Listening levels being relatively matched is very important for the mentioned reasons. What the origins of the method and reasoning are, is a long drawn out explanation.
eg, when testing cables the listening levels should never allowed to change. Switch to different input or mute whens swapping cables...but never change levels.
Other methods like long term are part of the equation (and fundamental-critical!), but direct comparisons - level match. Then try both again at another listening level. And so on.
eg, when testing cables the listening levels should never allowed to change. Switch to different input or mute whens swapping cables...but never change levels.
Other methods like long term are part of the equation (and fundamental-critical!), but direct comparisons - level match. Then try both again at another listening level. And so on.