Signal behaviour
Tracking Error
How a changing disturbance environment can make it harder for a system to follow the musical signal precisely.
Explore Tracking ErrorTHE PHYSICS OF QUIET / 06
Subsystem Protection
A quieter operating region begins with two boundaries: one controlling how unwanted energy enters, the other controlling how it returns and continues through a connected system.
The Tracking Error guide shows why a system can find it harder to preserve musical relationships when the electrical and mechanical conditions around it are changing. The Return Loss guide shows why unwanted high-frequency energy can return from a boundary. This page puts those ideas around a sensitive part of a system.
Matrix ONE sits at the entry to the region being protected. Matrix TWO sits at its exit. Together they define a subsystem: not an isolated box, but a more controlled part of a connected environment.
A note on the model: this animation is an explanatory view of boundary behaviour. It is not a calibrated measurement of a Quiescent product, a particular component, a cable run or a listening room.
Two boundaries, one protected zone
One way to picture the arrangement is as a quiet courtyard held between two permeable screens. The courtyard is still part of the wider landscape, rather than sealed off from it; the screens simply make the conditions within it more controlled. In the same way, Matrix ONE and Matrix TWO define a protected subsystem within a connected audio system.
In a connected audio system, disturbance does not approach from one abstract direction only. It can arrive through power, grounding, cable and structure; it can also be reflected back from a boundary further along the route. Protecting a subsystem therefore means considering both its entry and its exit.
Matrix ONE is the entry boundary. It reduces the unwanted disturbance that is allowed to cross into the protected region. Matrix TWO is the exit boundary. It limits unwanted disturbance leaving that region and reduces the part of the field that is reflected back into it.
Both Matrix devices are treated as bidirectional boundaries. Return Loss concerns reflection at a face. Insertion Loss concerns unwanted energy passing through the Matrix. The distinction matters because a field already outside Matrix TWO is not necessarily a field that has passed through it.
External field → Matrix ONE → protected subsystem → Matrix TWO → external field
See the protected region take shape
The animation shows the same idea from both sides of the subsystem. The green boundary is Matrix ONE; the blue boundary is Matrix TWO. The central plane is the part of the system being protected. Use the shared Return Loss and Insertion Loss controls to change the illustrative conditions at both Matrix boundaries together.
The courtyard image is a spatial analogy for this view: the still central pool represents the protected subsystem, while the two screens represent the Matrix boundaries. The animation then makes the distinction more precise by showing the changing field at each boundary and within the region between them.
Shared Matrix Return Loss
Shared Matrix Insertion Loss
- Musical reference
- System response
Read the animation as a changing field, not as a literal waveform or a power-flow diagram. The colours identify the two boundaries; the movement shows the changing disturbance they are intended to control.
| What you see | What it represents in this illustration |
|---|---|
| Green boundary — Matrix ONE | The entry boundary. Its insertion loss reduces unwanted disturbance crossing into the protected subsystem. |
| Blue boundary — Matrix TWO | The exit boundary. Its return loss governs reflected disturbance at both faces; its insertion loss reduces subsystem-originated disturbance crossing outward. |
| Central highlighted region | The protected subsystem: the area in which incoming and returned disturbance are being reduced. |
| Field beyond Matrix TWO | An exterior context. It can include disturbance already outside the Matrix and reflection from Matrix TWO’s outer face, as well as the attenuated portion that has crossed outward. |
What each boundary is doing
The controls are shared in this illustration: one Return Loss choice and one Insertion Loss choice are applied to both Matrix devices. This keeps the comparison legible. It does not imply that every installation must use identical Matrix values at every location.
At Matrix ONE, higher insertion loss reduces the disturbance that reaches the protected subsystem. At Matrix TWO, higher return loss reduces the portion of disturbance that is reflected back into that subsystem. Those are the two roles most closely connected to the Tracking Error discussion: they help create quieter, less reflective operating conditions around the system response.
At Matrix TWO’s outer side, the model makes a second distinction. Its insertion loss reduces the part of the field that has travelled from inside the protected subsystem and crosses outward. Its return loss still applies at that outer face, so low return loss can leave a visible reflected contribution outside the boundary. The two effects are related, but they are not interchangeable.
At the entry
Matrix ONE insertion loss reduces the unwanted disturbance allowed to enter the protected subsystem. Its return loss also determines how much of the exterior field is reflected at its outer face.
Within the protected zone
Matrix TWO return loss matters because a low-return-loss exit boundary can send more of an arriving disturbance back into the subsystem. Higher return loss reduces that reflected contribution.
At the exit
Matrix TWO insertion loss reduces the portion of subsystem-originated disturbance that crosses outward. An exterior field may still remain visible because some disturbance is already on that side of the Matrix.
A simple comparison
- Start at 3 dB Return Loss and 3 dB Insertion Loss. Notice the active field at both outer sides and within the protected region.
- Increase Return Loss while leaving Insertion Loss unchanged. The reflected contributions become smaller: at Matrix ONE’s exterior face, within the protected subsystem and at Matrix TWO’s exterior face.
- Return to 3 dB Return Loss, then increase Insertion Loss. Less unwanted disturbance crosses Matrix ONE into the protected zone, and less subsystem-originated disturbance crosses out through Matrix TWO.
- Look again beyond Matrix TWO. A remaining exterior-side field does not mean the Matrix has failed to attenuate transmission; part of that disturbance is already outside the boundary or is reflected at its outer face.
- Use the controls to understand the direction of change. They are illustrative controls, not a specification calculator for a particular product or installation.
From protected conditions to musical relationships
The Tracking Error model does not say that a Matrix creates the music or corrects a signal after the fact. The musical reference remains the reference. The purpose of controlling the surrounding field is to reduce unwanted conditions that can make it harder for the existing system to preserve level, timing and harmonic relationships.
Subsystem protection is therefore a system idea. It considers the route into a sensitive region, the route out of it and the energy that may return from either boundary. The aim is a quieter operating condition, not a new sonic character.
Explore further
Matrix Boundaries
Return Loss
How a controlled boundary reduces the energy reflected back into the system.
Explore Return LossMatrix Boundaries
Insertion Loss
How a boundary reduces unwanted energy that would otherwise pass through and continue onward.
Explore Insertion LossTechnical note and further reading
This page uses a conceptual field model. Its field scaling and the representative exterior disturbance are included to make boundary roles visible; they are not a published measurement or an energy budget for a Quiescent product.
- Return Loss in Audio Systems explains reflection at a boundary and the decibel relationship between incident and reflected power.
- Tracking Error in Audio Systems explains the musical-reference model that this page extends.
- Keysight — T and S parameters provides neutral engineering context for reflection and transmission parameters.
