Product Review

Aphex 204 Aural Exciter and Big Bottom Psychoacoustic Audio Enhancement System

July, 2004

Colin Miller



● Frequency Response 10 Hz - 38 kHz
   (± 0.5dB)
● Dynamic Range 120 dB
● Hum and Noise (Unweighted 22 Hz
   -22 kHz) -93 dBu
● Crosstalk (10 Hz - 22 kHz) -79 dB
● THD (10 Hz - 22 kHz at Max. Output)
● IMD (10 Hz - 22 kHz at max. output)
● Power requirements 90-250 VAC 50
   - 60 Hz 12W
● Dimensions 19"W x 1.75"H x 8.25" D
   1 Rack U
● Weight 6 Pounds (2.73 kg)
● MSRP: $399

Aphex Systems


I suppose that it's fair play. When I reviewed a particular 5.1 system some time ago, I had discussed some of the company's more prominent employees in a somewhat comic capacity, specifically in the context of super heroes bent on revolutionizing the audio playback industry from the direction of loudspeaker manufacturing and distribution.

Though I did make pains to mention others, my main target of interest was Captain Purple, (Barry Ober) “ . . . the weirdest super hero I've ever met.
“Grape costume aside, his exuberance for the seemingly mundane puts many Dungeons & Dragons buffs to shame, consistently riding an edge between irritated and overjoyed, radiating comedy, commentary, and sarcasm at a clip to put a Geiger counter into heat.”

I didn't mean it as an insult. Truth be told, I really admire these guys. But, we all know about paths of good intentions.

It's payback time. Barry's only reaction was gracious and good humored about that whole mess outwardly, in his own way. However, I suspect that on some level my remarks may have peeved a pickle or two.

Why? Well, I have no direct evidence, but I consider the circumstantial clues overwhelming.

Picking up on a qualification I made about accurate equipment not helping bad recordings sound good, or even interesting, shortly after that review Barry started yammering about this Aphex company and a gizmo capable of breathing life back into recorded music, almost as if it could put back what was lost in the recording process, and at a minimum do a pretty good job at faking it. He offered to hook me up with somebody in the company, set up a review sample, yadda, yadda . . . . Sure, whatever, how could it hurt?

Vengeance is a Dish Best Served Cold

Although I had agreed to take a listen to this mystery machine during several of our always interesting (for me) conversations spanning many months, the arrival of such a device did not materialize, and I moved on. Then our paths crossed once more regarding some other product. Barry was setting me straight on a couple of aspects about the recording industry, verbally throwing his hands in the air about recording engineers who committed improper bass management and misguided use of the ‘.1' LFE channel, Surround Processor/Preamplifiers whose design had been corrupted by software engineers run amok to the extent that you couldn't get an unadulterated, unprocessed signal to your speakers if your life depended on it, DVD-Audio titles mastered with great monitoring equipment in mediocre acoustic environments etc., all at the expense of the people who really cared about high fidelity.

Up until then, the conversation was delightful. I really appreciate an opportunity to talk to someone obsessed and knowledgeable about audio, particularly when they're not above telling me that any one of my listening habits might be idiotic. We had tipped over into the topic of DSP enhancement modes for stereo two-channel sources, and in my mere mentioning of DSP stadiums, churches, and rock halls, I felt the woods drop a few degrees right before Barry let loose a few comments on that subject and steamed it right back up.

After clearing myself of the dubious practice of arbitrarily adding foreign reverb to electronically paste an unrelated environment on top of my own, or for that matter whatever might be left in the recording, the topic of the Aphex unit returned, and Barry mentioned that one was coming. I didn't think anything about it, until Christmas when I get a card warning of an impending ‘present.' Two weeks later, the magic box arrived, a tangible, physical, entirely real entity!

Needless to say, my preparation was lacking. I was backlogged with relatively paying jobs. (JJ pays for articles, but I'm too slow to make a living at it.) In addition, when it comes to hooking up the experiment, as the adjustable and variable nature of this unit requires that the listener be nearby to make adjustments, and my source components and processor/preamplifier sit in an adjacent room, I had to make (pull) some Mogami multi-pair snake cable for the processing loop under the house up and the walls. Eventually, I got to it.
And then came the waiter with the cold dish. I was on the plate, apple in mouth. Go time!

What is the Aphex 204?

It is, under any ‘normal' circumstance, a piece of professional studio gear, broadly speaking like a compressor, noise gate, EQ, etc. In other words, an audio processor intended for the benefit of subjective effect. In the words of Aphex's manual for the 204, it is, “An Audio Enhancement System incorporating the patented ‘Aural Exciter' and ‘Big Bottom' processes to make recorded voices and instruments sound fuller, richer, and in the end, more realistic."

