Loudspeakers

The FS 407 is compact as floorstanders go, so even with a 4ohm nominal impedance its specified 88dB sensitivity looks optimistic. Our measurements recorded almost 87dB as a simple FFT mean but 86.1dB SPL for 2.83V at 1m on the industry standard pink noise input, and less on a typical music spectrum, so 86dB looks to be a more realistic figure. In addition to specifying a 4ohm nominal impedance ELAC quotes a minimum of 3.5ohm/200Hz, which is very close to the 3.5ohm minimum we recorded at 184Hz. Impedance phase angles are unusually tightly controlled, so the minimum EPDR (equivalent peak dissipation resistance) is a little higher than typical at 2.1ohm/210Hz – but other dips to 2.1ohm/20Hz and 2.6ohm/353Hz complicate the picture.

The forward frequency responses, measured at 1m on the tweeter axis [Graph 1, below], show a distinct dishing of output through the presence band – the famous 'BBC dip' – which suggests that the FS 407's stereo imaging will be somewhat recessed, although that's a presentation many listeners like. Despite that the response errors are modest at ±3.3dB and ±3.6dB, respectively. Although pair matching error over the same 200Hz-20kHz is disappointing at ±1.8dB, the largest disparities are narrowband and in the middle- and high-treble. Diffraction-corrected nearfield bass measurements – made more challenging by the 'open mouth' port – showed the expected fourth-order (24dB/octave) roll-off below 40Hz but a gentler transition to 70Hz. The cumulative spectral decay waterfall [Graph 2] shows some resonance associated with the response dip at about 2.2kHz and peak at around 4kHz. KH