Does wall behind wedge monitor affect sound? What about isolating from floor?

Hi.

I would without doubt say that everything around a speaker, and the room itself

with different wall material that the speaker is located in, affect the sound.

If you want more bass, keep it on the floor. You want even more bass, put in a

corner ....

Cheers !

Raising a speaker off the floor will decrease the bass. If a speaker is too bass heavy, doing that could improve the bass.

Quote from xxtwighlight

Since wedge monitors are closed back, does anything behind them (wall) or around them affect the sound?

It's the boundary effect, and it works in reverse order to how boundary mic's work:

Boundary microphone - Wikipedia

In speaker terminology this is called half-space positioning. A 90º corner would be quarter-space, and free-standing would be full-space.

Instead of picking the sound up on a boundary as the mic does, it's being transmitted there (obviously) by the speaker/s. Same principles apply 'though:

1) Most frequencies, especially long-wavelength (bass) ones, are reinforced because instead of creeping around (behind) the monitor and dissipating around the room and into the wall as heat, they're mostly reflected back and combine with the monitor's output.

2) Note that phase cancellation will start to creep in the higher the frequency. That's 'cause the driver/s in the wedge you're using cannot be physically positioned flush with the wall's surface due to their physical size and that of the enclosure, so the shorter (higher-frequency) wavelengths are more-likely to be phase-cancelled as reflections bounce back off the wall inverted 180º or any significant amount.

Soffit mounting overcomes this limitation; you might have seen speakers mounted into walls at "big" studios - that's what that is.