RDL STLEQ1 Loudness Equalizer

Herman # RDLSTLEQ1




The ST‑LEQ1 has two line‑level audio inputs and a single line‑level audio output. The audio signal to be equalized connects to the EQ INPUT. If it is desired to mix an unprocessed source with the output signal, this second source is connected to the DIRECT IN input. Loudness equalization is applied to the EQ INPUT signal as the CONTROL voltage is varied.

The ST‑LEQ1 may be operated together with any equipment which provides a 0 to 10 Vdc control. It is specifically designed to operate with other RDL equipment using 0 to 10 Vdc for level control. Because the ST‑LEQ1 works with any RDL VCA module, all RDL remote level controls are suited for use with ST‑LEQ1 Loudness Equalization.

The line‑level audio source is first fed through the RDL VCA product, then through the ST‑LEQ1. The audio output from the ST‑LEQ1 feeds the system amplifier or other equipment. The CONTROL terminals to the ST‑LEQ1 are wired in parallel with the 0 to 10 Vdc terminals on the RDL VCA. The remote volume control associated with the VCA/ST‑LEQ1 combination is adjusted to the normal low listening level, then the installer sets the desired loudness equalization on the multi‑turn trimming potentiometer on the ST‑LEQ1. As the listening level is increased by the remote control, the loudness equalization is progressively decreased until the audio is flat at normal higher levels.
  • Loudness Contour to Follow Volume
  • Improved Aural Flatness at Low Levels
  • Installer‑Defined Loudness Equalization
  • Automatic Loudness Equalization when used with any RDL® VCA Remote

Inputs (2):

Line‑level (+4 dBu nominal)

Input Impedance:

> 30 kΩ (balanced or unbalanced)


Unity nominal (into 600 Ω)

Output Impedance:

150 Ω (balanced or unbalanced)


> 16 dB (above +4 dBu)


< 0.005% (flat response)


> 50 dB (Either input, 50 Hz to 120 Hz)


< ‑90 dB below +4 dBu (flat response)

Frequency Response:

10 Hz to 40 kHz (+/‑1 dB)

Control Input:

0 to 10 Vdc


Flat to −15 dB max (1 kHz, effective boost of low and high frequencies)

Power Requirement:

GROUND‑REFERENCED, 24 to 33 Vdc @ 35 mA

Ambient Operating Environment:

0° C to 55° C

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