Short answer
Both are dongles, both at $60.
The Tempotec Sonata BHD Pro reaches 100 dB on 565 of the 567 models here, the Kiwi Ears Allegro Pro on 554.
| Specification | Kiwi Ears Allegro Pro | Tempotec Sonata BHD Pro |
|---|---|---|
| Power into 32Ω | 68 mW | 280 mW |
| Power into 150Ω | 15 mW | 60 mW |
| Power into 300Ω | 7.3 mW | 30 mW |
| Power into 600Ω | 3.6 mW | 15 mW |
| Output impedance | not published | 0.6 Ω unverified |
| Output noise | not published | 4 µV unverified |
| Price | $60 | $60 |
| Headphones it reaches 100 dB on out of 567 | 554 | 565 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Kiwi Ears Allegro Pro | Tempotec Sonata BHD Pro |
|---|---|---|
| Socket | 4.4mm | no separate rating |
| Power into 32Ω | 170 mW | — |
| Power into 300Ω | 18 mW derived | — |
| Output impedance | not published | — |
| Output noise | not published | — |
| Headphones it reaches 100 dB on out of 567 | 563 | — |
Only the Kiwi Ears Allegro Pro has a separate balanced rating from its maker; through it, it reaches 100 dB on 563 of the 567 models here. The Tempotec Sonata BHD Pro may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it. Derived figures are worked out from the loads the maker did publish.
| Load | Kiwi Ears Allegro Pro | Tempotec Sonata BHD Pro |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. Kiwi Ears Allegro Pro publishes at 32 Ω; Tempotec Sonata BHD Pro at 32 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.
11 headphones reach 100 dB on the Tempotec Sonata BHD Pro but not on the Kiwi Ears Allegro Pro — HiFiMAN HE-6se V2, HiFiMAN HE6 Remastered, HiFiMAN Susvara, 8 more.
554 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 Audio-Technica ATH-R70X: Tempotec Sonata BHD Pro has +11 dB of headroom there against +5 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 Kiwi Ears Allegro Pro and Tempotec Sonata BHD Pro because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Kiwi Ears Allegro Pro headroom | Tempotec Sonata BHD Pro headroom | Kiwi Ears Allegro Pro hiss | Tempotec Sonata BHD Pro hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +27 dB | +33 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +7 dB | +13 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +16 dB | +22 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +11 dB | +18 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +8 dB | +14 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +5 dB | +11 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +0 dB | +7 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -1 dB | +5 dB | not published | not published |
These two cost the same, $60, so price settles nothing. Out of the 567 models here, the Tempotec Sonata BHD Pro drives 11 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: Kiwi Ears Allegro Pro and Tempotec Sonata BHD Pro.