Hi all, first post!
 
I'm looking for advice on which headphones to buy. Some context: I'm mixing and recording sound in a live setting where musicians are playing through a PA system in the same room as I'm mixing, so I need headphones which will isolate - a closed back design. I'm a long-time audiophile, so I very much appreciate good sound and I'm looking for a headphone that will be neutral and fairly flat - ones which won't color the sound, so I can accurately dial in each instrument. I'm also a musician and new to mixing and recording, but wanting to stretch my legs. I started out with Sennheiser Momentum (ick), tried the AKG K240 but didn't have enough time to spend with them to form a solid opinion before buying a pair of AKG K701's. The open back design on the latter two doesn't isolate well enough (as I found out).
 
I LOVE the 701's - the soundstage, imaging, clarity and purity of the sound is simply the best I've ever heard, and they ARE extremely flat. I'm sure they will be incredible for mastering in a quiet environment, but I'm finding their lack of bass (correction: hyper-neutral response) to be throwing off my mix during live performances - my mixes are coming out bass-heavy, maybe because more bass is what my ears are wanting to hear, in the moment - or maybe because I'm trying to compensate for the external sound bleeding through while recording live.
 
I'm beginning to realize that mixing live sound is much different than mastering or just listening to music. I'm looking for headphones which will help me mix a good live sound, while the band is playing.
 
I think that what I'm looking for is the clarity of the 701's in a closed-back design with slightly more bass. I'm finding myself giving the 701's only about a 1-2 dB per octave boost below about 250 hz to get a sound that's closer to what I consider balanced bass, but that's listening critically in a quiet environment. A live band environment is a whole different animal, so I'm not sure what I should be listening for in a pair of headphones for that application.
 
I'll be keeping the 701's - forever - I can't wait to try mastering on them, they sound so....perfect! They're just not suited for what I'm trying to use them for.
 
I've read countless reviews and debates on these and other forums until my head is spinning with model numbers and opinions. Some of my top picks from what I've read are:
 
Beyerdynamic DT-770 Pro (but people say they're bass-heavy)
Sennheiser HD-280 Pro
Sony MDR7506 (I just don't trust Sony to provide an accurate, true sound!)
Shure SRH840
Audio Technica ATH-M50x
 
(It's all a blur at this point, so a couple of these might be semi-open designs, I lost track awhile ago...)
 
I'm hoping someone will chime in with "oh yeah, you want xxxxx headphones!" or at least help me narrow it down to a couple choices.
 
I'll be running these right off the mixing board, so amplification won't be an issue. My budget is up to $300.
 
Opinions? Suggestions? Help? Please? And thank you!

I might suggest you select the Sony MDR-7520s instead of the 7506s.  You should be able to check those out at the Music Store and see how they sound to you.  They can be had for $300.  I don't think they are bass heavy at all.  Of course, headphones won't sound the same to two different people.  Since you have a specific environment and need, the optimum solution is to actually try out the phones at your mixing board.  Maybe someone has the magic answer for you.

+ 1 on the 7520's, if you can afford them.  They normally come in just a bit above $300 with some shopping.
 
Sony, AKG and Beyer cans have been the choices of audio pros for decades.
 
I haven't heard the Senn, but all the other cans on your list are colored quite a bit away from neutral--with the M50X being the least so among the three.

Sennheiser HD 25-1 II is a popular headphone for live mixing and DJ's and such. I have no experience with them, but I do know they are used a lot for the type of work you want headphones for.
 
All the headphones you mentioned are standard classic headphones for studio use. They all sound different though.
 
Your best bet is to go to something like a Guitar Centre and have a listen, as that type of store will probably have all the models you listed for demo.
 
I do have another headphone in mind to suggest, but I have to give it a listen before I recommend it. The German Maestro GMP 8.35 D. That headphone was basically designed from the ground up for such professional uses. I should have my pair in next week and can give my thoughts on them after I heard them if you're interested.

After thinking about it, the ATHM 50 might be a good choice, cause I can see that headphone approximating a live club sound very well, and still being able to give good detail. The mids are slightly recessed. It's definitely got a U or V shaped frequency response, but I think it will work well cause it won't give a sound that's night and day different from speaker systems in typical live settings.

Thanks all
I'm surprised to hear that the headphones on my list are "colored", as I've read that most of them are tried and true standards for recording studios.
 
I'll check out the Sonys, although I'm still skeptical Sony just has never been a big name in audiophile circles, but I'm thinking of car and home audio...the headphone scene is new to me. My impression of sony in general is that of Beats and Skullcandy - aimed more at the mass consumer market. But I'll try to give them an objective listen somewhere.
 
As far as the ATHM50, I might not mind slightly recessed mids - I'm looking for "pretty close to flat", it doesn't have to be perfect. I've learned over the years that my ears are overly sensitive to the 1k band, so they might sound just right to me. After all, I am going for 'crowd-pleasing' for the live venues, and that usually means a V in the response curve anyway.
 
Good suggestion about Guitar Center - I'll try to get to to one this weekend and give a few different cans a listen. Hopefully they'll let me plug into a soundboard so I can get decent amplification and hear what they're really going to sound like from a desk.
 
I appreciate the feedback. Any other suggestions I should consider?

I hear live music often, usually 2-3 time a week. Having been around the local music scene for a few decades, I usually get a (show) pass from the promoter and situate myself right next to the house desk. There has never been a time, never that I saw, when the sound guy - whether he came with the band or was provided by the venue - wasn't using Sony 7506/V6. Never.

Marshall Monitors are great for what you need them for-I've always thought that mixing with bright headphones like the 701's lead to a bass heavy, muddy mix. The Monitors have a bit of top rolled off without sounding muddy, and for your purpose (live mixing) I think they have the perfect tone for helping things come out nice and sparkly. 
 
I know leakage is right up at the very top-even beating a lot of battery powered noise canceling cans, but imo the isolation is average at best. Still a lot better than the 701's, but average. 

Hi all
Thought I should follow up and let you all know what I went with. After listening to a few different phones, I went with the Focal Spirit Professional. The have a nice clean sound, well balanced, and very powerful - they were one of the only ones that could handle the deep punch of my kick drum without fault at higher volumes. They sound fairly flat - not as flat and airy as the 701's, but they have a frequency response that seems to match what my ears want to hear. The soundstage and imaging are not as good as the 701's, but are about as good as can be expected from a pair of closed back headphones. They struck a good overall balance between fit, sound quality, noise cancellation and they look durable enough to handle just about anything. So far I'm very happy with them.
 
Thanks everyone for the recommendations and advice.