Loudspeakers

Measured on the coaxial mid/tweeter axis, or between this and the bass unit below, the forward response trend of the Concentro S 503 is essentially unaltered and very distinctive. Three peripheral, magnetically-attached DCRs (Directivity Control Rings) are included in the box, the 'green' ring offering the median response seen here [Graph 1, below] though none significantly impact the general trend: very flat from 100Hz-2kHz before a sequence of (cancellation) notches at 2.1kHz (–4dB re. 1kHz), 6.3kHz (–10dB re. 1kHz) and 12kHz (–4.5dB re. 10kHz), the latter two within the passband of the JET 5c tweeter. The CSD waterfall [Graph 2, below] clearly shows resonances associated with each of these notches in response prior to the ~7dB uplift in high treble output above 13kHz.

Sensitivity is necessarily impacted with the 84dB/1kHz figure reduced to 82.5dB/500Hz-8kHz while the response uniformity is pushed out to an uncommonly poor ±8.8dB and ±9.6dB, respectively. By way of testament to ELAC's QC, however, the S 503's pair matching is a tighter 1.5dB while distortion – almost entirely 2nd harmonic – is very low at <0.5% (re. 90dB SPL, 100Hz-10kHz). The 180mm AS-XR coned bass unit offers a 66Hz-335Hz bandwidth (–6dB) reflex-loaded through a rear-mounted port tuned to 48Hz – both refreshingly clear of midrange resonances or pipe modes – to yield a diffraction-corrected bass extension of 50Hz (–6dB re. 200Hz). While sensitivity is low, the ease-of-drive is high with a minimum 5ohm impedance at 1.6kHz and a relatively 'friendly' EPDR of 2.45ohm/101Hz, rising to a positively agreeable >3.3ohm (130Hz-20kHz). PM