I’d certainly start with the speakers away from the back walls, toed in, maybe a bit of acoustic treatment behind them and into the corners, and have the listening position towards but with a gap to the back wall, and consider some kind of absorbing material on that wall too.
Also try to get the distance between the speakers roughly 80-85% of the distance from the speaker to the listening position as a starting point.
Then I’d measure the room and see what was happening, and iterate from there.
Pretty much what I was imagining. Will report back in a few months when he’s in and set up
My room is approx 5m x 5m and luckily no real issues when I had the hecos. These speakers could do with a 7m x 5m room I’d say,however the neighbours aren’t up for crashing the wall out and extending into their living room.
Wouldn’t have thought the direkts should be to fussy due to bottom firing ports
what is the room height?
Sadly I don’t have that detail - Typical 70’s bungalow though so low would be my guess
8 ft? 2.40m?
Why would you want to do this? Then you’d just end up with absolutely no bass of any kind.
no, you’d have a near flat response and just have to turn the volume up
That doesn’t make any sense whatsoever, and is either a highly successful troll, or one doesn’t understand how nulls work 
This solution is no different to adding gain to a null. You cannot fix a null with EQ. If you add energy to it, you increase the null. If you make everything else quieter, and then turn volume up, you’re still pushing energy into the null.
A decrease of every other frequency is the same as a boost of the affected range. This doesn’t fix the problem. You cannot electronic your way out of an acoustic anomaly
I was thinking of your space, and also @hermit’s lovely room.
So far, I am dissapointed in the lack of drawing in this thread, so here’s my contribution.
probably not understanding but that’s the way roomperfect did it, and it didn’t sound too bad.
It’s not 100% perfect but was my preference over lots of stupid looking panels everywhere.
The problem is it forces your amp and speaker to over work, to try and fill the null. It’s hugely inefficient and potentially damaging as you go looking for more volume and realise that whatever frequency is missing suddenly bottoms out your bass driver.
A better way to do it, if acoustics can’t be fixed would be to use very small speakers, and use a large number of small subwoofers spread across the room at varying wavelength points. With proper tuning, that can be used to flatten out the frequency response at the listening position
Embrace the boom …remove the blue tac …ease off the cart bolts … Have one of those beers in the fridge.
Just put a sub in all four corners….. can’t have nulls if ever corner is a source of bass
Let them fight it out to the death
A very quick monkey around with this:
hunecke.de | Loudspeakers Calculator
From the chap who wrote the CaraCad software about 25 years ago, suggests something along these lines, assuming 3.73m wall includes chimney, and longer 3.91m wall includes window
You can drag the speakers around, and the listener, and you can see the green room response graph change.
After a bit of messing about, I ended up with the centre of the bass drivers at 85cm in from the side walls, and 90cm in from the back wall, and the listener position is as shown, but there remains a big peak in response around 45Hz, which stays regardless of speaker and listener position, so this will be the primary room modes.
The eigenmode calculator suggests the big peak in response is due to two primary modes at 44 and 46 Hz, so these are best tackled with membrane absorber tuned to 45 Hz, such as the RPG Europe Modex corner:
The blue line on the first picture shows the room response without additional absoprtion, which is too lively, so some form of absorption from other panels in suitable positions would be useful to bring it down to the green line.
I have RPG Bad Arc panels behind the listener position, and panel absorbers next to the speakers.
If possible I would suggest diffusers on the side walls and ceiling at the first reflections, such as RPG Flutterfree, and RPG Skyline
Plus carpet on the floor, and curtains
Declaration: I have no ties with RPG Europe, and other room treatment manufacturers are available 
Best of luck
Above and beyond helpful. Genuine thanks this offers a good starting point - Will investigate RPG and their wares. - much appreciated
I also quickly threw up an untreated model in my very old copy of Cara software
and ran the positional optimisation, and it came up with:
Listener position: 2.72 m (rather than 3.00 shown above)
Speakers: 90 cm from the side wall, and 105cm from the back walls (rather than 85 and 90cm)
So similar, but slightly different. I suspect that either set would be reasonably ok
So sofa, or listening chair, pulled away from the back wall, and speakers brought in, so quite a tight little listening triangle, but should be ok provided speaker to listener is enough for the two drivers to integrate
