speaker and sub placement - is this good?

Can you put the subs in the room symmetrically? 

And which AV receiver are ou using?

Sorry if it is misleading...

I have only one sub... I am asking which place is the best according to the picture... under the desk or next to the door..

Regarding the AVR 99% I am going to get the Pioneer LX86

Apologies

A few option, I think. Either, place it behind the sofa with the bass driver firing into the wall and set the crossover point to 70Hz all round. 

Or, place it behind the front left or front right speaker - front left would be the better one of the two walls are solid brick. Again, face it not the wall (either one). Crossover can be set to either 70 or 80Hz.

Both recommendations will be out the way. I would put it at the front of the soundstage.

Thanks for the reply!

I have to see if it fits behind the RX6 (left one), probably will move the RX6 a bit forward. So sub will be pointing forward towards the sofa.

How much space do you think is needed between the RX6 and the sub?

Also yes, the walls are stone walls.

Also just in case it won't fit, do you think next to the door (agains the wall pointing towards the desk) is ok?

Thanks

No expert but with a similar layout I know David would also advise experiment plenty of advice on web. I settled for your 'door' position but my sub has two drivers and an eq setup. Most importantly I would try some modest bass traps to avoid holes in the bass. My posts have described how bass boom in one position and holes in another position have been resolved. I would suggest setting up some traps and then trying sub positions by 'crawling'. 

Good luck but remember I know nuffin'.

Cheers

I think centrally behind the sofa might be worth investigating too. If nothing else, visually and logistically a much neater solution.  

Problem is, there is not enough space bhind the sofa, and I cannot move the sofa forward because of the door!

yeah but 1.5 feet is just 45 cm so it would be squashed and tight?

Also, if I manage to fit it behind the sofa... which direction would it be? towards the back of the sofa or towards the wall?

And also, my sofa is recliner if that makes a difference

A couple of things you might like to consider, and hopefully a more expert person can comment. 

You might wish to consider a few variations to the RX6 AV12 package. Swap the FX out for something like the R90HD on their dedicated Radius stands. A real neat solution, the cable plugs into the base of the stand, so no worries about the wall mounting cable issues etc you've posted about. 

Consider a different sb woofer, one that is downward firing. ???

My mind didn't really register what 1.5 ft was

Great choice in speakers!

This is rather tricky for anyone else to give a definitive answer to. From the options you've mentioned I'd say you simply have to place it where is sounds the best. Tricky to acchive at times, I know, but it's the basic rule. The performance of your subwoofer will greatly depend on it's placement and the room itself, just like any other speaker. This is especially true if you do not have a good calibration/equalizing system to compensate, but even then placement is still essential. Compromise is difficult to avoid though, unless you have a dedicated room built from scratch.

My personal advice before settling for a permanent placement is to try out different locations, if possible, during an evaluation period to see which one works best for you. Here's a little tip: buy/borrow extra long subwoofer + power cable if needed (just to use for testing) so you can easily move the subwoofer around without restriction. Just don't forget to run a new calibration procedure after every adjustment (if you intend to use such) otherwise the sound will be unbalanced.

As long as they're not touching, it should be fine. As I mentioned, I would fire the drive unit against the strongest wall, but you can try both ways, and see which you prefer. Adding an Antimode (about £235) will EQ the sub down to 16Hz, which very few receivers actually do (the Onkyo TXNR3010 being one of them, and the nearest equivalent to the SCLX86). This will get rid of any bass issues, wherever you decide to place it.

If it doesn't fit there, then the position by the door should be fine. I personally don't like positioning subs off to one side that far into the room, as I like to keep them between the front speakers where possible, or at least somewhere along the front wall (unless using two).