This doesn't sound like something that fits the bill as a ‘Secret of High Fidelity,' does it? After all, by it's very self-description, it intentionally avoids the ‘what goes in goes out' pursuit, what is commonly referred to as the ‘straight wire with gain' ideal. Well, truthfully speaking, there are a whole range of components available in the consumer tweak market that serve the same general function, whether they masquerade as ‘Buffer Amps' to upgrade the output stage of your CD player, complimenting that union with a wee bit of gain, extra distortion, compression, microphonics, etc., or a particularly ‘musical' preamplifier, amplifier, or exotic cable combination that some reviewer or another will tout as so magnificent that their system just doesn't sound right without it. They might be right. They might be right. (Intentional repetition for effect, now Pause . . . .) But then again . . . .

Aside from the fact that tailoring a system to complement recordings by using the colorations of components leads to perpetual ‘upgrades,' it is important to concede that the very nature of the recording and mixing process is a flawed, imperfect, and highly variable process where ‘correct' is highly debatable. When it comes to reproduction, the most accurate playback systems still have enough wiggle room between them for hours of yelling between proponents. However, it is not debatable that with any system that can be considered in the accurate camp, the listener will hear the recording more or less as it is, most often an artificial reproduction, for better or worse, and in the overwhelming proportion of musical content, it is far from realistic. In most cases, we're lucky if it's even pleasant under the spectacles of a high fidelity audio system. Remember, most people make decisions about what new CD to purchase based on what they hear on the car radio to or from work. Playback on a system with fairly flat, extended frequency response, low distortion, and let alone any kind of soundstage, is rarely the case.

Unlike most of the manufacturers of tweaks and upgrades available in the high-end consumer market, be they components or accessories, Aphex is entirely honest about the nature of what their product does. They do not claim to reduce some mysterious form of distortion that objective measurements cannot verify, nor do they claim that their product makes the end result any more accurate. Aphex is very clear that the 204 is used entirely and exclusively for subjective enhancement (it feels good).

You can also adjust that enhancement, or tailor the effect to complement the particular recording. After all, anyone with a history of shopping for audio components based on quick and impulsive listening experiences can testify that swapping equipment for the best sound with a shifting music library can easily turn into a never-ending process. Multiple times we arrive upon a particular elixir, and the music sounds like music. Then we eventually notice that some other weakness, prevalent perhaps under different conditions, arises with never-ending despair and in our weaker moments of fading enthusiasm, disgust. Being able to make that change with a turn of a few knobs saves time, effort, money, and some degree of sanity.

And, unlike most products that offer the benefit of subjective experience through coloration, admittedly or not, the Aphex 204 has a more practical advantage. When you actually want to hear the recording for what it is, warts, pimples, road rash and all, you can turn it off completely, either by disengaging the process button, or simply through disabling a tape/record loop.

So what does the 204 actually do if it's not black magic? Well, the 204 has two basic functions. The first, named the "Aural Exciter", uses a patented “Transient Discriminant Harmonics Generator” to add zest and presence to the midrange and treble regions of vocals and instruments. In a mo' less nuttier shell without the fluffy flattery, it creates harmonic distortion selectively, targeting transients while leaving continuous tones more alone. This plain English explanation doesn't sound very beneficial to the audiophile who's subscribed to the notion of purity in music.

However, distortion in certain situations can actually make things sound clearer. Huh? Many pieces of electronic equipment have been harmonically enhancing their way to ‘Class A' ratings and sales in the high-end market for years, but doing it by claiming some sort of monopoly on a more correct means of reproduction. Who can blame them? What audiophile in his or her occasionally right mind is going to consciously sign onto the philosophy that a little more wrong might just be right?
Recording engineers have been sweetening the sound of vocals as a matter of tradition, partly out of an inclination to romanticize the experience toward the immediate, and partly because the nature of a microphone seems to fall a bit short.

One of our staff dug up an article a few months back touting the superiority of tubes over solid-state devices, operational amplifiers in particular, demonstrating the less audible and more pleasant even-ordered distortion spectra at a fixed THD level. It was a really good article, if not a bit misplaced in consumer electronics, as it was actually talking about how the distortion spectra behaved when the distortion levels were relatively high as a result of clipping. If you're getting distortion from clipping in a playback system, either your power amplifier is not up to task, your gain settings are screwed up somewhere in the chain, or a piece of gear is broken. Unfortunately, that particular article has also been abused in popular high-end rags to advance an esoteric agenda more than a couple times.

