How signal grades a chain.

Whether the amplifier and the passive speaker are sensibly matched on three independent sub-criteria: power into the speaker’s load, damping factor, and minimum-impedance compatibility.

Each sub-criterion fails in a different audible way. Under-power on dynamic content drives the amp into clipping; loose damping smears the bass; an amp that can’t hold the speaker’s lowest impedance dip current-limits on transients regardless of average power. The check’s overall outcome is the worst of the three — audible problems can’t be averaged away.

• Warn

  Amp power below the speaker’s recommended minimum

  Under-powered — dynamic peaks will compress

• Good

  Amp power within the recommended range

  In spec — amp drives the speaker as designed

• Note

  Amp power above the recommended maximum

  Ample headroom — careful with the volume knob to avoid over-excursion

• Fail

  Damping factor below 20

  Loose bass — driver back-EMF colours the response

• Warn

  Damping factor 20 – 50

  Adequate but not tight

• Good

  Damping factor ≥ 50

  Confident bass-driver control (audiophile standard)

• Fail

  Amp minimum-rated impedance exceeds the speaker’s impedance dip

  Current starvation — amp can’t hold the load on transients

Whether the amp/speaker pair can hit a listening-distance-scaled peak SPL target at the actual listening position — i.e., loud enough at the chair to reproduce dynamic-range material without compression.

A system that can’t reach the target peak SPL flattens out on transient material (orchestral climax, drum hit, film impact). The target scales with distance because apartment-scale listening and reference-capable rooms have different SPL expectations — 95 dB up to 3 m, 105 dB beyond.

• Good

  Peak SPL at the listener meets or exceeds the distance-scaled target

  Headroom for dynamic-range material — Toole §17.4 reference reached

• Note

  0 – 3 dB below target

  Comfortable everyday level with limited reserve

• Warn

  3 – 6 dB below target

  Headroom-limited — transients compress on dynamic content

• Fail

  More than 6 dB below target

  Under-powered for the room — large peaks will clip

Whether the speaker covers the full audible bass range, and how meaningfully a subwoofer (if present) extends below the speaker’s natural roll-off.

35 Hz is the bottom of the orchestral fundamental range (lowest organ pedal sits at 32 Hz). Above 50 Hz, the speaker can’t reproduce the kick-drum fundamental. A sub crossed within 5 Hz of the speaker’s roll-off adds SPL but not depth — the user should know which.

• Good

  Speaker reaches 35 Hz or lower, no sub

  True full-range — bottom of orchestral fundamental range covered

• Good

  Subwoofer extends ≥ 5 Hz below the speaker

  Sub adds meaningful depth

• Note

  Subwoofer matches the speaker within 5 Hz

  Sub adds SPL and room-mode coverage, not depth

• Note

  Speaker 35 – 50 Hz, no sub

  Typical bookshelf — room loading helps

• Warn

  Speaker above 50 Hz, no sub

  Bottom octave missing — consider a subwoofer

• N / A

  Headphone config OR speaker frequency-response missing

  Check skipped — no speaker low-edge data to evaluate

Whether a multi-way passive speaker’s crossover lands inside the Fletcher-Munson peak-sensitivity band (1.5–4 kHz), where the ear is most sensitive to driver-handoff artefacts.

Multiple peer-reviewed driver-handoff studies converge: a crossover in the 1.5–4 kHz band makes vocal sibilance and cymbal transitions audible as discontinuities. Speakers that engineer the crossover out of this band sound different on the same source material.

• Warn

  Any crossover frequency falls between 1.5 kHz and 4 kHz

  Crossover sits in the ear’s peak-sensitivity band — handoff artefacts more audible

• Good

  All crossover frequencies are outside the 1.5 – 4 kHz band

  Crossover engineered out of the critical band

• N / A

  Multi-way speaker but crossover frequencies not published

  Check skipped — no datasheet crossover values to evaluate

Whether the system has a derivable signal path from source to output — i.e., does every required stage exist, and do they connect.

