Thieaudio Monarch MKIV: how much amplifier do you need?

The Thieaudio Monarch MKIV is 10Ω. Its maker prints a sensitivity of 100.0 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 1.0 mW to reach 100 dB SPL, or 0.10 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 comfortable headroom. 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 20 dB harder to drive than the rest of this page assumes. The converter explains the difference.

Thieaudio publishes a sensitivity of 100 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 100 dB is per milliwatt, the figures on this page are right as they stand. If it is per volt, the real sensitivity is 80.0 dB/mW — 20 dB lower at 10Ω — 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.

Thieaudio prints the impedance as 10/9 ohms (±1 ohm) @1kHz, not as a bare number. Everything on this page is calculated with 10Ω, the first of the two figures the maker prints, and the rest of that line is quoted here rather than tidied away, because how a figure is qualified is part of the specification too.

Source: thieaudio.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 10Ω. “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 120.0 dB/V these are sensitive enough to reveal a source's own noise floor. The noisiest source in the database, the Schiit Vali 2+, would put its hiss at roughly 28 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 10Ω these want a source output impedance below 1.25Ω to satisfy the one-eighth rule. 46 of the 280 sources here miss it, the worst being the Bottlehead Crack (OTL kit) at 120.0Ω. Above that threshold the source starts shaping the frequency response. Check yours here.

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