Sennheiser HD 700s need a lot of break-in?

I appreciate all the helpful responses. For now I'll listen to my 600s while a burn-in CD plays on the 700s. I don't recall the 600s needing this much break-in but the Cardas cable did. It's interesting that none of the reviews on 700s mentioned break-in. Surely they did not review them straight out of the box. If and when Cardas comes out with a cable it will likely be well over $300 - a third the price of the 'phones. One would think on a $1,000 headphone a great cable would be standard. Oh well I won't judge too soon. I'll let the break-in run its course and post my findings.

Well after about 150 hours they do sound better but I'm just not sure it's the headphone for me (I've also tried and sold the AKG's). It's quite different than the 600s. Physically they're great - light and comfortable. But sonically I think I prefer the 600s. Certainly that could change after more break-in time and a different cable. I'm sure Cardas will have a cable out soon and I'm sure it will make a big difference. But I think for now I will just be content with the 600s a while longer.

If you listen, say, an hour a day thru phones, you can let us know NEXT Christmas how those babies really sound.

Why don't you guys just play it and leave it playing for 10 days? You'll be 240h into break in at that point..