Speaker placement and: The 38% Rule from Wes Lachot
“Several years back Wes Lachot (a very nice and gentle guy) came with a rule of thumb to define a distance from the front wall of a control room, in order to minimize x-axis (length) disturbances of the length axial modes.”

JBL: Sound System Design Reference Manual
“Sound System Design Reference Manual. Preface to the 1999 Edition: This third edition of JBL Professional’s Sound System Design Reference Manual is…”

Listening conditions for the assessment of sound programme material
“The European Broadcasting Union is the largest association of national broadcasters in the world. “

A Survey Study of Today’s Monitoring Conditions
“When speakers are put in a room all sorts of acoustical interactions occur. The criteria that define the performance and quality of a speaker are completely different from those defining the acoustical behavior of a room and both must be taken into consideration when setting up speakers.”

Survey Study Of In-Situ Stereo
“The in-situ responses of a total of 372 loudspeakers in 164 professional monitoring rooms around the world have been measured after acoustical calibration. All measured rooms have been equipped with factory calibrated three way monitors and acoustically calibrated with standardized apparatus.”

GENELEC: Flush Mounting to Wall
Flush Mounting to Wall:

flush-mounting minimizes diffractions
eliminates back wall reflection
boosts speaker output
removes the front baffle effect
low frequency room resonances need to be attenuated

Master Handbook of Acoustics, Alton Everest: 4th ed., Chapter 25, page 491 wrote:
Speaker-Boundary Interference Response:

The next type of acoustic distortion is due to the coherent interference between the direct sound of a loudspeaker and the reflections from the room. It is called the speaker-boundary interference response, or SBIR. The room’s boundaries surrounding the loudspeaker mirror the loudspeaker forming virtual images. When these virtual loudspeakers (reflections) combine with the direct sound, they can either enhance or cancel it to varying degrees depending on the amplitude and phase relationship between the reflection and the direct sound at the listening position.

Speakers mounted

SOFFIT MOUNTED MONITORS
“Speakers have two theoretically ideal working conditions. The first is if its radiation space is into a full space (spherical radiation) or into a half space (hemi-spherical radiation). To achieve ideal full space conditions the speaker needs to be small compared to the radiated wavelength. Because the speaker front baffle is small the higher the frequency the smaller the radiation angle will be.”

Soffit Mounted Monitors
“I’ve had clients who know their speakers really well and when they hear them soffit mounted they look at me with amazement!!”

Wall mounted speakers? Not approved.
“The idea might come from some big studios that you see them mounted IN the walls. This is fine, but doing soffit mounting is a pro job. There’s a lot more to it than just building a little shelf in the wall and mounting it flush.”

Soffit mounting speakers for Mastering
“Now, when you take a free standing speaker and flush mount it, you force ALL wavelengths to radiate in the forward hemisphere. This results once again in a 6dB response mismatch, only this time it’s heavy in the bass.”

FREESTANDING MONITORS
“If a speaker is placed near a wall, at low frequencies the wall will start to behave as an extension of the speaker baffle, and this will cause a boost in the bass level.”

Concrete Block Stands
“Studio Monitor Stands on Wooden Plank Flooring – Decoupling”

Soffit mounting of Genelec 8050?
“If I were going to attempt to flush mount those, and didn’t want to pay so much, here’s what I’d try – Build the soffit enclosure and leave a cutout larger than the largest speaker I’d ever plan to install. “

soffit mounting ATC scm 50 speakers
“I want to soffit mount my atc scm 50 s they are active so i understand they will need some air around the back for the amps”

Soffit Simulation Tests
“Whether a soffit-mounted monitor system is provided, or whether the speakers are placed on stands in the room at carefully chosen positions is really a matter for prayer.”