Short answer: a tie on sound quality. Both are rated 3.7/5 (#627 and #669 of 1291 in-ear headphones) at nearly the same price ($14.99 vs $12), so choose on features and fit.
The case for the 7Hz Aero: Across eight hobbyist measurements on squig.link it earns a Harman preference score of 70.6 with a smooth 1.97 dB deviation, an unusually even response for such an inexpensive single 9.2mm dynamic earphone. The catch: The 10 to 16 kHz air region runs about 5.3 dB above target, and a 5.3 dB peak near 8.4 kHz can make cymbals and sibilance a little splashy on bright recordings.
What the KZ EDX Pro 2 does well: A very cheap single dynamic IEM, the second generation EDX Pro. Watch for: Treble sits about 2.9 dB below target, a dark, relaxed balance.
Buy the 7Hz Aero or the KZ EDX Pro 2 on features: they are rated the same for sound quality at close to the same price.
Looking for alternatives? See the complete Headphones rankings.
Across eight hobbyist measurements on squig.link it earns a Harman preference score of 70.6 with a smooth 1.97 dB deviation, an unusually even response for such an inexpensive single 9.2mm dynamic earphone.
Amazon $14.99 eBay
A very cheap single dynamic IEM, the second generation EDX Pro.
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Specifications Side By Side
| 7Hz Aero | KZ EDX Pro 2 | |
|---|---|---|
| Price | $14.99 | $12 |
| Ranked | #627 of 1291 in In-Ear Headphones | #669 of 1291 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 71 (median of 8 squig.link measurements, calibrated to AutoEQ) | 70 (median of 3 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 1.97 dB standard deviation | 2.02 dB standard deviation |
| Tonal Tilt | -0.81 (negative is warmer, positive brighter) | -0.84 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+2.8 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (+1.2 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Dynamic | Dynamic |
| Drivers | 1 x 9.2mm dynamic | 1 x 10mm dynamic |
| Impedance | - | 24 ohms |
| Sensitivity | - | 107 dB/mW @ 1 kHz |
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 Aero from achoreviews, aftersound, bassyalexander, musicafe, pw, silicagel, soundcheck39 and vortexreviews; the KZ EDX Pro 2 from ankramutt, kuping-sensi and theaudiostore, all via squig.link.
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