[Brooko]

I'll give you another point of view if I may .....
 
It appears that with your Grados you are purposely reducing the mid range because you feel it's out of proportion.  From my experience with the lower end Grados - they do have emphasis on both the upper mids and highs.  I personally like an elevated mid-range, but I can understand what you're doing with your EQ.
 
That would suggest to me that you're taking a quite mid/high focussed headphone and trying to flatten it.
 
If that's the case, then I'd be recommending the DT880 over the DT990.  The DT880 is a flatter presentation - has nice bass impact and extension (especially compared to your 225s).  The mids are slightly recessed compared to the bass and upper end - but not excessively so.
 
Is there anywhere you can demo both the 880 and 990?  It's worth doing.  You'll find people on both sides of this particular fence.  I really enjoyed the 990s bigger sound stage - but in the end the 880s over all balance was more appealing for me.  It's something you really need to try to get a real appreciation.  Both the 990 and 880 are very good cans for their asking price.

 

[Aelius]

Thanks for all the responses. It's extremely difficult to choose between the 880 and 990 without having heard either of them. After searching hundreds of posts, I find that peoples' preferences between the two are pretty much evenly split. But whether I decide to go with the 880 or 990, I have no idea whether to get the 250 or 600 ohm version. I have no idea if I'd be able to drive them properly without another external amp, first of all. But even if driving them isn't a problem, I'm not sure if there's an objective increase in sound quality or a subjective one? Is it kind of like going from a 256 bit recording to a 320 bit recording, in the sense that it's objectively better quality? If the 250/600 ohm differences are purely subjective, however, is there any indication that one or the other would be better suited to my tastes (slightly elevated bass/treble, recessed mids)?

 

[Brooko]

I owned the 250 ohm 880 Pro, and now own the 600 ohm 880 Premiums.  Sonic differences are IMHO very small.  If anything the 600 ohm may have a very slightly smoother treble.  Not discounting that it's placebo on my part - but that't the way it seems to me.
 
Apart from the volume difference (between 250 and 600 ohm):
 - both out of iPod Touch G4 unamped  - the 250 ohm actually sounded OK - not as good as it can, but not bad at all.  The 600 ohm sounds a bit lifeless (not as dynamic).  Bass isn't as defined for sure.
 - The 600 ohm out of my Arrow sounds better - but still not quite as smooth as out of my desktop (this could be because the Arrow is quite linear, whereas my desktop amps aren't).
 - The 600 out of my NFB-12 or Little Dot MKIV are very full bodied, and just plain heavenly - both have a slight warmish mid-range colouration.
 
Not sure if that helps.

 

[colgatetotal]

Have you tried the Grado bass mods?
 
1) Venting the felt - Open the cups by using a hairdryer to heat up the glue. Feel the felt for holes underneath, then use a ballpoint pen and poke the felt in these areas. I have 2 large holes and 8 smaller ones and it's perfect for me. For reference, the high-end Grados all have 2 holes vented.
 
2) Tape the bowls - Cover the perimeter of the bowls with electrical tape. Ups bass impact, makes mids less airy. I don't personally do this.
 
Both of these won't really extend the sub-bass past below 30hz, but since you said the midbass was a concern, both of these will help.

 

[ayaflo]

if you dont want a theater bass sound i would suggest you stay away from the dt 990s ..
they have an in hall presentation with stunning bass, airy treble and clear and detailed mids..
in no way are they recessed ..
just a bit over shadowed but the full bass and full treble configuration (theater eq)