Franco Serblin Accordo Essence Loudspeaker Lab Report

Lab Report

Expanding the cabinet volume to accommodate a 180mm woofer brings the following top-line changes over the original Accordo standmount [HFN Jan '18]: bass extension is boosted from 62Hz down to a weighty 45Hz (–6dB re. 200Hz), THD is reduced from ~1.5% through bass and mid to just <0.5% here (re. 90dB SPL) but sensitivity is not improved over the original 86dB (1kHz/2.83V/1m) just as the amplifier loading is now that bit tougher. In practice the bass unit has a –6dB bandpass of 52Hz-270Hz [green shaded area, Graph 1], its output free of obvious spuriae, and is supported by the lower port which offers a useful 13Hz-75Hz (–6dB), albeit with a mode at 750Hz. The latter was also detected from the upper port, though this vent for the 150mm mid unit offers no significant LF reinforcement.

The dip in impedance also occurs at LF in the Essence, the 'easy' 4.1ohm/192Hz minimum of the standmount Accordo traded here for a more testing 2.76ohm/160Hz (<3ohm from 106Hz-250Hz). The biggest swing in impedance phase is also more aggressive at –72°/64Hz/7.7ohm. This result, and change in forward response [Graph 1], reflects the necessary recalculation of crossover points from two- to three-way in the Essence. Measured on-axis between the tweeter/mid units, the speaker shows an essentially flat response trend, albeit with notches at 520Hz/1.2kHz and a peak at 6-7kHz that account for the ±3.5dB response variations. The 1.2kHz dip is also resolved as a resonant mode in the CSD waterfall [Graph 2]. Otherwise, pair-matching is exceptional at <1dB (200Hz-10kHz) and the impact of the 'rubber band' grille minimal [cyan trace, Graph 1]. PM


Response inc. nearfield summed driver/port [green], freefield corrected to 1m at 2.83V [yellow], ultrasonic [pink]. Left, black; right, red; w. grille, blue


Resonances are quickly suppressed, albeit with a (woofer) mode remaining at 1.2kHz [see Graph 1]

Sensitivity (SPL/1m/2.83V – 1kHz/Mean/IEC) 85.7dB / 85.4dB / 83.4dB
Impedance modulus: minimum & maximum (20Hz–20kHz) 2.75ohm @ 160Hz, 16.8ohm @ 51Hz
Impedance phase: minimum & maximum (20Hz–20kHz) –72° @ 64Hz, +34° @ 515Hz
Pair matching/Resp. error (200Hz–20kHz) 1.5dB/ ±3.2dB/±3.5dB
LF/HF extension (–6dB ref 200Hz/10kHz) 45Hz / 35kHz/30kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 0.3% / 0.2% / 0.3%
Dimensions (HWD) / Weight (each) 1100x230x430mm / 30kg
Price £12,998

Franco Serblin Studio
Vicenza, Italy
Supplied by: Absolute Sounds Ltd, UK
0045 9684 5100