Topology is binary at v1: either the chain works end-to-end or it doesn’t. A phono-level signal going into a line-level amp without a phono preamp is silent; a digital source with no DAC is silent. Surfacing the broken link is the most useful thing the engine can do before scoring anything else.

• Good

  Source → preamp/DAC → amp → speaker chain derives with no signal-level conflicts

  Valid signal path — every stage present and connected

• Fail

  Required stage missing (e.g. phono preamp absent before line-level amp; no DAC for a digital source)

  Audible problem — wrong signal level or silent output

• Fail

  No path can be derived from the chain

  Chain is incomplete — start by fixing topology before scoring anything else

Whether the active interface between two stages is the best one the components support — digital > XLR balanced > RCA > 3.5 mm TRS, with credit for "best available."

This axis answers "is the connection quality leaving signal-to-noise on the table?" — not "is XLR objectively better than RCA?" An RCA-only build is good; we don’t punish components for what they don’t have. We surface upgrades (note) and active downgrades (warn) honestly.

• Good

  Digital path active (USB / S/PDIF / I2S)

  Bit-perfect, no analog noise pickup

• Good

  XLR balanced analog active

  Common-mode noise rejection — quietest analog interface

• Good

  RCA used, no XLR alternative on both ends

  Best the components offer — no penalty for what they don’t have

• Note

  RCA used, XLR available on both ends

  Upgrade opportunity — switch to XLR for lower noise

• Warn

  3.5 mm TRS used with a better alternative available

  Leaving SNR on the table — known weak connector

• Good

  DIN / internal / other functional interface

  Treated as functional — no audible penalty

Whether the spec data driving the analysis comes from manufacturer datasheets or is partial / pending verification, AND whether any primary check returned unknown because data was missing.

Transparency. The user should know whether the verdict is based on confirmed datasheet values or on reputable-secondary inferences. The note tier is honest about that without scaring the wedge user away from a perfectly functional build; a primary-check data gap is escalated to warn so it doesn’t hide behind an averaged score.

• Good

  All components verified AND no primary check returned "unknown · data missing"

  Every spec value used in the verdict is datasheet-cited

• Note

  Some components partial (reputable-secondary) AND no primary check returned "unknown · data missing"

  Verdict holds, but some figures await primary verification

• Warn

  One or more primary checks returned "unknown · data missing"

  Data gap hiding in the score — surfaced honestly rather than averaged away

Whether the amp can drive the headphone to AES reference orchestral peaks (110 dB SPL with transient headroom) at the ear.

110 dB = AES orchestral peak (~105 dB) + 5 dB transient headroom — the "transient-clean" reference for amp+phone matching. Below 100 dB, typical pop/rock peaks audibly compress. The 2× bracket caps the SPL uncertainty at ≈3 dB — outside that bracket, an honest unknown beats a confident wrong number.

• Good

  SPL_max ≥ 110 dB at the ear

  Hits the AES orchestral-peak reference with transient headroom intact

• Warn

  SPL_max 100 – 110 dB

  Reaches everyday peaks but transient material will audibly compress

• Fail

  SPL_max below 100 dB

  Under-driven — even pop/rock peaks clip at the amp

• N / A

  Headphone impedance falls in 64 – 150 Ω (no matched amp figure)

  Honest unknown beats a confident wrong number — bracket too wide to extrapolate

Whether the amp’s output impedance is low enough relative to the headphone’s driver impedance to maintain tight bass control — the 8:1 audiophile-standard rule.

Source impedance ≤ 1/8 of load impedance keeps voltage-divider losses under 1 dB across the audio band — small enough to be inaudible. Below 3:1, the impedance interaction tilts the frequency response by more than 2 dB and the bass actively colours with the headphone’s impedance peak.

