I have been to homes and shows where I was asked to listen to some really bad loudspeakers - kit that is so far away from accurate that it's laughable. And yet I can still hear differences in cables and electronics swapped out of those systems once I have become accustomed to the sound.
So if the speakers are bad enough to make me wince, why are they good enough to hear minute changes in electronics and cables in the chain?
Our ear/brain mechanisms are able to fairly quickly build a model of what we're listening to and adapt to gross misrepresentations of sounds we're familiar with. This is how we can still identify the sounds of a violin vs. a cello even under the worst circumstances in loudspeakers.
And what's really interesting is that once you've adapted to the auditory model any subsequent change in the chain feeding the loudspeaker can readily be identified, even with bad loudspeakers. Human skill sets are tuned to pick out minute differences regardless of the situation - it's one of the ways we survived as a species.
So bad loudspeakers are ok for discerning differences in the reproduction chain - but that doesn't mean you have to like them or own them.
