Buchardt S400II Loudspeaker Review

Exemplifying superb Danish design, excellent parts specification and build quality, and blessed with neutral and natural tonality, timbral accuracy and nuance, outstanding clarity, harmonic subtlety, and vibrant dynamics, the Buchardt S400II is a superb stand-mount loudspeaker capable of providing involving musical experiences in a range of settings and room placements.

Small Tweeter Design

Most loudspeaker manufacturers use tweeters measuring 25-29 mm in diameter. Larger tweeters have historically been popular because of their power handling and frequency bandwidth, which allows them to be crossed over at lower frequencies. The caveat is that larger tweeters often do not sound as good off-axis and struggle with uneven off-axis frequency response in the higher frequencies.

Buchardt uses a somewhat unconventional, smaller 19mm diameter tweeter for the S400II. Their reasoning for this is that it provides better-measured response and off-axis performance. Their development (see below) has shown that any of the limitations that would normally come from using such a small tweeter have been mitigated by the deep waveguide that brings the crossover point down without “stressing” the tweeter. Buchardt says that the integration of the small tweeter with the waveguide produces a top-end free of distortion, resulting in a cleaner more detailed, and authoritative presentation that integrates smoothly with the rest of the speaker’s frequency response range.

Although the same tweeter is used in the first version of the S400, the tweeter’s performance and audio quality are improved with the new crossover design. A unique attribute is that it’s very nicely balanced between detailed and relaxed. This was achieved using a new design/topology and higher-quality parts and components for the crossover circuit.

Controlled Directivity

What Buchardt refers to as their innovative Controlled Directivity design allows the S400II to produce nearly the same frequency response in the off-axis as it does in the on-axis position. Buchardt says that the Controlled Directivity design translates to a non-distorted, evenly distributed in-room frequency response that allows the S400II speakers to sound balanced even at extreme angles, which in turn allows the enthusiast to enjoy sundry benefits like improved imaging, a bigger soundstage, and better transparency. This excellent off-axis response will also result in a notably wider ‘sweet spot’ and most importantly, remains “stable” even as the listener may move around the room as the music plays.

Buchardt has found their Controlled Directivity design work allows the S400II to deliver consistent in-room performance in almost any room, even acoustically untreated rooms.

Deep Waveguide

Another innovation of the Buchardt S400II is the Constant Directivity Control (CDC) waveguide. This design was the result of a collaboration with loudspeaker designers, e.g. Ulrik Schmidt, developing several prototypes, and the use of an expensive holographic nearfield scanner that Buchardt was given access to. This scanner measures 5,402 points around the speaker and provides accurate and precise data as to how the speaker behaves from all possible angles, thus allowing the development of a waveguide designed to match the contour plot of the woofer down to 1000hz, effectively allowing the tweeter and woofer to function as a “single driver” at the crossover point.

Buchardt also phase-aligned the drivers, which is why the tweeter waveguide is placed under the woofer as well as angling the front of the speaker cabinet slightly backwards. Another benefit of using the small tweeter and a very deep waveguide is that Buchardt was able to reduce edge diffractions from the cabinet by 90%. Buchardt claims the result of this design approach is a powerful sound, evenly distributed, and projects freely into the presentation without “sticking to the cabinet”, enabling a small speaker to sound both full and natural.

Midrange

The tonality and balance of how the S400II presents human vocals was a very high priority in the design of the speakers and was one of the qualities that Buchardt put a lot of effort and attention towards when designing the MKII version. This is very apparent when listening to well-mastered vocal recordings.

New woofer for improved Bass performance

The S400II uses a 6” bass driver design which also delivers impressive bass and lower octave performance. The bass driver is a new design that Buchardt says delivers improved bass performance with defined, tight, and excellent articulation.

Some of the key woofer design attributes and features of the Buchardt S400II are:

– New bespoke woofer design by Ulrik Schmidt.
– Vented cast aluminum chassis for optimum strength and low compression.
– Proprietary paper cone material comprised of natural fibers with a soft low-damping
rubber surround providing a clean transient response.
– Nonconducting fiberglass voice coil former for minimum damping.
– Vented pole piece for reduced compression.
– Extended copper sleeve on pole piece for low inductance and low distortion. – Vented coil former.
– CCAW voice coil for reduced moving mass.
– Long-life silver lead wires.

Large Passive Radiator

While a passive radiator is more expensive to implement in a speaker’s design than a bass reflex port, a design that effectively integrates a passive radiator can provide advantages compared to a bass reflex port. These include a reduction in the size of the S400II cabinet by 30% compared to what would be required using a bass reflex/ported design with comparable bass response. It also means the S400II doesn’t suffer from some of the noise artifacts that can occur using ported designs, such as port chuffing and port compression. Not using a bass reflex port also provides more flexibility in speaker placement and is more forgiving of wall-boundary placement. This design provides impressive bass performance for speakers of the S400II size.

