[Clincher09]

How drastically do the Shure SRH750DJs change after burn in? I just got mine looking for an upgrade from my HD 485s, but out of the box I'm really disappointed. They don't have any more bass than my 485s, which was the main reason I wanted them, and if they don't change at all I'm going to return them.

 

[earerror]

After the first 50 hours or burn in you'll notice a sound improvement on them. 
I find the 750dj's with a good amount of bass, but if you don't like their sound...that means your ears are craving for more bass! 

 

[Clincher09]

Ha, I don't even know where I could go for more bass. I haven these plugged into an E5 with the bass booster on. The Denon 1100s are the only ones I've seen that seem to have more bass, but I feel like I'd be sacrificing the other frequencies. I might just wait to get a better pair of headphones and a nice amp.

 

[Digital-Pride]

Keep at it, many high quality headphones are a bit disappointing at first but after 50 to 150 hours of burn-in you really start to hear a real difference in sound.   Whether it's the smoothing of harsh highs, increased detail retrieval or in your case deeper more robust base responce.  So keep your Shures for a few more days and see if the sound doesn't change to your liking, I'll bet you'll be pleasantly suprised!

 

[MarkyMark87]

Hey,
 
   I know this is really late, but when I got these I was disappointed at first at well, especially the first 5mins I had them on.  However, after the initial 5mins I really started to like them.  I'm listening to them right now and I'm so happy with them that I sorta smile on the inside every now and then.  I only have one issue with these and that is there is a lack of boom in the bass.  It punches nicely and alot of people say punchy bass is good and boomy bass is bad (thats the impression I get from reading around, this is not my own opinion).  I am guessing people feel that too much boom will cause the sound to get muddy but still I still think a good level/amount of boom will make it more fun, and so I wish these had a bit more.  I ordered a Fiio E7 so hopefully it'll help a bit cuz I'm using this with a laptop and no amp and although people say its fine unamped they also say it will improve amped.  Some people reviewed it against the SRH840 on the macfeed if I recall and they said the bass unamped is not so much more than the 840 but amped it gets ALOT better that it really put itself in a league of its own so I'm hoping the E7 helps there.
 
I know this is not exactly what you asked so I'll get more specific to your question.  I have now 30hrs on them (I tend to underestimate so it may be a tiny bit more) and I will say I feel like the bass has gotten better.  Now usually (from what I hear anyways) its not like the bass increases, it usually decreases and gets tightened up so if anything you should get less.  But for some reason I feel like its better, like somehow it ended up getting a bit more boom which is weird.  Maybe its just my ears changing and becoming more sensitive or accustomed to the headphone cause I also find I don't need to put the volume as high as I first did to get it to a good listening volume.  But I can say for sure that now after 30hrs of use, my ears are definitely more satisfied with the sound which includes the bass which is what originally disappointed me. They also handle the mids very well (to me) and highs are good as well but can be a tad bit harsh at times, but just a little and definitely not as bad as my Klipsch Image S4.
 
So to sum it up, whether its the headphones burning in or your ears changing, you should become more satisfied with the headphones after 30hrs of use, I'm anticipating how I'll feel about it at 50.  After that I should have the E7 so that plus the &50DJ with 50 hrs of burn-in already should definitely be a good combo, or so I hope