I've heard some very good headphones referred to as 'grainy', and other headphones referred to as having a 'black background' - which apparently means free of grain.
'Grainy' sounds a negative connotation to me, yet I'm not sure that having a 'black' or 'grainless' sound is entirely good either - as it may be smoothing over the grain that is meant to be there.
This terminology confuses me.
Could someone explain what a grainy sound is? And is it always a bad thing? Likewise, is a black, grainless sound always a good thing? Are there some headphones that are grainy but overall better than grainless headphones?