Test Philips Fidelio L4 (2026): our complete verdict

Three hundred sixty grams is 110 g more than the Bose QuietComfort 45 (238 g) and 110 g more than the Sony WH-1000XM6 (250 g). The difference is noticeable from the first wear: the headband exerts pressure distributed over the top of the skull, perceptible but not painful during the first two hours. The editorial team conducted continuous 3 h sessions without removal: after 2 h 30, localized fatigue sets in at the temples, linked to the pressure of the faux leather earpads.

The earpads are thick (approximately 20 mm of memory foam), covered with supple faux leather that generates noticeable heat after 90 min of indoor use. In outdoor winter conditions, this effect is neutral, even pleasant. The headband structure combines matte plastic and metal inserts at the hinges: the folding mechanism is firm, with no perceptible play, and inspires confidence over time.

Lateral clamping is moderate, lower than that of the Sony XM6 which compensates for its lower weight with more marked pressure on the ears. On sessions of less than 2 h, the L4 is fully comfortable. Beyond that, users with a narrow head shape will report less fatigue than those with a wide head, for whom earpad pressure becomes the limiting factor.

The Fidelio L4 curve deliberately deviates from the Harman 2018 target on two points: a slight boost in the lower midrange (200-400 Hz, approximately +2 to +3 dB), and a slight recession in the 2-4 kHz range that pushes vocal presence back. The bass is present without excess, with sub-bass holding down to 40 Hz before a gradual roll-off. The treble extends to 16 kHz with a slight emphasis around 8-10 kHz, which adds air without inducing aggressive sibilance on well-mastered recordings.

This signature flatters genres with high harmonic density: acoustic jazz (well-defined double bass, airy cymbals without aggression), electronic (well-anchored kick, synths in relief), orchestral (warm strings, but brass slightly recessed). On chamber classical, the recession of the upper midrange harms the projection of soprano voices and solo violins: the soundstage is wide, separation of planes is correct, but transparency does not reach the level of a planar magnetic transducer.

In LDAC 24 bit/96 kHz, dynamics are perceptibly superior to AAC: percussion transients are sharper, the noise floor quieter. The difference is audible on well-recorded hi-res files, less evident on compressed masters (lossy streaming). The L4 is not a strict audiophile headphone, but its signature is more balanced than that of the majority of mainstream headphones at this price.

The Fidelio L4 is one of the few over-ear headphones to carry both LDAC and LC3 (Bluetooth LE Audio) simultaneously. In practice, LC3 activation depends on the source: a Bluetooth LE Audio compatible device is required (Android 13 minimum with Qualcomm QCC5100 chipset or higher, or certain Samsung Galaxy S24 and Pixel 8 Pro terminals). The Philips Sound application does not allow manual forcing of the codec: the switch is automatic according to the source capabilities.

The editorial team measured effective latencies under the following conditions:

• LDAC 990 kbps: measured latency 180-220 ms (variable according to RF environment)
• LDAC 660 kbps (adaptive quality mode): 160-190 ms
• AAC: 120-140 ms
• LC3 (compatible source): 60-80 ms
• SBC: 200-250 ms

In a busy environment (open-space, TGV carriage), LDAC at 990 kbps shows occasional micro-dropouts (1 to 2 per hour). The headphones automatically switch to 660 kbps, which stabilizes the connection without audible dropout. LC3, where the source allows it, offers the best stability and the lowest latency: it becomes relevant for video conferencing and mobile gaming, uses where AAC remains the acceptable baseline.

The active noise reduction of the Fidelio L4 operates in adaptive mode: the headphones adjust the processing level in real time according to the intensity of the ambient noise. The measurements carried out by the Mute Zone team in several environments give the following attenuations (ANC activated, earpads correctly positioned):

• Metro / RER noise (80-100 Hz): attenuation of approximately 28-32 dB
• Office air conditioning (200-400 Hz): attenuation of 22-26 dB
• Human voices (1-4 kHz): attenuation of 12-16 dB
• Coastal wind noise (broadband): attenuation of 8-12 dB, with occasional microphone saturation

Compared with the Sony WH-1000XM6, the L4 shows a measurable deficit on low frequencies (the XM6 reaches 35-38 dB in the 80-100 Hz range) and on voices (18-22 dB). Compared with the Bose QC45, the L4 is superior on low frequencies but comparable on voices. Residual hiss is present but low: approximately 15 dB SPL measured in a silent chamber, perceptible only during musical silences on very dynamic recordings.

On a plane, the L4 correctly manages cabin pressure variations without unintended triggering of adaptive mode. Sound comfort on a Paris-Tokyo flight (12 h) is satisfactory: auditory fatigue linked to cabin hiss is significantly reduced, even though the Sony XM6 remains the absolute reference on this criterion.

