ST-CX2 Line-Level Crossover Filter
The line-level crossover filter shall be an RDL ST-CX2. The unit shall provide one line-level input with a loop-through output, two line-level outputs, and equalization trimmers for each filter. Each output shall be filtered to pass a separate range of frequencies. One output shall be designated the FULL RANGE output, the other the WOOFER output.

The input shall be electronic balanced bridging with a nominal input impedance of 50 kOhms and shall be fully compatible with either an unbalanced or balanced line-level audio source. The unit shall provide nominal unity gain with equalization set flat.

A continuously adjustable multi-turn trimming control shall be provided to adjust the WOOFER OUTPUT audio level at 50 Hz from nominally flat to +8 dB.  This control shall be designated as the BOOST control. The audio frequency response at the woofer output shall be 40 Hz to 165 Hz (± 0.5 dB).  A continuously adjustable multi-turn trimming control shall be provided to adjust the FULL RANGE audio level at 2 kHz from nominally flat to -12 dB. This control shall be designated as the MID CUT control. The audio frequency response at the full range output shall be 100 Hz to 30 kHz (± 0.5 dB). Roll-off of out-of-band frequencies for both filters shall be 18 dB per octave. The slopes of the two filters shall be optimized for all settings of the equalization trimmers and for direct compatibility with an RDL ST-CX2S Subwoofer Crossover. The unit shall employ active filtering.
 
The unit shall provide a line-level balanced audio output at a nominal rated output level of +4 dBu with an output impedance of 150 O. The output circuit shall be configured to produce an unbalanced output of proper phase between the positive output leg and ground.  The unit shall provide minimum output headroom of 18 dB above +4 dBu. THD+N shall be less than 0.075% and residual noise more than 80 dB below +4 dBu for the rated frequency range of the full-range output. THD+N shall be less than 0.025% and residual noise more than 95 dB below +4 dBu for the rated frequency range of the woofer output.

The unit shall be constructed in an electrically non-conductive, thermally conductive enclosure. Internal circuitry shall be protected from moisture and vibration using a thermally conductive compound that permanently secures the circuitry within the enclosure.

The face of the unit shall provide graphical labels identifying wiring connections and operating controls. The controls shall be oriented toward the front edge of the unit.

Connection to external wiring shall be provided using a fixed terminal block on the edge of the unit. The terminal block shall accept wiring gauges from 14 to 22 and shall include a positive electrically conductive mechanism to prevent wire abrasion by the terminal screws.

The unit shall measure 3” (7.6 cm) x 1.6” (4 cm) x 0.7” (1.7 cm) and be compatible with all RDL STICK-ON mounting accessories. The unit shall be supplied with a two part re-closable polypropylene fastener system equipped with a rubber adhesive that bonds to low surface energy materials.

The unit shall be equipped to operate from either 24 Vdc ground-referenced power or from bipolar ± 12 Vdc or ± 15 Vdc power with a maximum current not exceeding 40 mA.  The unit shall utilize an external power supply. The unit shall be engineered, assembled and tested in the U.S.A. and be specified for continuous duty in professional installed systems. The unit shall be specified for operation in an ambient temperature between 0 and 55 degrees C. The unit shall comply with relevant EMC requirements and shall bear the CE marking.

The unit shall be an RDL ST-CX2.