Reviewed on: SoundStage! Solo, November 2021

I measured the Philips Fidelio L3 headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 QC audio analyzer. A Reiyin WP-04 USB Bluetooth transmitter was used to send signals from the Clio 12 QC to the headphones. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.

Frequency response

This chart shows the Fidelio L3s’ frequency response, using a Bluetooth connection with noise canceling on, which I assume is the mode that most people buying these headphones will use most often. The bass bump is somewhat Harman curve-like, but a few dB higher. There’s also a lot more emphasis around 1.5kHz than we’d normally see; typically this peak resides more around 2 or 3kHz. And there’s a lot more energy than usual between about 5 and 8kHz. This could be subjectively balanced out by that big bass peak, but material without much bass may sound bright, especially to younger listeners whose high-frequency hearing is good.

Frequency response

Here we can see the difference in response between the Bluetooth connection and the wired connection (which also employs the headphones’ internal amp). The wired connection shows a bit less bass energy but a few dB less upper midrange and treble, suggesting it’ll sound a little softer.

Frequency response

This chart shows the Fidelio L3s’ right-channel response compared with a couple of other Bluetooth models (DALI IO-4 and Master&Dynamic MH40 headphones) and the AKG K371 passive headphones, which are said to be very close to the Harman curve. You can see how much more pronounced the response of the Fidelio L3s are around 40Hz and 1.5kHz, and between 5 and 8kHz. These headphones are almost certain to have a somewhat idiosyncratic sound.


The Fidelio L3s’ right-channel spectral-decay plot (measured with the wired connection) appears to show some of the effects of that big bass bump sneaking in around 200Hz (the low-frequency limit of this measurement), but otherwise looks pretty clean.


Here’s the THD vs. frequency chart, measured using the wired connection at 90dBA and 100dBA (both levels set with pink noise). Distortion is low at even the loud level of 90dBA; at the insanely loud level of 100dBA, the very low frequencies start to distort, but even 8% THD at 20Hz is unlikely to be audible because our ears are less sensitive to low-frequency distortion.


In this chart, the external noise level is 85dB SPL (the red trace), and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. We’ll start by showing how the Fidelio L3s work in their different modes: ANC off and on, and Awareness, which seems to combine a little bit of noise canceling in the bass with a lot of leak-through in the mids and treble, to produce a flat overall response for external sounds.


Again, with the red trace showing an external noise level is 85dB SPL, here’s how the Fidelio L3s’ noise canceling stacks up against competitors. It’s not the worst, but it’s far from the best. Still, you’ll get about 10dB of cancellation in the “airplane cabin noise band” between 100 and 1000Hz, and that’s what I consider the minimum required to deliver noise canceling that’s worth paying for.


The impedance magnitude, running around 5900 ohms through the first seven octaves of the audio band, is that of a preamp or DAC input, not of a passive headphone driver, which shows that the Fidelio L3s’ internal electronics are always engaged. The phase response is similarly flat.

Considering that the headphones don’t work unless their internal electronics are powered up, there’s no point in measuring sensitivity. They’ll play plenty loud until the battery runs down.

Bottom line: The Fidelio L3s have a rather idiosyncratic frequency response, which suggests they’ll sound somewhat different from most other headphones, and the noise canceling is just OK.

. . . Brent Butterworth

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