Bass only when I stand up…

Speaker position is everything.  I have had this experience too.  The factors affecting the bass are distance from front wall, side walls and most importantly, distance between each speaker.  First, experiment by moving the speakers closer together in 3 inch steps.  When you hear a change go back and move them in finer increments.  Do the same procedure from the front wall.

As a rough generalization, very rough- the speakers want to be between 1.83-2.74 meters apart.  Sure, bigger speakers with big drivers can be further apart but in general 2.44 meters, plus/minus will be the sweet spot.  1 meter from the front wall minimum will help the bass and the soundstage.  Lastly, listening position is critical too.  Start with listening position equal to the distance between tweeters.  Then try moving back to 1.1-1.2 times the distance between tweeters.  Try to keep some distance from the back wall while moving those speakers away from the front wall as far as possible.

Bass traps in the corners will remove mudiness in the bass notes but they are not a cure for no bass. Ie. Bass traps don’t make more bass, they make the bass you have better.

Bass response is one of the craziest things in hifi.  Over the years and living in different houses with varying room sizes and volumes I would stubbornly set up my stereo with the same separation distance between the speakers and distance from the front wall.  I would notice that the bass would often sound better in the back of the room than in my listening chair.  The real head scratcher was when I had great bass while standing and it would all disappear when I sat down.  Finally, in desperation I moved my speakers closer together and Bam!  I had bass again.

The bass response relative to speaker position seems to be a function of bass driver size, room shape and volume.  If the drivers are too far apart the nodes rise upward and outward.  That is the part I did not visualize- the 3 dimensionality of the bass response until I hit on it.  The good thing is, or what I found is that the bass remains the same when moving the speakers closer and closer together once at the sweet spot.  So it is possible to attain the largest soundstage possible and have great bass by just finding that sweet spot for the bass. 1 inch or less movement of the speakers makes a difference.