But, the point is that tubes do indeed sound good in such a case where the harmonic distortion is substantial enough to hear but not so high as to be noticed as distortion. That's not all there is to the seductiveness of tube sound, but it's a significant component. Because of their gentle overload characteristics, tube microphone preamplifiers are especially advantageous. Microphone output varies widely, as the input level can change dramatically simply by a vocalist or an instrument moving forward a few inches or getting particularly frisky with a high note. Without the benefit of a known maximum level, limiters, or compressors before the input of the microphone preamplifier, overdriving a microphone preamplifier is fairly common, and for those looking for a bit more tube warmth, just a little desirable. The typical way to set the input sensitivity on a tube preamp is to run it hot enough to clip obviously, and then back it off just enough to keep distortion at the higher levels subtle. The objective rationale for keeping it on the higher side is the Signal to Noise ratio, but sonically, we've got a serious craving for the harmonic content, yielding fuller, richer, more ‘naturally sweet' vocal presentation.

But the 204 doesn't just add harmonics at peaks. It supposedly targets transients, low or high in amplitude. How it does this, I haven't a clue.

The Aphex also mentioned that the Aural Exciter adds selective phase shift. I don't know if this is just a side effect of the harmonic process, or a thug unto itself, but we do know that phase shifts can enhance a sense of depth, what many refer to as palpability in space, a ‘you can almost reach out and touch it' kind of experience. Phase shifts beyond simple linear delay require group delays. It's not quite like reverb, though in a basic sense it can have a similar effect without messing up the sense of specificity in the sonic image, if the delay is equal in both channels. Products like Carver's ‘Sonic Holography' created phase differences between channels (the argument was that the result was inherently a correction to make sure the left speaker only got to the left ear, and vice versa for the right, so as to create a binaural experience, but we don't have time to get into why it didn't work out that way). The result was that it widened the sound, made it sound more dimensional. Unfortunately, it also made specific placement of items within the soundstage so vague and overblown that when I found what I could do with a good stereo array using the reverb actually in the recording, I eventually chose to do without the holography.

Since the 204 is meant to do identical processing with stereo content, the phase shifting would conceivably only affect the degree of depth, and from what I can tell, it's a relatively subtle effect compared to the more drastic implementations that use all out reverb, subtle or not.

How it Supposedly Works

The Aural Exciter works its magic through a side chain. That is, the signal is split, and one half passes through to the output unfettered, making the purists in us feel good, and the other half goes to the processing leg, to be mixed back into the original signal as desired. The Aural Exciter has a ‘Tune' knob. This serves as the filter that determines what frequency range is going to undergo the harmonic enhancement. That signal then goes onto the harmonic generator that somehow or another targets transients. The character of the harmonics added is adjustable, though the ‘Harmonics' knob. The literature doesn't say, but I'd guess from use that higher settings give you more of the more obvious, higher order harmonics, though it's just a guess. Finally, you set how much of this enhanced portion you want applied to the original signal via the ‘Mix' knob. The whole combination lends itself to lots of fiddling for best subjective effect.

The "Big Bottom" circuit, unlike the Spinal Tap song, has very little to do with women having ‘mud flaps.' Unlike the Aural Exciter, it has nothing to do with harmonics. Instead, the Big Bottom circuit claims to increase sustain of bass transients, or in their words, bass density, explained as a lower peak-to-average ratio to enhance presence and perceived ‘slam.' To say it without glamour, it postpones the settling of transients, degrading the ‘speed' of the signal on the decay side, and in doing so keeps the average level higher long enough for our ears to pick it up more easily.

So, who the heck would want slower bass? We don't really think of slower bass as having much ‘slam.' We'd expect it to be fat and mushy. After all, if you dig up a favorite high-end review where the reviewer went bananas about the bass quality, terms describing speed and dynamic impact seem to go hand in hand. Intuitively, that makes sense. Consider, though, that perhaps that perceived speed wasn't really all that fast, objectively speaking. Sure, if the transient response is really poor, it'll sound poor. However, from a listening experience it may be of benefit that the bass be slow enough to catch our attention. The first time I tried subwoofer design beyond blinding stuffing some drivers into a box, I got it in my head to use 4 NHT 1259 12” woofers and throw them into a suitable box size. I got the units from Just Speakers, now out of business, and asked how they'd do in a box substantially larger than the 3 cubic feet enclosure volume that the 1259 FAQ recommended, say 4-5 cubic feet, or rather two pair lined up in isobaric fashion in a 2 ¼ cubic foot enclosure volume each, citing my desire for the smooth, ‘fast' bass that a larger enclosure allowed compared to higher Q alignments which were said to sound ‘warmer' but sacrificed transient performance.

