HarmonicDyne Poseidon: how much amplifier do you need?

The HarmonicDyne Poseidon is 64Ω. The shop listing this figure stands on prints a sensitivity of 103.0 dB and never says whether that is per milliwatt or per volt, so this page reads it as per milliwatt — on that reading it needs 0.50 mW to reach 100 dB SPL, or 0.18 V across the drivers. If the figure is really per volt, it needs far more.

That puts it in the easy category. A phone, a laptop headphone jack or the cheapest USB dongle will drive it to painful levels. Of the 280 sources in the database, 280 have at least 10 dB of headroom and another 0 have enough. The cheapest portable source that does the job is the Apple USB-C dongle (US) at $9.

This maker printed a decibel figure and no reference unit, so the number above is shown exactly as printed. Everything below reads it as per milliwatt, which is the commoner convention on a sheet that omits the unit — if it is really per volt, this headphone is about 12 dB harder to drive than the rest of this page assumes. The converter explains the difference.

HarmonicDyne, as the shop reproduces it, publishes a sensitivity of 103 dB and does not state whether that is per milliwatt or per volt — the spec sheet simply stops at the number.

Both readings are given here so you can judge for yourself. If that 103 dB is per milliwatt, the figures on this page are right as they stand. If it is per volt, the real sensitivity is 91.1 dB/mW — 12 dB lower at 64Ω — and everything above understates what these need by that much. The per-milliwatt reading is the one shown, because it is the more common convention on a spec sheet that omits the unit; treat it as an indication rather than a specification.

One caveat about the source. Almost everything in this database comes from a document the maker published. This entry does not: the figures above stand on someone else's product page — Linsoul, a Chinese-audio retailer and ShenzhenAudio, a retailer — and not on any page HarmonicDyne publishes. Shops usually copy the factory table faithfully and this one may well be exact — but a shop can also carry an old revision, and if HarmonicDyne changes the number there is nothing here that would notice. It is the weakest provenance on this site, which is why it is written on the page rather than left in a footnote.

HarmonicDyne does own a domain, harmonicdyne.com, but it serves a TLS certificate issued for a different name, so no browser that checks certificates will open it. Its product pages cannot be read at all, which is a different thing from a maker that never published: the document may exist and simply be unreachable.

Source: linsoul.com, shenzhenaudio.com. How this data was built.

Most people listen between 75 and 85 dB. The 100 dB row is the one worth planning around: it gives you headroom for dynamic peaks without designing your system for a volume that would damage your hearing in under fifteen minutes. The safe listening calculator puts numbers on that.

Every source in the database, judged at 100 dB SPL into 64Ω. “Headroom” is how much power is left over above what the headphone needs — 10 dB means ten times the required power, which is what you want for dynamic peaks.

Hiss. At 114.9 dB/V these are sensitive enough to reveal a source's own noise floor. The noisiest source in the database, the Schiit Mjolnir 3, would put its hiss at roughly 23 dB SPL in these headphones — clearly audible in quiet passages. The hiss calculator lets you check your own amplifier's noise figure.

Output impedance. At 64Ω these want a source output impedance below 8.00Ω to satisfy the one-eighth rule. Of the 192 sources that publish one, 34 miss it, the worst being the Bottlehead Crack (OTL kit) at 120.0Ω; the other 88 publish no output impedance at all, so they cannot be checked either way. Above that threshold the source starts shaping the frequency response. Check yours here.

Worked out in advance against its own stable: vs Zeus. Each of those pages counts the sources that drive one and not the other.

Or open the comparison tool to put any two models side by side, or browse all 578. Or see every HarmonicDyne headphone in the database, and how much of what this site says about them came from HarmonicDyne’s own documents.