I got that too with 2 of my pairs. It's bizarre. Both of them I thought were defects at first. I think there was another person who reported this muffled sound on some pairs out of the box. I don't think he's around anymore though.
I remember being able to compare a new pair with one that i've used for thousands of hours. It took about 3-4 days in a drawer (at night) to sound identical to my well used pair.
Burn in is stupid and a waste of time, but it doesn't cost anything and this is one pair that it actually helped. If it sounds great out of the box I don't bother. My Tony Bennett was perfect.
The DJ100/TB can vary in sound a lot too depending on what it's connected to. It seems to hate dark amps.
I clearly remember once thinking that new out of the box the mids didn't sound forward at all and the treble was almost non-existent. Obviously this is impossible, but that's what I heard. That impression soon changed.
My well used TB is crystal clear and has slightly forward mids. Less so than say my Philips Downtown (which I hate).
People say there is no way a headphone can sound bad out of the box and great after burn-in, but this may be one of those rare headphones
Luckily it doesn't need 1000 hours.
Just a good week of use is way more than enough.
I think it's due to the Titanium driver. Even the Pro4AAAT is said to need a little use to be at it's best.
I didn't get a chance to check my local store to see if they had them. Can't buy one anyway. It'd be nice to have an extra around.