FiiO M21 vs FiiO M27

Both are portable players, $599 against $1799. This page puts them side by side on the only three things a maker can be held to — power, output impedance and noise — and then asks the question that actually matters: which headphones do they treat differently?

The FiiO M27 reaches 100 dB on 567 of the 567 models here, the FiiO M21 on 566.

A figure marked not published is missing from the maker’s own material, which is not the same as being good or bad. Where one of these two publishes a number and the other does not, the comparison on that axis cannot be made at all — and saying so is more useful than guessing.

Both makers publish a power rating, which is less common than the table above makes it look: of the 280 sources here, 209 publish a figure at at least one load and only 2 publish one at all four. FiiO M21 publishes at 32 Ω and at 300 Ω; FiiO M27 at 32 Ω and at 300 Ω. Every other row is worked out from those — between two published loads, or beyond them holding voltage constant, which understates rather than flatters.

The two publish at the same loads, which is the one case where the rows of this table can be read straight across.

What each of these labels means, and why a derived figure is still worth printing, is set out in how this data was built.

1 headphone reaches 100 dB on the FiiO M27 but not on the FiiO M21 — Symphonium Titan.

14 headphones are left alone by the FiiO M27 under the one-eighth rule but coloured by the FiiO M21 (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 11 more).

30 headphones stay below the audible-hiss threshold on the FiiO M21 but cross it on the FiiO M27 (AFUL Performer 8, Audio-Technica ATH-CKS1100, Austrian Audio Hi-X25BT, 27 more).

566 of the 567 models here reach 100 dB on both. That is a power count and nothing more; whether either source suits a given headphone also depends on the two lines above.

The counts above say how many models the two treat differently. This says by how much. The same 8 headphones appear on every page of this kind, ordered from the easiest to drive to the hardest, so a row can be read across pages as well as across columns. Headroom is at a 100 dB SPL peak.

The widest gap on the list is the Campfire Audio Andromeda 2020: FiiO M27 has +26 dB of headroom there against +18 dB. 7 dB is about 5.5 times the power, which matters for peaks rather than for how loud the music sits.

Hiss is this source’s own noise, in decibels SPL, in that headphone — not a rating. Below about 20 dB SPL it is under the threshold of hearing in a quiet room; a negative figure means it is far below it.

The FiiO M27 costs $1200 more than the FiiO M21. Out of the 567 models here, that difference buys 1 more model driven to 100 dB and 14 more models left alone under the one-eighth rule.

It does not run one way only: the cheaper FiiO M21 keeps 30 models below the audible-hiss threshold that the FiiO M27 does not, which is the part worth checking against your own headphones before paying the difference.

Everything in this paragraph counts only figures the two makers published. An advantage on an axis one of them leaves blank cannot be counted, and is not counted — how often that happens is its own page.

Each has a page of its own with every power figure traced to what the maker published and a full headphone list: FiiO M21 and FiiO M27. Or put either against your own headphones in the source comparison tool.