• Good

  Damping ratio ≥ 8

  Within the 8:1 audiophile standard — frequency response unaffected

• Warn

  Damping ratio 3 – 8

  Audible response tilt — bass may sound bloomy or thin depending on the headphone

• Fail

  Damping ratio below 3

  Bass actively colours with the headphone’s impedance peak (> 2 dB swing)

• N / A

  Amp output impedance not published

  Check skipped — no source impedance figure to evaluate

Whether the speaker covers the full audible bass range, and how meaningfully a subwoofer (if present) extends below the speaker’s natural roll-off.

35 Hz is the bottom of the orchestral fundamental range (lowest organ pedal sits at 32 Hz). Above 50 Hz, the speaker can’t reproduce the kick-drum fundamental. A sub crossed within 5 Hz of the speaker’s roll-off adds SPL but not depth — the user should know which.

• Good

  Speaker reaches 35 Hz or lower, no sub

  True full-range — bottom of orchestral fundamental range covered

• Good

  Subwoofer extends ≥ 5 Hz below the speaker

  Sub adds meaningful depth

• Note

  Subwoofer matches the speaker within 5 Hz

  Sub adds SPL and room-mode coverage, not depth

• Note

  Speaker 35 – 50 Hz, no sub

  Typical bookshelf — room loading helps

• Warn

  Speaker above 50 Hz, no sub

  Bottom octave missing — consider a subwoofer

• N / A

  Headphone config OR speaker frequency-response missing

  Check skipped — no speaker low-edge data to evaluate

Whether the system has a derivable signal path from source to output — i.e., does every required stage exist, and do they connect.

Topology is binary at v1: either the chain works end-to-end or it doesn’t. A phono-level signal going into a line-level amp without a phono preamp is silent; a digital source with no DAC is silent. Surfacing the broken link is the most useful thing the engine can do before scoring anything else.

• Good

  Source → preamp/DAC → amp → speaker chain derives with no signal-level conflicts

  Valid signal path — every stage present and connected

• Fail

  Required stage missing (e.g. phono preamp absent before line-level amp; no DAC for a digital source)

  Audible problem — wrong signal level or silent output

• Fail

  No path can be derived from the chain

  Chain is incomplete — start by fixing topology before scoring anything else

Whether the active interface between two stages is the best one the components support — digital > XLR balanced > RCA > 3.5 mm TRS, with credit for "best available."

This axis answers "is the connection quality leaving signal-to-noise on the table?" — not "is XLR objectively better than RCA?" An RCA-only build is good; we don’t punish components for what they don’t have. We surface upgrades (note) and active downgrades (warn) honestly.

• Good

  Digital path active (USB / S/PDIF / I2S)

  Bit-perfect, no analog noise pickup

• Good

  XLR balanced analog active

  Common-mode noise rejection — quietest analog interface

• Good

  RCA used, no XLR alternative on both ends

  Best the components offer — no penalty for what they don’t have

• Note

  RCA used, XLR available on both ends

  Upgrade opportunity — switch to XLR for lower noise

• Warn

  3.5 mm TRS used with a better alternative available

  Leaving SNR on the table — known weak connector

• Good

  DIN / internal / other functional interface

  Treated as functional — no audible penalty

Whether the spec data driving the analysis comes from manufacturer datasheets or is partial / pending verification, AND whether any primary check returned unknown because data was missing.

Transparency. The user should know whether the verdict is based on confirmed datasheet values or on reputable-secondary inferences. The note tier is honest about that without scaring the wedge user away from a perfectly functional build; a primary-check data gap is escalated to warn so it doesn’t hide behind an averaged score.

• Good

  All components verified AND no primary check returned "unknown · data missing"

  Every spec value used in the verdict is datasheet-cited

• Note

  Some components partial (reputable-secondary) AND no primary check returned "unknown · data missing"

  Verdict holds, but some figures await primary verification

• Warn

  One or more primary checks returned "unknown · data missing"

  Data gap hiding in the score — surfaced honestly rather than averaged away