System Synergy

System Synergy: an incomplete guide

In searching for system synergy to achieve a level of personal satisfaction there are many factors to consider.

We will begin by examining a poor practice of comparing components using SINAD at a single level and frequency of operation. This will be followed by expanding the considerations exponentially. The reality is far more complex with many signal transformations as will be described below.


Example system depicting signal path from playback data to human perception. This diagram is still simplified from comprehensive reality.


Focus on signal path from Amplifier to Human Perception.
The journey of a mythical perfect source signal trough the path of various transforms, roughly in order in which they occur will be described.


Church of SINADology would have you believe this is all that is necessary to rank amplifier sound quality.


Same information as previous slide in a 3D format as we consider expanding the distortion profiles for amplifiers.


Vastly more information presented in both surface and contour format. Red dots represent oversimplified assessments.


Now consider dynamic behavior of music overlaid on a particular amplifier distortion contour.
Note how the oversimplified assessment isn’t even in the correct level range for the listener.
At this point the source signal has encountered the first gauntlet of transforms from the amplifier.

Sampling of amplifier performance characteristics which affect the system sound quality:
• Frequency Response
• Transient Response
• Distortion Profile
• Residual Noise
• Dynamic Range
• Output Impedance
• Voltage limits
• Current limits



Now consider additional amplifier – headphone interaction given any particular headphone impedance curve over the operating spectrum as part of the signal path.


Next add the Frequency Response and Distortion profiles for any given headphone to the signal path. This alone is a very complex set of transformations to our mythical perfect source signal.

The signal journey of transformation continues in the next post.

 

Continued from part one above.


Now add to the signal path a huge next level of complexity with the Human Auditory System (HAS) which varies among individuals.
1) Pinna size
2) Ear canal shape and size
3) Basilar membrane and auditory masking


Now add the non-linear generalized behavior of the HAS as depicted in the ISO Contours of Equal Loudness.
Keep in mind this is an average over many individuals measured. Any given individual may vary considerably from this chart.

In addition to Auditory Masking and HAS Non-Linear behavior there are other factors affecting final listening perception:

1) Damage to an individual’s HAS
2) Bias
3) Personal Preference
4) External Influencers such as listening environment for example
5) Mood of the moment

The path from playback data to perception has many complex transfer functions that work as a system.



Simplified summary aggregating transforms affecting system synergy.

It is ridiculous to purport a simple SINAD measurement at one specific frequency, level and load can infer anything useful with regards to listener perception of sound quality rendered.

When the entire set of transforms are considered, the reality of system synergy complexity is evident.

Helpful information (but not all inclusive) include:

1) comprehensive measurement data sets from reliable sources
2) Subjective observations from multiple sources considered to be both reliable and consistent
3) Personalized auditions keeping in mind individual bias, personal preference, external influencers in the auditioning environment and mood at the time.

Also note that a personal preference is not necessarily fixed and will likely change over time.