Thanks, taoster and bootman! (So, is the tuberolling really that urgent?)
News from the Etymotic front: After first being convinced of the stock filter's high-frequency extension, by and by I found the treble a bit too strident. So I tried some other filter material than foam, which has proven to give a slightly mellow characteristic. I tried it with lambswool – and that's exactly the right stuff! The greater the density, the less treble, but with less roll-off tendency than foam. Now the treble is ideally balanced, marvellously airy and accurate at the same time.