KEF Reference Series 103/4 loudspeaker Equipment

Sidebar 1: Equipment

Four power amplifiers were used in the course of this evaluation: the Threshold S/550e, the Mark Levinson No.23.5, the Audio Research Classic 120 monoblocks, and the PS Audio 100 Delta. The preamplifier was the Rowland Consummate, and the CD player was the Wadia WT-3200 driving the Audio Research DAC1-20 converter. (CD was the primary source in this audition.)

Interconnects were AudioQuest Lapis between CD and preamp and for the unbalanced link between preamp and power amp with the ARC and PS Audio amps. For balanced hookup to the Threshold and Levinson amplifiers, Cardas Hexlink (not the latest version) was used. Loudspeaker cables were AudioQuest Clear. (The KEFs were bi-wired.) The grilles were removed during the listening tests. In all cases, the loudspeakers were toed-in toward the listening position.—Thomas J. Norton

US distributor: GP Acoustics (US) Inc.
10 Timber Lane
Marlboro, NJ 07746
(732) 683-2356

kensargent's picture

I think what you mean is something other than that the woofers in the KEF 103/4 operate IN phase. For there to be any pressure generated in the central chamber, and thereby generation of any velocity at the port, the drivers must be OUT of phase, both electrically and mechanically. That is to say that as one of them moves away from its' frame, the other moves toward its' frame. As a result, the pressure in the central chamber is increased in one half of a cycle, and decreased in the other half of a cycle. This is the actual arrangement that would create the situation you describe: when the pressure is at maximum in the central cavity, it will be at minimum in the opposing cavities at the ends of the enclosure.

The rod connects the woofers' frames, surely, as this arrangement would, in fact, reduce vibration as the manufacturer states, but only if the cones were moving opposite each other. If the woofers were moving in phase, the rod would serve only to equalize, or average, the vibration, but not reduce it.

There are some arrangements in professional loudspeakers that put the woofers out of phase both mechanically and electrically, on an ordinary baffle, with one facing into the cabinet (front-loaded) and one facing out (rear-loaded.) In this arrangement, the advantage is said to be a cancellation of nonlinearities caused by the woofers' suspension, with the result reportedly being measurably lower distortion.