Loudspeakers

Very compact two-ways like the Vela BS 403.2 are always a trade off between sensitivity, bass extension and ease-of-drive. Let’s take the latter first because the 3.23ohm/242Hz impedance minimum is bang-on ELAC’s 3.2ohm/240Hz spec, confirming its 4ohm nominal rating. However, while the –52°/+42° swings in low frequency impedance phase contribute to a low 1.48ohm/139Hz EPDR there’s also a +36° upswing as the reactance of that 150mm ‘crystal membrane’ bass/mid unit climbs prior to crossover, causing another EDPR dip to manifest at 1.75ohm/740Hz. So the Vela BS 403.2 is no pushover for budget amps.

Sensitivity, meanwhile, is rated by ELAC at a very optimistic 86dB/2.83V/1m and while the bump in response [see Graph 1] yields an even higher 87dB/1kHz, the dished, recessive midrange and presence push this down to 84.7dB between 500Hz-8kHz. Pair matching would be a very tight 0.4dB (200Hz-20kHz) if it were not for the mistermination at 3.1kHz (just after the 2.4kHz crossover) where differences in a response notch – and associated modes [see CSD waterfall, Graph 2] – increase this to 1.8dB. The latter, and steady rise in HF output to 39kHz once the JET tweeter ‘lifts off’, is also largely responsible for the ±3.1dB and ±4.2dB response errors (200Hz-20kHz), respectively, though this flattens off to a very respectable +2.0dB and ±2.8dB once the Vela BS 403.2 is toed-in by just 10-15° [grey trace, Graph 1]. Finally, the diffraction-corrected bass extension, complicated by the position of the port, is estimated at 53Hz (–6dB re. 200Hz). The roll-off is steep but the 58Hz port tuning certainly boosts the 80Hz limit (–6dB re. 100Hz) of the bass/mid driver. PM