Moment sit in sofa, have you felt dissonant or not balmy? Besides possibly the condition of the spiral spring not good quality, mistake of sofa measure is proper reason you suspect. For example seat too in, although visual seen good, exactly progressively keep away back we are from arm rest, so also of the size other shares. Seat too high cause our foot palm cannot tread the floor better, the arm rest too low make the back become pain etc.
Then how is ideal of sofa size? For sofa of one seat length of 90 cm (including sofa arm), whereas width can around 95 cm (have including sofa back). Seat high from floor is about 40-44 cm. High of arm rest of floor is among 75-100 cm. This size of course still can be accommodated again, depend on the activity, habit sit, or other requirement but may not digress from measure standard which have been given.
Besides sofa size, according to size or proportion between sofas and room is also have to be paid attention. The sofa we choose not too big so that make the room looks not crowded. On the contrary, big room with undersize sofa also less delicate seen.