Crossover

Buchardt put considerable research and development into the development of the S400II speaker’s crossover design and final engineering specifications. During development, many different components were tested to achieve the sound qualities that Buchardt wanted. Buchardt says that one of the key requirements concerning the S400 MKII design goals was to spend money where it mattered the most in performance and for the listener, even though many of these improvements were internal, and not visible, per se, to the customer. Examples are the components used in the S400II are a mixture of parts from respected manufacturers, including Janzten Audio Cross capacitors, Superes resistors, as well as an ultra-high-end capacitor from Miflex, the KPCU-1. The large oversized baked air inductors in the new crossover design for the S400II are wound with 1.6 mm diameter high-purity copper wire which provides clean, low-distortion sound quality. The printed circuit boards for the crossover and the internal wiring were upgraded in quality and specification as well. The results of using these superior parts provide a clean, transparent, balanced, and neutral presentation.

For this review, I used my Lumin P1 as the streamer/preamplifier with music files sent from an upstream music server, an Akasa-cased NUC Roon Core located in another room. Digital music files from the Roon Core are sent using a Shunyata Research Sigma Ethernet cable to an Uptone Audio EtherREGEN Ethernet switch, and subsequently downstream using a single-mode 1310 nM Planet Tech (PT) optical transceiver in EtherREGEN’s SFP* optical port via Corning ClearCurve single-mode LC/LC optical fiber to a matching PT optical transceiver in the SFP port of the LUMIN P1 located in the listening room’s main audio rack.

The LUMIN P1 was connected to a Constellation Inspiration integrated amp with Shunyata Venom-X XLR interconnects. The output volume of the Inspiration was set to unity gain, with the actual listening volume set using the LUMIN P1’s LEEDH digital volume control, which I’ve found to sound superior to the Constellation’s analog volume control. In this configuration, the LUMIN P1 functions as the system’s streamer, DAC, and preamplifier, and the Inspiration integrated as the power amplifier. All components in the main audio room were powered with a Shunyata Everest power distributor and Shunyata power cords: Omega QR-s for the LUMIN P1, and Sigma NRv2 for the Inspiration amp.

The Constellation integrated amp powered the Buchardt loudspeakers using Shunyata Alpha V2 speaker cables resting on Shunyata Möbius cable elevators to mitigate the effect of floor-borne vibrations. The S400II’s were placed on stable steel speaker stands which placed them at the reference height for listening.

*-SFP: small form-factor pluggable; an industry-standard specification for optical transceivers.

The first impression the Buchardt S400II speakers give is one of tonal accuracy and harmonic richness, outstanding clarity combined with a dynamic and musically engaging presentation. The overall tonal quality is neutral, but there is also wonderful body and “weight” to the presentation that provides a natural and organic quality that adds authenticity to voices and instruments. The Buchardt S400II speakers also present the music with accurate, defined, and nuanced reproduction of timbre, the attribute that distinguishes, for example, a woodwind from a stringed instrument playing the same notes. These qualities are most notable on well-recorded and mastered vocal & classical recordings, where the Buchardt S400II speakers provide superb detail characterized by sophisticated and refined reproduction of instrumental overtones and lifelike vocals.

Some notable attributes of the S4000II are their ability to create lifelike width and in particular, depth to the presentation. These attributes create a large, spacious, and three-dimensional soundstage experience, providing the listener with a sense of being in the concert hall at the performance. With their “black background” provided by the use of very high-specification components, they deliver superb separation and precise placement of the instruments and vocals within the soundstage. Musical dynamics emerge effortlessly and seamlessly within the soundstage as well. Something I really enjoyed about the S400 MKII speakers was that they place the soundstage a bit further back than other dynamic speakers, and this provides a lifelike and natural space for the soundstage to unfold in terms of depth, width, and height.

With superb design and engineering, parts quality, and the capability to play any type of music with reference-level audio quality as well as with superbly engaging and natural musicality, the Buchardt S400II speakers are exceptional stand-mount loudspeakers and the foundation for a superb sounding audio system.

Musically, the Buchardt S400II stand-mount loudspeakers have neutral yet natural tonality, refined and accurate reproduction of vocal and instrumental timbre, a controlled and defined bottom-end, natural yet but exceedingly engaging musical presentation that conveys a lifelike and very engaging presentation. I’ve enjoyed the experience of listening to these wonderful recordings on the S400II speakers. Some of their most notable attributes are their tonal accuracy and timbral sophistication, presenting the music with sophistication, nuance, and finesse. In addition to delivering excellent detail, the S400II speakers refrain from overemphasizing this to the detriment of the overall musical presentation. Instead, they seamlessly integrate all these musical attributes into a greater whole, creating a listening experience that is dynamic and lively, lifelike and natural-sounding, and most importantly, musically engaging. These musical attributes are capabilities that are not showcased simply as standalone virtues but are seamlessly integrated into “a whole” that is greater than the sum of the parts in their reproduction of the overall musical experience.

The bottom line is that I love, love, love these wonderful loudspeakers, and as such, the Buchardt S400II speakers have my highest recommendation.