Check to make sure you have the headphone/ jack plugged all the way into the headphones. I bought two pairs and both have tons of nice sparkly treble and seem very flat, no flabby bass as long as you leave ANC off. if you have another 3.5mm audio cable, try that and seat it really well just to be sure. if it is seating OK, then you may have a defective pair, read similar complaints your yours on some reviews that were for either the cable not in enough or defective units. good luck!
Headphone Reviews and Discussion - Head-Fi.org
Wembely
GearMe
+1 to Wembley's comment...had cable seating issue.
Bought them for $99 based on Tyll's review for sound signature in 'Passive' mode. I find them a fun, engaging headphone as Tyll describes. "These cans simply deliver a full-bodied and nicely controlled listening experience across the board. I'd call it very good mid-fi..."
http://www.innerfidelity.com/content/surprisingly-good-logitec-ue6000-and-ue9000-page-2
Bought them for $99 based on Tyll's review for sound signature in 'Passive' mode. I find them a fun, engaging headphone as Tyll describes. "These cans simply deliver a full-bodied and nicely controlled listening experience across the board. I'd call it very good mid-fi..."
http://www.innerfidelity.com/content/surprisingly-good-logitec-ue6000-and-ue9000-page-2
HeretixAevum
There's definitely no cable issues, and I'm pretty certain the headphones aren't broken (they don't sound it at all). I just don't like the way they're tuned, I think the cheaper CAL! sounds way better.
MarcoGV
I look forward to your full review, but I already will comment based on what you have already writte.
I have both the CAL! and the UE6000. I am actually listening to Youssou N'Dour's "The Guide" in an airport with the UE6000 in passive mode as I type this. Before that, I listened to Bruckner's Fourth Symphony (Guenther Wand conducting the Berliner Philarmoniker, ) The UE6000 isolates well enough that I can listen to this rather complex music (from 320kbps MP3s ripped from CDs) at moderate level in a noisy environment. I think that I could not do that with the CAL! I even listened to some of Vusi Mahalasela ("Say Africa"---a good choice for a tribute to Nelson Mandela!) from my Android phone on the previous flight---a commuter propeller plane; in that case I turned the ANC on. One could not have done that with the CAL! I have compared the CAL! and UE6000 several times in a quiet office environment. Yes, the CAL! is airier and may be slightly better for the kind of music I like (classical, (mainly) West African, Italian pop), but the difference is small. In my opinion, the UE6000 and the CAL! are fundamentally similar (and both right): you hear almost the same sounds, just with different emphasis. There are headphones with more detail retrieval than either of them: one that I own is the Beyerdynamic DT250-250.
I have both the CAL! and the UE6000. I am actually listening to Youssou N'Dour's "The Guide" in an airport with the UE6000 in passive mode as I type this. Before that, I listened to Bruckner's Fourth Symphony (Guenther Wand conducting the Berliner Philarmoniker, ) The UE6000 isolates well enough that I can listen to this rather complex music (from 320kbps MP3s ripped from CDs) at moderate level in a noisy environment. I think that I could not do that with the CAL! I even listened to some of Vusi Mahalasela ("Say Africa"---a good choice for a tribute to Nelson Mandela!) from my Android phone on the previous flight---a commuter propeller plane; in that case I turned the ANC on. One could not have done that with the CAL! I have compared the CAL! and UE6000 several times in a quiet office environment. Yes, the CAL! is airier and may be slightly better for the kind of music I like (classical, (mainly) West African, Italian pop), but the difference is small. In my opinion, the UE6000 and the CAL! are fundamentally similar (and both right): you hear almost the same sounds, just with different emphasis. There are headphones with more detail retrieval than either of them: one that I own is the Beyerdynamic DT250-250.
HeretixAevum
Nobody is doubting that the ue6000 isolates well, or that there are more detail & more expensive headphones out there. I just think that given how much more expensive the ue6000 has been historically (released at 199!) it's really just not good enough in the sound department. The CAL just sounds noticeable more articulate and balanced to my ears, as well as being way more comfortable for me. I'll go into detail about in my full review, though 
