Hi Simon, thanks for that. They're closed box and I just had a piece of luck with them: pulled the caps out (they were secured with vast amounts of glue) and they were printed '3.3µF' on the backsides - had some polypropylenes at that value and I swapped them, and they're now sounding great! (airier, perhaps slightly lighter in balance, but certainly less 'degraded' and a little more informative). So worthwhile.