Why does bass have more “punch” when I stand up vs. sitting?

I experienced the exact same anomaly but in my in my room it was drastic.  Sitting the bass would just go away.  To fix it I just moved to a new house not because of the bass but it didn't hurt that my new location sounds better. 

My main speakers are flat to 20Hz. A standing wave is in the room with them- no bass at the listening chair, which I can't move (and if I did, the bass isn't in the middle, its to the side...). So I installed two subs (both are Swarm subs made by Audiokinesis, since they had to be as close to the wall as possible). One is to my left, the other more to the right and behind me. This asymmetry was enough to break up the standing wave; now the bass is fine anywhere in the room.

If you really want to fix this problem, this is really the best way to do it. Room treatment and room correction won't do it (but they help if the DBA is already in place).

standing also reduces the relative level of mid and high frequencies making the bass appear louder in addition to the room modes.
best results will happen if you can move your speakers well into the room, 4 feet to the wall if possible.  also if you can move your seated position closer but not too close to the wall behind you.  
if your positions are locked then a sub or two is a good option.  

As many have already advised, you are most likely sitting in na bass null. I had the opposite issue where I had a bass node in my seating position and it would disappear when I stood up. I used an online room mode calculator and voila, I had a vertical bass node. Suggest you try the same. Wont cost you anything. Just get your room dimensions and put them in to a room mode calculator and it will show you what's happening. In my experience, you cannot get rid of the null unless you change your seating position. Or like someone else also suggested, get 2-3 Subs around your room, which will help improve the situation. 

Yes, but only by 1/8”. 

Tonywinga.  Thanks. Did you change the angle (i.e. toe in) of your speakers as well?

You can try the "Sumiko Method" of speaker placement, which is a bit more systematic version of what tonywinga recommends.  If you try it, you will be surprise how much a tiny movement of the speaker will change bass response.  Above all else, proper placement of the speaker or listening chair will have the greatest impact on the sound (and any improvement will be free of cost).  You can find a description by Googling the method and buying a copy of Wasserman's "Duet" (A song called something like "The Ballad of the Runaway Horse" is used to find the best speaker location; you will get sick of the song).

It does make sense to put a rug on the floor between the speaker and the listening position to kill some floor bounce, and likewise, to not put a coffee table in front of the listening position (or put stuff on the table to break up reflections), but this really does not have an impact on bass response; bass waves are not affected much by putting minor obstructions in their way.  But, one aspect of floor bounce is important--speakers are often designed to account for the wave cancellation from floor bounce, so one should be cautious about introducing big changes in height of the speaker or the listening position.

I experienced the exact same thing.  I moved my speakers around in small increments.  I ended up increasing the distance of the speakers apart one inch and raised the front of the speakers about 1/4”.  I also had to move my chair forward about 2”.  Now the bass is close to the same standing or sitting. 

It’s reflection : you have to use. Bass-traps and/or diffusers. : you resolve the problem. Your music will only sound better, but also more 3-D. Also a better ratio : high-mid-low.

"Standing waves" compared to "sitting waves."

Mids and highs are the same

What happens to the high frequencies when you stand up? If they don't change maybe you could consider raising your seating position instead of the heavy speakers.

+1 Swarm (distributed bass array)

The rugs should be between you and the speakers; first reflection point is an imaginary straight line from the woofers hitting the floor, then an equidistant straight line to your ears on the couch. Also, the ceiling above that area is a reflection point.

Try putting a big thick duvet down to see if it helps.

Thank you all for not only responding but also for staying on point to my issue. I appreciate your taking the time to read about my issue and the time you took to respond. I will try to respond to all of you in one note.

 

NONOISE: My listening chair is a club chair that has some cushioning and it is about 8 feet from the speakers

LARRYi: I have been trying different speaker placements and do have tube traps. Per your suggestion I did move my listening chair back about 4 inches and it did help. I have been considering a subwoofer. I am not seeking booming bass. I want it to be natural and seamless with my speakers.

