Singer sounds lower than ear level, help raise it

Turn the speakers upside down.

Thanks for all the great advices.
1)Listening at particularly low volume levels - will try with higher volume.

2)Dead tweeters - they're working.

3)Room acoustics - can't really fix it, my room is sort of a U shape room, need to do too much to fix the problem.

4)A mismatch between amplifier output impedance and the speaker's variation of impedance as a function of frequency. Blue circle BC2 class a.

6)Listening off axis or with improper toe-in, as was pointed out - that means by changing the toe-in we can fix the problem? Definitely will try this.
Thanks

It helps to try all sorts of placement. Proper location of a speaker is largely a random hit or miss thing and even a movement as small as 1/2 inch can make a huge difference if you happen to be moving into or out of a strong mode.

For your particular issue, I would suggest working with the rake angle first (the backwards tilt). Many speakers are not actually meant to be heard with the tweeter at ear level. It may be the case that the ideal position, for both correct frequency balance and image placement is on a different axis.

It might seem counter intuitive, but, the ideal placement may be with the speaker lowered in height and tilted back a bit. That often raises the height of the center image. I am not saying that is going to be the answer, rather, I am saying try everything, including lowering the speaker to raise the image height.

10-25-12: Timrhu
Turn the speakers upside down.

you know, I almost wrote a post yesterday (10/25/12) with the same advice!! ;-)
I looked at it a bit more & decided that it would not make sense because the tweeter is in the middle (with the midrange above & the woofer below). it would have made sense had the tweeter been the top-most. Then turning the speaker upside down would have made the speaker time-aligned & would have accounted for the various acoustical centers.
My advice was going to be to lower the speaker such that the midrange was at ear-level.
In a speaker system that has minimal phase distortion & where the drivers are placed tweeter-mid-woofer going from top-down, then the vocals should come from just below the midrange. In such a speaker this would end up being about mid-speaker.