Get the geometry right first and most of a 5.1's problems never appear. None of this needs tools, only an evening of moving things 30 cm at a time.
Front left and right form a rough equilateral triangle with your seat: if you sit three metres from the screen, the speakers sit roughly three metres apart, angled slightly towards you. Tweeters near ear height when seated, which is usually 90 to 100 cm off the floor. Give them a little breathing room from the wall behind, 30 cm or more, or the bass thickens and imaging flattens. On a marble floor, stands or spikes matter more, not less.
Centre as close to screen height as possible, aimed at ear level. If it must sit low on a TV unit, angle it up. Not inside a closed shelf. Directivity matters most for voices, and the consonants that carry intelligibility are the first casualty when a centre fires at your shins.
Surrounds to the sides or slightly behind the seat, a little above ear height, roughly 90 to 110 degrees from the front. Higher than that and they lose the effect; on the floor and they are furniture.
Subwoofer where the room says, not where the cabinet has a gap. Our sub-placement answer covers the crawl method; the short version is that position matters more than model.
And the seat itself: hard against the back wall is the worst spot in the room for bass, because pressure piles up at the boundary and everything booms. Even 40 to 60 cm off the wall helps. Your sofa is part of the system whether it likes it or not.
Once the layout is right, run the AVR's auto routine, then check speaker sizes and crossovers by hand. Placement and settings together are the cheapest upgrade in audio.
Share your floor plan with the seat and screen marked and we will mark positions on it before you commit furniture. Moving a sofa is free; moving a wall unit after the electrician has left is not.
Not sure what fits your room and budget? Share your room size and budget on WhatsApp. It is a two-minute answer with a floor plan.
