Alumine Five of Stenheim
Stenheim is a relatively late entrant to the high-end speaker field. It was founded in 2010 by a collective of mainly ex-Goldmund engineers, and its products have inherited an unmistakable aesthetic and, to a lesser extent, sonic DNA, although it was a significantly evolved character that was to emerge in the shape of the debut model, the compact, two-way Alumine Two. It’s a developmental divergence that has continued and, if anything, accelerated with the emergence of each subsequent product. The latest Stenheim speakers, developed under the auspices of new owner Jean-Pascal Panchard, definitely have their own, unambiguous identity, both visually and musically.
I’ve been seriously looking forward to the arrival of the Alumine Five. Previous experience with the brand has included impressive exposure to the various versions of the enormous and enormously impressive Ultime Reference models, as well as a brief but highly rewarding flirtation with the stand-mounted Alumine Two in my own system. The possibility of combining the sense of musical articulation, enthusiasm and communication I experienced from the Alumine Two, with more than a hint of the clarity, scale and authority so effortlessly delivered by the Reference models, all in a package that, if not exactly affordable, at least isn’t completely out of the question, makes the Alumine Five a distinctly interesting proposition.
Yet, confronted with the Alumine Five in the flesh, there’s little to hint at the extraordinary promise lurking within. Resolutely rectangular in true Stenheim style, the Five’s aluminum cabinet, with its plate-to-plate construction, stands just 48" tall, 15" deep and presents a broad 11" face to the world, dimensions based on golden-ratio numbers. The front baffle is split by a physical break between the upper midrange-treble enclosure and the lower bass cabinet, independently ported by the laminated full-width slots above and below, a physical separation that is mirrored by the contrasting inlaid strips that help visually break up the one-piece side panels. The regular lines, smooth surfaces, flawless matte finish and lack of visible fixings could easily result in a bland, almost featureless appearance. But those trim strips and the offset midrange and treble drivers do just enough to give the Five a subtle hint of individual style without resorting to the sort of gauche and ostentatious flourishes that so often pass as design.
The result is a refreshingly clean, classical appearance that will blend seamlessly with a range of different decors. Despite the lack of grilles (although they are available as an option, does anybody really spend this kind of money on a speaker and then compromise the performance by fitting covers?), the beautifully profiled baffle and absence of visible fixings makes for a genuinely neat, finished appearance that matches the superb surface finish on the cabinet. The end result just looks right, in a way that makes you wonder why you’d want grilles anyway.
The first hint of its potent sonic capabilities comes when you try to pick it up. Each comparatively compact cabinet tips the scales at 220 pounds. That’s a grunt-inducing, two-man lift. Now, take a look at the figures for bandwidth and sensitivity, and an in-room response that digs down as far as 28Hz combined with 94dB efficiency should raise your eyebrows, especially given the compact cabinet dimensions. Which brings us to the first experiential disconnect: boxes this size shouldn’t produce this much bass or do it so easily. Nor should they weigh so much -- although therein lies the clue to this particular conundrum. When it comes to bass extension, it’s not the external dimensions of the box that matter, but its internal volume. Just like the Crystal Cable Minissimo, a thin-wall cabinet makes for a much larger internal volume than the external dimensions might suggest -- especially if we apply the expectations of more conventional wood-based construction. Throw in the sheer weight of the aluminum panels and the combination of mass and physical dimensions would subconsciously suggest massively thick walls -- and a correspondingly limited internal volume. Instead, what we have here is a deceptively large volume, which, combined with the inertia of the heavy cabinet and the mechanical stability provided by the material, makes for an effective mechanical reference for driver movement, meaning that more of the energy your amplifier sticks into the speaker comes out as sound and (at least in theory) it will be more precisely rendered.
