Short answer
Both are Bluetooth receivers, both at $109.
The FiiO BTR15 reaches 100 dB on 565 of the 567 models here, the HiBy W5 on 557.
| Specification | FiiO BTR15 | HiBy W5 |
|---|---|---|
| Power into 32Ω | 125 mW | 80 mW |
| Power into 150Ω | 28 mW | 17 mW |
| Power into 300Ω | 15 mW | 8.5 mW |
| Power into 600Ω | 7.5 mW | 4.3 mW |
| Output impedance | 1.0 Ω | not published |
| Output noise | 2.0 µV | not published |
| Price | $109 | $109 |
| Headphones it reaches 100 dB on out of 567 | 565 | 557 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | FiiO BTR15 | HiBy W5 |
|---|---|---|
| Socket | 4.4mm | no separate rating |
| Power into 32Ω | 340 mW | — |
| Power into 300Ω | 50 mW | — |
| Output impedance | 1.5 Ω | — |
| Output noise | not published | — |
| Headphones it reaches 100 dB on out of 567 | 565 | — |
Only the FiiO BTR15 has a separate balanced rating from its maker; through it, it reaches 100 dB on 565 of the 567 models here. The HiBy W5 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 BTR15 | HiBy W5 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. FiiO BTR15 publishes at 32 Ω and at 300 Ω; HiBy W5 at 32 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 300 Ω only the FiiO BTR15 figure is the maker’s own. On those rows the derived number is the one to doubt first.
8 headphones reach 100 dB on the FiiO BTR15 but not on the HiBy W5 — HiFiMAN Susvara, Moondrop COSMO, Moondrop PARA 2, 5 more.
557 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 Campfire Audio Andromeda 2020: FiiO BTR15 has +14 dB of headroom there against +8 dB. 6 dB is about 4.1 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for HiBy W5 because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | FiiO BTR15 headroom | HiBy W5 headroom | FiiO BTR15 hiss | HiBy W5 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +34 dB | +28 dB | 20 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +14 dB | +8 dB | 0 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +19 dB | +17 dB | -1 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +14 dB | +12 dB | -6 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +12 dB | +9 dB | -7 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +8 dB | +5 dB | -13 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +4 dB | +1 dB | -17 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +1 dB | -1 dB | -19 dB | not published |
These two cost the same, $109, so price settles nothing. Out of the 567 models here, the FiiO BTR15 drives 8 models to 100 dB — and on the other side there is no such advantage at all.
Only published figures count here; blank axes are counted separately.
Each in full: FiiO BTR15 and HiBy W5.