What makes the biggest difference in sound quality?

Sorry but if you read wiki Helmholtz resonators the basic fact are explained...

If you type imaging for example. scientific articles are there...

one of my main inspiration for example:

https://www.semanticscholar.org/paper/The-relation-between-spatial-impression-and-the-law-Morimoto-Nakagawa/ba829e4e0788024adb236c16c89572ab43d7e838

It is an optimization method with many resonators...You tune them one at a time...

You LEARN how to listen at the same time...

i design it , no one explain that to me...

but with just the basic elements i described anybody in a dedicated room can begin to LISTEN and have fun at NO COST...

Helmholtz is the creator of room acoustic but nobody ever said it this way why?

Because small room acoustic existed only for the few last decades ONLY with the consumers access to small audio system...

And why nobody ever dare to talk about H. method before me?

Because all consumers audio market conditioning is directed towards the GEAR engineering and not toward acoustic and psycho-acoustic method..

Most people think they listen music directly from the gear.... The room is passive object which dont exist and must not obstruct the sound coming from the speakers... But small room acoustic is not big Hall acoustic....

Small room acoustic is more of a contemporary phenomena, but even in ancientime some H. method were used before H created them in modern context...

Amphiteater acoustic exidted for millenia....13 feet square acoustic room control, or near these dimensions , is a few last decades old and was bown with the recent audiophiles consumers ...

It cost nothing but it take the time to learn how to hear and listen timbre and it take a dedicated room... It is not for most people....But if i did not speak about that who will?

Even acousticians debate the rignt way to accomodate a room like mine:

13 feet irregular square with 2 windows... 8 1/2 feet roof....

i take the bull by the head, i sit, listen and i have the fun of my life ...

It is described in my now abandoned thread journey : "miracles in audio... "

I have tuned my system by ear, chasing that human voice.

Thank you for the info @mahgister, I’ll read up on this method, sounds very interesting. My next project is to build some diffusion panels. side/front walls, and ceiling as well.

My speakers are about 8 feet into a 25 foot long living room, and I prefer a live/dispersed room over an overly treated one.

I have as well...using a wealth of information synthesized over the years and well documented from various sources.

I agree based on experience its fruitless to focus on gear alone without first a focus on integrating the gear into the room properly, starting with the speakers. Lots of proven references for that and many services available to do it for you right if in doubt, if you can afford it. It has made a night and day difference for me. Acoustics are 90% of the battle.

Transducers (speakers and phono cartridge: these are the areas to focus on most of all. 

Transducers are the points that transform energy from one to another. (electrical to mechanical/mechanical to electrical).  These two processes have the most variability in design, engineering and manufacturing.  The difference between two preamps is small compared to these.      

 Brad

It seems that this thread has brought out some important aspects about pursuing high end sound. Lots of things matter. The breath shows how everything matters… since individual experiences are so widely distributed. It also shows one of the reasons it is such an intriguing pursuit… you can continuously improve your system by working on the finer points. Speaker placement, room treatment, power cords, cable elevators… etc.

I completely upgraded my system about a two years ago. Just plunking down new components each created a “wow” moment. I enjoyed every minute as the component broke in. Then after some time, I would actively make a change… new interconnect or, power cord. One by one interconnects as the first confirmed my views. I was lazy. I didn’t get around to fiddling with speaker toe-in for over a year. My speakers were known to disappear… voila, they disappeared, soundstage increased greatly. Most other pursuits don’t offer such opportunity for improvement. While the character of my system has not changed a bit since I established the major components… the details of imaging, detail, soundstage… have improved dramatically.