Alesis M1 Active Mk2 Reference Manual page 24

Speaker Installation
V
ERTICAL
Vertical placement of the M1 Active Mk2 as shown in Figure 3 is highly
recommended. This position will simulate the soundfield that will be heard in
most consumers' homes and (to a great extent) their cars. For this reason,
even if the M1 Active Mk2s are positioned horizontally for all of the mixing,
the vertical position should always be used in the final "playback check"
mode. (See next section)
There are a couple of possible drawbacks to vertical placement of a nearfield
monitor relating mostly to room interaction effects. Vertical placement allows
the M1 Active Mk2s to portray your mix with the widest and deepest
soundstage possible, so many people in the control room have an image of
the "sweet spot". However, this wide a dispersion pattern in a control room
with walls in too-close proximity to the speakers can add strong reflections to
the sound you hear, muddying your mix. Page 29 shows the control room
placement/ distance recommendations, which should help you determine if
your available recording space would work well with the M1 Active Mk2s set
up vertically.
22
P R
LACEMENT ECOMMENDATION
M1 Active Reference Manual