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There are two ways to describe Wisdom’s ‘line source’ loudspeakers. One is to talk tech — explaining the advanced long thin film membranes and their planar magnetic operation, along with the Regenerative Transmission Line in the company’s unusual ‘Suitcase Subwoofer’.
But we reckon it makes sense first simply to under-stand how convenient they can be compared with conventional box-and-cone loudspeakers, and how spectacular the technologies can make them sound.
We’ve long had a great admiration for Wisdom Audio’s line source speakers. On this occasion we listened to the L8i models from the company’s Insight range. We have in the past heard its top ‘Wisdom’ range, where a full system could set you back hundreds of thousands of dollars. A ‘Sage’ series sits between these, with the Insight range below so that they are relatively affordable. Yet the L8i maintains the principles behind the highest models, and the technologies too.
This is a line source, very different to the ‘point source’ of conventional box speakers. The high frequencies are handled by a pair of 61cm membranes in each 131cm-high speaker running almost the full height of the speaker, flanked by eight more conventional woofers, though these are carefully configured to be dynamic yet well damped, so their handling of lower frequencies can have comparable speed of operation to the membranes. These woofers use the wall cavity as their ‘enclosure’, working rather in what’s known as an infinite baffle design, so all the critical damping required has been engineered by Wisdom into the motor and suspension system of these woofers.
The resulting ‘line’ of the membrane delivers a wholly different way of moving air than does the point source of a cone-based speaker. Most of the energy from a cone expands outward into the room as a spherical wavefront. The sound level reduces exponentially with distance, while the edges of the sphere bounce off walls, ceiling and floor, delivering reflections that reach the listener later, potentially muddying or smearing the sound.
The energy dispersion of a line array is very different. It delivers a column of energy which beams forward, spreading in what might be described as an expanding cylinder, but hardly at all vertically, drastically reducing floor and ceiling reflections. (If you want hard shiny concrete floors in your music room, these are the speakers for you!)
Another effect of the reduced spread is that the perceived volume of line speakers doesn’t decay in the same way as it does with box-and-cone speakers. It’s an odd thing to experience when listening to line speakers, how the volume is barely louder right up close to the speakers than it is at the listening position, or even at the back of the room. Indeed the ‘listening position’ is less obviously defined, with a far more generous ‘sweet spot’ both front to back and side to side. Together with the reduced room reflections, this gives Wisdom’s line designs a great advantage in home cinema environments.
We heard the L8i speakers in just such a home cinema environment, in the demonstration room of the Australian distributor Network Audio-Visual. Yet we never saw them, as the left, right and centre were installed in-wall behind an acoustically transparent Screen Innovations projection screen as part of a full surround set-up, with the rears being the smaller P2i models from the Insight range (see below). Each P2i uses two of the dynamic woofers, with a smaller planar magnetic delivering the high frequencies.
then the point-source P6i, P4i and P2i models.
The system was being driven by a healthy 200W per channel Storm Audio eight-channel amplifier, and the voice coils in the L8i are exceptionally good at dissipating energy, the membranes being so long and exposed on both sides to the air, and distributed among eight units in the case of the woofers. Yet another of Wisdom’s surprises is how easy its line speakers are to drive — only a single channel of amplification is required for each full set of membranes and woofers, which combine to offer a high 91dB sensitivity and a nominal impedance of
Few things demonstrate speed of response like a good shooting scene, and we enjoyed from Blu-ray the subterranean drone attack sequence from Oblivion, which powerfully demonstrated the Wisdom system’s ability to steer a complex sound mix in concert with the visuals, reorientating at dizzying speed and with snapshot accuracy.
Although we heard them in a home cinema, these are not speakers limited to movie sound. Planar magnetic designs share with electrostatics a unique ability to deliver speed and detail to music that is likely to astound anyone used to regular tweeters. In electrostatic designs the ribbon diaphragm is held at a fixed charge, with the varying voltage applied to metal plates on either side. In a planar magnetic design the arrangement is reversed, with conductors woven through the membrane itself, the movement induced as the electrical signal varies within a fixed magnetic field generated by magnets on each side. In both speaker types the membrane is driven across its entire surface, creating enough energy to compete with the pistonic motion of a conventional cone, but with a fraction of the moving mass (extremely low in comparison with cones or dome tweeters), and with movements so small that they avoid the blurring effects of inertia to create the detail and speed for which these designs are justly famous.
Such delicacies are best heard with music, and we enjoyed a series of concert performances delivered in surround by the Wisdom system. The Police’s Wrapped Around Your Finger on Blu-ray, from their 2007 reunion tour — not only was the delicacy of Copeland’s percussion a delight to hear, the physical impact of his timpani was massive, a combination of the prodigious bass from the miracle SCS subwoofer (see below) and the dynamic edge of speed lent by the L8i panels. The L8i panels can be used alone as full-range speakers, but they’re optimised to be supported by a subwoofer, ideally one of Wisdom’s transmission line subs such as the SCS used here.
Wisdom further notes that its planar drivers benefit from using not the usual Mylar diaphragm but more advanced polyimides, also pleating its diaphragms to increase surface area, along with recent improvements in magnetic materials, notably neodymium. The combination of these allows Wisdom’s planar magnetics to be far smaller than would an equivalent electrostatic speaker; they can also be configured to avoid the back energy inevitably created by electrostatics. That’s important when you’re working inside a wall, and don’t want to annoy the people on the other side!
A second example of their impressively weighty slam came from Four Minutes, a song from Madonna’s ‘Sticky & Sweet’ Blu-ray, her stage festooned with images of conventional cone speakers, ironically, given the Wisdom’s line sources were showing they could handle this electronic music as impressively as they did acoustic fare such as the Adele Albert Hall concert, the Wisdom’s portrayal of her live rendition of Dylan’s Make You Feel My Love rejuvenating our regard through its delivery of a beautifully-toned and widely thrown piano, and an impeccable delivery of her strong yet intimate vocal. It seemed an ear-pleasing way to leave our all-too-brief time with these remarkable speakers.
Wisdom SCS subwoofer
One of the great wonders in our audition with the Wisdom Insight system was the performance of the single Wisdom SCS subwoofer in the system. Not only did this deliver prodigious levels of bass for its size, there was only one of them in the room yet it neither ‘pulled’ the bass to its position nor seemed to cause any nodes of less or more bass around the room. This is Wisdom’s Suitcase Subwoofer (hence ‘SCS’), with no driver on display, but inside a pair of 5 x 7.5-inch oval woofers which together provide the equivalent cone area of a 13-incher, not to mention a 400W amplifier module, specified to deliver 120dB at 25Hz, and from what we heard, we can well believe it. It uses a long transmission line within the cabinet, a folded path down which the sound travels (Wisdom calls it a Regenerative Transmission Line) before
exiting into the room from a small port area. Indeed the port can be configured to several different exit points, allowing the SCS to be hidden in-wall, under couch, wherever convenient — although we thought it so compact a design compared with normal cubic subwoofers that it hardly dominates a space even if, as during our audition, it’s out on display.
Understanding the technicalities behind Wisdom’s implementation of planar magnetics in the L8i
will certainly allow you to appreciate how they manage to deliver such a clean yet powerful sound, delicate yet strong. On the other hand you can simply enjoy the way they disappear into your décor compared with conventional stereo boxed speakers, or entirely behind a screen when used in a home cinema, all the while delivering such a sensational level of high-fidelity performance.
Wisdom Insight series
L8i in-wall line source: $12,000 each
SCS active subwoofer: $8000 each
P6i in-wall point source: $6995 each
P4i in-wall point source: $4200 each
P2i in-wall point source: $3195 each