So far, not very much that’s new. It’s not like Stenheim (or Magico, or YG Acoustics) has exclusivity when it comes to aluminum cabinets. But what does make Stenheim different is the unique material they use in damping their cabinet panels. Of course, the separate enclosures and the internal baffles they demand make for an inherently heavily braced structure, but look inside a dismantled Alumine Five and you’ll find strategically placed pads stuck to the cabinet walls. These three-layer, self-adhesive pads combine a heavy damping layer (adjacent to the cabinet wall itself) with added foam and impervious layers, allowing the low-volume pads to influence both the mechanical behavior of the cabinet itself and the enclosed volume. It’s an interesting solution because it manages to overcome the weakness so often audible in simple, braced aluminum cabinets (the all-too-recognizable resonant signature of the material itself) while maximizing the benefits (large volume and rigidity) by obviating the need to stuff the internal space full of wadding or long-haired wool. In fact, if the Stenheims were stood behind a sonically transparent curtain, you’d be hard-pressed to recognize the music as emanating from an aluminum cabinet at all. The absence of the bleached, grainy or lean colorations, the lack of sterile, mechanistic reproduction, is one big half of the Stenheim story, living, breathing proof that it’s not what you use but how you use it that counts.
The other half is down to the drive units, and after the cabinets, those come as quite a surprise, both the lineup and the chosen materials. In stark contrast to the use of the latest, precision CNC techniques, complex damping pads and finishing options, the Alumine Five's drivers are as traditional as they come, with a coated silk-dome tweeter and pulp or laminated paper midrange and bass drivers. The cone drivers use textile double-roll surrounds and massive magnets more normally found in pro-audio applications, and while Stenheim doesn’t build its own drivers, the company works closely with its chosen supplier (PHL, definitely not one of the usual suspects) to specify the electrical parameters, mechanical characteristics and precise details of the surface coating.
The use of such lightweight cone materials and large motors aids the system efficiency, while a hybrid second-order/Linkwitz-Riley crossover, the result of extended listening and evolution, ensures phase coherence and excellent out-of-band attenuation and makes for easy non-reactive load characteristics, despite the three-way topology. The other aspect of the driver lineup that might be considered slightly unusual is the use of a large-diameter (6 1/2") midrange unit -- although less so since Vandersteen’s patent on the approach lapsed some years ago, resulting in a rash of companies suddenly exploring the possibilities of the topology.
Perhaps more important, in the case of the Alumine Five, it means that you are getting the tweeter and midrange drivers from the Ultime Reference series speakers, teamed here with a pair of 10" woofers but without the benefit of a super tweeter. Even so, Stenheim quotes bandwidth out to 35kHz, which should suffice for most purposes. The review speakers arrived with the optional second set of terminals installed, allowing for biwiring or, more significantly, biamping, an upgrade opportunity that makes this an option you should take. If, in the meantime, you are single-wiring the speakers, make sure you factor in a set of jumpers that match your speaker cables: the Alumine Five's overall sense of musical coherence makes the benefits especially obvious. Likewise, good wiring practice is essential, both in terms of cable dressing and diagonal connection (red to midrange/treble, black to bass, with jumpers arranged accordingly).
Aside from the speaker's substantial weight, the parallel sides and flat surfaces of the four-square cabinet make setting up the Fives an absolute joy. Precise, repeatable, angular adjustments are easily achieved, while changes in attitude are just as straightforward, helped by the beautifully profiled stainless-steel spiked feet and deeply cupped footers. Both the cones and their locking rings have nice, large ports to take the supplied pry bars, but it’s worth greasing the threads before installation. One other thing to watch out for: the spikes are seriously (refreshingly) sharp -- sharp enough to penetrate a thick rug and score the floor below, so be careful where you stand the speakers once the feet are installed. Final positioning disposed the speakers on a broad front with minimal toe-in. When it came to dialing in their considerable musical energy, the most critical factor proved to be height off the ground, with tiny adjustments of the spikes making profound differences to the weight and pace of the presentation. Likewise, equal weighting of the four spikes was crucial to a proper sense of grounded weight and dynamic authority.
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Price: $60,000 per pair.
Warranty: Five years parts and labor.
(Source: The Audio Beat)
least square solution 在 [理工] 線代least squares solution 問題- 看板Grad-ProbAsk 的推薦與評價
先附上題目:
左邊那那題目，只須解A^T * A * X = A ^T * b
解出X 即得到 least squares solution
若要求第二小題的正交投影，再乘上矩陣A即得到。
而右邊這題，他先做完Gram-schmidt 得到 orthogonal basis
再代正交投影公式
這樣算出來不就是正交投影向量了嗎?? 怎麼又是 least squares solution 呢?
還是說題目說的 least squares approximation 是指 正交投影??
而且不是指least squares solution?
請各位高手幫忙解惑，3QQ
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