Like the MDR-1RNC, the MDR-1RBT's frame is well-built. The plastics and metals are skilfully combined in an object that looks as though it can stand the test of time. There's just one difference: here the earcups are made of (good quality) plastic instead of metal. The headbands appear identical, but the 1RBT's is more flexible, probably due to the reduced weight. On both headphones you'll want to watch out for wear on the headband's lining.
Along the edges of the earcups you'll find a gamut of connectivity: NFC (see inset), Bluetooth, play, next/previous track, answer call, volume, a micro-USB port and a mini-jack. It's all made to look discreet, but it's also easy to get lost in all these functions.
The accessories are: one conveniently compact, semi-rigid carrying case (the earcups pivot inward so you can lay the headphones down flat in the case); one detachable cable; and one USB charger cable. Lacking the active noise cancellation, the MDR-1RBT has a significantly longer battery life than the MDR-1RNC: 30 hours.
Just Short of Balanced
The MDR-1RBT suffers less from the inconsistency that plagues the MDR-1RNC. On the whole, the sound is actually quite neutral.
The ups and downs in the MDR-1RBT's frequency response curve are subtler than the 1RNC's, and you can hear the difference. The little bump at 100 Hz does a pretty good job at making up for the drop in the lowest register. Unfortunately, it falls again right afterward—we would have preferred a bit more body in this register. The rest of the spectrum holds its own and on the whole the MDR-1RBT has a clean sound (though a bit dull at times, especially when using the cable).
Left: THD+N as a % Right: THD in dB
Leaving aside the issues due to the Bluetooth (latest generation), the 1RBT is more precise than the 1RNC. Both have harmonic distortion and background noise, but once again the active components and wireless signals have a considerable impact on the sound.
Where you can tell the difference is with square waves: they're not as clearly chiselled as on the 1RNC and that causes a noticeable gain in precision and responsiveness. As a result, despite the reigned in frequency response, the soundstage is much clearer here.
The sound on this model is definitely an improvement, but at this price you necessarily end up looking at the competition. Parrott, for example, consistently churns out technological powerhouses at similar prices (though certain functions veer dangerously close to novelty features). Meanwhile, Sony is struggling to achieve the same level of excellence.