If your speakers are a good couple years old or more, more than likely the ferrofluid in your tweeters has all but dried out. Check with Quad to be sure your tweeters use ferrofluid.
If so, to refurbish, you may do the operation yourself, once you learn how to disassemble the tweeters, clean out the old residue and add some fresh fluid and reinstall. Or, you can remove the tweeters and send them to Quad (or to another speaker repair place you trust) and let them do that, if they do that sort of thing, many speaker companies do.
Being a 'quart low' on fluid robs teeters of their power handling and there is a profound high end roll off. You don't really have to worry about it if you don't really listen Rilly loud, but the fluid keeps the voice coil cool (to allow more power), so if you push the volume too hard before the fix, you could blow them up.
But the loss of highs is only temporary, top them off and they'll be good as new.
If so, to refurbish, you may do the operation yourself, once you learn how to disassemble the tweeters, clean out the old residue and add some fresh fluid and reinstall. Or, you can remove the tweeters and send them to Quad (or to another speaker repair place you trust) and let them do that, if they do that sort of thing, many speaker companies do.
Being a 'quart low' on fluid robs teeters of their power handling and there is a profound high end roll off. You don't really have to worry about it if you don't really listen Rilly loud, but the fluid keeps the voice coil cool (to allow more power), so if you push the volume too hard before the fix, you could blow them up.
But the loss of highs is only temporary, top them off and they'll be good as new.