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What else made the 4pi Plus.2 beat all comers on paper? Big surface area again for improved power response and dynamics; plus very flexible adaptability. The latter is served up by two chunky knob adjusters. One handles sensitivity. This matches the Elac to your main speakers. It covers 84dB-92dB efficiency in 2dB steps. 88dB is represented by the zero indent. That leaves two increments in either direction. My Albedos are 85dB. My soundkaos are 92.5dB. I was covered either way. High-efficiency speakers from Lowther, Rethm, Voxativ and sundry horns aren't but with stated self interest at play, none of those were my concern*.

The other knob inserts Elac's high pass at 10'000, 12'000 or 15'000kHz. Before another bad Nicholson imitation has you raise your eyebrows particularly at the latter two values, do remember. No analog audio filter behaves like a true brickwall. Even set highest, there's enough leakage from a limited filter slope to make for an audible contribution below it.

* A workaround for hi-eff speakers is to drive the super tweeter with a dedicated variable-output amp.

Of course you might throw a hissy fit if you ran the Elac solo set to 15K. You might hear nothing at all. Or perceive some very minor inner-ear pressure at best. Nada might very well be the case. Explaining then how it does make a pesky difference once you reconnect the mains now becomes a subject of endless speculation and self doubt. Are there intermodulation effects at work just like higher amplifier bandwidth of Spectral or Goldmund reach makes for purer treble? We certainly don't hear to 1MHz. Playing back a steady-state 15kHz tone (if we aren't old enough to no longer hear it) won't sound any different over such an amplifier. Yet we are sensitive to HF phase shift with complex music signal. That consists of fundamentals plus plenty of higher harmonics all riding on steep transients. And it is phase shift or timing errors which such circuits eliminate over say a transformer-coupled valve amp that's 3dB down at already 30kHz.

Getting embroiled in theoretical discussions on this subject unless one had the requisite know-how is, I believe, more apt to contribute to urban audio myths, confusion and ongoing ignorance than it is to achieve anything useful. Restricting things to personal experience on the other hand contributes to a growing body of evidence by fellow users. Whilst none of us might be in possession of the explanation or even a semi plausible derivative thereof, we can certainly throw our hat into the ring. We can state that yes, for us such devices have audible merit; list their specific benefits; and trust that with enough such feedback, fellow hobbyists might feel motivated to experiment. The rest is for psychoacousticians, engineers and audiologists to sort out.

This conveniently returns us to the physical object at hand. Available only in gloss black—the anthracite gray called Titan Shadow has been discontinued—this cast 4kg affair with its mushroom top is rather more substantial and sizable than isolated photos let on. As you'll see when perusing their website, our Germans from Kiel in the country's northern Bundesland of Schleswig-Holstein have extensive experience with exotic tweeters.

They are amongst those who early on exploited the expiration of Oskar Heil's patent for the air-motion transformer to roll their own. That in-house development is now in its 5th generation and even includes a wicked dual-concentric which combines a dynamic midrange with an AMT tweeter (whose positioning in the center is adjustable in the top version).