Monitor Audio Bronze 100 Loudspeaker Lab Report

Lab Report

Despite the Bronze 100's compact dimensions the specified 87dB sensitivity is not overly optimistic, the newcomer achieving a mean sensitivity of 87.7dB (500Hz-8kHz) without recourse to an evil impedance trend. MA quotes a minimum of 4.5ohm and this was proved on test with 4.6ohm occuring at 37Hz, close to the Helmholtz resonance of the reflex port, and again at 160Hz where, in both cases, the attendant swings in phase are within ±15o. The highest phase angles are also experienced at low frequencies but –49o/86Hz and +45o/63Hz are accompanied by a reasonably benign 11ohm load, so a 6ohm nominal impedance is wholly justified here. The Bronze 100 will be an easy enough drive for most competent budget amplifiers.

Measured on MA's preferred axis (between bass and treble drivers), the response trend is flat to within an impressive ±1.6dB (200Hz-20kHz) while pair matching between the two speakers was better than 1dB over the same span [see Graph 1, below]. Fitting the grille [blue trace] causes a small loss in presence/treble output while the small notch at 900Hz corresponds with a resonance detected from the port and also seen, along with minor driver modes at 3-4kHz and 10-20kHz, on the CSD waterfall [Graph 2]. The 'C-CAM Gold Dome' tweeter resonance occurs at 28.6kHz/+5dB [within the pink ultrasonic band of Graph 1] but the CSD [Graph 2] indicates this is swiftly quelled. Diffraction-corrected summed nearfield measurements [green area, Graph 1] show the bass falls away below 80Hz, following a +2dB lift from 90-140Hz, although the 51Hz extension (–6dB re. 200Hz) will be further improved by near-wall siting. 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 within bass/mid driver at ~3-4kHz are mild but complex. Note 29kHz dome breakup

Sensitivity (SPL/1m/2.83V – 1kHz/Mean/IEC) 87.7dB / 87.6dB / 85.2dB
Impedance modulus: minimum & maximum (20Hz–20kHz) 4.6ohm @ 37Hz, 28.4ohm @ 75Hz
Impedance phase: minimum & maximum (20Hz–20kHz) –49° @ 86Hz, 45° @ 63Hz
Pair matching/Resp. error (200Hz–20kHz) 0.9dB/ ±1.8dB/±1.6dB
LF/HF extension (–6dB ref 200Hz/10kHz) 51Hz / 23.9kHz/43.8kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 1.3% / 0.45% / 0.3%
Dimensions (HWD) / Weight (each) 376x231x325mm / 7.8kg
Price £325

Monitor Audio Ltd
Rayleigh, Essex
Supplied by: Monitor Audio Ltd
01268 740580