Short answer
Both are Bluetooth receivers, $59 against $50.
The FiiO BTR13 reaches 100 dB on 565 of the 567 models here, the Fosi Audio N3 on 562.
| Specification | FiiO BTR13 | Fosi Audio N3 |
|---|---|---|
| Power into 32Ω | 100 mW | 138 mW |
| Power into 150Ω | 21 mW | 30 mW |
| Power into 300Ω | 10.0 mW | 15 mW |
| Power into 600Ω | 5.0 mW | 7.5 mW |
| Output impedance | 0.6 Ω | not published |
| Output noise | 1.0 µV | not published |
| Price | $59 | $50 |
| Headphones it reaches 100 dB on out of 567 | 565 | 562 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | FiiO BTR13 | Fosi Audio N3 |
|---|---|---|
| Socket | 4.4mm | no separate rating |
| Power into 32Ω | 220 mW | — |
| Power into 300Ω | 55 mW | — |
| Output impedance | 1.0 Ω | — |
| Output noise | 1.0 µV | — |
| Headphones it reaches 100 dB on out of 567 | 564 | — |
Only the FiiO BTR13 has a separate balanced rating from its maker; through it, it reaches 100 dB on 564 of the 567 models here. The Fosi Audio N3 may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it.
| Load | FiiO BTR13 | Fosi Audio N3 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. FiiO BTR13 publishes at 32 Ω and at 300 Ω; Fosi Audio N3 at 32 Ω and at 300 Ω. The other rows are worked out from those.
The two publish at the same loads, which is the one case where the rows of this table can be read straight across.
3 headphones reach 100 dB on the FiiO BTR13 but not on the Fosi Audio N3 — Moondrop COSMO, Symphonium Crimson, Symphonium Helios.
562 of the 567 models here reach 100 dB on both.
Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Shure SE846: FiiO BTR13 has +32 dB of headroom there against +30 dB. 2 dB is about 1.7 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Fosi Audio N3 because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | FiiO BTR13 headroom | Fosi Audio N3 headroom | FiiO BTR13 hiss | Fosi Audio N3 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +32 dB | +30 dB | 14 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +12 dB | +10 dB | -6 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +18 dB | +19 dB | -7 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +13 dB | +15 dB | -12 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +11 dB | +11 dB | -13 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +6 dB | +8 dB | -19 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +2 dB | +4 dB | -23 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +0 dB | +2 dB | -25 dB | not published |
The FiiO BTR13 costs $9 more than the Fosi Audio N3. Out of the 567 models here, that difference buys 3 more models driven to 100 dB.
Nothing runs the other way: there is no axis here on which the cheaper of the two does better.
Only published figures count here; blank axes are counted separately.
Each in full: FiiO BTR13 and Fosi Audio N3.