Originally Posted by mandragora
Room is like 4mtx3.8mt ~2.5mt height and a massive glass door just behind where I'm going to be seated ....
no treatments for now
Thanks for the dimensions and pictures Ben, I can see you have limited options !
I suppose the big question for me, is what are you trying to achieve, and how flexible are you prepared to be ?
For example, the Trinnov is a very valuable piece of kit so, if money is tight but your goal is to get the best sound quality you can, you will end up with a much better result if you sold the Trinnov and switched to a good but more modest brand (eg. Arcam) and put the difference into buying passive treatments for the room.
However that may not be what you're trying to achieve so, to answer your specific questions...
- to create a 4.2.6 layout you could indeed start with the 9.1.6 default and add/remove speakers until it matches what you have
- to get the "best" phantom centre place the front left and right as close together as you can (though the width of your screen will constrain you)
...but in more general terms, you need to maximise the signal to noise ratio. That means getting as much of the energy from the speakers to your ears as you can - ie. maximise DIRECT SOUND, and as little of anything else as you can, ie. minimise REFLECTED SOUND.
Subs don't matter so much, and the ceiling speakers are probably fine, but from the pictures it appears that there may be things between you and the 4 base layout speakers. It's important you remove any obstacles or objects that might interfere, such as the desk chair between you and the front right and the corner of the desk and the back right. I don't know how tall you are, but it does look like most of the sound from the rears will simply hit the back of the chair in the main seating position, so either have a lower chair back or lift the speakers higher and tilt them down.
So in summary, point all of the speakers directly at your seating position and then do what you can to ensure your view of them is uninterrupted.
Now that the direct sound is as good as you can make it, you need to tackle the reflections.
Sadly your room is all hard and flat surfaces, including the floor, and you need to have at least 30% of all of that to be covered. A thick rug on the floor in front of your seating position is an easy win, and then put as big and thick absorbent material in the corners of the room as you can squeeze in. And when I say corners, the first four are where the walls meet each other, but the next four are where each walls meets the ceiling.
There are loads of DIY options available online which can save you a lot of money. It won't look as nice or be tuned as well as a professional installation, but it will still be massively better than relying on the digital world to fix the problems in the physical world.
Hope some of that is useful -