CTC, considering the room dimensions, having the sub in the right corner just a few inches from the walls is highly likely to be the best location. So, although you may be looking for a different answer, my thought at this point would be yes, your expectations weren't realistic. Keep in mind that the sub, when properly calibrated, isn't supposed to be heard as a separate sound source, but that the impression should be that it isn't working and the other speakers are putting out more bass.

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Enjoy the music, not the equipment.