Bass only when I stand up…

I have the same issue without a solution except hanging the speakers for the celling to invert the problem.

I'm hoping someone somewhere has solved this.

Standing waves and null zones.  Only way to really solve is experiment with placement (speakers and listening position), and then augment with bass traps.  Analyzing using REW or the like will help in a more efficient journey towards a solution, as I wouldn't look forward to lugging those phenomenal speakers you have across the four corners of the room.

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.

Those are some serious speakers, producing a lot of bass. The manual has advice regarding placement

https://www.pmc-speakers.com/sites/default/files/attachments/web-Se%20Series-manual-July2022_0.pdf

I would:

1. make the 128 lb monsters movable

a. remove the spikes

b. I would prefer 3 wheels, two front, 1 rear center. dual wheel furniture casters have tight axels that do not wobble. 3 is more weight/wheel than 4; and 3 always settle without wobble wherever you put them.

c. OR add soft or hard ’skid’ plates to the bottom of the frame where the spikes used to be. felt pads on a hard floor, smooth plastic on carpet. move with force, stay put.

Now you have the ability to move them various distances from rear and side walls, until things improve. In current and any future space.

Doubt about movement/stability? See my system, my speakers on 3 wheels with Donna’s precious things on top of the angled enclosures. They move, they don’t move, nothing vibrates off the top. It’s about the correct ’tight’ wheels/amount of felt/amount of plastic (minimum material relative to speaker weight to allow movement)

9th photo shows bottom of speaker: (click FULL SCREEN top right, to see entire image/bottom of speaker/captions)

https://www.audiogon.com/systems/9511

flat 2x4 block on top of front wheels creates vertical angle when upright; 3 wheels (came on JSE Infinite Slope Model 2s. I tried ’superior’ wheels, all had wobbly axels, these dual wheel type are the best, no wobble when in position, with those 37lb 15" woofers doing their thing. Over 100lbs, they stay where I move them.

2. Alternate Toe-In

a. 1 listener: angle so each speaker is aimed directly at the listening position

b. 2 listeners, presumably a small chair in between, or ends of a sofa:

leave inside front corner where it is, rotate so that left speaker is aimed directly at right listener, aim right speaker directly at left listener. Imaging is ’maintained’ to a decent degree because each listener gets more volume from the opposite side due to directivity, as well as somewhat equal volume from speaker his side due to closer distance. It works, fiddle with it.

3. Angle the Speakers Vertically

so that they project the sound UP slightly. Ideally tweeter aimed directly at seated ear height. The combination of angled toe-in and angled vertically alters the direction and reflection of sound waves to and from floor/ceiling/side/rear walls.

In your case, anti-tipping solution(s) need to be solved.

4. Now, measuring tools to help find best location:

a. Sound Pressure Meter

https://www.amazon.com/BAFX-Products-Pressure-30-130dBA-Warranty/dp/B00ECCZWWI/ref=sr_1_4?crid=XHO5MM8W5I8V&keywords=sound%2Bpressure%2Blevel%2Bmeter&qid=1683981123&sprefix=sound%2Bpressure%2Caps%2C85&sr=8-4&th=1

On a tripod, at listening position, seated ear height

b. Test Tones to Measure (CD, not LP)

I use tracks 9-38 of this CD

https://www.discogs.com/release/7290000-Various-Amazing-Bytes

Single 1/3 octave tones, select;play/pause/....... not pink noise, single tones: make a chart, record what you are getting at your initial placement. Make copies, see what changes when moved .....? Take your time, take a break, back at it tomorrow .... Takes careful work, but you will save yourself the trouble/money/ugliness of a lot od room treatment. Perhaps some needed, but less for sure.

Live anywhere near me, Plainfield, NJ. It would be fun to help and hear those puppies!