Originally Posted by antonyfirst
Did you burn in the C551?
Originally Posted by dura
Do you have your other Denons yet? I'm interested in your comparison.
Yes I did

. . and here's what I think.
They are an amazing backup pair for the C700, or as a primary pair for anyone who likes the C700 sound signature but found the treble too fatiguing.
In my opinion, using these with the Sony A808, the only differences sonically are the treble detail (slightly softer with the C551s), bass impact is heavier, and the soundstage - which is a tiny bit smaller. Because the treble detail is quite a bit softer/less detailed, it does make the bass appear
louder compared to the C700s. In fact, cnet said in its review of the C700 that most of the work had gone into achieving the 'crystalline' high end detail, and it's very easy to spot the difference.
Cosmetically, I prefer the C700s even though they are bigger. The housing tapers off towards the end making them look 'shapely' - but the C551s look like Denon were about to make the housing the same - and then decided to chop them off in the middle, leaving them short and fat.
Don't get me started on the cable. One of the editorial reviews claimed it was tangle free, and it's not. It's a lot thinner than the C700, but still seems sturdy enough, unlike various stock Sony headphones that stretch like a piece of liquorice!!
On the train, I'd find the shorter cable of the C551 easier to control as I wear the A808 round my neck so the cable is almost exactly the right length (so I don't need the extension cable). At home I don't need to 'wear' the 808 so cable length isn't an issue at all with the C700s.
Fit wise, I found it quite hard to get a good fit. I can't wear them over the ears at all as I can't get them to stay in that way. They're fine to wear straight down, but I can wear the C700s either way, and it's nice to have the option.
Overall, I think both sets of headphones offer really good value for money. With the C700 currently priced at $99, (same as the C551) - it's well worth picking up them up, especially if you like lots of treble detail and a 'magic' tangle-free cable. Otherwise, the C551 is a great alternative for anyone who finds excess treble too fatiguing.
If my C700s broke, I would be more than happy to use the C551s as their replacement. I happen to prefer the C700 for the cable and the slightly bigger soundstage, but when I'm listening to the C551s, I tend to forget about the C700s to a certain extent. It's very easy to get 'lost' in the C551s as they are also very musical and a lot of fun. It's only when I go back to the C700s that I realise I definitely prefer them. They have a warmer fuller sound which is a sound my ears happen to prefer. But that's not slating the C551s at all, it is a very very good headphone and I really can't see anyone being disappointed with them.
The C551s cost about the same as the Sony EX90 and the Sennheiser CX500 and I think they sound a whole lot better than either of them. I've tested my b/f's CX500 and the bass impact is very weak compared to either of the Denons, which was a surprise as I expected a lot of bass from the Senns. Denon do bass very very well in both sets of headphones, as I said, I'm more than happy with both of them. But the C700s remain my favourite with the C551 in firm second place
Originally Posted by dura
The comparison to the E4G's isn't even funny, the denons offer so much more of everything, more detail, more dynamics, more bass...
I totally agree!
EDIT: I definitely prefer the treble on the C700s, it's much more sparkling. That is the most noticeable difference between the two.
ANOTHER EDIT: I really really like the C551 bass. The softer treble is more than made up for by the great bass. But while it seems to have more impact than the C700, it does become intrusive (for my own ears) and I actually prefer the more evenly balanced presentation of the 700s, especially for longer listening bouts. One other thing I noticed was the very slight 'ringing' in my ears after using the C551. I don't get any at all with the C700s, the only difference I can think is that the very upfront vocals seem closer to the head with the C551s - maybe that's what causing it? Even so, i love them both and if I had 4 ears - or gorilla ears, I would definitely wear both!