RAM Audio LMS244 Digital Controller
11
Normal Configuration
The four columns Xover1 to Xover4 represent the crossover filter configuration of the four outputs.
Each column is divided into Low and High differentiating between Low cut-off (High-pass filter) and
High cut-off (Low-pass filter) allowing the configuration of the individual cut-off frequencies, the type of
crossover filter used and the Order of each filter.
Values are adjusted by clicking on the desired edit box and entering values with the keyboard or with
the mouse via the up and down arrows. Change of value becomes effective either by pressing Enter
or leaving the edit box.
The activated Xover appears as the response curves in the graphic window. As with the Input EQ
window, the information bar shows the frequency and amplitude or phase of the current mouse
position.
In Normal configuration (selectable on the left-hand side of the window), standard and traditional
crossover filters can be designed. The following filters and slope values are available:
Bypass
No separating filter
Butterworth
6, 12, 18, 24, 30, 36, 42 and 48 dB/Octave
Linkwitz-Riley
12, 24 and 48 dB/Octave
Bessel
6, 12, 18, 24, 30, 36, 42 and 48 dB/Octave
Custom
Customisable filter. Custom configuration.
Adjust the high-pass and low-pass filter of each path by selecting the desired option from the
Frequency, Filter and Order scroll bars.
Custom Configuration
The LMS244 incorporates a Custom crossover Mode which is completely customisable and much
more versatile than the Normal Mode. It allows the customising of crossover filters taking into account
the self-resonant response of the transducers.
CAUTION:
THE CUSTOM MODE IS AN ADVANCED WORKING MODE REQUIRING GREAT
ENGINEERING KNOWLEDGE ABOUT HIGH ORDER ELECTRONIC FILTERS AND
THEIR LINKAGE WITH THE FINAL ELECTRO-ACOUSTIC RESPONSE. SHOULD
THE USER NOT UNDERSTAND THESE PRINCIPLES, IT IS HIGHLY RECOMMENDED
THAT NORMAL MODE IS USED INCORPORATING THE OUTPUT EQUALIZATION FOR
FINAL CORRECTIONS.
The Custom mode allows a skilled engineer to adjust a multi-way system incorporating the possibility
of configuring the resonance frequency and Q (Quality factor) of each 2nd order of a separating filter
thus defining the whole filter.
This way, the derived crossover filters can be much more complex and allow the response to match
the self-response of the transducers without utilising too many Output EQU filters for the final
correction. The resulting filter order is as such, lower and has consequent advantages in as far as
phase response and group delay are concerned.
To be able to work in Custom mode, it is be necessary to set the type of Filter in Normal Mode
otherwise the program will not permit modifications to parameters. Only the current values of
frequency cut-off and Q for each filter of second order in the selected option (Butterworth, Linkwitz-
Riley or Bessel) will be shown on-screen.
Should the numerical order value of a filter be odd (1,3,5,7), then the program will show the value of
the frequency cut-off at -3 dB of the first order filter, and no adjustment for Q will be available.