Two Band Active Line-level Crossover

The RDL ST-CX2 is a two-band active line-level crossover designed to divide and shape audio for independently amplified full-range and woofer paths. It combines active low-frequency woofer equalization, active full-range equalization, adjustable equalization, and a loop-through output in one component. Balanced +4 dBu interfacing, documented low-noise and low-distortion performance, and RDL SupplyFlex power compatibility support dependable integration into line-level audio systems.

Ideal Use Cases

The ST-CX2 is designed for systems in which full-range speakers and woofers are amplified independently. Its full-range output is intended for speaker systems that do not contain a woofer operating below 100 Hz, while the woofer output provides a dedicated low-frequency path. The available loop-through output also supports systems that use an RDL ST-CX2S Subwoofer Crossover.

• Separating full-range and woofer signals before independent amplification
• Adding adjustable equalization to full-range speaker systems without a woofer below 100 Hz
• Applying active low-frequency equalization to an independently amplified woofer
• Feeding an RDL ST-CX2S through the loop-through output
• Integrating balanced +4 dBu equipment with a 24 Vdc-powered crossover

Why Choose This Model

The ST-CX2 provides distinct equalization behavior for each part of the system. The full-range path has a 100 Hz to 30 kHz passband and an equalization adjustment centered at 2 kHz. Its smile-curve can provide up to 8 dB of attenuation through midband audio frequencies. The woofer path has a 40 Hz to 165 Hz passband when set flat, with its boost adjustment centered at 50 Hz. These controls allow the full-range and low-frequency sections to be shaped independently while maintaining unity nominal gain when equalization is flat.

Installation and Integration

The input is a 50 kΩ balanced line-level connection operating at +4 dBu. The two specified outputs are 150 Ω balanced line-level connections at +4 dBu, supporting direct integration with compatible downstream amplification. The loop-through output connects to an input on the RDL ST-CX2S Subwoofer Crossover when an expanded subwoofer arrangement is required.

RDL SupplyFlex power input configuration permits operation from ground-referenced, floating, or bipolar 24 Vdc power. The stated power requirement is 24 Vdc at 40 mA. Recommended power supplies are the PS-24AS for the USA and PS-24AX for international use; a power supply is not included. The specified ambient operating range is 0°C to 55°C.

Performance Highlights

The ST-CX2 is specified for greater than 18 dB of headroom and an 18 dB-per-octave out-of-band rolloff. Its listed frequency response is 100 Hz to 30 kHz within ±0.5 dB. With equalization set flat, gain is unity at its nominal setting. THD+N is specified at less than 0.075% from 100 Hz to 30 kHz, while residual noise is below -80 dB when referred to +4 dBu.

• Full-range passband: 100 Hz to 30 kHz
• Woofer passband when flat: 40 Hz to 165 Hz
• Full-range equalization center: 2 kHz
• Woofer boost center: 50 Hz
• Maximum stated midband attenuation: 8 dB
• Out-of-band rolloff: 18 dB per octave

What Makes It Different

Rather than providing crossover filtering alone, the ST-CX2 combines two purpose-specific signal paths with adjustable equalization. The full-range smile-curve addresses midband response, while the woofer control focuses adjustment around 50 Hz. The loop-through connection adds a defined path to the ST-CX2S, and SupplyFlex accommodates several 24 Vdc power configurations. Together, these features provide crossover, equalization, and expansion capabilities within the same signal-processing stage.

Final Assessment

The RDL ST-CX2 is a focused solution for balanced line-level systems requiring independently processed full-range and woofer feeds. Its specified passbands, adjustable equalization centers, 18 dB-per-octave rolloff, greater than 18 dB headroom, and low residual-noise figure provide concrete performance parameters for system planning. The loop-through output and flexible 24 Vdc power configuration further support integration with compatible RDL and balanced audio equipment.