Muffled vocals

Your room is very close to the size of mine, cal91. From what I had read when I was setting things up, I was very hesitant to move the speakers closer to the front wall or further apart.
I finally kept pushing them further out, one week, and now they're 30" off the front wall (to the front of the speaker), and 28" from the side walls (from the center of the speaker), which puts them 8' 10" apart.
They're toed in about 20 degrees.
The sound-stage is now the best it's been; wide and deep; and the vocals are more centered.
However, I've always found that vocals are offset L or R a little, especially if there is more than one singer. One sings to left the other sings from the right. And Elton John's piano is never at center stage.

My ears are just under ten feet from each speaker.

Anyway, hope this helps.

Dave

When I got a new DAC/SACD player, (and pretty new way better speakers) I found using female vocals I could better arrange the speakers to give me a better defined soundstage with perfect vocal reproduction.. ONLY by moving the speakers to find that spot.It was close to where I had them, but without moving them the vocals were still indistinct. It was a matter of inches.

The distance between the from wall and side walls need to be greater. The front wall is for base and soundstage, the side walls are for timber and image . You need to find a good recording like Jennifer Warrens Famous Blue Raincoat where her voice is dead center and adjust your speakers front to back till her voice is dead center. Your speakers at 30 from the front and 28 from the sides are to similar, try further apart and adjust the toe in so you can barely see the inner side of the cabinet. The distance between the speakers and your listening position should be 1.2 X the distance of the distance between your tweeters.

The above speaker suggestion is WASP and takes time to fully understand and get correct but if you take the time you will be greatly rewarded. Speaker placement I believe is another component and is as important has your other primary source,dac/server, TT, pre, amp, power, cables.

The front wall is for bass' not base.

Geez mon, I hope we're allowed spelling errors. Lol.
As soon as I read your bit about the similar dimensions side and front, it clicked. Yes, everything I read suggested unequal distances.
I was concentrating so much on the music, and trying to ID and assess the changes that I forgot that point.
It sounds pretty good right now, but not for all genres of music. Rock, female vocal and orchestra are quite good, but Jazz doesn't stage well.
I'll alter the dimensions this week and maybe I can improve it more.
Thanks.

Dave.