I've tested hundreds of people and never once was the curve the same for both ears. About 15% or so have a "noticable" difference between ears as you seem to. You cold spend many hours testing yourself and money/gear trying to correct it. You could play around with a supertweeter and an L-pad on the left side but as we don't know the exact curves of both ears no one could say how much improvement that would bring or any other method of correction. But I would try the tweeter/L-pad. My guess is you would want something that crosses at 3-5K - again a guess.
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