What is HiFi?

High Fidelity derive from the Latin word fidēlis, meaning “faithful or loyal”. It is about how faithful and loyal sound is recorded and played back by audio systems.

HiFi has no accepted standard.

Explain something, that is not standardized, you relate to self-experience and as such, it is always subjective. As with colors. Lets talk about white, we may have a distinct color in mind. However, as we all know, white is not like white, colors have many nuances. A carpenter, who fixes a scratch on a white kitchen door, requires the NCS, the RAL or any standardized number of that white. Luckily for color we have clear defined standards.

Or ask about the driving capabilities of a car, one says, they are quite good. Meaning the car is comfortable and quiet. While you are interested in its sports capabilities. Ok, but how to rate the sports capabilities of a car?

Likewise, how to rate sound quality or HiFi?

Sound quality is subjective.

Nowadays, we often use the iPhone with a music alarm-clock-app. When the alarm goes off, people listen to the music provided by the iPhone speaker. To a certain degree, it is surprising what Apple created into this little iPhone. However, it is still not a high-quality sound reproduction.

Plugging in headphones, while the music is still playing: bam, significantly better sound. Bam? Do we really experience this as a positive shock? Is our attention drawn to positive improvement in sound quality? We usually accept change to the positive as something expected, without much attention. Sometimes we leave the house while we continue to listen to that new music we just found. For this, we change from our good home music system or extra ordinary good headphones maybe to the iPhone speaker, which would be a much worse experience.

We experience this better to worse step much more extreme. Without direct comparison, we are not very good in matching the sound we hear to a pattern, of what we would call a bad or good sound, unless it is extreme.

These big jumps to the worse, in sound quality usually happen between HiFi and non-HiFi systems. Jumping between HiFi and HiFi systems, or between bad and bad systems would mostly not create shocking moments.

TestHiFi objectively tests sound quality.

Many of us are not trained over decades to have the patterns in mind to match good or bad sound. Therefore, to create a measurable reference, a standard, we developed TestHiFi.

TestHiFi objectively measures the sound quality and rates whether it could be HiFi (green), close to HiFi (amber) or be far away from HiFi (red).

Want to hear the difference?

Experience the difference in sound reproduction immediately!

Play this video on your mobile device. At about the middle of the video, a TestHiFi testing is simulated and the TestHiFi test signal is played three times. The test signal starts, it has a pause and finishes and then it starts again, has a pause and finishes.

Listen to the same video on a better quality music system or headphones and observe what happens to that pause in the test signal. – This is an example of incomplete reproduction –

simplified test

Technical explanations

If you buy a TV, existing standards like „High Definition“ or „4k“ define the visual display resolution.

If you buy a music system, there is no corresponding HiFi (High Fidelity) sound reproduction standard in use today. „High definition audio“ refers to certain digital audio data formats, but that does not say much about the aural quality of the reproduced sound.

 

In terms of technical parameters – what should a HiFi system do?

HiFi music system to replays recorded sound without unpleasant distortions and with full quality.
Ooookay, but what is full quality? When do distortions become unpleasant?

There is no standard answer to the question what a Hifi system should be capable of today Therefore we reverse the question and define what it should not do:
TestHifi analyzes common weaknesses of music systems and rates them. Ratings are RED (far below HiFi), AMBER (closer, but still not HiFi) and GREEN (no weakness found, deemed to satisfy at least entry level HiFi quality – meeting the HiFi standard).

Unpleasant distortions are certain levels of harmonic distortion, intermodulation distortion, interference frequencies, distortion components outside the aurally weighted mask or wrong frequencies.
(Experts – please mind: we abbreviate ‚nonlinear distortion‘ to ‘distortion’ – producing sounds that are not contained in the original signal. Distortions can also extinguish parts of the original signal.)

A reproduction is incomplete if stereo effects are not reproduced, or if there are significantly low levels in certain frequency ranges, lack of frequencies due to intermodulation and so on.

TestHifi sends a complex, but short test signal through the sound system and analyzes the acoustical output in three microphone positions to achieve a final test result. While we devoted much effort to minimize parasitic influences, please mind that acoustical measurements capture the sound system including some degree of the room’s acoustic and ambient noise.

In detail, a sound reproduction system could be HiFi if the following weaknesses are below certain limits:

  • Frequency response amplitude drops, such as early high- or low frequency decline or dips in-between:
    • Incomplete reproduction of recorded information, leading to missing sounds.
    • You will not experience the full sound intention of the artist.
  • Frequency response amplitude peaks: some frequencies are reproduced with higher level than others.
    • Experience of distracting coloration, certain sounds appear too warm, thin or bright or over accentuated /rough.
  • Loudness at harmonic distortion limit:
    • Systems that cannot generate a minimum low frequency level within acceptable distortion limits obscure deeper sounds, adding artificial distortion noise, leading to a loss of clarity and transparency.
  • Low / High frequency intermodulation distortion (LF / HF IMD):
    • Accumulated level of all distortions compared to level of multiple low/high frequency test tones.
    • Systems with high LF or HF IMD reproduce lower frequencies (such as base, drums, low voices) or higher frequencies (such as violins, guitars, flutes) very inarticulate, opaque, and without contour; in worst cases, the artificial noise exceeds the recorded sound.
  • Aurally weighted intermodulation disconsonance:
    • Frequencies with higher level of upper order harmonic distortion components compared to level of lower order harmonic distortion components are disconsonant with human hearing.
    • Such systems tend to sound unnatural, compressed, fatiguing, rather sharp; they slow down transients, constraining vitality, reducing musical contrast.
  • Stereo incompatibility:
    • Systems with one channel only or summed left and right channel cannot reproduce stereo effects.