The guy selling the drivers said that there wasn't anything technically wrong with the idea, but that I might not like the results, as it might sound a bit thin by comparison to the more common, higher Q alignments. I, of course, assumed myself simply more discriminating than their average clients, and opted to ignore him, only to realize later that he was right. I had the sickeningly deep and smooth extension I wanted. Doors rattled, windows creaked and groaned in panic, but the bass just didn't seem quite all there. It was missing punch. More accurate? Certainly, but it seemed like most recordings translated better with that higher Q, punchier bass. I later rebuilt a pair of standard boxes (one driver, one cabinet) with 3.3 cubic ft of volume, and got a good compromise, ending up with a Qtc of somewhere about 0.8 or so. Tight, smooth, and with a bit of kick, and in most cases, sounding more natural.

And so a question remains, why would slower bass sound more natural? Like many things, I've got a theory for that. Recording engineers make a lot of decisions on how they process tracks based on mere convention.

If you've ever heard a live kick drum, you've probably noticed that most recorded kick drums don't sound anything like the real thing. Part of this is simple compression, in that a kick drum at real levels would destroy most loudspeaker setups, and even fairly good ones, if it were presented in its full dynamic range. For this, they heavily compress it. The part relevant to our conversion is that kick drums, while they've got one heck of an attack, also have a substantial boom that follows unless they're really damped with a blanket or something. In order to keep the mix ‘tight', engineers will typically apply a ‘Gate' device to the drum, or other instruments. The gate functions such that when signal levels falls below a certain point for any amount of time, fractions of a second, the gate will mute the signal entirely. This does two things. First, it minimizes noticeable background noise. When a signal goes through, so does the noise, but the signal, being much higher in level that the noise, masks it from our hearing. Secondly, it silences the decay of the initial transient once it falls below a set threshold, therefore making it sound tighter, more damped.

A kick drum is an easy example, but the general habitual overuse of noise gates and compressors is a problem, particularly to us audiophiles who don't really care about 30 watt amplifiers and speakers to match. (As a point of interest, for truly uncompressed recordings, you can eat up headroom at moderately high listening levels right quick, even without lots of bass content, in which case 30 watts/channel with moderately efficient passive loudspeakers isn't even suitable for a near-field application.) I was once fiddling around with a Mackie mixing console trying to monitor uncompressed Hungarian folk music, and with a 30 watt amp, I couldn't get much more than moderate audio levels with the speakers just 4' away. So, I agree that there should be some compression on the final mix as a matter of practical reality, but in most recordings, tracks are compressed, recompressed, and then compressed again, including the mastering stage. The result is loud, but mush and lifeless.

But, back on track, How it works . . . .

Like the Aural Exciter, the Big Bottom also processes through a side-chain, so that the original signal passes on through, and you add the processed effect to taste at the end of the chain. The Big Bottom circuit functions much like a reverse noise gate, up to a point. It doesn't restrict the speed or dynamic range at all during the leading edge of the attack, and so we get our fast hit, theoretically, but it does keep that following decay around just a little longer, and how it does this is really interesting indeed. Unlike a resonant device that keeps the signal around by stretching it out in time, the Big Bottom keeps it around by simply pushing any remaining decay, before the noise gate nipped it, up in level.

Let's go back to the side chain. The ‘Drive' knob sets the length of sustain, and the interesting part is that it's essentially adjusting the threshold of a compression circuit. The result is that it generates a signal where, for a short time, the attack and the immediate decay stay at relatively the same level. If this were a straight compressor, that'd be really annoying, as it'd crush whatever dynamic range we had to begin with. However, remember that this is only the added effect. The leading edge and dynamic peaks of the original signal remain intact on the ‘pure' side. The ‘Tune' knob adjusts what frequency range we wish to apply the effect, and the following ‘Mix' knob then sets the level of that effect. The result? We maintain the leading edge speed and dynamics of the initial attack, force the decay, and the average bass level up so that our ears have more time to notice the hit, but don't lengthen the duration of the signal beyond what's actually on the recording. We apply a kind of counter gate so long as there's content, when the decay drops farther the sustain shuts off. As a result, we have our quick finish, and subjectively tight bass.

Compared to Other ‘Corrective' Options

●    EQ     Equalization (EQ) can be a useful tool at any frequency, but it's more often abused than used. The most common anecdote is the top and bottom of the spectrum cranked, in a smile type curve, but I've seen graphic equalizers get set to all kinds of interesting patterns. It can be very useful to do slight tonal alterations on your recordings, or do room ‘correction' by notching the signal to counter a problematic room resonance (in which case you'll need the fully adjustable parametric variety), but in terms of dynamic range, EQ is an expensive enhancement device. Boosting output at, say, 40 Hz, by 6 dB will have a noticeable effect, but it may or may not be enough, and the cost is substantial. A 6 dB boost means that any peaks centered at the boost frequency will be four times higher in peak output. While it doesn't affect the average power output level, or the perceived output level anywhere as much as raising the volume 6 dB, it sucks up power on those peaks, and in the case of low frequencies, driver excursion. When you consider that a 10 dB boost in a high energy band will likely cause peaks 10 times as high, you run out of options fast. Don't get me wrong. I'm a full-fledged proponent of the careful use of EQ, but it has limitations.

