Short answer: a tie on sound quality. Both are rated 4.0/5 (#438 and #452 of 1291 in-ear headphones) at nearly the same price ($249 vs $249.99), so choose on features and fit.
The case for the HUAWEI FreeBuds Pro 4: A broadly balanced tuning with a preference score of 74 against the Harman target. The tradeoff: The rating reflects sound quality only; comfort, build and noise isolation are not part of the score.
What the OpenAudio Siren does well: The median of 4 hobbyist measurements gives it a solid Harman preference score of 73 with a 1.94 dB spread, and its mids sit within about 0.5 dB of target, so vocals and instruments sound natural. Watch for: A 6 dB peak near 8.2 kHz can make cymbals and sibilance sound sharp.
Buy the HUAWEI FreeBuds Pro 4 or the OpenAudio Siren on features: they are rated the same for sound quality at close to the same price.
Still deciding? The full Headphones rankings cover every ranked option.
A broadly balanced tuning with a preference score of 74 against the Harman target.
Amazon $249 eBay
The median of 4 hobbyist measurements gives it a solid Harman preference score of 73 with a 1.94 dB spread, and its mids sit within about 0.5 dB of target, so vocals and instruments sound natural.
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Specifications Side By Side
| HUAWEI FreeBuds Pro 4 | OpenAudio Siren | |
|---|---|---|
| Price | $249 | $249.99 |
| Ranked | #438 of 1291 in In-Ear Headphones | #452 of 1291 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 74 (median of 3 squig.link measurements, calibrated to AutoEQ) | 73 (median of 4 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 1.73 dB standard deviation | 1.94 dB standard deviation |
| Tonal Tilt | -0.60 (negative is warmer, positive brighter) | -0.44 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+2.4 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (+2.1 dB at 30 Hz) |
| Connection | True Wireless | Wired |
| Driver Type | Hybrid (dual driver: dynamic + planar tweeter) | Hybrid (1 dynamic + 2 balanced armature) |
| Drivers | 1 x 11mm dynamic + 1 x planar tweeter (per ear) | 1 x 10mm dynamic + 2 x balanced armature |
| Impedance | - | 10 ohms |
| Sensitivity | - | 107 dB/mW |
| Frequency Response | - | 10Hz - 45kHz (Manufacturer specified) |
| Built-in Microphone | - | No |
Frequency Response Compared
Both headphones’ measurements overlaid on the Harman target. Above the target sounds louder in that range, below it quieter. Each curve is the median of several independent measurements, shifted so its 500 Hz to 2 kHz average sits at 0 dB, so only the tuning is compared.
Measurement data: the HUAWEI FreeBuds Pro 4 from boizoff, dhrme and regancipher; the OpenAudio Siren from atechreviews, hu-fi, jaytiss and superreview, all via squig.link.
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