How to make small room sound bigger

If you're a DIY kinda person there's a whole series of U tube videos from a German acoustic engineer by the name Jesco. They are excellent. The videos on GIK are also informative. If you're not interested in learning how to fix the acoustic short coming in your room and build treatments yourself, there's a whole world of companies that will be glad to help at a cost, but hey it's part of the hobby for me. Good luck, it can be a rabbit hole if you get into it.

sure modify your components  begin with power supply capacitors, install better resistors like Audio Note non-magnetic silver, add filter chokes to the AC and inputs, etc.  

Happy Listening.

Use small speakers on low stands like Isoacoustics with upward tilt to effectively make the room sound larger.

I have a similar sized but carpeted room. To make the room play bigger I always keep the room door open. I also had a closet in this bedroom, I removed the closet doors and got about 4 feet of more depth. Now that can cause other sonic issues, so I have some acoustic absorption panels in the closet. I worked with GIK Acoustics to fix other sound issues with acoustic panels. Cost me $700 for the ugly panels.

I have a floor stander speaker in this small room, and I think I am getting about 90% of the best abilities on the speaker. Still not good as a big room but the sound is fatigue free and rather good. My virtual system of the ’Office’ has some photos.

Office System | Virtual Listening Room (audiogon.com)

You could also work in some DSP using someone like

https://accuratesound.ca 

to put any sized speaker into your room. I used Convolution files (DSP), loaded into ROON Core, that was created by Accurate Sound. That worked great. However, I was able to physically remove reflections by adding an additional acoustic panel and also moving some things away from the speakers. The taming of these reflections made me realize I no longer needed the DSP. Not everyone can do that, so DSP is a good choice to tame a room.

Quite a number of posts here are not answering OP's question, which I must say I find a strange one.

How to make a small room sound bigger.

Why?  My objective would be to improve the SQ.  As some have posted, making the room sound better will not necessarily do that.  In a concrete shell the sound will sound like it's in a big room because of the multiple reflections with extended overhand period.  Agreed it certainly won't sound good, but it will sound big.

Room treatments such as those sensibly advocated above will certainly improve the SQ but they won't make the room sound bigger.

OP, perhaps you will explain your objective more fully?