As part of the preliminary test work, the KUBE was subjected to some basic lab tests for crosstalk, headroom, distortion, and noise. These were all passed with no trouble at all; we then ran off some response curves at the various settings. For example, fig.1 (one horizontal division equals 5dB) shows the effect of the bass-extension control for a constant Q of 0.5, Contour set at Zero. Given that the speaker has a falling low-frequency response, increasing its extension requires various degrees of bass boost. On line 1, with the minimum extension of 50Hz, the…
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John Atkinson reviewed the KEF R107/2 in May 1991 (Vol.14 No.5):
Bass. A small word. But a profound one: bass is the base of all Western music, the underpinning that organizes the overlying structure. Basically speaking, music without bass is music without roots or soul. Yet how many loudspeakers do justice to that concept? "You don't understand bass," said a St. Louis reader in a recent letter, who concluded that I (once a professional bass player) was "either deaf below 60Hz, didn't have room for decent-sized speakers, or never listened to bass-heavy rock." (Not one of the three, as it…
Apart from the new tweeter, other changes between the original 107 and the 107/2 involve a completely new crossover (although this still features KEF's Conjugate Load Matching, where additional circuit elements are used to make the unit's impedance fundamentally resistive and constant in nature), said to eliminate a slight thinness in the earlier model's lower midrange, and a new KUBE equalizer.
The 107/2 KUBE is less complex than the one supplied with the original version of the speaker, which offered control of both LF Q and extension. The new equalizer has just two rotary controls,…
Time for truth. I reached for that same Sibelius 5 recording (London 410 016-2).
Have you noticed that when something is working right in the system, it seems hard to concentrate on the hardware? Such was the case here. By the end of the symphony, I had forgotten what exactly it was I was supposed to be listening for.
Oh yes, that bass discord. I put the third movement on again, this time trying to shut out the music. Mmmmm. Just as I remembered it from the original 107, the E-flat and F close but far, melded but differentiated—but there's so much more going on, so much wider a…
The adjective "neutral," however, while held to be a positive quality in a hi-fi component, can also imply a lack of commitment, a shrinking from extreme positions. Thus it was with the KEFs. "They're a little polite?" ventured Tom Norton after I forced him to listen to the Dorian Pictures. Yes. They are. Compared with, for example, the Avalon Eclipses or Wilson WATT 3/Puppy combination, the R107/2s lose a little immediacy, offering a less dynamically vivid sound picture. They are also less forward-balanced than the similar-in-concept B&W 801 Matrix. But they still present all of the…
Sidebar: 1991 Measurements
Looking first at the performance of the KUBE, its distortion and input and output impedances measured to spec, while fig.1 shows its fundamental response with both contour controls set to their 12 o'clock positions. Note that the treble is shelved down by 1dB while the gentle, 2dB boost below 1kHz is presumably to compensate for the midrange driver's diffraction loss. The sharp rise in output level below 50Hz is to extend the speaker's bass below the bandpass enclosure frequency (where a slight, 2dB suckout compensates for what must be a slightly underdamped…
Thomas J. Norton wrote about KEF's Reference Series "Raymond Cooke Special-Edition" 107/2 in October 1995 (Vol.18 No.10):
It's a little mind-bending to recall that KEF first introduced their Model 107 loudspeaker in 1986. KEF, like most British loudspeaker manufacturers, tends to be conservative when it comes to its high-end models. Why mess with a good thing? The Model 107 has never been a radical design—that wouldn't be KEF's style. But the original 107 built on a solid background of innovation from KEF products in the immediately preceding years.
Take the twin coupled-cavity…
"Whoa! What happened?" I blurted aloud to no one in particular as the first bars of music rolled toward me. The left-right spectral balance was now all wrong. One channel appeared to have lost its top end, with a resultant skewing of the sound to the unaffected side. I listened more, to other material. Same result. I pulled the speakers out and set them close together. No change. I reversed the midrange/tweeter heads (they come packed separately and may be easily installed or removed by the user). The problem moved with the change in heads, indicating that it lay with the tweeter itself.…
That quality was enhanced by a bottom end that tilted more toward a full, rich quality than punchy tightness. In this respect, it also differed from the Thiel CS7. But when I say "tilted," I really mean it. In my large listening room, the 107/2 was full-bodied through the bass range, but in no way overblown. Bass definition was good. There was no muddle or confusion. The richness did reduce the overall transparency of the sound compared with that from a loudspeaker with a vise-like grip—particularly through the mid- and upper bass.
I did note a slight sonic fog in this region,…
Sidebar: Specifications
Description: Three-way, floor-standing loudspeaker with Conjugate Load Matching, Coupled-Cavity bass loading, and line-level equalizer. Drive-units: 1" (25mm) metal-dome tweeter, 5" polypropylene-cone midrange unit, two 10" (250mm) pulp-cone woofers. Crossover frequencies: 160Hz, 2.5kHz. Frequency response: 20Hz-20kHz ±2.5dB (-6dB at 18Hz, Q=0.5). Directional axis characteristics: within 2dB of reference up to 10kHz for ±10 degrees vertically, ±30 degrees horizontally. Position of reference axis: 40" above cabinet base, not including feet. Nominal impedance: 4…