JBL Studio L Series Home Theater Speaker System Page 3
Test Bench for Web JBL Studio L Series Speaker System by Tom Nousaine
Frequency response (at 2 meters) front left/right: 84 Hz to 20 kHz ±3.0 dB center: 84 Hz to 20 kHz ±3.6 dB surround: 84 Hz to 20 kHz ±3.6 dB subwoofer: 37 Hz to 110 Hz ±2.1 dB
Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input) front left/right: 88 dB center: 89 dB surround: 85 dB
Impedance (minimum/nominal) front left/right: 3.4/4.3 ohms center: 3.2/4.4 ohms surround: 5.0/8.0 ohms
Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room) front left/right: 80 Hz at 90 dB center: 80 Hz at 93 dB surround: 80 Hz at 91 dB subwoofer: 20 Hz at 85 dB SPL 104 dB average SPL from 25 to 62 Hz 112 dB maximum SPL at 62 Hz bandwidth uniformity 92%
All of the curves in the frequency-response graph are weighted to reflect how sound arrives at a listener's ears with normal speaker placement. The curve for the left/right front channels reflects response of the L820 averaged over a ±30° window, with double weight at 30° (the most typical listening angle). The center-channel curve reflects response of the LC2 averaged over ±45°, with double weight directly on-axis of the primary listener. The surround-channel curve shows the response of the L810 averaged over ±60°.
The L820's offset woofer gives it slightly different directivity to its left and right sides. The roughness at 3 kHz and above was evident in either case, but the mild depression between 200 Hz and 1.5 kHz when the microphone was moved toward the central listening position (shown) was replaced with a moderate elevation between 200 and 800 Hz when the microphone was moved toward the outside of the speaker.
The LC2 had a similar response shape, but its symmetrical woofers and the vertical array of its midrange driver and tweeter provided tightly controlled directivity in the horizontal plane. Likewise the L810 surround, which again had a highly similar response shape - but that helps ensure that direct and reflected sound from all channels will have the same timbre.
Note that the LC-1 and L820 showed somewhat low minimum and nominal impedance - significantly lower than their published specification of 8 ohms nominal. Users should be mindful of that when matching these speakers with a receiver or power amplifier.
The L8400P subwoofer's bass limits were measured with it set to maximum bandwidth and placed in the optimal corner of a 7,500-cubic-foot room. In a smaller room users can expect 2 to 3 Hz deeper extension and up to 3 dB higher sound-pressure level (SPL).
The L8400P had 109 to 112 dB SPL capability from 50 to 62 Hz at 2 meters (the optimal seating distance from a subwoofer). But output fell at nearly 16 dB per octave below 50 Hz. And although it had useful response up to 145 Hz when the LFE input was used, upper-frequency bandwidth was more limited with the Normal inputs selected than the dial markings or specifications suggest. There was also a moderate (-4-dB) crossover/level-control interaction over the full range of the crossover control as the selected frequency was lowered.