Giant vs Helios: which needs more amplifier?

The Symphonium Giant is 7.0Ω at 88.5 dB/mW; the Symphonium Helios is 8.5Ω at 83.3 dB/mW. This page covers what they ask of an amplifier, not how they sound.

The Helios needs 5.2 dB more than the Giant to reach the same loudness — 47 mW against 14 mW.

Side by side

The numbers that decide it

Specification	Giant	Helios
Impedance	7.0 Ω	8.5 Ω
Sensitivity	88.5 dB/mW	83.3 dB/mW
Sensitivity (voltage)	110.0 dB/V	104.0 dB/V
Power for 100 dB	14 mW	47 mW
Voltage for 100 dB	0.31 V	0.63 V
Current for 100 dB	44.9 mA	74.2 mA
Highest source impedance that leaves them alone (one-eighth rule)	0.88 Ω	1.06 Ω
Sources that reach 100 dB out of 280	252	179

What separates them

Where the two part company

73 of the 280 sources have the power for the Giant but not for the Helios — FiiO SnowSky Tiny A, FiiO SnowSky Tiny B, FiiO BTR11, 70 more.

34 sources are low enough in output impedance for the Helios under the one-eighth rule but not for the Giant (FiiO SnowSky Tiny B, FiiO BTR15, FiiO BTR5 2021, 31 more).

179 of the 280 sources here reach 100 dB on both.

At the level you actually listen at

What each one needs from 80 to 105 dB

The Helios is more demanding than 98% of the 567 non-electrostatic models in this database; the Giant than 76%.

dB SPL	Giant power	Giant voltage	Helios power	Helios voltage
80	0.14 mW	31 mV	0.47 mW	63 mV
85	0.45 mW	56 mV	1.5 mW	0.11 V
90	1.4 mW	99 mV	4.7 mW	0.20 V
95	4.5 mW	0.18 V	15 mW	0.35 V
100	14 mW	0.31 V	47 mW	0.63 V
105	45 mW	0.56 V	148 mW	1.12 V

What drives both

The cheapest source that satisfies both

Source	Price	Headroom, Giant	Headroom, Helios	Output impedance	Noise
FiiO KA11	$29	8.8 dB	4.4 dB	0.7 Ω	1.7 µV
FiiO BTR13	$59	5.7 dB	1.3 dB	0.6 Ω	1.0 µV
FiiO KA3	$79	5.7 dB	1.3 dB	0.5 Ω	1.7 µV

Of the 280 sources here, 179 reach 100 dB on both. 43 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.

The cheapest of the 43 is the FiiO KA11, at $29. It leaves 8.8 dB of headroom on the Giant and 4.4 dB on the Helios, its output impedance is 0.7 Ω against a one-eighth limit of 0.88 Ω and 1.06 Ω, and its noise figure puts the hiss floor 25 dB and 31 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.

Try any other source.

Frequency response

What each sheet prints, and what it is worth

Model	As printed	Tolerance	Standard
Giant	5Hz - 18kHz, ± 2 dB	±2 dB	not printed
Helios	12Hz - 24kHz, ± 2 dB	±2 dB	not printed

Symphonium prints 5Hz - 18kHz, ± 2 dB for the Giant and 12Hz - 24kHz, ± 2 dB for the Helios.

Both sheets print a tolerance, which is rare enough to be worth pointing at: only 58 of the 490 models with a printed range do. These two ranges can be set against each other, because each of them says how far down the response is allowed to be at the ends.

Not a measurement; maker by maker.

Both pages in full

Both have a page of their own. In full: Symphonium Giant and Symphonium Helios. Every figure on this page comes from what Symphonium published, or is derived from it — what that maker publishes, counted.