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 | Cambridge Audio L R X digs deeper - 35Hz against 48Hz. |
| What you buy | depends | Cambridge Audio L R X is a complete system - just add a source. Q Acoustics 3030c also needs an amplifier: more money and another box, but you choose it. |
| Connections | depends | Cambridge Audio L R X has HDMI built in. With Q Acoustics 3030c that all comes from the amplifier you pair it with. |
| Upgrade path | depends | Q Acoustics 3030c can be re-amped later and outlive several amplifiers; Cambridge Audio L R X ages as one unit. |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Cabinet | depends | Passive Radiator vs Ported. |
| Price | B | Q Acoustics 3030c is cheaper - $699 against $2,299, about 70% less; arguably a different class. Speakers only - an amplifier narrows that gap. |
A Cambridge Audio L R X B Q Acoustics 3030c
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?
Cambridge Audio L R X suits you if you want one box, ready to play, with nothing else to buy. Q Acoustics 3030c 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 48Hz anyway, which makes the cheaper Q Acoustics 3030c much easier to justify. Think about the whole system, not just the speakers: the roughly $1,600 saved by taking the cheaper pair would buy a subwoofer or a better amplifier, and either usually does more for the sound than the difference between these two.
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.