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This review first appeared in the September 2012 issue of hi-end hifi magazine of Germany. You can also read this review of the Abacus C-Box 2 in its original German version. We publish its English translation in a mutual syndication arrangement with the publishers. As is customary for our own reviews, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of fairaudio or Abacus - Ed.

Reviewer: Jochen Reinecke
Sources: iPod Video 80GB with Pure i-20 dock, Marantz SA 7001 CD/SACD, Yamaha CD-S 1000,
Pro-Ject Xpression III with Ortofon OM 30 Super
Amplification: Funk LAP-2 preamp, Dynavox TPR-2 preamp, Trends Audio TA-10.2 SE, Yarland FV-34C III,
Myryad MXA 2150 power amp
Loudspeakers: Neat Momentum 4i monitor, Nubert nuBox 101 with AW 441 subwoofer, DIY TL with Fostex F120A, Canton Plus GX monitor
Cables: AVI Deep Blue interconnect, Ortofon SPK 500 speaker cable
Review component retail: €490/pr

“So that’s traffic red.” That was my first thought upon – um, heaving the small Abacus box out of its carton. It’s the official designation of the loaner’s color. To suit conservative as well as modern decors, the C-Box 2 comes in seven color options: deep black, traffic white, silver grey, traffic red, yellowish green, water blue and melon yellow. Sweet. Admittedly I saw as red as I did because this begged to be leashed to my gleaming equally red Clavia Nord Piano digital keyboard. But since fairaudio is first and foremost a hifi ‘zine, I left such fun and game for last. As per its maker’s site, key employ for the C-Box isn’t merely what reviewers casually refer to as listening room aka living room. It's also audiophile oversights like the home office or kitchen. This includes pimping out the audio qualities of a flat screen—and thus mostly flat sound—telly. I thus duly strapped the C-Box 2 to my desk, my living room and even (really) my digital piano. Some theory first though.

At first sight the C-Box 2 seems a honey-I-shrunk-the-A-Box-5 which I reviewed 30 months ago. It’d be an overly quick assumption though just because both are samples of the compact active breed. There are differences. What’s shared is power from standard Abacus-style transconductance amps with 100% electromechanical feedback or EMK regulation. The A-Box 5 then eschewed a traditional filter network in favor of direct drive with two discrete amps for midrange and tweeter and a DSP stage for amplitude and phase control.

The C-Box 2 meanwhile runs a pure analog active filter sans DSP. Designer and company founder Karl-Heinz Sonder described it as being embedded in the amplifiers’ negative feedback loop. This is said to reduce noise and particularly steady-state hum from a lower parts count in the signal path. Bean counters eliminated the power-up circuitry which has music signal wake the A-Box 5 from standby. I’m no friend of auto circuits and thus didn’t miss one in the C-Box.

The drivers diverge as well. While both models run midrange cones, the A-Box gets 6.5 inches, the C-Box a mere four. In the treble Sonder gifted the C-Box with a 1" Neodymium-powered ring radiator whose phase plug creates a distinctive appearance for the speaker. Its immaculate fit’n’finish and rounded corners looked marvelous and at least to my eyes more advanced than the somewhat Teutonic charm of the A-Box 5. Around back it’s equally sorted with a two-prong ‘shaver’ style IEC (technically a small appliance connection), an RCA input, a pot and a bass EQ control. The latter looks like a continuous hi-pass filter but is more advanced. This active low-freq EQ has two functions. One is compensating for the peak enforced by the enclosure’s resonant frequency. The other is a significant boost with falling frequencies below box resonance. This equalization curve ideally sums with the box tuning and driver roll-off to neutral. The obvious goal is maximized linearity in the listening seat down into the low bass despite very petite chassis dimensions.