Crossover

The SPL Crossover is an active crossover for integrating bass loudspeakers or subwoofers with top or main speakers. Its Low section handles the bass channel, while the Mid-Hi section feeds the top speakers. Each crossover frequency can be set independently between 50 Hz and 120 Hz across 6 positions. The Low filter has a 24 dB per octave slope, while the Mid-Hi filter can be switched between 12 dB and 24 dB per octave.

Variable phase control helps align the top speakers with the bass loudspeakers or subwoofers. A toggle switch activates either 0° or -180° phase, after which the control can be used to establish simultaneous operation. The phase control can also be switched off, removing it from the signal path.

The Low section can operate in mono or stereo. Set it to stereo when using 2 bass loudspeakers or subwoofers, with 1 connected to the left channel and 1 to the right. With a single bass loudspeaker or subwoofer, the mono setting creates a mono signal from the Low frequencies and sends it to both Low outputs, L and R.

The Mid-Hi filter can be switched off when the top or main speakers are to operate full-range. A Low Cut filter removes frequencies below 20 Hz, reducing the need for the power amplifier to reproduce inaudible low frequencies and relieving the loudspeaker.

The bass loudspeaker or subwoofer level can be adjusted from -10 dB to +10 dB. This allows corrective adjustment of the speaker system and can also add bass to recordings with limited low-frequency content.

2 mechanical VU meters show the input levels for the left and right audio channels. The VU switch allows the display to be optimised for different signal levels. Inputs include balanced XLR sockets and standard inputs using gold-plated RCA sockets.

Balanced XLR Low and Mid-Hi outputs connect the power amplifiers or active loudspeakers, together with the bass loudspeakers or subwoofers. Balanced connections also support long cable runs, including connections to mono power amplifiers positioned next to the loudspeakers, without the risk of interference.

AMP CTL Out can switch the standby mode of up to 4 devices with 12V trigger inputs on and off together with the SPL Crossover. This is particularly useful for power amplifiers. AMP CTL In allows a preamplifier, such as the Director Mk2 or Phonitor x, to switch the standby mode of the Crossover itself on and off.

The SPL Crossover uses VOLTAiR Technology, a 120V audio circuit technology operating at a DC voltage of 120V. This is 4 times the voltage used by IC-based semiconductor operational amplifiers. The audio circuitry operates at +/-60 V and uses SPL 120V SUPRA operational amplifiers, which were developed to handle this voltage. Conventional components and operational amplifiers would be damaged by it.

The 120V circuit design provides technical benefits in dynamic range, signal-to-noise ratio and headroom, as well as detailed and relaxed audio reproduction. The 120V designation refers to the internal operating voltage used to process the audio signals, not to the local mains voltage.

Inside the unit, the mains voltage is converted to the required secondary voltage by a linear power supply with a toroidal transformer. Rectifiers then convert the AC voltage into the DC voltage required by the audio circuitry.