Both are Bluetooth receivers, $109 against $109. 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 BTR15 reaches 100 dB on 565 of the 567 models here, the FiiO BTR5 2021 on 563.
| Specification | FiiO BTR15 | FiiO BTR5 2021 |
|---|---|---|
| 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 | 1.0 Ω |
| Output noise | 2.0 µV | 2.0 µV |
| Price | $109 | $109 |
| Headphones it reaches 100 dB on out of 567 | 565 | 563 |
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.
| Load | FiiO BTR15 | FiiO BTR5 2021 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
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 BTR15 publishes at 32 Ω and at 300 Ω; FiiO BTR5 2021 at 32 Ω. Every other row is worked out from those — between two published loads, or beyond them holding voltage constant, which understates rather than flatters.
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.
What each of these labels means, and why a derived figure is still worth printing, is set out in how this data was built.
2 headphones reach 100 dB on the FiiO BTR15 but not on the FiiO BTR5 2021 — HiFiMAN Susvara, Symphonium Crimson.
563 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 Shure SE846: FiiO BTR15 has +34 dB of headroom there against +31 dB. 3 dB is about 1.8 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.
| Headphone | Impedance | Needs | FiiO BTR15 headroom | FiiO BTR5 2021 headroom | FiiO BTR15 hiss | FiiO BTR5 2021 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +34 dB | +31 dB | 20 dB | 20 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +14 dB | +11 dB | 0 dB | 0 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +19 dB | +17 dB | -1 dB | -1 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +14 dB | +12 dB | -6 dB | -6 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +12 dB | +10 dB | -7 dB | -7 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +8 dB | +5 dB | -13 dB | -13 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +4 dB | +1 dB | -17 dB | -17 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +1 dB | -1 dB | -19 dB | -19 dB |
These two cost the same, $109, so price settles nothing. Out of the 567 models here, the FiiO BTR15 drives 2 models to 100 dB — and on the other side there is no such advantage at all.
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 BTR15 and FiiO BTR5 2021. Or put either against your own headphones in the source comparison tool.