An open-backed circumaural ribbon headphone that needs a transformer box or ribbon-capable amp and a fair amount of power. Reviewers and owners broadly agree on its strengths: very high resolution and speed, a wide, open, speaker-like stage, and generally good imaging. Comfort is decent once you adapt to the unusual fit. All four measurement rigs show an unusual frequency response with a dip through the upper mids (roughly 1.5–4.5 kHz), and the presence peak sits up in the lower treble, near 5–6 kHz on the rig that resolves it, rather than in the upper mids. The two pads give two tunings: the slotted pads are leaner and airier, the sealed ones add several dB of deep bass but sound closed-in to most. Most of the arguments trace back to that response. Opinion splits on whether the treble is hard and tizzy, smooth, or dull; whether the overall tuning is near-neutral or needs EQ; whether the vocals are natural or coloured; how much bass and slam it has; whether the raw foam-and-polycarbonate build is honest engineering or unfinished; and whether it is a bargain or hard to justify once you add the box, an amp and EQ.
About this product
RAAL-requisite's circumaural true-ribbon headphone, launched in mid-2022 at $2,000 on its own or $2,500 with the TI-1b transformer interface. The ribbons can't be plugged into a normal headphone amp, so you need that box (or RAAL's TI-1c for tube amps) or an amp built to drive ribbons. It also sold in special finishes as the CS-1a. Not the open-baffle SR-1a/SR-1b ear speakers, and not the later RAAL 1995 Magna or Immanis.
RAAL is a Serbian maker of ribbon tweeters, and with its US partner Requisite it made the SR-1a, an open-baffle "earfield monitor" that hovers ribbons beside your ears and needs a speaker amp. The CA-1a puts the same idea into a conventional circumaural headphone: one aluminum ribbon per side in faceted polycarbonate cups, a bent-steel headband with a leather strap, and two sets of bare open-cell foam pads, one slotted and one sealed, that clip in. Its TI-1b transformer box lets an ordinary balanced headphone amp drive the near-zero-ohm ribbons.
At $2,000 ($2,500 with the box) it drew some of the most polarized coverage of any headphone in its class. Audio Science Review measured a deep upper-midrange hole and called it unrecommendable without EQ. Many owners on Head-Fi and Super Best Audio Friends call it a bargain that rivals far pricier flagships. In 2024 RAAL moved on to its pricier RAAL 1995 models, and the CA-1a now lives on mostly through dealers and the used market.