●     Dynamic Expanders      DBX used to offer a dynamic expanders. It functions in a manner opposite that of a compressor. A compressor has a threshold, or a level that if the signal exceeds, it will compress that signal by a ratio, say 10:1, or wherever you set the compression ratio. As an opposite function, an expander will increase the level of a signal when the input rises above a threshold by a particular ratio. Expanders can make the sound more ‘Live', but obviously, by achieving their goal of increasing dynamic range of a recording, they increase the required dynamic range of the system at any playback level.

While the dynamic range cost is steep, and in a sense the whole point, the initial experience can be exhilarating. I was once bamboozled out of a pair of loudspeakers in trade for another pair when I auditioned the speakers for trade with just such a device. To be fair, the lawyer didn't lie, and showed me exactly what equipment he was using. He just didn't point out what that DBX unit was doing. I say initial experience because dynamic expanders have an inherent problem. Even if you've got more power handling and power than you know what to do with, dynamic expanders cannot undo previous compression accurately. Compression is a variable function of amplitude that applies variable thresholds and compression ratios, and if the threshold and ratios are not lined up between the compressor and expander, what comes out of the combination is not a neutral in-between.

Considering that thresholds and ratios are twiddled all over the place, and recordings are compressed many times over in many different ways (may compress a track, then compress the whole mix all over again, then compress it more on mastering), it's pretty much a guarantee that you won't be able to get anything natural-sounding out of a dynamic expander, regardless of the extra excitement. Add that to the fact that most systems suffer from very limited dynamic range, and it really makes the practical, long-term, non-fatiguing use of a dynamic expander difficult.

●    Subharmonic Synthesizers      Audio Control called theirs a Phase Coupled Activator. DBX supposedly made one for Disco use, before my time. (The only polyester pants I ever owned were made by Ben Davis.) Instead of extending frequency response by boosting the lowest frequencies, they essentially look at your lowest frequencies and generate frequencies at half of that. For instance, if you've got a note with a 30 Hz fundamental, it'll create a 15 Hz tone, in which case you've technically dropped the note an octave (it leaves the 30 Hz signal there as well). What it imparts is extra thump and weight. They're really great for getting extra low-frequency energy into a system capable of dealing with it, and superb for doing crunch tests and trying to instill a sense of awe in your friends. While it is good for showing what really low frequency content feels like, it wasn't my personal cup of tea for listening pleasure. The marketing language argues that it only puts back what was originally there in the first place, though I don't buy that. If the low frequency information was filtered out, it would still be there, just attenuated, in which case you could ‘restore' it by boosting, not generation.

By the mere fact that information must be synthesized, i.e., made out of nothing, confirms my listening experiences which find the effect, though impressive, unnatural and eventually irritating. To be fair, the Audio Control implementation was adjustable, so you could dial in as much or little as you wanted, and some bass freaks (ahem . . . low frequency connoisseurs) love theirs so much you'd sooner get one of their children than their subharmonic bass synthesizer. I'm not one to get judgmental about what other people like, so long as they keep their personal preferences as such and don't pretend to use it as proof of what others should be doing.

I won't say there's anything necessarily wrong with this family of enhancers. But, there is a practical hurdle associated with them. While it is a good way to work out your subwoofer, it can REALLY work out your subwoofer, eating up amplifier power, and more significantly, cone excursion, limiting your total playback dynamic range, potentially increasing distortion, and possibly endangering the subwoofer driver itself. Even moderately large subwoofers may have problems with gobs and gobs of infrasonic content. Should you have the benefit of four 18” monsters accompanies by a kilowatt each, well…good for you.

●    Harmonic Saturators       Harmonic Saturators are the most like the Aural exciter in basic concept, though they work more like the aforementioned tube microphone preamp in practice, adding harmonics in proportion to signal amplitude as opposed to transients. A company once sold a very popular CD player analog output stage “upgrade” unit which served as a buffer between the CD player's own analog output and the preamplifier's input. Some reviewers gave it some wide praise, and truth be told, I have no doubt of the subjective benefits. It supposedly provided 1 dB gain, which is the easiest way to make people hear ‘veils lifted' and ‘inner detail', but it was also a tube stage that possibly imprinted its own harmonic signature.

