Brilliant Adventure

Taking the Clarisys Auditorium Active

By Roy Gregory

I recently spent some considerable time writing an enthusiastic review of the Clarisys Auditorium loudspeakers, large planar devices that are both the spiritual and technological descendants of the Apogee ribbons of yore. That piece covered the history and development of the two brands as well as detailing the mechanical facets and construction of the Auditorium speakers themselves, as well as the various system topologies that they allow. If you missed it – or just want to refresh your memory on the details – you can read that review here:

The sonic and musical description revolved around running the speakers in passive bi-amp mode, along with its benefits over and above using a single stereo amplifier. But it also noted that the use of external, passive crossovers allowed users to consider active operation. It seemed like too good an opportunity to miss, especially given the recent positive experiences I’ve enjoyed driving the Avantgarde speakers in active mode. But first, let’s look at what you are going to need, over and above a passive set up.

Nuts and bolts…

Normally, converting a passive system into an active one is a pretty expensive proposition, involving the addition of multiple amplification channels, additional signal and speaker cables as well as the active crossovers themselves. Converting the Clarisys speakers is no different, except that, the option to run passive bi-amped – an option the company actively encourages – at least gets you part of the way there. I was already running the Auditoriums with a pair of CH Precision M1.1 amplifiers, operating in passive bi-amp mode, so going active meant adding two more channels of amplification and the necessary crossover electronics.

The golden-rule of successful bi-amping (don’t try and mix different amplifiers in a single system) is just as relevant to active operation. Whilst I don’t have a spare M1.1 lying around, I do have a pair of its smaller siblings, the A1.5. Employing an identical topology but fewer output devices, I configured them for mono operation and applied them to the high-frequencies. Then it was just a case of substituting the active crossover for the passive ones (and arranging the necessary cabling). And therein lies a tale…

Normally, active crossovers are supplied by the speaker manufacturer or, occasionally (as in the case of the Linn/Naim or Nytech/ARC systems of yesteryear) by a partnering electronics brand. There is actually considerable logic behind this latter arrangement. Consider where an active crossover sits in the system’s scheme of things and it becomes self-evident that it needs to match the line-stage in terms of quality. Except, that isn’t easy. In many respects, as simple as it appears on the surface, the line-stage is both one of the most critical components in the audio chain and one of the most difficult to design. Which is why there are so few really World-class line-stages out there – and even fewer active crossovers that don’t do more harm than good. Clarisys is a young company that’s still developing and refining its loudspeaker designs. Even if it possessed the necessary electronic design acumen to produce its own active crossover, it would likely be a project too far at this point in their developmental arc. Instead, they looked for an existing product that would meet their needs, and settled on the CSPort ACN400 Active Crossover from Japan. An all-analogue device, it offers two, three or four-way operation, second-order (12dB/octave) slopes and zero phase shift. It’s a stereo unit (which at least saves the price of a power cord – which is not to be sniffed at, these days) with both balanced and single-ended connections. Crossover frequencies are pre-defined and not adjustable, but happily the suit the Auditorium’s requirements. The level of each pass-band is adjustable in 0.5dB steps across a 0 to -30dB range. The unit is equipped with a massive, bright orange and astonishingly garish, numerical status display. A real boon during set up, thankfully it can be turned off once you have settled on the optimum configuration/values.