Wow, deja vu all over again! Another guy had almost the exact same question recently. There's nothing wrong with your speakers or your room. What you are hearing is perfectly normal. In order to fix it you first need to understand why it is there in the first place.
All you are hearing is bass modes. All frequencies reflect off walls and when the reflections come back and hit the wave coming from the speaker they either cancel or reinforce. When they cancel you hear less or nothing. When they reinforce you hear it louder than it should be.
All that is happening is that when you are sitting you are in a cancellation area, and standing up gets you out of that area. This has nothing to do with the direction the speakers are pointed. High frequencies are short waves and highly directional. Low bass is very long waves and the direction the speaker is pointed is so meaningless many speakers are designed with inward or back firing woofers, and subs can be pointed directly at the wall.
This happens in all three dimensions, by the way. You notice it standing, but listen, you will also notice it moving to the left or right, closer or further away.
This is why normally the first step in speaker placement is to move around both the speakers and the listening chair listening to bass looking for the smoothest bass response. Don't forget - move both the speakers and the listening chair.
All you are hearing is bass modes. All frequencies reflect off walls and when the reflections come back and hit the wave coming from the speaker they either cancel or reinforce. When they cancel you hear less or nothing. When they reinforce you hear it louder than it should be.
All that is happening is that when you are sitting you are in a cancellation area, and standing up gets you out of that area. This has nothing to do with the direction the speakers are pointed. High frequencies are short waves and highly directional. Low bass is very long waves and the direction the speaker is pointed is so meaningless many speakers are designed with inward or back firing woofers, and subs can be pointed directly at the wall.
This happens in all three dimensions, by the way. You notice it standing, but listen, you will also notice it moving to the left or right, closer or further away.
This is why normally the first step in speaker placement is to move around both the speakers and the listening chair listening to bass looking for the smoothest bass response. Don't forget - move both the speakers and the listening chair.