I don't think a five cornered room is a challenge for Audyssey once speaker placement is done properly. Please allow me to give you some "tips & hints" that may improve your SQ in your otherwise nice living room.
1. Front L&Rs would be better placed if they were toed-in to face the MLP. Even though they are placed on the front wall, the use of speaker wall-mount hardware would allow proper angling. When done that would surely improve on-axis (to the MLP) performance both for FR issues and SPL issues and would also reduce reflections coming from the side walls.
2. Center speaker issues: as I see, that poor center speaker is now placed too much to an un-preferred position. Pullling it out just by 2-3 cms would improve dialog intelligibility, though it seems that a tilt made in order to face seated ear height is a "hard row to hoe". Nonetheless, there is also room for improvement here.
3. Sub placement:: if it were me I would relocate that little rack on the left side of the TV accomodating the Denon leaving enough room on the sides for the down-firing Jamo sub to perform better, while the Denon AVR could be placed into the central rack under the TV.
4. Can't see the rest of the room on your single photo, so at this time I can not comments on your surround placement.
Thank you for your suggestions.
I do like those reflections, I always liked larger than life sound. At one time I fancied Mirage omnis, but funds were tight, and now I have other priorities in life.
The speakers, the electronics and the TV are located in the "chopped off" corner of the room. So, in a sense, it is a diagonal setup. The surrounds are in the worst possible place. The plane of the two surrounds is not parallel with the plane of the two mains. I don't mind the center's position, I have no problem with dialogues. After all, why have I RC if it can't cope with a suboptimal center speaker placement?
Regarding the subwoofer, it is a front firing sub and it is not a Jamo. All speakers are dirt cheap System Fidelity. The 5.1 setup was some 150 USD (32000 HUF).
I tried three places for the sub, and the current place is the best possible. The freq. response of the other speakers are not bad, but they all have a nasty sounding peak around 4K so a good EQ is necessary. Audyssey took care of it.
This is a very-very compromised setup but thanks to Audyssey it is far from unlistenable. Without room correction (and DEQ) I would be forced to argue with the wife about the floor plan, the placement of furniture, and so on. Doesn't worth the hassle. Before the complete makeover of our apartment I had a more regular setup (not diagonal) and it was better, but the room looks much nicer now (she was right), and it will remain this way.