Merlin VSM... how far from the walls ?

In a normal home environment, IMO, I think the answer is always
the same - put on a CD with fairly deep bass and a female vocal
and move the speakers around until you get the best balance of
bass and natural vocal timbre. That should get you in the
ballpark and you can adjust from there. Everybody's home is
different and it's impossible to predict how things are going to
sound in yours. I think the early Nora Jones stuff works well,
as her voice is very up front and clear. Her voice should sound
very natural and not bassy or chesty when you get it right. Good
luck.

FWIW,

I've found that this speaker - particularly in the early SE version - really changes character when moved closer to/further from the wall behind it (at least in the rooms in which I've used it). As it gets within a foot and half (or so) of the wall behind the speaker, the bottom end fleshes out quite a bit. For a lot of (tho not all) program material, this is a welcome change in tonal character. The trade-off is that the stage collapses significantly and the presentation "shrinks"

At the four foot distance the OP uses, the staging is full-blown, but the tonal signature of the speaker is leaner. If the bass balance in your room is adequate when the speaker is away from the wall, it's the best of both worlds. If the speaker feels lean, pulling it closer to the wall may (or may not) be a net gain trade-off.

BTW, I had my speakers upgraded six or seven years ago and haven't really had the opportunity to repeat the experiment, so I'm reluctant to speculate how later versions would react to the same placement changes.

All room and system dependent, IME, and MHO, etc.

I had changed my room 3 times in last 7 years,rooms were not very similar..

Merlin ended up in somewhat same position....

so was wondering....

It's all about the room size!!

There is no such thing as one size fits all in speaker placement.