Bookshelf Speakers — Buchardt Audio S400 MK3

The S400 MK3 is the third generation of the S400 stand-mount speaker from Buchardt Audio, the Danish loudspeaker company that sells direct. The S400 was first shown as a prototype in 2016 and became a cornerstone of the Buchardt range. The MK3 is a ground-up redesign that carries over only the binding posts from the MK2, and Buchardt covers it with a 10-year warranty.

Key specs that matter

A 7.5 in SB Acoustics Satori Papyrus paper-cone woofer driven by a neodymium motor partners a custom 26 mm aluminium dome tweeter set in a 7.5 in aluminium waveguide. The crossover point is 2.2 kHz. Frequency response reaches down to 33 Hz, sensitivity is 88 dB and nominal impedance is 4 ohms, and Buchardt asks for more than 30 W. The cabinet measures 392 x 198 x 280 mm and weighs 8.5 kg.

Engineering and use context

Inside the woofer are a BIMAX spider, a CCAW voice coil wound on a non-conducting fibreglass former, a vented pole piece and a copper sleeve that lowers inductance. It moves 65.5% more air than the 6 in driver of the MK2, while cabinet volume has grown by only 18%. Where the MK2 used a passive radiator, the MK3 is ported, venting through the rear panel, and foam plugs are supplied for reduced bass output. The 19 mm soft dome of the MK2 gives way to the 26 mm aluminium dome, driven by a matrix neodymium motor with copper in the magnet system. A low resonance from its back chamber allows a quasi-first-order tweeter filter. The dome is bonded directly into the waveguide, which controls directivity and keeps the response consistent on and off axis, giving a more even in-room response and a wider listening area. The crossover was developed with Jantzen Audio and has a simpler topology than the MK2's, using air-core inductors with wire up to 1.6 mm, Jantzen Cross Cap polypropylene capacitors and Superes wire-wound resistors. The first S400 was also the first hi-fi speaker Buchardt developed with a Klippel Near Field Scanner. That original model had a deep waveguide extending below the woofer, and the MK3 keeps the waveguide principle. Standard finishes are black or white, with walnut and natural wood veneers at extra cost.

Pairing

Any amplifier that is stable into a low nominal load will drive the S400 MK3, ideally with 60 W per channel or more. The bass extension from a compact cabinet suits rooms of 12 to 30 m2.

Alternatives

Buchardt Audio's S400 MK2, introduced in 2021, is the previous generation with a 6 in woofer and a passive radiator.