"Unless the EQ is parametric you're better off without them. It is the objective of any home hi-fi reproduction to playback the sound of a source as it was recorded. While adminttedly, your room accostics will color what gets to your ears, using an EQ will not restore the original frequency reponses but will further color the sound. Most, if not all high-end equipment don't even have tone controls!!!
But if you insist on getting one, make sure it's a parametric EQ with controls on frequency centering and the Q factor or the way each frequency is boosted or attenuated. Such EQs are rather expensive and usually are marketed for studio gurus. Don't go for those fancy graphic equalizers with spectrum displays. They are just comlicated tone controls that shift the phases of each frequeny they control."
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I'd have to agree with AV on this one. Matching up uncapable electronics (especially amps) to external EQ devices is a bad combination. One needs a decent amp to even implement meaningful EQ-ing to their system...not to mention the expertise and knowledge along with it. An external EQ device is not for the AV novice or beginner. You don't necessarily have to be an A/V expert, but one needs to be comfortable and well versed in the applications and options out there for a properly balanced system.
I am by no means an "Elite A/V Authority", and even I would not implement one of these devices until the equimpent I own merited this level of calibration. I worry more about proper room setup, placement, and moderate EQ-ing at this point. In a couple years when seperate amps find their way back into my system, I will indeed step up to such external devices, as they would be justified at that point.
If one jumps into this level of system calibration prematurely, the desired end result may be further away from that user's grasp than expected... I would suggest getting a $500-$1000 unit (give or take) and become comfortable with its versatility and setup options to begin with. Basically, just know what your getting yourself into before you jump into the deep end of the pool!
best,