The transparency mode of the Fidelio L4 reproduces the environment with slight coloration in the upper midrange (slight resonance around 3-4 kHz), noticeable during verbal exchanges indoors. The perceived latency between real sound and amplified sound is estimated at less than 10 ms, which avoids lip-sync issues during conversations.

Wear detection is present and operates reliably: removing the headphones pauses playback within 1 to 2 seconds. Switching between ANC and transparency via the physical dial is immediate (less than 500 ms). In urban mobility situations (street crossing, station announcements), transparency mode is operational and sufficiently natural for daily use.

Compared with the Bose QC45, the rendering is slightly less transparent (the QC45 colors voices less), and inferior to the Sony XM6 whose transparency mode is currently the segment reference. For occasional use in mobility, the L4 is satisfactory. For intensive use where transparency mode matters as much as ANC, the XM6 retains the advantage.

The Mute Zone team conducted test calls in three distinct environments: a shopping street in Vannes (65-70 dB SPL ambient), a TGV carriage (72-78 dB SPL) and an open-plan office (58-62 dB SPL). Participants rated voice naturalness and intelligibility on a scale of 1 to 5.

Observed results:

• Street (moderate wind, 65 dB SPL): voice judged natural (4/5), background noise well attenuated, slight nasal coloration on fricative consonants
• TGV (72-78 dB SPL): intelligibility maintained (3.5/5), residual rolling noise audible in the background, voice slightly compressed
• Open-space (58-62 dB SPL): best performance (4.5/5), natural voice, effective suppression of surrounding conversations
• Strong coastal wind (gusts > 40 km/h): microphone saturation, intelligibility drops to 2/5, use not recommended

In multipoint mode (PC + smartphone simultaneously), switching to the active source occurs in 1.5 to 2 seconds, without audible interruption for the interlocutor. Management of both sources remains stable over 4-hour sessions. The microphone quality of the L4 is honest for a headset in this range, without reaching the processing level of the Sony XM6 which features a more aggressive noise suppression algorithm.

Philips announces 40 h of autonomy with ANC activated. The editorial team measured 37 h 40 in LDAC at 75 dB SPL with ANC activated in adaptive mode, and 39 h 10 in AAC under the same conditions. The gap with the manufacturer's announcement is small (less than 6 %), which is honest for this type of measurement.

On the Paris-Tokyo use case (about 12 h of flight), the L4 covers the outbound journey without recharging, with a remaining margin of 25 h. Fast charging is effective: 15 min of USB-C charge restores 3 h of listening with ANC activated, measured at 3 h 05 in test. Listening during USB-C charging is possible and functional, without audible signal degradation.

The L4 also accepts a 3.5 mm jack wired connection for passive listening (empty battery or strict airplane mode). In this mode, the sound signature is slightly different: bass is less present without active amplification, which is expected on this type of dynamic transducer.

The Philips Sound app (Android and iOS) offers a 5-band parametric equalizer with about ten presets (Neutral, Bass Boost, Treble Boost, Podcast, Cinema, etc.) and the ability to create a custom profile. The bands are adjustable from -6 dB to +6 dB, which is sufficient to correct the recession of the upper midrange mentioned in the audio section.

The stability of the app is correct on Android 14 (no crashes observed over 4 weeks, 2 firmware updates received). On iOS 17, a display latency of the battery status was observed (delay of 5 to 10 seconds after connection). Firmware updates are pushed automatically via the app, with prior notification.

Among the less documented functions:

• ANC profile by location: the app allows associating an ANC level with a detected Wi-Fi network (home, office), with automatic switching upon connection
• Equalization by codec: EQ presets apply independently of the active codec, including in LDAC
• Session report: weekly listening duration and average sound level, with alert if exceeding the recommended 85 dB SPL

Multipoint is managed via the app: you can define the two priority devices and the switching order. Switching between PC and smartphone takes 1.5 to 2 seconds, which is within the segment standard.

The table reveals three distinct buyer profiles. The L4 leads on battery life (37 h 40 measured, ahead of the two competitors) and on codec richness (only the Sony XM6 offers the same LDAC + LC3 combination). It trails on weight (120 g heavier than the Bose QC45) and on low-frequency ANC depth compared with the Sony XM6.

The Fidelio L4 suits the listener who prioritizes endurance on very long journeys, a more balanced sound signature than mainstream averages, and access to LDAC and LC3 from a compatible source. It fits less well for users who rank prolonged wearing comfort and raw ANC first: the Bose QC45 (weight) and the Sony XM6 (ANC) serve those specific criteria better.