Short answer: a tie on sound quality. Both are rated 4.2/5 (#258 and #298 of 1291 in-ear headphones) at nearly the same price ($75.99 vs $71.99), so choose on features and fit.
Why pick the 7Hz Sonus II: A hybrid dynamic and planar in-ear with a 76.5 preference score, a smooth 1.7 dB deviation and slightly warm, natural bass. The catch: The 3 to 6 kHz presence range sits nearly 4 dB under target with a 5.2 dB dip near 6 kHz, so vocals and guitars can sound a little distant and less crisp.
Why pick the KZ PR3: The median of 11 hobbyist measurements gives it a very good Harman preference score of 76 with a 1.93 dB spread. The tradeoff: A 10.4 dB peak near 10.3 kHz can make cymbals and sibilance sound sharp.
Buy the 7Hz Sonus II or the KZ PR3 on features: they are rated the same for sound quality at close to the same price.
Looking for alternatives? See the complete Headphones rankings.
A hybrid dynamic and planar in-ear with a 76.5 preference score, a smooth 1.7 dB deviation and slightly warm, natural bass.
Amazon $75.99 eBay
The median of 11 hobbyist measurements gives it a very good Harman preference score of 76 with a 1.93 dB spread.
Amazon $71.99 eBayPrices on this page were last checked October 16, 2026 at 5:46 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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Specifications Side By Side
| 7Hz Sonus II | KZ PR3 | |
|---|---|---|
| Price | $75.99 | $71.99 |
| Ranked | #258 of 1291 in In-Ear Headphones | #298 of 1291 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 77 (median of 2 squig.link measurements, calibrated to AutoEQ) | 76 (median of 11 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 1.66 dB standard deviation | 1.93 dB standard deviation |
| Tonal Tilt | -0.45 (negative is warmer, positive brighter) | +0.26 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-0.3 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (+0.2 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Hybrid (1 dynamic + 1 planar magnetic) | Planar |
| Drivers | 1 x dynamic + 1 x planar magnetic | 1 x 13.2mm planar |
| Impedance | 29 ohms | 15 ohms |
| Sensitivity | 108 dB/V | - |
| Frequency Response | 10Hz - 20kHz (Manufacturer specified) | 20Hz - 40kHz |
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 7Hz Sonus II from aftersound, bassaudio and jaytiss; the KZ PR3 from enemyspider, flare, jaraba, jaytiss, obodio, pw, riz, soundcheck39, tdl, therollo9 and tonedeafmonk, all via squig.link.
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