I own a pair of 280's and whilst their isolation is GREAT for tracking,

Do you think the 280s exaggerate the treble?
 
Are the 290s better for mixing?

I have 280s, but I use them only for tracking and reference.  I always mix with studio monitors, I have found JBL LSR305s to be accurate for me.   

Tripecac

I own a pair of 280's and whilst their isolation is GREAT for tracking,

Do you think the 280s exaggerate the treble?
 

Hell no, they are quite warm and quite well balanced. I'm surprised that you haven't overcompensated on the treble when mixing with them and given the top end more boost than what you're hearing.
 
Are you absolutely sure there's nothing in your monitoring chain that could be hyping the top end?
 

The monitoring chain is just:
 
Sonar -> M-Audio Delta 44 -> M-Audio OMNI I/O (breakout box) -> headphones
 
I  love the sound of the HD 580s.  I just wish my songs would sound the same on all my other speakers and headphones, but everything else sounds muffled in comparison.

wow, this has thread been hanging around out here for a year... anyway, I just bought a nice tool that I've just started to use...        https://www.youtube.com/watch?v=qx5GaZ8-zxY
the Melda MMultiAnalyzer is a vst that you can add to several tracks and analyze the waveform of each track separately... you can put it on say, the drum bus and bass bus, then look at the interaction of the two waveforms.  There's even a collision option to view frequency collision depth.  Very nice.
Just another tool in trying to get the low frequency end under control.  

Some great suggestions have been made in this thread, many of which will only cost you time to try out. Look, I know you're looking for a simple fix, but believe me, there ain't no such animal, and I know this because I have been where you are looking for it. I do this for fun, not for a living, and in my lifetime I will not build the kind of experience pros accrue in a month. But I have read the same advice given in this thread by others and I have used that advice and it's worked for me to the extent that I've put the time in to learn the techniques and apply them properly.
 
1. Adding EQ at the Master bus is done all the time, but that's a final mastering kind of step, and for mixing it's a pretty blunt hammer. The suggestion to EQ each track using Quad Curve EQ in pro channel is a truly great one. The question is, how do you know what each track needs? On to number 2:
 
2. Mix in mono while striving to give each instrument it's own sonic space in the spectrum. Easy to say, harder to do but this will absolutely work for you. Use google to find charts detailing guidelines for the frequencies various instruments use and try emphasizing those frequencies for those instruments in your tracks, and de-emphasizing the frequencies they don't belong in. Hi and lo pass filters are your friend. It's useful to set up track templates by instrument with these EQ bands pre-set, and you can always adjust to taste. 
 

3. Understand what your monitoring equipment is telling you. You don't have to buy new phones, just learn what your gear is emphasizing or de-emphasizing and keep that knowledge in mind while you mix. The will help you get the most out of step 4:
 
4. Use reference tracks of tunes you want your mix to sound like. This is a FANTASTIC piece of advice and you will learn a great deal by giving these tracks a critical listen, particularly side-by-side in your mix. Better yet, use software that helps you visualize the differences in EQ between your track and a reference track to see where you're being heavy-handed. I use Izotope's Ozone v7 for this. It's mastering EQ has a feature that is designed to allow you to compare a reference track to the EQ of your mix, and it will overlay a graph showing the differences. It will even allow you to apply that graph to your mix. It's indispensable to a time-constrained amateur like me. 
 
I wish you the best of luck in your musical endeavors, and remember, it's the journey, not the destination!
 

The suggestion to EQ each track using Quad Curve EQ in pro channel is a truly great one.

I don't think I would ever have the discipline to do this.  Due to time constraints (and habits), I work very, very quickly.  I do almost all my editing on the fly (during playback), stopping only occasionally.  Having to fiddle with an EQ effect on every single track would totally kill my flow, and probably my enjoyment and therefore motivation for making music.

Plus, as you pointed out, I would have no idea how much *extra* treble to add to each track, since it would always sound "too trebly" on the HD 580s.

It seems like the simplest solution is to mix with the HD 590s (or my Edirol monitors) rather than the HD 580s.  That way, the final mix would be more WYHIWYG (what you hear is what you get).

