Different kinds of product: one is active with its amplifier built in, the other passive and needs one. Judge them on how you want to own the system, not just the specs.
| Area | Better | Why |
|---|
| Bass | A | Q Acoustics Q Active 400 digs deeper - 35Hz against 42Hz. A subwoofer would even that out. |
| What you buy | depends | Q Acoustics Q Active 400 is a complete system - just add a source. Sonus Sonetto III also needs an amplifier: more money and another box, but you choose it. |
| Connections | depends | Q Acoustics Q Active 400 has HDMI built in. With Sonus Sonetto III that all comes from the amplifier you pair it with. |
| Upgrade path | depends | Sonus Sonetto III can be re-amped later and outlive several amplifiers; Q Acoustics Q Active 400 ages as one unit. |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Expandability | B | Sonus Sonetto III: bi-amping. Sonus Sonetto III sits in a wider range (11 models), so a matched surround system is easier later. |
| Price | evenly matched | Much the same money ($2,999 vs $2,999 a pair) - though the passive pair still needs an amplifier. |
A Q Acoustics Q Active 400 B Sonus Sonetto III
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Q Acoustics Q Active 400 suits you if you want one box, ready to play, with nothing else to buy. Sonus Sonetto III suits you if you already have an amplifier, want to choose the electronics, or expect to upgrade in stages. Neither is the better speaker in the abstract. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 42Hz anyway, so judge these on the other rows instead.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.