Lectrosonics LE Series User Manual download pdf (Page 4)

EQUALIZATION AND NOTCH FILTERING

FOUR BAND PROGRAMMABLE EQUALIZER

The four band programmable equalizer contains both low and high frequency shelving filters, as well as mid bass

and mid treble bandpass type filters. The low frequency (bass) filter hinge frequency (the frequency at which cut or

boost begins) is 1 kHz. The mid bass center frequency is 300Hz, and the Q of the filter is 0.33. The mid treble

center frequency is 3 kHz, and the Q of the filter is also 0.33. The high frequency (treble) filter hinge frequency is

1.2 kHz. All filters can be adjusted for 10dB of cut or boost. The LE8 uses one filter set with programmable

parameters (instead of eight separate filter sets) to implement the tone controls and notch filters. The filter set is

"time-shared" between up to eight mics. This time sharing is accomplished using the logic outputs from the AP4 or

EP4 module to signal which microphone is active at any time. The filter parameters associated with the active mic

are then loaded into the programmable filter. Needless to say, only one mic at a time may be equalized. When

two or more mics are active, the mic which activates the highest number Logic In on the LE8 will have its filter

parameters loaded. For instance, if mics 2 and 4 were both on, the filter parameters for mic 4 would be loaded.

0 dB

+5 dB

+10 dB

-5 dB

-10 dB

BASS

MIDBASS

MIDTREBLE TREBLE

201011004010

Hz Hz Hz kHz kHz kHz

Figure 2 - LE8 Tone Control Curves

NOTCH FILTERS

The three programmable notch filters are of the fixed depth, variable frequency type. Notch depth is 12dB, and the

notches are 1/7 of an octave wide. The filters are designed to be easily tunable, while being completely inaudible.

The center frequency can be varied from 50Hz to 5kHz. Frequency resolution from 50Hz to 500Hz is 1.76Hz, and

resolution from 500Hz to 5kHz is 19.4Hz.

dB 0

-6

-12

20 200 2K 20K

FREQUENCY IN HERTZ

Figure 3 - LE8 Notch Filter Example

REQUIRED NOTCH

FILTER

ROOM RESPONSE WITH

RINGING

ROOM RESPONSE

AFTER NOTCH

FILTERING

1 2 3 4 5 6 7 8 9 ... 12 13

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Lectrosonics LE Series User Manual Page 4