JBL 4309 Loudspeaker Lab Report

Lab Report

With that mid/treble horn front-and-centre there's hope of good sensitivity from this little box, and JBL's 4309 does not disappoint, achieving 87.8dB/1m/1kHz and 86.1dB from 500-8kHz, according well with the rated 87dB. Neither is there a sting in the 4309's tail as regards its amplifier loading, presenting a very 'driveable' minimum of 4.06ohm/150Hz with a near-zero phase angle (–4o). Moreover the inductive upswing to +52°/1.74kHz – as the 25mm Teonex compression driver takes over – coincides with an easy modulus of 12.3ohm on its way up to a >20ohm span from 2.5kHz-9.4kHz. So the 4309 should be a great match for owners of low-power tube amps...

The forward response is more impressively integrated than we saw with the larger 4349 [HFN Mar '21] where a cancellation mode in the throat of the horn produced a notch at ~1.4kHz. Not so here as the 4309 offers a substantially flatter output, true to within ±1.8dB from 200Hz-18kHz just prior to a +9dB peak in output at 20.6kHz [see Graph 1 and waterfall, Graph 2]. Pair matching is a superb 0.6dB (200Hz-8kHz) but a wobble in the response of one speaker from 8-13kHz results in a poorer 2.4dB from 200Hz-20kHz. Meanwhile the 69Hz-335Hz (–6dB) bandpass of the 165mm pulp woofer is supplemented by the 'peaky' 43Hz tuning of the dual ports to deliver a fine 42Hz bass extension (–6dB re. 200Hz). Finally, the UHF pads offer a –2.2dB/+1.8dB cut and boost from 5-20kHz [grey traces, Graph 1] while the snug plastic grille exerts little influence [blue trace] – so any subjective 'colour' is just as likely to originate from the mild resonance at the 1.6kHz crossover [Graph 2]. 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


Mild cone modes are at 900Hz and 1.6kHz while treble is clean up to ~21kHz dome resonance

Sensitivity (SPL/1m/2.83V – 1kHz/Mean/IEC) 87.8dB / 86.1dB / 83.7dB
Impedance modulus: minimum & maximum (20Hz–20kHz) 4.06ohm @ 150Hz, 24.8ohm @ 4.6kHz
Impedance phase: minimum & maximum (20Hz–20kHz) –40° @ 94Hz, +52° @ 1.74kHz
Pair matching/Resp. error (200Hz–20kHz) 2.4dB/ ±5.0dB/±4.8dB
LF/HF extension (–6dB ref 200Hz/10kHz) 42Hz / 33.9kHz/33.1kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 0.55% / 0.25% / 1.1%
Dimensions (HWD) / Weight (each) 419x260x227mm / 11kg
Price £1799
Harman International Industries
Supplied by: Harman Luxury Audio Group, Cambs
01223 203200