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When I step away from my listening position, the boom stops. Strange. Funny though, 'cuz even though the boom stops when I step away, those "C" notes can make the drum kit rattle which is 10 feet away. But standing by the kit, you don't hear the extra boom.
Sorry if I sound like an idiot, the intricacies room acoustics is all pretty new to me.
No...you're not an idiot.
What you are noticing and describing is a very common issue in many rooms...and you're describing it perfectly.
It's a LF node at your listening position, so when you are there you hear it, but when you step away, it seems to disappear, bit of course it's still there, and the LF sound waves are moving through the room.
Not sure how you have things set up...but you might move the speakers/desk a bit forward or back...sometimes even by 3-4", and that node may also move away from your listening position. It's not gone...it just moves to a different spot.
By moving your speakers the speakers you alter where the same outgoing and incoming/reflecting soundwaves/frequencies are intersecting.
Where they intersect (mostly a LF issue), you can get a node or a null.
The frequencies for "C" notes are: C0-16.35Hz, C1-32.70, C2-65.41, C3-130.81, C4-261.63...and so on up.
Middle C is C4...so it sounds like your "low C" is probably the C2, which means you have a node at 65Hz.
Try moving the speakers
How far away are they from the *front* wall? If they are just a few inches...try pushing them right up to the wall, almost touching.
Are these rear-ported monitors or front ported...?
Did I make any sense?