Lance, another welcome to Axiom. You've already gotten some good suggestions here, but depending on the extent of your hearing damage, none of the adjustments that we suggest may be enough.
Many center channels in movies are mixed at a low level with respect to the other content, and making a 3-4dB boost in the center from the balanced level set with test tones can help with this part of the problem. Your situation however compounds the difficulty by apparently adding losses in the upper mid/lower treble frequencies(about 2-6KHz, see this brief discussion
) which affect the consonants most strongly and can make speech intelligibility poor even at loud levels.
It's highly unlikely that a speaker with a "colored" mid/high frequency response could be more than at best a hit-or-miss proposition with its uneven or distorted response "correcting" the problem in differentiating the consonants.