Mo,

A mate of mine bought a pair of 780s about 2 and a half years ago. Now he never plays music really loud cos he lives in a new semi with thin walls and has got a couple of small kids etc. Anyhoo, about six months ago one bass driver started to distort/crackle then go off almost completely. If he then turned up the volume a bit it would come back to life for a short while. After a couple of weeks of this it eventually went bang(sparks were seen shooting from the cone centre, followed by a bit of smoke :MILD: 

Back to the dealers they went, who told us that another customer that day, and one last week had returned their 780s for exactly the same reason, and that they had seen one or two in the past with this fault as well.

The dealer ordered two new drivers from Mission which were updated versions apparently(i reckon Mission know whats going on here), and fitted them himself at the shop FOC.

That's been a few months ago and no probs yet, but as i say he doesn't play em loud so i don't trust them and would get rid if i were you, once repaired of course.

Hope this helps.

Cheers.

MM.

PS. Forgot to mention, on the return visit to collect said 780s, i went along to listen to a Well Tempered deck with my usual dealer, and he told me that they have seen quite a few Missions with blown drivers over the years, but never Dynaudios, which kinda fits in with what Technobear said. I'd be looking at a pair of ex dem 42/52s if i were you. A bit dearer i know but i doubt you'd ever have to change them again.