The search for magic sound, part 1

Harmonics – basic tone with 6 overtones

The essence of music is in harmonics. Sound is a complex mixture of basic frequencies and higher harmonics. When the overtones are close to even multiples of the basic tone, we don’t hear separate sounds. Our brain miraculously interprets such mixtures as one tone (one pitch), but with a certain timbre or tone color. Our complex hearing system has a natural preference for harmonic relationships, and it is perfect for detecting and interpreting them. For instance, our ears do not detect sound as a single wave (like a microphone membrane), instead the different frequency contents each have its own detector (lots of microphones tuned for different frequencies).

There’s a wide variety in timbres or tonal colors. Instruments can be recognized by their unique mixture of tones and overtones. But there’s more to timbre than just recognition. Timbres are able to produce various subjective sensations in our brain (warm, cold, organic, sterile, woody, metallic, fat, hollow, etc.), they are part of our subconscious and sometimes conscious experiences. If not accurately reproduced, we automatically identify that the sound is not part of our direct environment. We hear a loss of timbre, a bleaching of tonal colors. Our brains can not be fooled, there’s a clear difference between the endless variety in sounds that surround us in our daily lives and the more limited timbres that equipment can reproduce.
Of course there are other important qualities in audio, but many are directly related to timbre (dynamics, transparency, resolution), and these qualities on their own are not the limiting factor in a good system with good acoustics.

The rich variety of timbres can be recorded and reproduced accurately only if the harmonic structures ares kept intact. Each component in the chain has different behavior for different frequencies (non-linear). Note that we’re not talking about the linear frequency response. Frequency response on its own is relatively unimportant (acoustic sounds always sound live and perfectly natural, regardless of the acoustic environment). To judge audio on frequency response would be a ridiculous simplification. In reality a tone is not just a frequency, but a complex spectral composition of the basic tone with a range of overtones with different relative strengths and phases, fluctuating/changing in time. Timbre is a multidimensional quality. Dimensional research is complex and highly time consuming. So the most essential quality is not part of measuring practice in audio. Which declares why measurements hardly relate to listening experiences. (The inability to reproduce natural tonal colors means that the harmonic structures are distorted. Probably you have heard of THD, Total Harmonic Distortion, a commonly measured value, but this value has no relation with the ability to reproduce harmonics accurately.)

Timbre, harmonic coherency is extremely difficult to achieve and preserve. Once lost, it can not be recovered. It is impossible to tune an element in the chain for reproducing tonal colors, unless the rest of the chain is perfect already. Just one âblack-and-white’ element will break a full color chain. Systems that are able to reproduce a large variety of timbres are extremely rare. Each system has its own sound signature, and so-called neutral sounding systems are usually just boring, hardly able to reproduce natural tonal colors.

A large part of the audio community (designers, manufacturers, reviewers, audiophiles) seems to concentrate on other qualities. The lack of realism is compensated by creating an impressive sound (instead of reproducing what’s impressive). This leads to typical ‘high-end’ sound: edgy highs, thin midrange and over-damped bass, this flavor mimics qualities like transparency, resolution, dynamics, greatness, scale.
But manipulation leads to more loss of timbre (loss of harmonic coherency). And the frequency extremes get disconnected from their source (instruments), losing all tangibility and realism. As a result ‘high-end’ sound has a short attention span, and usually leads to an endless search in the wrong direction.

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