Mixing with the Edirol monitors might work, except I hate mixing loudly with other people in the house, and I also don't know where to position them.  Right now they are both on my left (on either side of my Triton keyboard), because there isn't a good place to put them in front of me.  This is because I have 3 computer monitors in front of me, for work (2 for my main PC and one for my laptop, on which I am typing).  If I were to put the Edirols on either side of my 3 computer monitors, it would be a very wide triangle, a bit wacky.  Plus, the one on the right would block traffic and the one on the left would block my view of the mountains and lake.  I wish I could hang them from the ceiling, but I'd rather not drill holes into the ceiling until I know it's absolutely necessary.  Anyway, this is why I've been mixing with headphones.

(Note: I guess since both Edirols are on the left, I could still mix with them, since I'd be effectively "mixing in mono" as both would be in my left ear).

So why not simply move the HD 590s to the Delta?  Well, I find the 590s more comfortable than the 580s, so would prefer to listen to music all day with the 590s.  This means they will spend most of their time plugged into the Xonar (my main sound card).  So in order to mix on the 590s I'd have to unplug them from the Xonar and plug them into the Delta. This would be an inconvenience, and I need to make music making as convenient as possible, or else it just won't happen.

Anyway, this why I was hoping for a quick software solution.  

I haven't tried the reference mix solution.  It would be easy, since I have all my CDs on my computer.  What sort of song do you recommend I use as a reference?  I listen to a lot of 80s post-punk, most of which was cheaply recorded.  And recently I've been listening to lots of 60s music, again with less-than-perfect mixes.  Of newer music, I like the recent New Order album.  Would a song off that be a good reference track?

And finally, I wish I could find a single sound card so that I could get rid of the whole 2-headphones business.  My Delta supports 2 headphones so perhaps there is a way to just direct all audio to the Delta and stop using the Xonar.  Hmmm...

One fallacy which is curiously prevalent is that you have to mix loudly on monitors.
 
Take it from me - you don't! If I was in your shoes I would hook up your Edirols and mix on them.
 
Arrange them so they form an equilateral triangle with your head, maybe 4 to 6 feet apart.
 
__________________________________________________
 
Take a look at Bob Katz Honor Roll for reference tracks:
 
http://www.digido.com/media/honor-roll.html
 
 

Realizing that not all monitoring situations are ideal, even with reference tracks you may not be hearing the entire spectrum accurately. As you want a master buss solution, Google "EQ matching." I only know of two with good reviews (FabFilter has one, and iZotope the other).

Also realize that both of those are not free, and using them on the master buss would take dynamics out of the mix, but iZotope has a good write up on it at the link below. I am not sure if free alternatives are viable, nor at which level iZotope offers this feature offhand. Please research this further if you choose to try this route.

http://help.izotope.com/d...odules_matching_eq.htm

Tripecac
 
.....................
Plus, even if someone bought Sonarworks for me (care to volunteer, Vastpockets?), I would have no idea how to use it, or how to trust my ears.  What sounds "right"?  I have no idea.  No clue. 
 ......................
So, I'm after a simple, convenient, FREE solution, and to me, that means looking for a single "button to push" which will fix the mixes. 
 
 

It seems to me you´re looking for something TOO simple. I don't think there's anything that actually saves you the time and trouble of careful listening and decisionmaking, no matter if you have money to spend or not.
"What sounds "right"? If it sounds good to your ears in a somewhat similar way some of your favourite commercial tracks do, then it can't be bad. If you confess you don't know what you're looking for, then it's even more questionable to look for a "push button to fix it all".
  
I repeat my FREE method: Reference tracks and SPAN. Take the reference track in the project so you can audition it every now and then, and compare the frequency spectrums side by side. IMO that's also a very good way to learn the tricks of your monitoring gear and train your ears.
 
In one of your posts you're asking what should you pick for a reference track. Pick something that has the sound you're after and instrument combination that about matches your project, of course. How else would the reference be of any help?
For basic countryish rock with acoustic guitars, for example, I always have something from Tom Petty in the project as a reference. They are not the finest examples of studiowork in the world, but they have some old fashioned dynamics left and have some "handicraft" left in the sound. For music with synths and pads I pick something different.
 
I'm definately not a man with golden ears, and I've never had the luxury of good acoustical environment or classy gear, and also I have a very, very limited time to spend by my DAW. You need teach your ears approximately what you're looking for, no matter what your monitoring with.