In the video, a regular Nexus 7 tablet has been modded so that it can switch between its stock 3V audio system and the new 9.5V system from NXP. The speaker and all other variables remain the same. When the mod is activated, things get seriously, noticeably louder -- to the tune of between 3 and 6 dB by the crude reckoning of our microphone. There's no distortion, just good, clean sound that reveals a decent level of detail.

How's this possible? Because the feedback system replaces the safety margins that a manufacturer must normally build into a device. A Nexus 7 or or any other phone or tablet could have its speaker grill blocked by a cover, or have a sine wave played through it (as we've actually done many times), or have sounds played at its over-sensitive resonant frequency. All these events could cause damage unless the speaker's power is conservatively capped or software filters are applied (or both). By switching to a feedback system, which can adjust on the fly to blockages, temperature increases and shifts in the resonant frequency, no safety margin is required and the speaker can be pushed a lot harder.

We think Apple uses similar (but not NXP-made) tech in its recent devices and has reached at least 7V, while the HTC One uses dual feedback controlled speakers. The use of this type of circuitry is becoming an industry trend to meet demand for better movie watching, sat nav instructions, speakerphone modes and everything else speaker-related. We're certainly keen to try out a 9.5V device when one hits the market, and we may well run a more scientific comparison among rival products at that point.