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Klangwerk @ HighEnd Suisse 2013
Despite the easily grasped advantages of active speakers, most audiophiles shun them. They assume their built-in amplifiers are crap. From Wikipedia, an amplifier "is described by its input and output properties where some kind of gain or multiplication factor relates the magnitude of the output signal to the input signal. Gain may be specified as the ratio of output voltage to input voltage (voltage gain), output power to input power (power gain) or some combination of current, voltage and power.


"Power gain of an amp depends on source and load impedances plus voltage gain. Audio amps usually have input and output impedances optimized for least loading and best quality. An amplifier said to have 20dB gain might have voltage gain of x 10 and available power gain of >20dB (100 x power ratio) yet deliver a much lower power gain if for example the input is a 600Ω microphone and the output a 47KΩ power amp input socket." Amplifiers custom-tailored to their exact load increase power efficiency.


"Power amp output stages are classified as A, B, AB and C for analog designs and D and E for switching designs based on the proportion of each input cycle during which an amplifying device passes current.

PSI Audio A-215-M monitors at Switzerland's Echochamber
"Class A uses 100% of the input signal. The active element remains conducting at all times. Class B only uses 50% of the input signal. The active element carries current half of each cycle and turns off for the other half. Intermediate class AB has its two active elements conduct more than half of the time. Class C uses less than 50% of the input signal. Class D uses some form of pulse-width modulation to control its output devices. Here the conduction angle of each device no longer relates directly to the input signal but varies in pulse width. Each output device is switched fully on or off and does not carry current proportional to the signal amplitude."

How about class G? "A variety of amplifier designs enhance class AB for greater efficiency at low distortion. Class G and H are used interchangeably and vary in definition from one manufacturer/paper to the next. Class G uses several power rails at different voltages and switches between them as the signal output approaches each level. Thus the amplifier increases efficiency by reducing power waste. Class G is more efficient than class AB but less than class D yet doesn't suffer class D's negative EMI effects. Class H amplifiers create an infinitely modulated supply rail where at any given time the rails are only a few volts larger than the output signal. Switch-mode power supplies can be used to create these tracking rails."


Class G thus is a more efficient low-heat form of class AB where multiple power rails use a constant tracking mechanism to switch between them relative to power demands. Now the Ella 3 power modules from Relec SA make more sense. PSI Audio's €5'474/pr pro monitors called A-215M are shown at right. They exhibit shared genetics with the Ella 3 and are even sold in the Klangwerk retail facility. The PSI Precision Sound Image moniker refers to "being able to see what you're listening to". This video of Relec's facilities in Switzerland's Yverdon-Les-Bains gets us started. Founder Alain Roux built his first PSI-branded speaker in 1975 whilst still studying at the EPFL of Lausanne. Two years later he founded Roux Electroacoustique. In 1988 it became an Ltd company named Relec SA. His own house built around a 150m³ anechoic chamber with 4 tonnes of isolating materials rising over 7 meters tall demonstrates seriousness of professional purpose extending into private life.


Markus Thomann on Ella 2 versus 3 versus A-215M. "For my new iteration the tweeter now sits in the center of the three mid/woofers for a quasi coincident sound source. The tweeter sat on top before. The 5" units sport the same lightweight HDA membrane but now use die-cast chassis ventilated behind the spider. Their impedance is 16 ohms to work in parallel. The tweeter moved from Titanium to Magnesium and from a ferrite to a Neodymium motor for higher efficiency and a touch more subtle detail. No ferrofluid is/was in the gap of either. The power electronics shifted from class AB to G and are now in their own sub enclosures decoupled with silent blocks. Before they shared the same internal air space with the drivers. Finally the overall enclosure volume grew by 10%. The PSI Audio model uses a textile-dome tweeter with ferrite motor and a different wave guide; two 5" polypropylene mid/woofers; a pure MDF enclosure without bracing; a front rather than down-firing bass reflex port; and its electronics share the main air space with the transducers. My forthcoming subwoofer console which I've previewed at a number of shows will be based on the PSI Audio A-225 dual 10" model with class G power. My bass roll-off feature doubles as the perfect low-pass for seamless integration. I'm still working out final details but the Klangwerk Base will probably be available in 2014 and sell for ~7.000 Swiss."

Back to Relec, a core principle is all-analog signal processing and optimization. That too is Klangwerk's credo. It's where Swiss precision studio monitor technologies meet then merge with audiophile demands. Ella's drivers sit in the feedback loop of the amplifiers. Here velocity not motion feedback triggers the impedance compensation feature specific to each transducer. The many trim pots on their all-pass filters allow for precise amplitude adjustments without affecting phase response. After receipt of Relec's electronics modules Markus Thomann calibrates these pots for each individual speaker. This process levels out small manufacturing inconsistencies between raw drive units exactly as DSP would. Except that here it's all done in the analog domain.

Swiss shoppers can sample the results in Klangwerk's own Zürich showroom on the Wieslergasse 6 below.


Combining architectural/acoustic services, Klangwerk is about home integration to offer various A/V installation services. Co-owner Thomas Junker provides added consulting expertise via his K-Technik outfit. For our purposes all it means is that Ella 3 comes in various finishes, baffles* are built by Coristal, cabinets by Schellenbaum; and is an openly collaborative effort between various Swiss specialist firms under the team leadership and vision of Markus Thomann. The extra price to pay is small scale of production and higher per-unit build costs. The long-term benefit is a sustainable business model.
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* By request the synthetic stone baffles can be lacquered in any RAL color. The standard raw Creanit used by Klangwerk comes in either white or grey. Creanit is identical to Corian. When DuPont's patent for Corian expired, various competitors trademarked their own version. Creanit is one of those trademarks.