By Carlos Garza
Originaly Published in Pro Audio Review.
|Aphex Systems, celebrating 26 years in the pro-audio industry, has unleashed a revitalized version of its famous Aural Exciter. The Model 204 Aural Exciter with Optical Big Bottom is a big name for this single rack space box that packs a lot of flexibility into an affordable package. Engineers are constantly dealing with customers who want the loudest mix. “It has to go to 11 and have a big bottom.” Aphex was obviously listening and came up with a pair of effects that create the impression of a cleaner, louder mix without dangerous side effects.
The manual is loaded with useful information on cable wiring and avoidance of ground loops. This includes diagrams for “pseudo-balanced” wiring of unbalanced equipment (for example, 1/4-inch TS to XLR).
The Model 204 also has separate controls for the Aural Exciter and Big Bottom. This means that you can use one channel as a low-end enhancer and the other as a high-end enhancer and bus each channel into separate effects sends on your console. The Aural Exciter and the Big Bottom sections each have a tuning knob that lets you select the range of frequencies for processing. You have to refer to the manual if you want to know exactly which frequencies you are selecting. A continuously variable knob is used to select the amount of harmonics added by the Aural Exciter.
The big story is the Optical Big Bottom circuit. This new circuit features a Light Dependent Resistor (LDR) that allows coupling of a controllable light source to a variable resistor. After passing the signal through the low-pass filter, the signal is fed through the adjustable drive circuit, which feeds the LDR. In principle, the LDR reacts immediately to the bass signal but fades slowly like a long release on a compressor. If you have the drive knob set correctly, you should hear more sustain from only the loudest notes. This is designed to produce a dynamic and resonant bass without a big increase in peak level.
Of course, it will not fix a bad mix, but it can help produce a cleaner overall sound. When bypassed, I felt like I had to work to hear all of the instruments. With the effect in, I had no trouble hearing each part. The whole mix was up front, wider, and more balanced. Every instrument seemed to sit more consistently in its own space. The guitar had more bite, the keyboards were shimmering, the vocal was present and the words more intelligible.
One important aspect of the Aural Exciter and the Big Bottom is that the effects are more perceptual than physical. It sounds like there is a lot more bass and high end than is present on the signal meters. I found myself using less EQ in general. The Model 204 can also be used to preprocess tracks for low-quality playback. Listeners can be fooled into not missing the high frequencies that are lost in typical MP3 and cassette recordings if the high end that they do hear is enhanced.
I created some MP3 files and found that the effect was less noticeable than I had hoped. Cassettes had a more noticeable improvement (possibly because I used a high-grade tape). Some of my customers ask me to prepare backing tracks for dance and vocal competition. The final product, which goes out on cassette, has to sound clear and big. I found that the Big Bottom added a lively punch on most mixes.
Some of these sessions are rush jobs and it’s nice to be able to quickly see the when the input signal is being processed by the Big Bottom. I started with the Tune set at “12:00” and drive knobs turned all the way down. I then raised the drive slowly until the LED showed that the effect was active on most of the bass hits. Then I adjusted the Big Bottom Tune to focus the effect on the kick drum.
The result was more interesting than just adding low end EQ. The louder notes seemed to hang a bit more than the quiet notes. The intelligent transient sensitivity also made a muffled kick drum on one track sound crisp and clear. The effect was like changing a soft beater to a wooden beater. This is a very musically useful effect.
I only had a few quibbles with the 204: I would like to see the frequencies labeled on the front panel for the tuning knobs. I can imagine in a mixing situation dialing in frequencies on a shelving EQ and wanting to adjust appropriate frequencies in the Aural Exciter.
The harmonics that it constructs are useful and musical. You will hear each part with more clarity and presence. The versatility of inputs and separate channel processing makes this a worthy addition to any studio rack or live sound rig. At a suggested retail price of under $400, it is something to get excited about.
(c) 2001 Carlos Garza