Our favorite budget audiophile brand launches new flagship planar magnetic headphones that aren't so budget — but a next-gen 86% thinner diaphragm with 'full-face diamond coating' could make them worth the price for head-fi fans

(Image credit: FiiO) Fiio launches FT15 planar headphones with bigger, thinner diaphragm and a lighter weightThey're open-back successors to the five-star Fiio FT5They cost $499 / £499 (about AU$999) — but that's not bad for planarsBreakout affordable audiophile brand Fiio has been riding high with its debut planar magnetic headphones, launched in 2024, called the FT5 — they scored the full five stars in our Fiio FT5 review. The brand clearly thought it was time to revisit the tech, because it's launched a follow-up. No, not the FT6; meet the Fiio FT15.These new wired open-back headphones bring refinements across the board, including some new internals and a lighter build. Numbers are up (or down, depending on which direction counts as an improvement).The price is up too. The new FT15 cost $499 / £499 (about AU$999), and for comparison the FT5 sold for $449 / £429 / AU$799. So it's not a huge price hike, but given that Fiio is reliable as a budget brand, it's notable.The Fiio FT15 are on sale right away, joining the brand's growing 2026 roster including the KA15 DAC dongle and FG3 gaming headset. Here's why they're exciting to audiophiles who are, well, maybe not quite on a budget, but like to optimize their spending.Thinner, Better, Faster, Lighter (Image credit: FiiO)Fiio decided that its new planar cans needed some spec increases, and so the driver now measures 101mm (compared to 90mm in the FT5), but most notable is that it's now 800nm thick, which Fiio says is 86.7% thinner than its previous planar driver.That's pretty notable, because the whole thing about planar drivers is that you have a super-thin, super-responsive diaphragm suspended between two magnetic fields, capable of excellent dynamic response and therefore detail.Fiio also says the driver has a "full-face diamond coating", which is presumably to add stiffness. A much larger, much thinner, super-stiff diaphragm is a very interesting prospect when it comes to both dynamic range and detail in the sound.Sign up for breaking news, reviews, opinion, top tech deals, and more.The overall design has seen some improvements too. The FT15 is 31g lighter than the FT5, at 425g, using a carbon fiber headband and natural wood earcups. There are also multiple pairs of earpads in the box, as well as a range of adaptors for 4.4mm, 6.35mm and XLR-4, so it can fit into a range of hi-fi set-ups.That's doubly true with the FT15s' sensitivity (95dB/mW, and a 24 ohms impedance), and the brand says it was designed to work with a range of dongles, DAPs, amps and CD players — including smaller and lighter dongles without external power. Fiio also sells all this kind of tech. Coincidence? I think not.We gave the FT5 a perfect review, and it's hard to imagine how this range of improvements could result in a lower one, even with a slight price increase — but is with anything audio-related, the proof will be in the testing. Stay tuned. Follow TechRadar on Google News and add us as a preferred source to get our expert news, reviews, and opinion in your feeds. Tom Bedford is a freelance contributor covering tech, entertainment and gaming. Beyond TechRadar, he has bylines on sites including GamesRadar, Digital Trends, Android Police, TechAdvisor, WhattoWatch and BGR. From 2019 to 2022 he was on the TechRadar team as the staff writer and then deputy editor for the mobile team.