Heil Sound of Bob Heil explaining the Parametric Audio Systems (PRAS)

The Heil Sound Parametric Receive Audio System (PRAS) is a state-of-the-art audio system that enhances the internal audio systems of amateur radio, shortwave, commercial, and CB receivers. The PRAS allows radio operators to modify, shape, and improve the audio output of their receivers using three separate equalization controls.

Midrange frequencies are the most critical for achieving clear voice articulation in receive audio. The Parametric Receive Audio System allows operators to have unique control over these important frequencies. First, operators can adjust the parametric midrange filter from 400 Hz through 4 kHz, with the recommended sweet spot being at 2.5 kHz. In addition, operators can control the presence of these midrange frequencies plus or minus 15 dB. Combined with a low-frequency filter down to 160 Hz, and a high-frequency filter up to 6 kHz, the Parametric Receive System provides operators unparalleled control and quality of their receive audio.

The PRAS has three audio inputs; a standard XLR, a 1/8 in. (3.5mm), and a 1/4 in. mono 8 ohm input that can accept the 8 ohm external speaker output of any radio.

There are three audio outputs on the PRAS: balanced XLR and 1/4 in. outputs on the rear panel, and a 1/8 in. output on the front panel for recording audio. The PRAS also has two built-in headphone amplifiers with separate level controls and dual 1/8 in. headphone outputs.

The PRAS Parametric Receive Audio System includes the specially designed Heil HPS-5 Powered Speaker. (The PRAS must be used with a powered speaker). The HPS-5 contains a 24-watt, two-way, ultra-low distortion amplifier that drives a specially designed 5 inch low-frequency speaker with a 3 inch magnet assembly mounted in a resonant sealed enclosure. A passive extended crossover drives a 3.5 inch high-frequency tweeter. The HPS-5, in combination with the PRAS, provides superb audio balance without distortion. The unit comes with a 2 amp power supply, and a 2 amp fuse is mounted on the rear panel. Dimensions are 9″ H x 7″ W x 6″ D. The system comes with an XLR-to-XLR cable to connect the PRAS to the HPS-5.