ST-CX2S Line-Level Subwoofer Crossover Filter
The line-level subwoofer crossover filter shall be an RDL ST-CX2S. The unit shall provide two line-level summing inputs, one line-level output and an adjustable 32 Hz boost trimmer. The output shall be filtered to attenuate frequencies above 80 Hz.  

The inputs 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 inputs shall provide common mode rejection greater than 60 dB at 30 Hz and higher frequencies. The two inputs shall actively sum the two audio sources while preserving audio isolation between the two source signals. The unit shall provide nominal unity gain at 63 Hz.

A continuously adjustable multi-turn trimming control shall be provided to adjust the audio level at 32 Hz from flat to +5.5 dB.  This control shall be designated as the BOOST control. The audio bandwidth at the output shall be 22 Hz to 80 Hz.  Roll-off of higher frequencies shall produce attenuation of at least 45 dB at 400 Hz. The upper slope of the filter shall be fixed for direct compatibility with an RDL ST-CX2 Line-Level 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 with the BOOST control set to maximum level. THD+N shall be less than 0.05% and residual noise more than 90 dB below +4 dBu.

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 control 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 30 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-CX2S.