Yep only as good as the weakest link. If you can hear 12-13k you must be able to hear below that, so maybe you need new headphones.Thanks for the input (so far) everyone! Damn dogs. Tom, I tried your audio test files. I could easily hear 20HZ but only started to hear the upper frequencies somewhere between 12k and 13k but I suppose my results were effected by the headphones I was using. I'll try another pair later.
Tom N.