I do notice that, as with my stand mounts, there less bass at my siting position vs standing in the same spot.
Of course you do.
Sound travels in waves. Walls reflect sound waves the way glass reflects light, the main difference being sound waves are so much longer. When waves collide they can cancel, or reinforce, or add together.
If you had a perfectly rectangular room with nothing in it, like I did when my listening room was first built, you could hear this very easily across a whole range of frequencies. But as you put more and more stuff into the room, stereo gear, furniture, anything really, all this stuff breaks up and diffuses and scatters all the shorter wavelength higher frequency sound waves. So in most rooms all you’re left with is bass. But the same happens to all of it.
So the bass wave travels out into the room and in no time flat runs into its own reflection. Which at this point if they are both wave crests then they add together and the bass at that location and at that frequency is louder. But where the crest meets a trough they cancel and the bass is very weak.
This is what you’re hearing, and now you know why. Move slowly around the room, not just left and right but up and down, while playing a repetitive bass line. With only one sub you should be able to find at least a few places where the bass is barely audible, and others where its very loud.
When you find one of these spots remember where it is, move the sub, and go back and listen again. You will find it is completely different now. Moving the sub moved the modal area.
This is why subs get such a bad rap. Its not that they’re bad. Subs are awesome! Its the physics of low frequencies in small rooms that is bad. With one sub all you can do is move the modes around. Its impossible to ever get good smooth bass response with one sub. Impossible. Literally. It would require a sub able to defy the physics of sound waves.
But wait, what’s that? Physics has the answer! Lots of subs! Everything above still applies. But more subs can be placed in more locations, resulting in more but smaller modes, resulting in much smoother, faster, more articulate bass.
Its what we call a distributed bass array, and you can search around and read all about it. Everyone who has tried this raves about it, and because its so incredibly awesome a bunch of us write about it every chance we get. Which I have done many times already. But its a hard concept to get across, so I keep searching for better and better ways of explaining.
Because I’m telling ya, they sure aren’t paying me for it!