Check my system updates. I recently added a few very inexpensive Auralex SonoLite 2 x 2 x 1 Inches Panels on my sidewalls that work as advertised. Just over $50 for 3 on sale on Amazon. They also sell wall mount bass trap panels and other isolation devices that I would readily try as well if needed.
Going from hard reflective to soft absorbent surface at prime wall reflection points is bound to have an effect on the sound, probably noticeable in most/many cases. Office partitions as well. Perhaps not to the same extent per square foot as other materials that are designed for the job. Could be a good or bad thing. As usual, it all depends...
KIjanki, by chance, I have similar bare insulation material from house construction covering the concrete wall behind my old OHM Ls in my basement unfinished area. Works to good effect there.