Need Basic Help: Loudspeaker Postioning

I'm new to hi-fi and have a few questions about loudspeakers:

1. Should the listener's ears be on the same horizontal plane as the front L/R tweeters in each speaker? I was listening to some Vandersteen 3A Signatures last Saturday and my ears were a few inches below the tweeter which in turn made the vocals from the music seem to be over my head. Should the listener use a chair which positions his ears on the plane of the speaker tweeters? I would think that on a sloped baffle designed for time alignment that you would want your ears to be slightly above the tweeter so that all drivers would be equidistant from the listener:

---------L
T
-M
--W

where L is the listener, T is the tweeter, M = midrange, W = woofer
actually on an arc of some radius not a straight line like I've drawn;
ignore the dashes
Another alternative would be to tilt the speaker forward.

2. Vandersteen doesn't recommend having the 3A's pointed directly at the listener. Why is this? Frequency response is usually a 'little' worse off-axis but still very good within 30 degrees. WSR's Reference Home Theater setup uses Dunlavy SC-Vs which are pointed directly at the main seating position. Why the difference?

Regards,
A.D.
 
Generally, yes, your tweeter should be at ear level. In some instances however, I position them slightly higher, and have my ears more aligned with the midrange. I find vocals to be much better that way. However, its a matter of preference.

If the speaker has a sloped baffle, you don't necessarily want to be equidistant from all of the drivers. This is why the baffle is sloped to begin with; it compensates for the alignment of the drivers, so that the sound coming from each of them reaches you at the same time. I believe that the voice coils of the drivers should be aligned in reference to where you're sitting.

However, in some speakers, the baffle has a relatively deeps slope, and yes, you could have your ears slightly higher than the tweeter. Some cabinet design of some speakers already compensate for the fact that the drivers are angled, such as the Wilson MAXX and SLAMM, whereas their WATT does not. Other speakers keep certain drivers on a vertical plane, to compensate for the alignment. (The Totem Wind speaker keeps the bass/midrange angled, but the tweeter is vertical).

In any case, the best positioning can only be found through trial and error, based on the listeners preferences.