I don't mean to sound down on these things. I owned a very effective tube saturator that sounded absolutely splendid with many recordings, adding warmth and texture to pretty much anything I threw at it. I miss that single-ended, Class A tube preamp, and if I could pull a redo, I wouldn't have traded it as part of a system in exchange for a motorcycle. Come to think of it, I think I got the worst of that deal as well. I should have kept it around to keep in a tape loop as an analog two-channel enhancement mode, available on my touch panel right next to Anthem Music Logic.

So, where are we?

The Test Drive!

Disclaimer. In most of my tests, the Aural Exciter combined with the Big Bottom improved my subjective listening experience, and I think the two processes are typically complementary. As the 204 is fully adjustable, to the point where you can make it do nothing at all, if you adjust to fit the recording optimally, the worst scenario is that it doesn't sound worse, and as I mentioned before, a tape loop or such makes it possible to actually have no extra path at all with the touch of a remote button. But, like any tool with substantial capabilities, the Big Bottom and especially the Aural Exciter can do way too much. One size, color, or shape in no way fits all. This isn't Spandex. This is the very reason the unit is adjustable. More is not always better, and if you misuse it, what you get will sound really BAD. Too much harmonic enhancement, and it gets brittle, harsh, and pasty. Too much bottom biggering (a la Dr. Seuss's Onceler) and the bass gets thick like molasses and difficult to distinguish.

That said, LET'S DRIVE!

We bounced over the technical aspects of the controls, but we should run over the practical use of the knobs.

The Aural Exciter has three controls:

• "Tune" determines the range of harmonic enhancement. Turn it up and you'll be getting more ‘air' and whispy fluff. Turn it down, and you'll get more midrange body.

• "Harmonics" determines the spectrum of added harmonics. The manual suggests higher harmonics for instruments and lower harmonics for vocals. I suspect they say this because we're more familiar with human voice, and therefore we are less tolerant to coloration, however enticing it may sound. I didn't really like the higher harmonics settings for much of anything. I found that I preferred it set at or just below half way.

• "Mix" adjusts how much of this effect you put back into the original signal. I found this adjustment to require the most variation for my taste. Too little mix and it's relatively harmless, but it limits what you'll get out of the process. Too much mix, on the other hand, is REALLY annoying. Cranking the mix level up is handy to hear the nature of the effect when you're trying to contour the character, after which time you can turn it down for the best proportion. I found that I typically wound up turning the mix level down just a bit after having set it by first impressions, very much like setting a subwoofer level by ear. At first you look to hear the effect, and then you want something more subtle.

The Big Bottom also has three:

• "Drive", as mentioned before, adjusts the length of sustain. Subjectively, it was kind of like adjusting the thickness of the soup base. I don't know if the audio output of my CD player was just higher than usual, but I tended to keep the drive control on the low side, meaning shorter than recommended sustain, or quicker punch vs. a longer kind of throb. Maybe I'm just a speed junkie.

• "Tune", like the same function in the exciter, adjusts the frequency of the effect. Deep bass aficionados will probably want to keep this on the low side, though turning it higher adds a little smack to the mid-bass.

• "Mix", like the same function in the exciter, adjusts the proportion of the effect, so that it sets the level at which the added sustain takes place. Generally speaking, I preferred to have the mix level higher than the suggested range. Perhaps it's related to my preference for the low drive, compensating the shortness of extra sustain by higher amplitude, or maybe I just like the Big Bottom effect more than most people. Don't really know. If any of you have the opportunity to try this out for yourself, maybe we can do a chat session on the topic.

In the ‘Real' World

Keep in mind that whenever I make a % reference on the controls, I mean the position of the knob, not the absolute proportion, though it would be interesting to know what those objective enhancement levels were.

From a bibliographical standpoint, I'm an absolutely horrid reviewer. Until I get all of my CDs on hard disc, I've got them loaded in a changer. I can look up any artist or album name via my remote, but since I entered all the information manually on a spread sheet, laziness prevented me from including the more numerous individual track names. So, if I get the song name wrong on a particular album and you catch it, chances are you probably know the right name, so give me a break and worry about something important. When I get my remote to control Windows Media Player on a machine with a reasonable sound card, I'll get you're the right track names. Until then, accept my apologies and put up with it.

Jewel, "Spirit", that ‘I've been down so long' song - I noticed that if I set the Tune control too low, the effect made vocals nasally. If I turned it up too high, it seemed to miss the vocals altogether, leaving them relatively flat-sounding. Harmonics was the most subtle adjustment, though the differences were still obvious listening real-time and fiddling with the knob. Lower Harmonics settings sounded flat and relatively dull compared to the optimal position, and if turned it too high, the sound became unnaturally sparkly, like a particular solid-state amplifier that was attempting to sound like a Conrad Johnson tube amplifier I had listened to some time back- still interesting, but distracting. The Mix level determined whether our effect came out as a dash, sprinkle, spoonful, or downpour. All the way down obviously defeats the purpose. Turning the level up just enough lifted the immediacy and presence of the performance forward, toward the listener, almost like the vocalist was sitting up, opening her shirt, and making an effort to enunciate between flirtations. Going much beyond that level became absurd, accentuated, and finally shrill, edgy, and thin. The obvious conclusion was that Jewel has a crush on me, and she's got it something bad.

