22-02-2017, 10:59 AM
100 watts per channel isn't really all that much if you're using high quality loudspeakers that are inefficient. I have many (!) pairs of speakers that vary between 83 and 87 dB/W at 1m. And 100 watts is only 20dBW, so maximum levels from each at 1m would be 103 and 107dBSPL. Obviously, I don't sit that close to them.
But main factor is the programme material. Ignoring modern hyper-compressed stuff, well-recorded music has a PMR (peak to mean ratio) of at least 20dB. That means that if you adjust the volume so the amplifier is just on the verge of clipping on the peaks, the average level is only 1W. And when we as humans assess loudness, we're more concerned about the average level rather than the peak level.
Loudspeaker designers are very happy about this scenario. Given that more than 95% of the electrical energy is converted to heat, it's a good job that tiny voice coils aren't asked to dissipate >95 watts of heat when driven from a 100W amplifier.
Flip this argument on its head - how come you can fill a room with a 3 watt Mullard amp? Partly because you're hopefully using more efficient speakers, but mostly because when you turn it up, the thing is in clipping. When playing pure tone, we are quite sensitive to clipping, but when playing music, we're surprisingly tolerant to it. For it to sound bad, clipping actually has to be gross.
More efficient speakers might make better use of watts, but nothing is free, and they usually have "interesting" measurements. Luckily, power is cheap.
The sad irony for hi-fi designers is that most people judge loudness by the level of distortion, and if you demonstrate a powerful amplifier, they don't think it's all that loud because it's clean and undistorted. People are used to distortion, and quite like it. Of course, people especially like valve distortion, which is where the fallacy about "valve watts" being better than "solid-state watts" comes from.
All this explains why hi-fi amplifiers are rarely fitted with clipping LEDs, which of course are the norm in professional applications.
But main factor is the programme material. Ignoring modern hyper-compressed stuff, well-recorded music has a PMR (peak to mean ratio) of at least 20dB. That means that if you adjust the volume so the amplifier is just on the verge of clipping on the peaks, the average level is only 1W. And when we as humans assess loudness, we're more concerned about the average level rather than the peak level.
Loudspeaker designers are very happy about this scenario. Given that more than 95% of the electrical energy is converted to heat, it's a good job that tiny voice coils aren't asked to dissipate >95 watts of heat when driven from a 100W amplifier.
Flip this argument on its head - how come you can fill a room with a 3 watt Mullard amp? Partly because you're hopefully using more efficient speakers, but mostly because when you turn it up, the thing is in clipping. When playing pure tone, we are quite sensitive to clipping, but when playing music, we're surprisingly tolerant to it. For it to sound bad, clipping actually has to be gross.
More efficient speakers might make better use of watts, but nothing is free, and they usually have "interesting" measurements. Luckily, power is cheap.
The sad irony for hi-fi designers is that most people judge loudness by the level of distortion, and if you demonstrate a powerful amplifier, they don't think it's all that loud because it's clean and undistorted. People are used to distortion, and quite like it. Of course, people especially like valve distortion, which is where the fallacy about "valve watts" being better than "solid-state watts" comes from.
All this explains why hi-fi amplifiers are rarely fitted with clipping LEDs, which of course are the norm in professional applications.
