The S400 has been a fixture of Buchardt Audio’s passive loudspeaker line-up since its prototype debut in 2016. Nine years on, the Danish direct-sale company has announced the S400 MK3 – a third-generation standmount that it describes as a “ground-up redesign”, with only the binding posts carried over from its predecessor.
The most consequential change is a new 7.5″ woofer: the SB Acoustics Satori Papyrus, a paper-cone driver with a neodymium motor more commonly found in high-end DIY builds. Buchardt says it offers 65.5 percent more displacement headroom than the MK2’s 6″ driver, translating to stronger bass authority, deeper extension, and greater physical impact from a cabinet that has grown by only 18 per cent in volume. Gone too is the MK2’s passive radiator: the MK3 uses a rear-ported bass-reflex arrangement instead, with a minimum 5 cm of clearance from the rear wall recommended to allow the port to breathe freely.
The tweeter has been overhauled in a similar manner. Where the MK2 used a 19 mm soft dome, the MK3 moves to a custom 26 mm aluminium dome housed in a redesigned 7.5″ aluminium waveguide, crossing over at 2.4kHz via a simplified first-order network. Buchardt says the goal was not to push brightness upward but to improve transient precision and perceived resolution while retaining the fatigue-free character the S400 series has always offered. The crossover, developed in collaboration with Jantzen Audio, continues to specify air-core inductors and polypropylene capacitors throughout.
The waveguide serves a secondary purpose beyond housing the tweeter: controlled directivity. Buchardt says the MK3 maintains a consistent frequency response both on- and off-axis, which it argues produces more even in-room sound and a wider listening sweet spot – a characteristic it considers especially useful in untreated rooms.
On basic specs, the MK3 is almost identical to the MK2 – 4 ohm nominal impedance, 88 dB sensitivity, -3dB at 33Hz – but the newcomer puts an extra kilo on the scales and recommended amplifier power now starts at 30 watts (down from 40).
The S400 MK3 is available to pre-order now via a limited campaign of 75 pairs per finish, with estimated delivery slated for late summer 2026. Prices include import costs: black or white finish – €2100 (pre-order) / €2300 (standard); real wood veneer – walnut or natural oak – €2250 (pre-order) / €2450 (standard).
Further information: Buchardt Audio
