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ACU FIRMWARE VER. -
This is a read-only parameter that indicates the current firmware revision of the m905
ACU. Attempts to edit this parameter will be ignored.
XMOS FIRMWARE VER. -
This is a read-only parameter that indicates the current firmware revision of the
m905 XMOS processor. Attempts to edit this parameter will be ignored.
RESTORE DEFAULTS -
This menu item is used to restore the system to factory defaults. Executing the follow-
ing sequence will erase all user defined setup data and return values to their default states.
Once restore defaults is the selected parameter, press the knob. The parameter “no” will turn red. Rotate
the knob clockwise to change the value to “yes”. Press the knob again and the restore defaults se-
quence will execute. If you do not wish to execute this, instead rotate the knob counter clockwise back
to “no” and press the knob to exit edit mode.
SPL METER SETUP
The m905 provides a real-time type IEC Type 2 SPL measurement display. This setup mode allows the
user to configure the different SPL meter parameters. SPL meter setup parameters are as follows:
SPL METER -
This parameter is used to turn the SPL meter on and off. The default is on. When the SPL mea-
surement is on, it is displayed in the normal and setup screens. An off status is indicated on both screens
as well.
FILTER TYPE -
The SPL measurement is calculated based on the desired filter type. Available options are
unweighted, A-weighted and C-weighted. The default is A-weighted. The selected filter is displayed on
both the normal and setup screens.
For more information about SPL filtering, see: http://en.wikipedia.org/wiki/A-weighting
PEAK MODE -
This controls the behavior of the SPL peak measurement. Available options are decay (3s),
decay (5s), decay (10s) and hold. The default is hold. When decay is selected, the peak will decay after the
selected time. When hold is selected, the peak is held until the user clears it by pressing and holding the
MON>CUE /spl clear button.
RESPONSE -
The response controls the ballistics of the SPL meter. Available options are slow and fast. The
default is fast.
12 About Crossfeed
When listening to loudspeakers in a room, your left ear hears sound primarily from the left speaker (and
vice versa) but also receives a signal from the right speaker at a lower level and with some time delay
compared to the right ear. As well, the right speaker sound that reaches the left ear does not have a flat
frequency response as the sound waves have traveled around the shape of your head before reaching
your left ear. The brain uses delay, level and frequency response characteristics to process the location
of a sound and hence, create an aural image.
When listening through headphones, each ear only hears the sound from one transducer and the
mixing of signals between the ears does not exist. In this situation the brain is left without many of the
psycho acoustic clues required to generate a properly distributed image and an accurate sound stage.
The result is that instruments seem to cluster in the far left, far right or center of your head. Since the
vital clues are absent, the brain has a difficult time deciding how to process the sounds coming from the
headphone, which can result in listening fatigue when listening for extended periods of time. The m905
contains circuitry which electronically simulates the signal cross-feed that occurs in a real acoustic space
and helps the brain establish instrument locations across the entire sound stage. While it is difficult to
perfectly model the very complex level, delay and frequency response characteristics of the head, the
cross-feed circuitry in the m905 gives the brain some of the basic clues it needs and the result is a very