FiiO M27 vs HiBy R8 II: Which Drives More Headphones?

FiiO M27 vs HiBy R8 II

Short answer

More power: the FiiO M27, with 1.80 W into 32 Ω; the HiBy R8 II has 225 mW (balanced: 5.00 W against 710 mW). The FiiO M27 drives 2 headphones to 100 dB that the HiBy R8 II cannot (Moondrop PARA, Symphonium Titan).
Quieter with sensitive IEMs: the HiBy R8 II. 14 headphones stay below audible hiss on it but not on the FiiO M27 (Audio-Technica ATH-CKS1100, Austrian Audio Hi-X25BT, Beyerdynamic DJ 300 PRO X, 11 more).
Output impedance: 14 headphones are left alone by the FiiO M27 under the one-eighth rule but coloured by the HiBy R8 II (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 11 more).
Price: the HiBy R8 II costs $200 more; what that buys on these numbers is set out further down, under What the price difference buys.

Both are portable players, $1799 against $1999.

The FiiO M27 reaches 100 dB on 567 of the 567 models here, the HiBy R8 II on 565.

Specification	FiiO M27	HiBy R8 II
Power into 32Ω	1.8 W	225 mW
Power into 150Ω	391 mW	48 mW
Power into 300Ω	200 mW	24 mW
Power into 600Ω	100 mW	12 mW
Output impedance	0.5 Ω	1 Ω
Output noise	3.9 µV	3.2 µV
Price	$1799	$1999
Headphones it reaches 100 dB on out of 567	567	565

Specification

FiiO M27

HiBy R8 II

Power into 32Ω

1.8 W

225 mW

Power into 150Ω

391 mW

48 mW

Power into 300Ω

200 mW

24 mW

Power into 600Ω

100 mW

12 mW

Output impedance

0.5 Ω

1 Ω

Output noise

3.9 µV

3.2 µV

Price

$1799

$1999

Headphones it reaches 100 dB on
out of 567

567

565

The 4.4 mm or XLR socket, rated on its own

Balanced	FiiO M27	HiBy R8 II
Socket	4.4mm	4.4mm
Power into 32Ω	5.0 W	710 mW
Power into 300Ω	805 mW	76 mW derived
Output impedance	0.6 Ω	1 Ω
Output noise	7.6 µV	5.4 µV
Headphones it reaches 100 dB on out of 567	567	566

Through the balanced sockets the FiiO M27 reaches 100 dB on 567 of the 567 models here and the HiBy R8 II on 566. Derived figures are worked out from the loads the maker did publish.

Where each power figure comes from

Load	FiiO M27	HiBy R8 II
32 Ω	Published	Published
150 Ω	Derived	Derived
300 Ω	Published	Derived
600 Ω	Derived	Derived

Both makers publish a power rating. FiiO M27 publishes at 32 Ω and at 300 Ω; HiBy R8 II 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 M27 figure is the maker’s own. On those rows the derived number is the one to doubt first.

What the labels mean.

The headphones that tell them apart

2 headphones reach 100 dB on the FiiO M27 but not on the HiBy R8 II — Moondrop PARA, Symphonium Titan.

14 headphones are left alone by the FiiO M27 under the one-eighth rule but coloured by the HiBy R8 II (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 11 more).

14 headphones stay below the audible-hiss threshold on the HiBy R8 II but cross it on the FiiO M27 (Audio-Technica ATH-CKS1100, Austrian Audio Hi-X25BT, Beyerdynamic DJ 300 PRO X, 11 more).

565 of the 567 models here reach 100 dB on both.

Headroom and hiss on 8 models, both sources

Headroom is at a 100 dB SPL peak.

The widest gap on the list is the Shure SE846: FiiO M27 has +46 dB of headroom there against +32 dB. 14 dB is about 24 times the power, which matters for peaks rather than for how loud the music sits.

Hiss below about 20 dB SPL is inaudible in a quiet room.

Headphone	Impedance	Needs	FiiO M27 headroom	HiBy R8 II headroom	FiiO M27 hiss	HiBy R8 II hiss
Shure SE846	9 Ω	0.04 mW	+46 dB	+32 dB	26 dB	25 dB
Campfire Audio Andromeda 2020	9 Ω	4.0 mW	+26 dB	+12 dB	6 dB	5 dB
Audeze LCD-2 Classic	70 Ω	0.79 mW	+30 dB	+21 dB	4 dB	3 dB
Beyerdynamic DT 1990 Pro (250Ω)	250 Ω	0.63 mW	+26 dB	+17 dB	-0 dB	-2 dB
HiFiMAN HE400se	25 Ω	7.9 mW	+24 dB	+13 dB	-1 dB	-3 dB
Audio-Technica ATH-R70X	470 Ω	1.6 mW	+19 dB	+10 dB	-7 dB	-9 dB
Sennheiser HD 600	300 Ω	6.6 mW	+15 dB	+6 dB	-11 dB	-13 dB
HiFiMAN Susvara	60 Ω	50 mW	+13 dB	+4 dB	-13 dB	-15 dB

The gap in dollars, against the gap in numbers

The HiBy R8 II costs $200 more than the FiiO M27. Out of the 567 models here, that difference buys 14 more models kept below the audible-hiss threshold.

It does not run one way only: the cheaper FiiO M27 drives 2 models to 100 dB and leaves 14 alone under the one-eighth rule that the HiBy R8 II does not, which is the part worth checking against your own headphones before paying the difference.

Only published figures count here; blank axes are counted separately.