MILLERCARBON: My speakers are 62.5 inches from the front wall and 38 inches from the side walls.

MOTOKODUSANAGI: The speakers sit on rugs now and as mentioned above, I do have tube traps in the corners.

DWELLER: The platform you suggested sounds like a good idea. However, the speakers weight 200 lbs, and the base has a good size footprint

ATMASPHERE: As mentioned above, I have started researching subs, but have not looked at the Swarms. Thanks for the tip.

KLIKOMAN: Thanks for the idea of diffusers. I have visited the Gikacoustics site many times, but not the others you sent. I have no intention of changing speaker as I really like my Rockports and I am satisfied with my amp.

MTROT: Thanks for responding

You are sitting in a bass null.  So am I, but since it's a family room and there's not really another way to situate the sofa, there's not much I can do about it.

Room acoustic treatment is most important thing, and a small portion of Hi Fi enthusiasts takes care about it.
I always say - start treat your room at proper way, upgrade it in small steps adding absorbers and diffusers rather than selling the speakers to buy more expensive ones, or buying concert hall amplifiers to prove yourselves that I have bigger and stronger d.ck than my neighbor.
Just follow few basic things in your room treatment from people that know their business:

https://gikacoustics.eu/?gclid=Cj0KCQjwlOmLBhCHARIsAGiJg7nWjJmqN91NALm-aCYxJR0zlkci-s5K7B-NSf-KKc1zU...

https://ssteu.com/acoustic-tube-bass-trap-copy-2E_AUvgHRMDR4S77zrTGl

https://www.rspeaudio.com/ASC-IsoThermal-TubeTrap-11-p/asc-tubetrap-11.htm

Enjoy the sound

Regards
Klikoman

@ditusa - Thx

 Suggestions as to how to have the bass response while sitting as I do when standing?  

@lourdes  Sure- you want to look into something called a Distributed Bass Array. This is a set of subwoofers that allow you to break up the standing wave that you are sitting in. The subs have to be places asymmetrically in the room. They must not have any output above 80Hz or so; else they will attract attention to themselves. They can be fed by a mono bass signal because an 80Hz waveform is 14 feet long; by the time your ears can even acknowledge the bass in most rooms, the bass has bounced off of every surface in the room, meaning its entirely reverberant.

The best subs for this purpose IMO are the Swarm subs made by Audiokinesis. They are designed to be as innocuous as possible- they are designed to sit inside the room boundary effect (IOW right against the wall) and so give bass flat to 20Hz. They have garnered three Golden Ear Awards to apparently others think they are pretty good too.

Try raising your speakers. I had some Hales Revelation speakers that didn't come into "focus" until I put them on chairs. I have my Klipsch Forte's on 8 inch platforms.

Sounds like a null in the room at the seated position; maybe from floor bounce. Experiment with rugs in between and something on the rear wall behind you.

Right. Bass modes aren't just left to right and front to back, they are also vertical. Another common thing bass is reinforced near walls and so almost always more full and round or even boomy, and gets tighter and more punchy as you move away, so standing up is also moving you away from the boomy floor bass towards the middle of the room tight punchy bass.

By standing, you are changing the position of your ears.  Bass modes—where waves are either summing together (increasing in amplitude) or cancelling each other (wave is out of phase)—occur in all directions, including up and down.  These interactions are so complex that there is no formulaic answer— you can only experiment with speaker placement, placement of your chair, try some corner bass traps, or utilize room correction/equalization, or install subwoofers.

Once upon a time, I had my Tonian Labs speakers and listened to them on my overstuffed, microfiber sofa with built in chaise. I was never satisfied with the base. I sold the speakers and then got new chairs before I shipped the speakers.

With the new chairs (Knoll knockoffs) the base improved to the point where I wanted to cancel the sale but the buyer was hot to get them. Turns out the sofa was killing the base performance by absorbing too much of it.

This leads me to ask you what are you sitting on? It could be your furniture and/or it could be your room.

All the best,
Nonoise