In a typical UK living room the 25-24s would be considered quite large but in your room there a huge amount of air to move 
How nice the furniture layout looks and the best place for the speakers are not usually the same thing 
Why about lengthways with say 2-2.5 meters between the speakers?
Just a thought, double check they are in phase…sometimes happens in the heat of the moment
Definitely and unfortunately yes.
What do you mean with that?
Sorry, still not used to the forum yet.
It’s a large and very nice room and should be possible to make it work.
I disagree with having to move the sofa up to the wall, it is good to have a meter behind to avoid early reflections from the back interfering. (And I get the walking path, I have it quite the same in my room, (click here for link) )
I also disagree that the speakers are too far apart, an equilateral triangle is just fine and if the room works well you can even have the speaker distance larger. I have 2.6 from speaker to listening position and 2.9 between speakers and there is most definitely no hole.
That said, clearly your listening position happens to be in a bass null, and there may be other issues, so something has to change. The asymmetrical walls of your room should be preferable and will help avoid excessive standing waves, but it can also make it less obvious to find a good positioning.
With bass issues, you have basically 3 options: Move speakers around, move listening position, move both. The listening position will be most important. As said, I totally would not move the sofa up to the back wall (try to keep at least 0.9 meters from listening position to back wall, which will give you more than 1.7 meter runtime difference of backwall reflection), but do try to move it a bit, between the “overblown bass” and “no bass” spots. Also try to move forward. And try different speaker distance from front wall, more or less, together with different sofa positions
If this does not help within the available space, it becomes more difficult because you may have to change more and I am not seeing too many options. But I doubt that this is the case. In this case (or in any, if you want) I would recommend a structured placement method. E.g. google for “The DIY Sumiko Master Speaker Setup Guide”. And/or check this thread:
Just looked at your pic again and I don’t think lengthways is an option.
Oh I got it.
No it won’t be possible. Also the wall where the TV is now has separate audio groups and has PVC pipes for audio cable inside the wall so can’t really deviate from that layout.
Reverse the room side to side?
This will give you the possibility of maximising the width,with the walk through being in front of the speaker/TV position.
Would indeed have been a better layout now that you mention it. However I don’t have electricity on that side nor, coax or UTP connections on that side 
Also the TV can’t be wall mounted on this side because of the windows
If they were out of phase, they wouldn’t sound ok further back by the wall surely.
Great idea bruss, makes perfect sense. This will also prevent 1st reflection from left channel causing time smear and muddling of the sound stage 
ATB Peter
It seems the least upset to domestic harmony but it sounds as though it will need a little work to rewire.
Happy new year to you Peter.
If I ever get over to the UK I will try and come and have look at your system, oh, and your car.
…and meet my wife who is also a counsellor. You shall be most welcome and feel free to email me via Richard Happy New Year to you too. All the best Peter
I haven’t read other people’s responses, but it sounds like a classic case of cancellation. The only solutions are changing speaker and listening positions, and/or (possibly and more than or) room treatment. Whatever you do, don’t try to use DSP to boost the missing bass as that is pretty much guaranteed to destroy speakers
I would second the idea of Sumiko Masterset if you’re struggling with positioning, all it costs is time, though something to aid moving the speakers helps. Herbie’s Gliders make it easy but there will be other options.
Big room maybe too big for your speakers.
A copy of REW (free software) and a measuring microphone such as the UMIK-1 as recommended by REW creators (around £120 new, 2/3rds of that secondhand - and easily sold on if no longer wanted) makes light work of speaker and listening position assessment, showing you visually within a few seconds what the sound is doing at each position you try. More accurate than listening, as well as quicker, though of course you must make a final assessment by ear to be sure you like it!
Just move the sofa back into the sweet spot simple.
Every home and system is a compromise just enjoy it while you can.
Some take it far too far. 
It is weird: did you consider to cover the tv and put the curtains in the two windows behind the sofa?
