Audient iD24 vs IK Multimedia AXE I/O

Short answer

Power: about the same. The Audient iD24 has 119 mW into 32 Ω, the IK Multimedia AXE I/O 115 mW. Both drive 561 of the 567 non-electrostatic headphones here to 100 dB, so on that test the difference changes nothing.
Hiss with sensitive IEMs: cannot be compared — neither maker publishes a noise figure.
Output impedance: 561 headphones are left alone by the IK Multimedia AXE I/O under the one-eighth rule but coloured by the Audient iD24 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 558 more).
Price: the IK Multimedia AXE I/O costs $199 less, and wherever both makers publish a figure the Audient iD24 shows no advantage for the extra money.

Both are audio interfaces, $599 against $400.

On raw power they are level: each reaches 100 dB on 561 of the 567 non-electrostatic models here.

Every published figure, next to each other

Specification	Audient iD24	IK Multimedia AXE I/O
Power into 32Ω	119 mW	115 mW
Power into 150Ω	80 mW	60 mW
Power into 300Ω	58 mW	30 mW
Power into 600Ω	52 mW	15 mW
Output impedance	50 Ω	<0.1 Ω
Output noise	not published	not published
Price	$599	$400
Headphones it reaches 100 dB on out of 567	561	561

Not published means the maker leaves it out, so that axis cannot be compared.

Where each power figure comes from

Load	Audient iD24	IK Multimedia AXE I/O
32 Ω	Derived	Derived
150 Ω	Derived	Derived
300 Ω	Derived	Derived
600 Ω	Recomputed	Derived

Neither column is a maker’s power rating at these loads. Of the 280 sources here, 209 publish a figure at at least one load; these two do not, so every row above is derived — between or beyond the loads each maker did publish, holding output voltage as the maker’s own figures imply. The method understates rather than flatters, but it is still arithmetic rather than a rating.

What the labels mean.

The headphones that tell them apart

On power they are interchangeable across this whole database: there is no headphone here that one reaches 100 dB on and the other does not.

561 headphones are left alone by the IK Multimedia AXE I/O under the one-eighth rule but coloured by the Audient iD24 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 558 more).

561 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 Audio-Technica ATH-R70X: Audient iD24 has +15 dB of headroom there against +11 dB. 4 dB is about 2.8 times the power, which matters for peaks rather than for how loud the music sits.

The hiss columns are empty for Audient iD24 and IK Multimedia AXE I/O because neither maker publishes no output noise figure.

Headphone	Impedance	Needs	Audient iD24 headroom	IK Multimedia AXE I/O headroom	Audient iD24 hiss	IK Multimedia AXE I/O hiss
Shure SE846	9 Ω	0.04 mW	+29 dB damping	+29 dB	not published	not published
Campfire Audio Andromeda 2020	9 Ω	4.0 mW	+9 dB damping	+9 dB	not published	not published
Audeze LCD-2 Classic	70 Ω	0.79 mW	+22 dB damping	+22 dB	not published	not published
Beyerdynamic DT 1990 Pro (250Ω)	250 Ω	0.63 mW	+20 dB damping	+18 dB	not published	not published
HiFiMAN HE400se	25 Ω	7.9 mW	+11 dB damping	+11 dB	not published	not published
Audio-Technica ATH-R70X	470 Ω	1.6 mW	+15 dB	+11 dB	not published	not published
Sennheiser HD 600	300 Ω	6.6 mW	+9 dB damping	+7 dB	not published	not published
HiFiMAN Susvara	60 Ω	50 mW	+5 dB damping	+5 dB	not published	not published

The gap in dollars, against the gap in numbers

The Audient iD24 costs $199 more than the IK Multimedia AXE I/O, and on these three axes the money buys nothing: among the 567 models here there is not one that the Audient iD24 handles and the IK Multimedia AXE I/O does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper IK Multimedia AXE I/O leaves 561 models alone under the one-eighth rule that the Audient iD24 does not.

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