Hi-Fi Myths and 3TIUM Truths
The evolution of Hi-Fi is quite similar to evolution of the education system with Hi-Fi specs resembling college grades. The education system was created to grade everyone's talents and help find the niche. However, the education of most successful men on Earth is quite average. The same principle applies to Hi-Fi. The best sounding audio equipment never has the best specs. Read on to understand why.
The audio reproduction industry standardized the specs to compare the products theoretically. Standard parameters include THD, frequency response, output power and many others. Ironically, the Hi-Fi standards came out in the era of Elvis and Beatles, when the quality of audio recording and reproduction fell dramatically. Equipment producers then pushed studios to replace tube amplifiers with transistor rivals and chose characteristics, by which transistors outperformed tubes. The marketing hypnotized consumers that synthetic sound of transistor amps is closer to the original because of lower harmonic distortion compared to tube-driven sound. Similarly, many expensive speakers with super linear frequency response sounded dull, with no audio scene depth, whereas some radios from 1940s sounded quite deep in spite of being mono with limited bandwidth. The myth about linear frequency response as a primary measure of quality was quite audible and even inspired Amar Bose to establish his now well respected global corporation. The specs have little to do with sound quality nowadays, just like half a century ago. In part because the parameters are measured in an artificial manner and in part because some important characteristics are intentionally omitted. Let's demystify current situation in the audio industry.
Truth 1: Thermal Distortion
Thermal distortion is not rated even for $100,000 configurations. It greatly affects the perception of audio fidelity nonetheless and is one of the major reasons tube amps sound better against their semiconductor rivals.
Main cause of thermal distortion is thermal inertia of the silicon crystal, thermal resistance of all junctions to the heat sink and its heat capacity, combined with parameter fluctuations in a semiconductor, inflicted by abrupt temperature spikes. Additionally, it may be caused by differences in dynamic thermal drifting across components. Just use the sine test signal, modulated with light infrasonic triangular waves of 0.2Hz, for instance. The amplitudes of both signals could be way below the maximum power. The results for one-chip power amps are quite astounding. Intermodular distortion may easily reach four percent on an ideal resistive load. Not surprisingly, most of Hi-Fi amplifiers made in 1970s handle the triangularly modulated test signal flawlessly as their every transistor simply has more volume to dissipate the peaks of heat and more space for the current to flow through. The Class-A amplifiers have low thermal distortion by design as their operating temperature is high yet stable. Vacuum tubes also introduce barely notable thermal distortion by cooling the cathode upon current spikes, but of substantially smaller harmonic amplitudes and narrower distortion spectrum. Audiably, it's not the "warmth" that gives tubes an edge. It's clarity or fidelity.
Truth 2: Transient Intermodular Distortion
Transient intermodular distortion (TIM), although known since early 1970s, was eliminated from the specs till this day even for audiophile equipment. TIM is notable as a veil over the audio picture. The more veil you hear over the sheer sound attacks, the bigger the transient intermodulation.
Typically, TIM is caused by deep negative feedback being the signature of modern semiconductor amplifiers with ultra-low THD. Once you see a 0.005% THD or lower in the specs, there is a 99.9% chance for that amplifier to have highly audible TIM. It's that synthesizer-sounding "transistor sound" semiconductor amplifiers are blamed for. Upon a sharp signal front, some cascades inside the deep feedback loop get overloaded, affecting the output linearity. Besides negative feedback being too deep, the causes of TIM are the inadequate slew rate, amplifier schematics and linearity of semiconductors in the signal path. Amps with smaller slew rate attempt to make up for the lack of amplifier's dynamics on transient spikes, causing parasite outbursts often twice bigger than the expected output signal. Just for the reference, the widely used TDA7293/94 microchip amp has a slew rate of 5.6-7V/microsecond whereas the respected Hi-Fi power equipment has it at least a dozen times higher. For the sake of truth, high slew rate is a prerequisite that does not guarantee low TIM. Amplifier must also have loosened control loops and be built only around components that work accurately without much control. Only then the Hi-Fi stands a chance to literally unveil the true high fidelity sound.
Truth 3: Current Feedback
Great power amplifiers had the current feedback since early vacuum tube era. In 1967 the concept was brought to semiconductors in one of the best Hi-Fi amplifiers ever made - the Fisher TX-1000. Traditional speaker in a sealed enclosure has the sound pressure linearly correlating to the current in its coil. Therefore, distortion is measured and corrected by analyzing speaker's output current. Every time the coil goes astray, it generates extra current or lack thereof against the magnet and that current is used as a corrective signal. The 360-degree review process could be a metaphor from real life to illustrate the current feedback between the amp and the speakers resembling the management and their subordinates respectively.
