Lexicon MC-12HD - Page 3

These room modes affect the way you hear in several ways – the most pronounced effect of room modes
is to make certain frequencies too loud, but the most difficult to solve is the tendency of some resonances
to linger in a room after the speaker has stopped reproducing them. A very strong resonance can linger
as long as half a second and, in the worst cases, also has a distinct pitch.
These lingering resonances are not always noticed because the frequencies are so low; but they do
present problems because a lingering sound often obscures the details in the following passages of the
music or soundtrack. For example, the lingering sound from a kick drum could mask details of the
following vocal passage. Trying to fix this problem by tweaking your audio controls doesn’t provide a
satisfactory solution because each can cause detail loss in other areas. The other problem is that each
seat in the listening area potentially has different room modes affecting it.
Correcting Room Modes Using the MC-12HD
The only way to properly correct these lingering resonances is
by applying the appropriate filter to each frequency where a
problem room mode exists. The MC-12HD Room EQ
calibration measures the impulse response of the room at
frequencies between 19 Hz and 150 Hz; anything higher than
150 Hz has too small of a wavelength to accurately predict.
The MC-12HD then analyzes the results and applies the
proper parametric filters to neutralize the problem frequencies.
Unlike the typical solutions to these lingering resonances, such
as using graphic equalizers or filters that are targeted to the
peaks instead of to individual frequencies, the MC-12HD
Room EQ calibration takes a different, innovative approach.
The MC-12HD measures the decay time of the resonant
frequency to within 0.732 Hz to identify the problem
frequencies, and then treats each individual frequency with up
to seven separate parametric filters.
2 Microphone Responses (of 4 total)
The calibration then performs a second pass for each speaker to apply general response smoothing from
25 Hz to 250 Hz and to examine the spectrum for peaks and dips; the result of this second pass is
generally a subtle tweaking of the initial calibration response. In addition, during this second pass, the
calibration applies an additional filter at 120 Hz to provide a bass compensation boost.
The two graphs below demonstrate the effectiveness of the Room EQ calibration.
AFTE
R
BEFORE
4 Microphone Responses for the Left Front Speaker – Before and After the Calibration
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