Sarah McLachlan, Surfacing, "Witness" - Although there's a fair degree of variation on vocal recording through this album, it's all quite close (in terms of proximity to the microphone,) be it buried in reverb or right up on you. When dialed in the a lower Tune value, the lower side of Harmonics, and a moderate Mix level, the Aural Exciter brought vocals out of the background with an increased perception of clarity. It wasn't etched like an EQ set for a narrow boost or a peaky midrange driver, but just with depth and dare I indulge in the guilty use of the term ‘tangible palpability.' JJ and Brian are going to give me grief for that kind of potty mouth. When defeating the process for comparison, the results were monotonous and less interesting.

Ben Harper, Burn to Shine, "Suzie Blue" - The beginning of this song is intentionally altered to sound ultra vintage, i.e., old. Ben Harper sounds like he's not only using old equipment, but that they recorded him inside a little box. During this period of the song, the Aural Exciter brought the voice just a little more out of the box and emphasized the distortion. It still sounded old, it just sounded more freshly pulled from the archive, with more vibrant dust. When the recording went regular, and Ben came out of the box, there were still audible benefits. I set the Harmonics to about 40% on the dial, and the Mix level to about 45%. The vocals increased in clarity, and the clarinet lit up its own life. During the next track, "Steal My Kisses", the opening spit box performance had more spit through the Aural Exciter, and the Big Bottom put more kick in the kick drum. Without a doubt, with the 204 disengaged, the performance was a less engaging experience.

Chris Isaak, Heart Shaped World, "Wicked Game" - This was quite interesting, as it was one of the CDs that I would have thought needed something like the 204 the least. I had no problems with the CD as is, and yet I liked it a little better through the 204. Dialed in, cymbals were more vibrant, vocals more embodied with a better feel for detail on sibilants, and the whole ensemble felt more ‘harmonious.' During "Blue Spanish Sky", the 204 brought out the outlines of the horns, and pulled the vocals out of the sea of reverb, yet still wet.

Beck, Sea Change, "Paper Tiger" - When previously set for Sarah McLachlan's ‘Surfacing' Album, the resulting effect was entirely inappropriate. Strings were too plinky, voices overly sibilant. I turned the Mix control down to about 20%, and everything got good. I pushed the Harmonics on the Aural Exciter up to about 30% on the dial, and then right back down. However, the kick drum seemed to benefit from more of the Big Bottom, helping to fill out the bass, make transients richer. It felt less ‘lean and mean', so to speak, but still not mud.

Crash Test Dummies, God Shuffled His Feet - It was now 2:00 a.m., and I'm listening to this whole album. This is a great piece of work, in my opinion, and the 204 made it just that much better. In particular, I noticed that on the "Coffee Spoons" song that the bass was punchier, more tactile, with greater weight. The vocals almost shined with highlights and better intelligibility. String transients improved in attack definition. This was just plain lovely.

Overall, the 204 is addictive. In a way it's reminiscent of an EQ set to a Fletcher Munson kind of smile curve, except that it didn't get fatiguing or take away from midrange detail or sink the sound stage back. Used properly, it's no mere boom boom, tizz tizz widget. The Big Bottom and Aural Exciter effects, in fact, seem to complement each other quite well. While some CDs didn't seem to need as much enhancement as others, the vast majority could be made slightly more attractive with a little polish from the 204.

Captain Purple's Revenge

Well aside from the obvious aforementioned, potentially greater enjoyment of recorded music, I'll tell you about the revenge laid upon me. Consider . . .

• I've just stated, admitted really, that I prefer the sound of a product that not only imparts a substantial sonic coloration, but that I prefer to listen to sound that is intentionally distorted (any change from the original signal is defined as distortion). I'm not even saying that it sounds good despite a lack of neutrality. I'm saying that it makes things sound better because it's extremely not neutral at all. My future carousing with the ‘purists' tweaks at the Alexis Park and that sideshow offshoot, ‘The Show' has officially been cancelled due to a blown cover. In addition, anyone can reference this article and use it to refute any of my opinions by showing where I admitted that I preferred the path of the infidel. That might be a distortion of context, but it's never stopped members of the press before, particularly members of right wing extremist groups. I could possibly then defend myself and counter by pointing out that others have preferred the same, but without the honesty, but what's the point?

