ELAC Vela FS 407 Loudspeaker Lab Report

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


Broad depression of presence output in the forward response is indicative of the classic ‘BBC dip’


Cabinet modes are adequately suppressed but there are driver resonances at 2kHz and 4kHz

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

ELAC Electroacustic GmbH
Kiel, Germany
Supplied by: Invision UK Ltd, Diss, Norfolk
01359 270280