OK, but not sure about this.
A watt’s a watt, or is it? The technical definition of a watt is a unit of power, equivalent to one joule per second, corresponding to the power in an electric circuit in which the potential difference is one volt and the current one ampere.
To get a watt out of our audio amplifier we need voltage and current. Once we have that unit of power the magnetic motor system in the drivers converts that energy into movement that compresses the air and we hear sound. A watt is a watt, yet not all stereo amplifiers at the same wattage sound the same. So what’s going on?
Amps with identical wattage ratings sound different because moving watts are different than steady-state watts.
If we were instead looking at wattage steadily powering a lightbulb we’d not really see any difference if that watt was produced by hydro or steam power. But in audio, we don’t listen to steady-state tones. Instead, we’re listening to rapidly moving air pressure. How that air moves defines what we hear.
Thus, we’d be more accurate to suggest that the motion of watts is what matters, not the watt itself.
Measurements can explain certain things regarding how an audio component might sound, but to design just around measurements is usually a bad idea. Paul goes into this a bit more deeply.
Beware the measurements
For readers of this blog, it will come as no surprise my thoughts and attitudes on measurements of audio equipment. Yes, measurements are important, but only when in concert with listening—and then too only if you look deep into those measurements to find out how/why what you measure sounds the way it does.
If you’re interested in diving deeper into this subject there’s perhaps no better way than to sit down with an experienced designer and have them take the time to explain how and why measurements simply do not tell you the whole story.
Take for example global feedback in an audio amplifier circuit. If we have an amp circuit with relatively high levels of distortion, we can simply wrap the output back to the circuit’s input and voila! lower distortion. The feedback is a fix-it mechanism correcting for the failings of an amplifier’s design. But at what cost? Nothing in engineering is free. Loads of negative feedback offer low distortion figures but at the same time, harden and constrain the sound. Knowing this is invaluable to a designer who can then ask the question, “what if we don’t have distortion in the first place?”
If you’re interested in diving deep with a designer, here’s your chance. Our own Darren Myers, one of the brightest and best engineers in the industry, spent a good hour and a half with John Darko in a great podcast titled, Beware the Measurements.
Have a listen and enjoy.