Subwoofer placement - does it matter?

The lenghth of a 40 hz sound wave is 28 feet.  I don’t see placement of a sub to matter all that much unless it’s in an auditorium

Placement makes a huge difference that is easily measured with a real time analyzer and measurement microphone.  I did a bunch of that when I was younger and differences can be huge.  Resonances build up and the sub in a certain spot will excite certain resonances way more than in another spot.  You can just put on some bass heavy content and walk around the room and notice huge differences.  Some places will be very bass shy but if you stick your head near a corner the bass will be much stronger.  It's not subtle.

If I need to measure it, it seems it can’t be heard.  Diff spots in room are diff for sound which makes sense.  It sucks that main speakers generally don’t do well with wide dispersion, which is another issue.

Hi OP,

So the buzz words you are talking about are "room modes" and "Shroeder frequency" and "standing waves."   They are VERY much in play in your average living room, creating almost perfect nulls and up to 200x power (~ 20 dB or more) magnification in tight bands.

I strongly encourage you to read up on the subject outside of here. It is exactly because of these issues that trying to get a flat response down to 20 or 16 Hz is the most dangerous and vexing problem for most audiophiles. In these depths is where the mermaids and dragons live.

Best,

Erik

This is an easy place to start.
https://www.youtube.com/watch?v=AV3oLLMgS-M

Even if you can’t locate your subwoofer in your rooms main mode locating it the general area can help the effect at your listening position.