In XXI century the current feedback has been outlawed by high end brands, possibly for formally higher distortion with an acoustic system plugged in. In reality, incorrectly measured as amplifier's distortion, the output contains corrective signal that improves phase response and lowers distortion of the speakers by an order of magnitude. The decadent trend in modern audio industry is to make perfect voltage-driven acoustic systems and ultra-linear voltage-output amplifiers. However, every move in any electromechanical system, including speakers, is driven by the current, not voltage. This is how perfect does not mean compatible and some super amplifiers do sound dull with some very expensive speakers, just like some rock stars do not sing well in duet. Current feedback is the symbiosis between the speakers and the amplifier, establishing common ground between them and squeezing the best out of both. The result is in speakers' gain-phase characteristic and distortion improved to a higher class. The quality speakers, such as mid range with at least 95dB sensitivity (not to be confused with SPL) and ±2dB frequency response, Heil's or ribbon and electrostatic drivers may need less of a current feedback as their distortion and non-linearity is typically inaudibly low by design. By the way, electrostatic speakers a la mode in the last decade have very nonlinear impedance. But even when using the best speakers, control current is the natural approach to maximize overall sound reproduction performance and track it in real time. Can still locate satellite speaker positions blindfolded? Use the current feedback. This is when the air starts to breathe. Once you clearly feel the room geometry where the recording was made instead of the listening room, the world of Hi-Fi will never be the same. Then you will easily tell real acoustic recording from high quality artificial 3D sound, engineered with phase offsets or reverbs and panning. To hear the natural acoustic recording, try orchestral music or even "Only the Lonely" by Roy Orbison. To hear artificial scene mastering, try some glam rock. In general, the feel of space is preserved in the recordings made predominantly with microphones unprocessed through space/voice enhancers, Dolby-A, Dolby-SR or other phase-garbling equipment. The system with properly built current feedback, such feel of space is deliverable even with just two satellites and a sub. You may say two satellites and a sub is Low-Fi with the sub sounding lumpy or honky. You could have been right two years ago. With 3TIUM heart, the 2.1 3TIUM Hi-Fi sounds closer to original performance than everything else there is, including the most expensive professional studio acoustics.
Truth 4: Digital vs Analog
Let's remember that sound is naturally analog. All great musical instruments are analog. Human voice is analog. All digital musical instruments of modern age do sound synthetic and unnatural. There is no such thing as digital microphone membrane to record directly in digital. There are no digital speakers to directly reproduce the digital. There are no digital human ears to listen to the digital. Why must there be digital conversion in the middle?
With all due respect for Tripath Technology, their Danish followers and other designers of high quality class-D chips, the pulse density/width modulated sound is artificial by design. THD is measured low, however the spectrum of audible harmonics is wide. In switching mode, especially at higher frequencies, besides the infinite harmonic and intermodular spectrum of square waves, output stage transistors produce oubursts, similar to Truth 2 stated above. Even low-level harmonics past the 4th order do sound digitally irritating. The BBC R&D method of prorating THD by spectral width along with measuring RIMD as described in Myth 5, shows how little the switching power modulator is really worth in analog world. Digital media is obviously great for eternal information storage and endless distribution, but not at the audio recording or reproduction stages. Parallel digital-to-analog converter (DAC), typically used to produce line output from a digital device, is essentially the resistor network that is extremely linear by design. But for power amplifier things are radically different. To remain technically accurate, "class-D" does not mean "digital". It was introduced in 1958 and "D" stood for delta-modulated signal, which does look like an encoded sequence of ones and zeroes, so could also be considered digital.
Obviously, the digital quality gets much better when coupled with analog Truth 3 above, i.e. by applying the current feedback. But why should digital be there in the first place? The main advantage of class-D amplifiers is their super efficiency. Let's remember that analog class-AB amplifiers could be nearly as efficient. Just consider a bridged configuration and toss the digital amps. In spite of class-D amplifiers being promoted as the new generation, it is nothing but purely unnatural and unnecessary evolution branch in high class audio.
Truth 5: Capacitors In Signal Path
A single multilayer ceramic capacitor in signal path could distort the sound more than a typical Hi-Fi system including the speakers. The sound, processed through a multilayer ceramic capacitor gets heavily veiled and colourized with signal, audibly similar to pink noise. A strange hissing sound that crops up when a drummer hits cymbals is one of artifacts produced by a ceramic or polymer decoupling capacitor, often mistakenly blamed on digital encoding of modern age. Cymbals produce a lot of naturally coherent high level harmonics and thus reveal intermodulation distortion audibly well. The high end audio makers are aware of this phenomenon and use the highest quality polypropylene, polyester or even paper capacitors. Therefore, distortion typically comes from a portable audio source, especially if it was designed in China or Korea. As they say, an audio system tuned for iPhone is only good for iPhone. By the way, iPhone's line output fidelity is quite decent and all jokes about it would be just for teasing. However, almost all iPhone "rivals", "killers", knock-offs, clones and copies from Korea and China are nowhere near as good. Portable devices, designed in Japan, typically deserve the highest honor in terms of audio fidelity.
