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Field Report: Aphex 204 Aural Exciter and Optical Big Bottom

Field Report: Aphex 204 Aural Exciter and Optical Big Bottom

Jan 1, 2002 12:00 PM, By S. Parks Hall, CPBE

In our world of ones and zeros, we tend to overlook the analog devices still in use throughout the broadcast and recording industry. Not only is analog not dead, many audio professionals seek its use in specific areas. Even vacuum tubes are used in microphone preamps and audio processors in many leading facilities for the perceived warmth and presence they provide.

Performance at a glance

  • Simple controls
  • Broad range of effect
  • High- and low-frequency enhancement
  • +4 or -10dB switchable operating level
  • XLR and 1/4″ I/O

Few products intrigue an analog enthusiast more than a piece of equipment that may contain a little audio black magic. Enter the latest enhancement of the Aphex Aural Exciter, the 204 with Optical Big Bottom. The ancestor of the 204 dates back more than a quarter of a century. When first released in the mid ’70s, it took the recording industry by storm. Many album liner notes boasted of its use. One even boasted of not using it. To this day, they are ubiquitous wherever audio and electronics come together. The 204 was preceded by the Model C2, introduced in 1992, and was the first unit to incorporate the added Big Bottom circuitry.

The back cover of the owner’s manual lists no less than 21 audio environments in which the Aural Exciter may be found useful. Our focus will be where and how to use this product within the radio broadcast environment and to what success. But first, what is it supposed to do?

Aphex believes that electronic sound recording and reinforcement diminishes critical harmonic detail that is at the center of the difference in recorded and live audio sound. The Aural Exciter’s mission is to restore lost detail and nuance by recreating these lost harmonic features.

The 1RU device has two independent channels, each with six front-panel controls: three for Big Bottom and three for the Aural Exciter. Also included is a process bypass pushbutton switch for each channel. For Big Bottom, the controls are drive, which sets circuit input level, tune, which sets process operating frequency range from 50Hz to 190Hz, and mix, which sets the amount of processed audio that is combined back in with the overall audio content. A green LED indicates the optimum setting of the drive control.

The controls for the Aural Exciter circuits are similar to those for Big Bottom. The tune control sets the corner frequency of a high pass filter, which establishes the frequency region within which the enhance process will be applied. The range is roughly 600Hz to about 6kHz. A harmonics control sets the degree to which harmonics are generated from the selected fundamental frequency operating range. These are primarily second-order harmonics.

The mix control varies how much enhanced audio is mixed back into the original audio signal. The 204’s rear panel allows balanced or unbalanced inputs and outputs using either XLR or �” TRS jacks. Separate -10dB or +4dB operating level switches are provided for each channel.

Processing enhancements for Big Bottom and the Aural Exciter take place in a side chain. The results are combined with the original audio in a summing circuit. Since the basic Aural Exciter has been around for years, its use and technology are more readily understood than the more recent Big Bottom. Big Bottom provides the perception of dramatically increased bass power with little or no increase in peak energy. In the Big Bottom side chain, a sample of the original audio is delayed slightly and then recombined.

Going to work

Using Chattanooga-based Brewer Broadcasting’s Urban AC station WMPZ-FM, the Model 204 was placed at the input of an uncompressed digital STL. A pre-processor leveling amp precedes the 204. At the transmitter, overall final processing is accomplished with an Orban 8200. Listening off air while adjusting the Aphex 204 demonstrated just how powerful this tool is. I have used many types of equalizers but none have enhanced the bass region in such a musical manner as Big Bottom. I ended up with the tune controls at about 130Hz and the mix at 12 o’clock. A little bit of Big Bottom goes a long way. I recommend no bass or high frequency enhancement in the global processing. Let the 204 do the work. As for the Aural Exciter, a sense of air and revealing openness can be achieved with careful adjustment. I ended up with the tune control set for about 2kHz with harmonics set at one o’clock and mix set at two o’clock. However, I never felt I could achieve optimum results without the highs sounding a little brittle and on the harsh side. From this experience, one might conclude that the 204 seems more at home when combined with purely analog processing, as this negative side effect did not show up in future pairings.

Using Brewer’s Mainstream Urban WJTT-FM, the 204 was inserted in the air chain between the output of Gentner Audio Prisms and the Orban 8100A with the Card 5. The Big Bottom frequency ended up at about 80Hz. with the mix at 11 o’clock. At times, the bass seemed to pass right through the body, and it was clean. The Aural Exciter was set for about 4kHz, with harmonics and mix both at one o’clock. The effect in the higher region was a nice unveiling of the more subtle instruments and voices with none of the earlier harshness. The impact of the Aphex 204 was so positive here that I hated to take it out for further testing.

To test the unit as a microphone enhancer, it was placed between the output of a Valley 401 mic processor and the input to the Logitek digital console. Each of the 204 channels was used for separate RE-20 mics positioned in front of the console. Male announcers used the mic processed with Big Bottom, and female announcers used the mic processed with the Aural Exciter. With careful adjustment while listing to the individual DJs, stand-out presence could be achieved. Unfortunately, best results called for different settings for each air talent. Good results could be achieved, however, using settings derived from the average of the individual settings.

In the production area, the 204 was placed into the input of a digital audio workstation. The 204 was best used for providing sound enhancements to individual tracks before the final mix. It was particularly helpful in improving the clarity of agency spots or those recorded with less than full care at another station. Using the 204 on the voice tracks can render results that make the announcer’s voice ear-catching.

The Aphex 204 is a real bargain of process power and versatility that is useful in multiple locations. However, obtaining the results I have mentioned takes time, patience and objective listening. Personnel must be trained in its use. Otherwise, a good thing can be misused, resulting in bad sound.

S. Parks Hall operates a contract engineering service in Chattanooga, TN.



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Editor’s note: Field Reports are an exclusive

BE Radio feature for radio broadcasters. Each report is prepared by well-qualified staff at a radio station, production facility or consulting company. These reports are performed by the industry, for the industry. Manufacturer support is limited to providing loan equipment and to aiding the author if requested. It is the responsibility of BE Radio to publish the results of any device tested, positive or negative. No report should be considered an endorsement or disapproval by BE Radio.

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