• While the effects of the Aphex 204 properly adjusted for a particular recording can be exceptional, the fact is that every recording requires a different combination of control settings for optimal effect. In fact, if we could apply a 204 channel to every track in the mix independently, I think we could make some very average mixes sound great, but we can't. I do like the fully adjustable nature of the unit, particularly since I consider it necessary, but I resent that I must touch the thing. There's no remote, no RS-232 communication, no presets to access, no automation at all. And to throw insult on top of injury with a little bit of salt and lime, since stereo operation requires identical settings of both channels, I have to do twice as much knob turning, AND I have to take pains to make sure the settings are identical. Uneven adjustments throw everything out of whack. If you're going to use one of these, you're going to have to keep it nearby the listening spot, preferably with the ability to swing it out on your lap, and it doesn't give a hoot if your equipment rack is on the other side of the room, or in a closet in another room. You'll need cables to and from the 204, and they better be the good stuff. If somebody could do this with decent DSP processing within an SSP, that would be ideal, but I'm not holding my breath.

• This is a piece of studio gear. It's nice to have access to it, but we shouldn't need it! It'd be much better for consumers if we could have this kind of processing tastefully applied on the mixing/mastering side of things, where it belongs. It's likely that some recording studios do use the 204, but from what I've heard, not enough, and those that do, don't do it well. If they don't want to use something like the 204 out of purist notions of fidelity, they should start to get the rest of the process right. I submit that if a recording engineer has any Yamaha NS-10s, the old standby nearfield monitors for engineers stuck in misplaced convention, subsequent mastering with an Aphex 204, as well as generous but tactful EQ is mandatory, and for the sweet mercy of everything in heaven, at least do the mastering with a decent monitor.

• The mere fact that this product makes recordings sound so much more convincing shows that there are serious, fundamental problems with our recording process in general. Poor microphones, habitual, routine and thoughtless processing, or simply lousy DSP implemented without compensation for sampling delay between processors, and it's a wonder we get as many listenable recordings as we do. Make no mistake. The Aphex 204 is a band-aid. It's a delightful band-aid, but it's still a crutch, and the fact that I've been shown, yet again, how broken our legs are is very much irritating. Where is our power as consumers? Why can't Ralph Nader take on the less conscientious recording engineers and champion the few good ones who not only know what they're doing, but really do care? Why can't we demand good recordings? Why? Because most people don't have a freaking clue, let alone give a darn. After all, don't most of us query about loudspeaker quality by asking, “How many watts are they?” Never mind what that says about the state of physics in high school. It'll bum you out for a week.


Despite having worked myself into a rather upset state with the precariousness of a product that has the potential to render a listener dependent on a constant fix of one more box, in my incredulousness at standards of the music recoding industry in general, I can only demonstrate my opinion that the processes offered by the Aphex 204 are of undeniable benefit to the recreational listener. I must admit that I'm grateful for the introduction. It's opening up my eyes, figuratively, and my ears somewhat literally, to more of what recorded audio has to, and should, offer.

As a side benefit, it's also validated my philosophy regarding playback equipment. As I've auditioned many piece of gear in an obsessive quest for audio inner peace, I have gravitated toward what I felt were more neutral, more reliable components, but the side effect is that because most recordings lack anything of drama, the presentation follows. I had heard more magical, more sensual sounding equipment, but in the end avoided it, as long-term listening left me feeling as if I weren't being dealt with honestly, as that magic remained constant, and such seemed to be characteristic of the gear, not the music. The fact that the Aphex 204 can inject so much of that magic at will, tailored to taste, seems to prove my point. The fact that this magic comes with knobs implies the pointlessness of buying alternative fixed colorations that you can't adjust, let alone turn off.

I think it would be false to claim that the 204 does everything you'd ever want in terms of sprucing up all but your 10 best recordings. What I'd really want is the ability to have somebody go back and do the whole process from the beginning. But, of the single components I've seen that exist for the purpose of enhancing the listening experience, this is one of the most useful I've met. It provides much of the unbelievable illusionary capacity that the monopoly of high-end ‘tweak' components have, without the requirement of swapping cables, spiking isolation platforms, or changing out capacitors or tubes to tailor the sound. You can still do that, if you want, but I think turning a knob or two, though still inferior to a full RS-232 interface and command set, is an easier option. What's more, the box performed better in the enhancement realm than any single tweak boutique gear ever did, giving me a flood of sensuality, presence, tickling detail, warmth, slam, kick, splash, and sizzle upon request, no questions asked. Have your cake, eat it, and have it again, all without eating disorder side effects!

- Colin Miller -

© Copyright 2004 Secrets of Home Theater & High Fidelity
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