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The Model R107 represents the flagship of KEF's Reference Series, and is second only to the Professional Series KM-1 in KEF's product line. Anatomically, the 107 resembles a person. Beneath a decorative "hat," there's a special head assembly akin to the head on the old Model R105. This head assembly contains the brains of the 107, namely a T33 ferrofluid-cooled tweeter and an improved version of the classic B110 midrange driver, featuring a better voice-coil and a new polypropylene cone. The nerve center is also here, in the form of two passive dividing networks and load-impedance equalizing…
KUBE stands for KEF Universal Bass Equalizer and takes the form of a separate solid-state component that connects in the tape monitor loop or between the preamp and power amp. The KUBE supplied with the 107 includes a speaker-specific equalization module that provides level equalization for the tweeter and mid driver, as well as an inverse of the 107's LF response. Furthermore, the KUBE allows the user to control several parameters not previously accessible. First, the LF cutoff is adjustable in four steps: 50, 35, 25, and 18Hz. Second, "Q" of the bass response is continuously variable from…
Sidebar: 1986 Measurements
I decided to measure the 107 before doing any serious listening (something I usually do not do) so I could sort out the KUBE options and optimize the 107's response for my favorite placement. With the bass cutoff set at 18Hz (the setting I used for my auditioning), the 107 puts out energy down to 20Hz, which is as low as I can measure. In fact, bass output is so extended that the 107 can readily overload a listening room. Standing-wave resonances were excited in my room like never before, including an especially nasty one at 60Hz. The contour control cannot…
Martin Colloms wrote about the KEF R107 in March 1987 (Vol.10 No.2):
Dick Olsher first reviewed the R107 in Stereophile in Vol.9 No.7, and readers should read that review for a complete description. Briefly, bass is handled by two 10" pulp cone woofers mounted in small infinite-baffle enclosures within the R107's main box. The chassis of these drivers are coupled by a bracing bar to reduce the mutual vibration contribution to the enclosure. Their acoustic outputs are summed in a central chamber with the filtered "bandpass" energy emerging from the large port/grille on the enclosure top…
Sidebar: 1987 Measurements
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…
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…