I guess we have to thank james444 - a head-fier I quite like and respect, BTW - for the introduction of the term "timbre", a term that has somehow become fashionable (almost mandatory now when discussing good SQ) and adopted by a few H-fiers in the last few months. Apparently, DD IEMs offer the best "timbre". My very limited experience tells me this isn't necessarily so but, you know, the word gets round and then certain things suddenly become facts - much like the not so infrequent view that custom IEMs destroy all universals when it comes to SQ. When james444 'introduced' the term I didn't have a problem with it but now, to me, it's almost become like the term 'audiophile', a term that makes me cringe every time I see it.
Uh-oh, I wasn't aware that using the term "timbre" would inflict such hardship on trusty fellow members. If I'd known beforehand I certainly would have settled for more established and useful terms like "accuracy" and "balance". Anyway, let me state in my defense that the term has been right here in this Head-Fi glossary since 2007.
On a more serious note, IMO there's no cure for the inflationary (mis)use of certain terms, so we'll just have to live with it. But tbo, reading in some posts that IEM A have more timbre than IEM B makes me cringe, too.
Speaking of which, I don't think I would have bought and subsequently given away several BA IEMs (even pretty expensive ones like the CK100) just for the sake of proving a point. And I'm not claiming that DDs like the FX700 or EX1000 have more natural timbre than all BAs, but definitely than the ones I've heard. However, some BAs like the vented Final Audios or even the SM3 are pretty good, so I've not given up hope yet. In fact I'm pretty tempted by the W4 right now. But I'm certainly not going to venture into customs territorium unless I've heard a pair of universal BAs that win me over in this regard, since I'm not trusting the logic by which custom BAs should magically have more natural timbre than their proper fitted universal counterparts.