Perhaps the past, present and future. I edited this paragraph in for relevancy. The past is just as important as the future. We cherish many works of old and some of them are still within the "state of the art". Listen to some classical vinyl of the late 50's and it is simply STILL outstanding in clarity and reproduction translation. The 60's provided us with hits a many that still sound great. Our work today must fit the mould of high fidelity reproduction and the frequency balance that was established long ago still remains..balanced. It those days, recordings were done with utter care by lab coat technicians. People put a lot of heart into what they did for future generations to enjoy in its full splendor. Also I will add in this edit, it is not simply that a loudspeaker system must sound great. The loudspeaker system must be DYNAMICALLY accurate as well and to hear accuracy in loudspeakers is to realize the mids are definitely tilted up a shade because of fletcher-munson and this goes along with my argument of: when we mix and master, we should crank the volume for at least a short period to make certain we are not mixing undue pain into our work on critically accurate systems. Remember, we have to translate to inexpensive "box" type systems as well.
OK, original text from 2 hrs ago...
I have been in the same boat but really really early on. I posted some history in Brads forum (in short form) of how I evolved from musician first, to speaker nut and then to recording engineering and mastering. From 69-75, I was very unhappy with consumer loudspeakers in the early 70's to the point of creating my own designs. My first real studio experience was in 75 when everyone and their brother had 4310/4311 control monitors as mixing devices and mastering was simply the transfer from tape to disc (vinyl) with small changes to accommodate the lacquer. Mastering had evolved into many different things now but the purpose of it is to convert from the professional format to the consumer format(s) for proper translation with a wide variety of systems.
This said, going back to 75, my favorite LP's simply sounded very "right" on the JBL's and especially the L200's and L300's which were large scale studio monitors, not control room monitors. Most recordings sounded *"right". If they did not, it was oftentimes the recordings and engineering themselves were the problem. A standard was used and this standard was consistancy.
Skipping ahead to the 80's and digital involvement, studios shied away from the JBL's simply because they were on the harsh side with the CD's (all the while the major problems were the first generation converters and lack of experience in transfer) and began using other various types. NS10's have the ability to reproduce the simple snare drum properly and this by no means is an easy feat for a loudspeaker. I find many modern monitors to be very bass heavy, especially around 50hz (hence the thin mixes) causing engineers to back off on the bottom to balance to the loudspeakers. This and that their seems that through the 90's, their were no fewer than one hundred companies producing what is called "a studio monitor" and no telling how the mix will translate and this began the dawn of "mastering engineer" trying to get things back to a form of translation or back to "level".
SO there you have it. The paradigm has changed and truly accurate monitors (with flat phase and amplitude response) were traded in for those which "sound better" on cruddy material. This is the wrong way to go.
Going back to 75, it is still the material here that needs the hard work and mastering helps..but it should not the industries "band aid". As their will be many more monitors built and different levels of competence in recording, balancing and paying attention, the need for "mastering" grows ever stronger. A good set of full range low distortion cones should sound really good with music. This is not the ultimate criteria but one that is a "standard" to be kept in mind.
We haven't even talked about people who are using "cans" to mix with.
Engineers, really good ones can learn to use whatever monitors they get used to. It is the skill of that engineer how well the translation works and hopefully an incompetent mastering engineer *won't* mess it all up, or the other way around where it is messed up and the mastering engineer has to try to "fix it"..but the latter is the case many times these days..and it is mainly due to monitors, rooms and levels of competence.
*One recording in particular was H. Lewis and the News or the "back to the future 1" soundtrack album