Loudspeakers

JBL’s revised horn profile and new 38mm compression driver has realised an improved vertical dispersion, allowing the listener to be seated above or below the main axis without any significant deviation in response [black trace, Graph 1]. One of our pair [red trace] had a more exaggerated ‘bump’ at 1.1kHz and deeper midband dip leading to a higher ±3.4dB response error while the other was flat to within ±2.5dB (200Hz-20kHz). The 800Hz ‘step’, seen in previous JBL bass/treble horn designs [HFN Jan ’22 & Mar ’21], integrates out over a longer distance, while the new Teonex treble dome is now free of any ultrasonic break-up [pink shaded area, Graph 1]. JBL recommends the Ama is toed out to cross behind the listener’s head – this obscures an axial horn mode at 8kHz [CSD, Graph 2] at the expense of a 1.5dB drop in sensitivity and further dip through the presence band [blue trace].

Axial sensitivity is significantly higher than JBL’s 84dB spec. at 86.2dB/1kHz (85.1dB, 500Hz-8kHz) but distortion is also higher than average at ~1% at the bass/treble extremes before falling to 0.3% in the midband (all re. 90dB SPL/1m). Bass is also very generous. The ‘200mm’ mid/woofer spans 86-426Hz (–6dB) with a sharp but clean port tuning of 36Hz, realising a diffraction-corrected bass extension of 33Hz (–6dB re. 200Hz), falling steeply thereafter [green shaded area, Graph 1]. To a degree, all this is leveraged against a fairly tough amplifier load as the measured 2.8ohm/212Hz minimum is lower than JBL’s rated 3.1ohm/239Hz. Moreover, there are substantive +57°/–71° swings in phase angle that incur a minimum 1.1ohm/100Hz EPDR that remains sub-2ohm from 63-700Hz. PM