Article Index
Yamaha NS-F901 Soavo
page 2
page 3 Conclusion
page 4 Measured Peformance
All Pages



Our frequency response analysis shows a nice even result right across the audio band, with a small amount of lift around 6kHz, enough to add just a fraction of ‘light’ onto the sound, without obvious brightness. There is absolutely no sign of any crossover dip around 3kHz that can soften the sound, and detail delivery will be strong. This was an optimum result, with our measuring microphone on the axis of the top bass midrange unit. Moving it up or down introduced phase dips, suggesting phase alignment of the drivers wasn’t perfect – a surprise considering Yamaha’s technical ability and high technical standards. This was attributable to wide driver spacing, a styling imposition; high frequency drivers need to be very close, less than half a wavelength.  

   Bass extends down to 50Hz, a port frequency of 34Hz working to support lower bass output. The NS-F901 goes low and should deliver firm deep bass, these results suggest. Because there is no bass peaking, quality will be good and balance accurate.

   Sensitivity was very high, measuring a good 90dB sound pressure level from one nominal Watt (2.8V) of input – and with a measured impedance of 7 Ohms overall this was a real Watt, meaning the Yamaha’s are efficient. They need little power to go loud, 40 Watts being plenty enough for high volume. The impedance curve is normal enough, with twin residual and reactive peaks around port resonance that these days are commonly tuned out, a trick Yamaha have missed. 

   A 200mS decay analysis showed the speakers to be clean across midband and treble, but suffering box overhangs below 200Hz that correlate with bumps in our frequency response analysis. The box is quite lively, a decay map showing it is relatively ‘hot’ in the bass regions, likely to add fullness at least to bass. 

   The NS-F901 measured well, if with minor flaws. It is, all the same, accurate, has low coloration and is very sensitive, all properties that will ensure a high standard of sound quality. NK





Green - driver output

Red - port output








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