ELAC Vela FS 407 Loudspeaker Lab Report
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
Sensitivity (SPL/1m/2.83V – Mean/IEC/Music) | 86.8dB / 86.1dB / 85.5dB |
Impedance modulus: minimum & maximum (20Hz–20kHz) | 3.5ohm @ 184Hz, 12.7ohm @ 75Hz |
Impedance phase: minimum & maximum (20Hz–20kHz) | –40° @ 92Hz, 37° @ 25Hz |
Pair matching/Resp. error (300Hz–20kHz) | ±1.8dB/ ±3.6dB/±3.3dB |
LF/HF extension (–6dB ref 200Hz/10kHz) | 48Hz / >40kHz/>40kHz |
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) | 0.5% / 0.1% / 0.1% |
Dimensions (HWD) / Weight (each) | 1000x229x266mm / 19kg |
Price | £3670 |