Is this a mastering technique? I am very confused as to what exactly "his personal stereo EQ" is...? I think more information would be needed to even give feedback to this post. Not trying to be an A$$ but I have no idea as to what this post is asking?

Is he setting an EQ in software just the same as his stereo's EQ is set?

Ok a little background, I am no professional I'm good at recording but its that mastering that gives me trouble and my cousin who i record with very often came up with this idea that if he matched the EQ he has on his stereo at home that what we could do mix the song matching the EQ that is on his stereo and then when it sounds good remove the EQ and it will be a flat mix. He is all about it but i just don't get it. I think is rubbish but I would like to know if it is an actually technique that is used before I tell him he full of bologna.

Personally I believe there is so much more to mastering than just a quick fix. Yes this sounds interesting to balance a stereo EQ of known system and mix to the specs of that domain. However, this is still just a short cut that in time you will think damn why not try it a hundred different ways. It's like a guitarist who is trying to perfect his tone, and for a lifetime he is buying all sorts of amps/guitars/effects. He will spend countless hours to achieve this perfect tone, but even then he will still hear mostly the imperfections. He will always try to figure out how to improve a sound scape and will never settle for too many shortcuts. Other people will hear the works and sounds of this guitarist and tell him that his tone is out of this world. He will still grunt and complain about some small factor of his imperfections.

I don't think any approach is a bad one when it comes to making a mix sound good on many systems. However, just keep an open mind to this approach and the many many many more you can achieve. I think the great engineers are the ones that don't get totally self defeated by the process and follow through with some sort of process to achieve the proper balance of the mastering process.

His method may work well for him on his own stereo system - but those are the EQ settings he chose for those speakers, in that room - take it into the garage and it'll all need to be different. Mastering is partially about portability, making something that not only sounds good on your monitors, but sounds fairly consistant from system to system (though this is largely also part of the recording and mixing process, every step of the journey is part of what actually pulls this off). Mastering goes far, far beyond simple EQ settings on the master tracks though.

What he's come up with is a way to compensate for the difference between the system/room he mixes on/in and the system/room he listens to the music on/in, nothing more than this in my opinion. I think you were right to question this practice, as in my (NOT a Mastering Engineer, just a recording/mixing guy here) very personal opinion his technique is actually the opposite of productive, he's making a mix that works with his personal stereo system in mind, and forgetting all about the rest of them. Once in a while and with certain other systems/rooms it might totally work out for him, but I doubt very much that his mix actually comes out truely portable.

Well thank you all for your in-depth replies, I try my best to keep an open mind because as you said and as I experience there is no one method to anything when creating a good recording. I just feel what he is doing is working backwards but at the same time you never know this may be the exact thing wqe need to produce a killer recording, which drives me crazy. hah.

Anyway, Thanks again for the input I really appreciate it and will pass this on to my recording buddies as well!