Alesis M1 Active MKII Reference Manual page 28

Speaker Installation
A
VOIDING DAMAGE
The best protection against speaker failure is to mix at a reasonable listening
level. With a +4 dBu input and the input level control set to "6", the M1
Active Mk2 speakers produce a sound pressure level (SPL) of 85 decibels at 1
meter, which is a good working level for mixing. At maximum output before
clipping, they can generate peak levels
which may cause hearing loss after prolonged exposure. While the
biamplified design of the M1 Active Mk2 avoids the common "blown
tweeter" problem of conventional designs (when a broadband amplifier clips
on a bass note, it sends unusually high energy to the tweeter, which tries to
reproduce the square wave), it is not invulnerable. If you need higher power
levels, you are not using the speaker in a near-field application. For
extremely loud mid-field and far-field monitoring, we recommend the Alesis
Monitor Two speaker with a 300-watt per channel amplifier. Many studios
will check recordings on both systems, alternating to avoid ear fatigue and to
gain perspective on the mix.
30
118 dB SPL at one meter – a level
M1 Active Reference Manual