Ken, the anechoic sensitivity rating on the M60s is 89dB per 1 watt at 1 meter. Taking into account both direct sound and room reflections, sound level in typical rooms at home drops off at about 3dB per doubling of distance(e.g.,Toole, p.60). At a typical listening distance of around 10' the sound level for 1 watt would be about 85dB. 10dB lower would use a tenth of a watt(95dB would use 10 watts, 105dB would use 100 watts).

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Enjoy the music, not the equipment.