I use a bassboost on my FiiO E 10 for my Sennheiser HD 600 s . They are pretty neutral and I think the bass boost from the FiiO is just what they need to sound good to me . EQ isn ' t bad , but some software EQs like on iTunes or whatever are pretty bad . If it sounds good to you , though , hey , more power to you . IMO as long as you hear everything in the music , it ' s all good . I know some people will say the neutral flat is the way to go , but there are so many variations between headphones and equipment it ' s nearly impossible to get exactly what the artist intended . Do what feels good to you . <| sep |> At a top level i . e . defining a group over a set A this doesn ' t really make sense what is B ? You usually see closure of multiplication appear when talking about subgroups i . e . we want the restriction of multiplication to be confined to the subset of A we are focussing on .