Short answer: a tie on sound quality. Both are rated 4.2/5 (#279 and #273 of 1291 in-ear headphones) at nearly the same price ($50.99 vs $55), so choose on features and fit.
What the 7Hz Sonus does well: The median of 27 hobbyist measurements gives it a very good Harman preference score of 76 with a 1.77 dB spread, and its mids sit within about 0.6 dB of target, so vocals and instruments sound natural. Watch for: Presence sits about 3.3 dB low with a 6.2 dB dip near 6.3 kHz, so vocals and instruments lose some bite.
What the Tin HiFi C3 MKII does well: The median of 11 hobbyist measurements gives it a very good Harman preference score of 76 with a 1.55 dB spread, and its mids sit within about 0.5 dB of target, so vocals and instruments sound natural. The catch: A 4.9 dB peak near 8.2 kHz can make cymbals and sibilance sound sharp.
Buy the 7Hz Sonus or the Tin HiFi C3 MKII on features: they are rated the same for sound quality at close to the same price.
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The median of 27 hobbyist measurements gives it a very good Harman preference score of 76 with a 1.77 dB spread, and its mids sit within about 0.6 dB of target, so vocals and instruments sound natural.
Amazon $50.99 eBay
The median of 11 hobbyist measurements gives it a very good Harman preference score of 76 with a 1.55 dB spread, and its mids sit within about 0.5 dB of target, so vocals and instruments sound natural.
Amazon $55.00 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 | Tin HiFi C3 MKII | |
|---|---|---|
| Price | $50.99 | $55.00 |
| Ranked | #279 of 1291 in In-Ear Headphones | #273 of 1291 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 76 (median of 27 squig.link measurements, calibrated to AutoEQ) | 76 (median of 11 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 1.77 dB standard deviation | 1.55 dB standard deviation |
| Tonal Tilt | -0.37 (negative is warmer, positive brighter) | -0.56 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-0.4 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (+1.1 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Hybrid (1 dynamic + 1 balanced armature) | Dynamic |
| Drivers | 1 x dynamic + 1 x balanced armature | 1 x 10mm dynamic |
| Impedance | 30 ohms | 32 ohms |
| Sensitivity | 109 dB/V | 106 dB |
| Frequency Response | 10Hz - 20kHz (Manufacturer specified) | 10Hz - 40kHz (Manufacturer specified) |
| Weight | - | 0 lbs (4.1 g) per earbud |
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 from achoreviews, aftersound, atechreviews, audioamigo, bassaudio, cqtek, csi-zone, enemyspider, fernandagunsan, harpo, hbb, ianfann, jaytiss, joshtbvo, lown-fi, mmagtech, musicafe, practiphile, pw, sl0the, soundcheck39, soundignity, theaudiostore, timmyv, tonedeafmonk, treblewellxtended and vortexreviews; the Tin HiFi C3 MKII from arn, avishai, bassaudio, csi-zone, jaytiss, pw, silicagel, soundcheck39, soundignity, tonedeafmonk and vortexreviews, all via squig.link.
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