I've had my SHL5 for a few months and like them very much - one of the best speakers I've heard including those several times more costly. The transparency rival that of electrostatics & the musical involvement is enthralling .
But while listening to some CD's which come out a bit lean (I prefer warmer sound) I decided to fiddle around with the port by stuffing it with newspapers, for a start, and that certainly warmed up the sound. The tradeoff is a slight loss of transparency but not details. Wonder if others have gone down the same path and care to share their experience.