Speakers in corners - room resonances

I believe hifi speakers almost never sit in a corner (except maybe for Klipsch).
If speakers - with very good drivers (at least with ribbon tweeter & PHL mids) are mounted in or close to a corner of the ceiling & two walls, or about as close in as a Pivotelli wall bracket allows, for a 20 litre box – how many room resonances might it stimulate?
😕
Compared to a more normal position (at ear height, along a wall) - what would it sound like?
Any experience, or acoustics theory?

Thanks

Found an Acoustic Control Manual which states:

The speaker will excite various standing waves of the room depending on where it is located. If it is in a room corner, it will of necessity excite all the standing waves.

If it is placed out from the walls a few feet and not close to a corner it will selectively excite those standing waves which have maxima near the speaker. (A sound source located at a minima of a standing wave will not excite that particular resonance very much. If the minima were truly a null, it would not be excited at all.)

Therefore, the location of the speaker in the room has a great deal to do with how much energy it puts into the room as a function of frequency.

In particular, the proximity to reflecting surfaces greatly affects the efficiency with which low frequencies are radiated. A corner location provides the most low-frequency energy, and a side wall location provides somewhat less, while a location away from walls provides the least. Some loudspeakers are designed to be flat when in a corner or against a wall, while others are designed for mounting away from these surfaces.


My question: What is meant by “standing waves which have maxima near the speaker”?

Thanks