I hadn’t looked at the photo, so credit to the ever lovely @tablejockey. First impressions on that score- get the rack on a side wall and at a minimum cover the TV- I like dead space in between the speakers and nothing reflective. People can argue about diffusion or absorption between the speakers but I think it depends on the room and needs. Having the gear between the speakers and the TV screen there is definitely an issue in my book. Others may disagree.
I never owned Tannoys but I get my speakers out from the front wall and aim ’em. Granted, different speakers fire differently- I know people tend to want a big soundstage and also to have more than a single spot for ideal listening, so a lot has to do with positioning. There’s a ton of articles about good guidelines, but somebody who knows Tannoy may be better able to help than general guidelines. Jim Smith (who was ailing last I heard) was the Avantgarde distributor back in the day and had some good ideas on room set up (that was his business, as a service), but went with Tannoys after that. These days I know zero about what he is running. He might be receptive to a paid for call to consult. He used to go to people’s houses to do set up.
My set up may be unique to my system and room, so I’m not saying "my way" is best for you but I’ll tell you what I did:
My subs are actually centered between the speakers but away from the walls as well. I DSP’d them and then roll them off steeply 24 db/octave at 55 hz- my mains--Avantgarde Duos-- are unaffected and run full range directly from my tube amps with no DSP in between. I also adjusted phase and gain of the subs sitting in the listening chair and having help handle the controls.
Although I’ve owned the core of this system since around 2006-7, changing a few things made a big difference:
1. room- I moved. This is a bigger, longer room that is narrow at the speaker end (front wall) and widens. That alone makes a difference. I don’t use a lot of treatment: bass traps, and window treatment in addition to some nice rugs.
2. I worked on the power feeding the system-- checked the meter (with the power company guy’s help), main service panel and feeders were run to a subpanel that connects to big iso transformer (10kVa). I’m not suggesting you get spendy, but just an audit of the power coming in (you have control after the meter, and if you saw the Fremer video, his meter contacts were corroded). I prefer commercial electricians-- they are usually experienced and can deal with the demands of audiophiles, though you may have to educate them.
3. Set up in the room- I was able to set up the system after I moved pretty quickly with some help-- college football players from UT who moved the heavy stuff, I had rough positioning with little effort. My wife helped me dial it in. An inch or a small increment in angle of the main drivers made a difference. And I have a pretty large sweet spot with a back "row." She also helped me with adjusting the subs, and with VTA (something you need not worry about).
4. I changed cartridges, in addition to adding subwoofers and improved turntable isolation. All of it made a difference, particularly in the articulation and "filled in" quality of the bass. Since I'm not urging you to go in records (LPs), such changes as may be made to your digital playback will probably improve your results, but I can't recommend anything. (I do have the facilities to play digital sources on the two systems set up here, but I am primary a vinyl LP guy).
5. Are there reflective surfaces- like windows- in your room? Those need to be dealt with and you don’t have to go all "audiophile" spendy to treat them.
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I guess there are paid gurus to help. I do have a hard time evaluating systems without being in the room, and make no pretensions about expertise. I do know when it sounds better or worse. But, I’d also start a thread on Tannoy speaker positioning because I think that may be where you aren’t getting all out of your system that you could. The rest can be done to the degree of your ease.
Have fun, good luck!
Bill