Multilayer ceramic capacitors produce a wide spectrum of harmonics up to the 13th, making the veil harshly audible. Electrolytic capacitors largely differ in terms of distortion. The worst are with polymer electrolyte membrane or tantalum anode. The best caps for audio are with the highest power density, made of graphene sheets, for example. Among massively produced electrolytes, Elma, Nichicon MUSE and Rubycon MBZ/MCZ sound quite good. Just to reiterate, electrolytic capacitor's audio fidelity is not directly related neither to a Q-factor, nor to ESR. It is primarily capacitor's ability to quickly and linearly transfer the energy from one end to another.
Truth 6: Stereo, Surround Sound Mono. 2.0, 2.1, 3.1, 5.1, 7.2, 7/11
- I don't know, kid. Compare that to the sound of my old Graetz and tell me.
Human ears represent a highly advanced technology, far more advanced than audio engineers currently know. Among other things, ears allow us to aim at high precision in the darkness. Hearing has been our 3D night vision system as important for survival as the optical vision. But since the invention of binaural recording, engineers have been trying to deceive the aural perception with bells and whistles, creating an illusion of reproduced sound being naturally real. The history of 3D audio goes back to 1881, Paris Opera Theatrophone. From then on, the concept hasn't changed much. The recording and reproduction quality technologically improved along with advances in physics, math and chemistry until semiconductors came out. Semiconductors were great. It was the people who then thought they could simplify many obvious things, critical for accurate sound reproduction. The Hi-Fi evolution went down the path of Myths and ruined the feel of the music, leaving just the linear frequency response and low THD measured exclusively on steady oscillating sine wave. By the way, steady oscillating sine audio waves are so unpleasant that Gestapo used them to torture people.
In early audio recording days, the process from sound source to the listener of the record had very few signal transformations and preserved the phase coherence. That kept the feel of space even on mono records. In the years after the "Hi-Fi" concept was presented, the attempts to linearize frequency response at the expense of phase characteristic turned epic and listeners discovered that having more speakers doesn't mean a better scene depth, but rather pleasant jingling around the room. The fact of sound coming from several locations does not mean it has the immersive feel to it when the phase information had been compromised.
Modern home theaters with more speakers expanded the sound field, in which the ears could be tickled, creating very immersive illusions. But after listening to it for 10-15 minutes, human brain announces the verdict of cruel deception. The brain matches the natural room echoes against synthetic signal delays in satellite speakers and notes the dissonance. For a good well-tuned surround sound system it takes time to feel deception because at first the synthetic sound is quite sweet, prompting to say wow. It also prompts to turn the system louder in hope that the synthetic audio scene will outscream the natural sound field of the room.
How useful are sound effects from the rear? For the first time it's clearly a wow. But for the 10th time it is going to be nothing but increased sound pressure level causing headackes. The screen on the wall is designed to be the window to a different reality. Do we hear the related rear sounds when looking through an open window? Guess not. Do we hear relevant rear sounds in a theatre? Nope. In a good theatre, rear echo is negligible, preserving sound performance on stage and in the orchestra pit. Playing music or a movie is, in essence, the frontal presentation, so should be the sound scene. Systems with superior frontal reproduction create much deeper realistic spacious effects than artificial yet immersive jingling and whistling sound pressure from the rear produced by 7/11 acoustics.
To understand the ridiculousness of 7.2 systems, think why theatres never put extra drums and cellos in the gods. Makers of 7/11 home theaters may speculate about the room modes. Musicians or people of good taste would give a much simpler explanation: makers of non-magic acoustics still know too little about how to accurately reproduce the sounds in a given room. It takes a little magic to play it right, not extra speakers.
Truth 7: More
There is a lot more the marketing people hide from you. The high quality audio world is far out of mass consumer electronics stores these days. A typical home theater consists of a ported subwoofer not delivering even 27Hz and annoyingly booming at 40-50Hz with satellites playing out of phase and frequency often not making it linear to 18kHz. That is what there is in stores these days. Obviously, the immersive experience is promised at the cost of deceiving the ears with signal delays, phase shifts, frequency filtering and other tweaks to trick our ears instead of trying to simply play it right without the tricks. On the bright side, a 20L subwoofer with 3TIUM Heart may produce a real high fidelity bass including infrasound in real room and just a couple of 3TIUM satellite speakers with it will make you melt in the sound scene as no other system on Earth. There are quite a few secrets about high fidelity sound reproduction we keep. We stand for the quality sound reproduction without ear-deceiving tricks.