It's been said by many others and we go by this rule also, listening to our finished productions through different monitors is the key to a nicely balanced mix for all systems. As we mix, depending on the day and our mood, we generally use either the Adams or NS 10's to get our mixes in generally the right place. NS 10's are a lovely monitor after years of use and are nice to work on for long periods of time. The Adam's are great too, although we do sometimes end up with ringing ears. A long time on these monitors with mixes that are not finished, pushes our ear drums too much. This often goes unnoticed as we work on a lot of electronic music with heavy subs. Which feel great, although after a few hours become really fatiguing. Especially if there is too much sub. So generally it's the NS 10's where most of the work is done.
Once the mix is sitting nicely, we check the bottom on the Adam's and the overall balance on the Avantone. It's quite a thing to hear the mix through the Avantone as this really shows up the minor adjustments that are needed to complete the balanced mix.
We then go onto a boom box, mobile phone and into the car to see if anything has slipped pass. generally though NS 10's, Adam's and Avantone do the job well.
It's taken us a long time to understand each monitor sound and how to work the mix into the right place. Also we learnt the hard way that the room plays a massive role in what you hear. We found that moving rooms can be as big an issue as getting new monitors. If it's a nicely treated room, then generally its not too much of a problem, though we have moved into any different rooms in the past and they are not always treated as we would like. As many peoples rooms are.
The Mirror on a wall trick, where someone sits in the listening position and someone holds a mirror up against the wall. Is a good method to show where Acoustic treatment should be. If the person in the listening position can see any speaker monitor in the mirror, as it is moved around all the walls in the room, then putting some kind of acoustic treatment in them places really helps with the top end reflections. We are no experts at room treatment, but have found this to help in each room we have been in.
Bass problems are the issue when working in untreated rooms. We have bass traps and also use IK Multimedia's Arc 2 to help with this. If we were to build full size bass traps in the room we are in, there would be no space to get anything else in. We find using Arc 2 helps us get a clear bottom end that really is tough to get otherwise.
Listening to finished, mastered, released tracks in our room, there is no problem with what we hear. The mixes 'Picture' is really clear, which shows us that when everything is right wth the mix, its sounds great. Using the Arc 2 is like having another set of monitors... well another 10 sets really as they have different models to listen through on playback. Personally I'm not 100% sold on working entirely through the Arc as at the end of the day, it's EQ curves. Though to help put us in the right place it is a great tool