Audio-Technica ATH-M40x by keystation
True confession: The original reason I bought the ATH-M40x's was because I was cheap.
I went to Guitar Center with a $100 gift certificate in hand and looking for a pair of cans. Once finding the rack with the phones, a young GC employee approached. Naturally, he tried to sell me up to a $300 pair of Beyer Dynamics. But that sales job just woke up my inner miser.
To silence the GC kid, I shuffled around the headphone display rack where I found the ATH-M40x's. Looked good, $99 - matched my gift certificate, I was sold! At checkout, the GC kid allowed that "you should be happy with those, they do sound pretty good."
Turns out, he was right.
Now, I've had these things for the better part of a year. Overall, the ATH-M40x's offer clean, semi-colorless sound, with imaging and detail suitable for tracking and mixing. Here are the bullet points of my findings:
1) Overall Frequency Response: Since all headphones claim 20hz-20KHz, +/- whatever the manufacturer claims, let's just say these do too and move along...
2) High Frequencies: Clean, not peaky or smeared.
3) Mids: Very good imaging and detail - important stuff does not get lost in the mix. Conversely, bad stuff in your mix doesn't get lost either, which is a good thing.
4) Lows: I guess Audio Technica had to throw a fish towards the EDM crowd, because there is a definte, slight "bass enhancement voicing" going on with these. Tolerable and work-around-able, but still there. Otherwise, the bass detail holds together very well.
5) General good things: The comfort, fit & finish, the two removable cables, the 1/4" screw-on adapter, the nifty little leatherette pouch to carry this stuff in.
6) General not-so-good thing: Some fumble-fingered folks (like me) can find ways to twist and turn the cans in bizzare ways. A simple fold-up hinging to fit into the case would have been good enough for me.
7) Isolation: Some say these don't isolate sufficiently, but I have not experienced a sound bleed problem tracking voices with these as monitors. However, these are not "The Cones of Silence" - if you track north of 96dba coming out of your monitor mix, you are on your own.
In summary, I recommend the ATH-M40x's. These compete well with other (very good) headphones in the sub-$100 price range, such as the Sony 7506s, Sennheiser 280s and AKG 240s.