [Graph 1, below] measured at 1m on the tweeter axis and saw the premature treble roll-off, I suspected they were not entirely as in their youth. But checking back on Yamaha's published responses, they too show a marked roll-off above 10kHz. The other notable departure from flatness, the dip at 4kHz, is tempting to ascribe to the crossover between the midrange driver and tweeter but as this occurs at a high 6kHz there may be a different cause – and it's possible that it could be eliminated or at least ameliorated by careful choice of measurement/listening axis.

Even with these departures, the response error for one speaker is a fine ±2.6dB (300Hz-20kHz), the ±4.3dB of the second reflecting its earlier treble roll-off. (Ignore the apparent low-frequency roll-off below 400Hz, which is an artefact of the measurement process.) Pair matching over the same frequency range is poor at ±2.3dB but again this can be laid at the door of the high-treble disparity. Below 10kHz it reduces to ±1.4dB. Yamaha claimed 90dB sensitivity for the NS-1000 which accords well with our measured pink noise figure of 89.7dB. Despite this it is easy to drive, in a modern context, with a minimum modulus of 4.6ohm and minimum EPDR of 2.3ohm at 70Hz. Given that the impedance peaks at 39Hz, bass extension may well be a little better than the measured 53Hz (–6dB re. 200Hz). Finally, and despite those beryllium domes, the CSD waterfall [Graph 2, above] still shows some low-level treble resonances. KH

Sensitivity (SPL/1m/2.83V – Mean/IEC/Music): 89.7dB / 89.7dB / 89.6dB Impedance modulus: minimum & maximum (20Hz–20kHz): 4.6ohm @ 99Hz / 30.1ohm @ 39Hz Impedance phase: minimum & maximum (20Hz–20kHz): –55° @ 53Hz / 39° @ 27Hz Pair matching/Resp. error (300Hz–20kHz): ±2.3dB / ±2.6dB / ±4.3dB LF/HF extension (–6dB ref 300Hz/10kHz): 53Hz / 21.8kHz / 18.7kHz THD 100Hz/1kHz/10kHz (for 90dB SPL/1m): 0.3% / 0.1% / 0.1% Dimensions (HWD) / Weight (each): 675x375x328mm / 31kg