MBL Radialstrahler 101 E MkII Loudspeaker Lab Report

Lab Report

Measured on the tweeter magnet axis, the impact in forward response of the various 'Natural/Rich' and 'Smooth/Natural/Fast' mid/treble modes is minor – the difference between the three treble settings amounting to just ±0.1dB (5-12kHz) while the 'Attack' Low setting offers a +0.7dB upper bass lift (100-150Hz) vs. 'Smooth'. In all instances the response of the 101 E MkII is impressively flat from 200Hz-6kHz with errors of just ±1.1dB and ±1.3dB and a tight 0.8dB pair matching [see Graph 1, below]. There's a mild peak in treble output at 13kHz following a limited dip from 7-10kHz, although the HF output rolls away thereafter to an early 15.4kHz (–6dB re. 10kHz). The huge grilles cause reflections appearing at 0.87msec (33cm) intervals, matching the width of the perforated cage [blue trace, Graph 1]. There's an ultrasonic peak at 48.4kHz, a resonance in the carbon-fibre petals of the treble melon [pink shaded area, Graph 1], but other in-band modes are very well controlled [see Waterfall, Graph 2].

Down below, the –6dB bandpass of the tuned bass enclosure extends over a narrow 30Hz-66Hz, peaking at 38Hz and rolling off very steeply at ~24dB/octave (>100Hz), while the diffraction-corrected LF extension is a deep 28Hz (–6dB re. 200Hz). Due to the Radialstrahler's 360° output its low 'axial' sensitivities of 81dB (1kHz) and 82dB (500Hz-8kHz, all re. 2.83V/1m) are not especially indicative of the perceived in-room loudness. However, the low 3.6ohm/40Hz (3.7ohm/460Hz) impedance – typically <8ohm from 50Hz-20kHz and toughest at 4.15ohm/37Hz/–42° – suggests it must be partnered with powerful, load-tolerant amplifiers if the rated 104dB/3m SPLs are to be achieved. 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


With no main cabinet, resonances are minimal, and any driver modes quickly suppressed

Sensitivity (SPL/1m/2.83V – 1kHz/Mean/IEC) 80.3dB / 79.8dB / 76.8dB
Impedance modulus: minimum & maximum (20Hz–20kHz) 3.6ohm @ 40Hz, 12.4ohm @ 26Hz
Impedance phase: minimum & maximum (20Hz–20kHz) –56° @ 32Hz, +37° @ 612Hz
Pair matching/Resp. error (200Hz–20kHz) 2.3dB/ ±7.3dB/±9.1dB
LF/HF extension (–6dB ref 200Hz/10kHz) 28Hz / 15.4kHz/15.3kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 0.65% / 1.1% / 3.5%
Dimensions (HWD) / Weight (each) 1526x450x540mm / 80kg
Price £51,000

MBL Akustikgeräte GmbH & Co. KG
Berlin, Germany
Supplied by: Stranger High Fidelity, Real World Studios, Wilts
07702 155847