JBL L100T Speaker System Review

The JBL L100T is a floor-standing speaker system in a handsome oiled-walnut cabinet. It has a 12-inch woofer, a 5-inch cone midrange driver, and a 1-inch dome tweeter. The woofer port opens to the rear of the cabinet. The recessed binding-post terminals on the rear are spaced on 3/4-inch centers to accept dual banana-plug connectors. The L100T has no external controls or adjustments.

The black grille cloth is supported about an inch from the speaker-board on plastic mounting posts, which snap into sockets on the board. Since the speaker-board is finished to match the rest of the cabinet, the grille can be removed if desired. The woofer is centered laterally on the board, but the mid-range and high-frequency drivers are vertically aligned and offset about 1-1/4 inches right of center. This arrangement is apparently not related to imaging, since the left and right speaker units are identical (not mirror image). The JBL L100T measures 37 inches high, 16 inches wide, and 13 inches deep. It weighs about 70 pounds. Price: $525 each.

Lab Tests

The room response of the JBL L100T was among the flattest and widest we have yet measured from a speaker, within ±6 dB from 20 to 20,000 Hz. The differences between the response curves of the left and right speakers—measured separately, with the microphone on the axis of the left unit and about 30 degrees off the axis of the right speaker— were very small. Bass response was also relatively unaffected by boundary effects. Although the raw room response of a speaker is almost as much a property of the room as of the speaker, the response we measured from the JBL L100T was nothing less than remarkable.

The close-miked woofer response, measured separately at the cone and the port, varied only 7.5 dB overall from 20 to 900 Hz and a mere 3.5 dB between 35 and 700 Hz. Splicing the woofer curve to the room response resulted in a composite frequency response of ±3.5 dB from 20 to 20,000 Hz, which is a very impressive performance for any home speaker. With a 2.83-volt input, the system’s sensitivity was 92 dB sound-pressure level (SPL) measured at 1 meter. When we drove it with 2.25 volts (corresponding to a 90-dB midrange SPL), the woofer distortion was between 0.2 and 0.5 percent from 100 Hz down to 60 Hz. Below 60 Hz, the port was contributing much of the sound output, but the distortion was still a very low 3 to 3.4 percent in the 20- to 35-Hz range.

The impedance of the L100T was at a minimum of about 5.3 ohms at 120 Hz and 5 ohms from 15,000 to 20,000 Hz. It peaked at 24 ohms at 50 Hz and varied between 5.5 and 13 ohms over most of the audio range. A 6- to 8-ohm impedance rating would seem to be reasonable for this speaker. During our pulse-power tests (one cycle on, followed by 128 cycles off), the woofer cone reached the end of its linear travel range with an input of 550 watts at 100 Hz into its 5.5-ohm impedance. The 8-ohm midrange driver handled the full 1,400-watt output of the test amplifier at 1,000 Hz with-out distortion, and the tweeter began to show nonlinearity when driven with 300 watts at 10,000 Hz (into its 6-ohm impedance).

Our quasi-anechoic FFT frequency-response measurements confirmed the exceptional width and smoothness of the L100T’s response. It was flat within ± 2.25 dB from 180 to 24,000 Hz when measured at 1 meter on the tweeter’s axis. Although we had no information on the crossover frequencies used in the system, response measurements with the microphone placed approximately equidistant from the woofer and midrange cones and from the midrange to the high-frequency dome revealed sharp cancellations at approximately 900 and 3,000 Hz, which would be reasonable crossover points. There was no clue to the actual crossover frequencies in the room-response measurements. The phase linearity of the system was very good; the group delay was constant within ± 0.1 millisecond from 3,000 to 20,000 Hz, and the maximum change was 1 millisecond at about 1,000 Hz. The frequency-response curves measured on-axis and 45 degrees off-axis differed by no more than 4 or 5 dB up to 10,000 Hz, the difference increasing to 8 or 9 dB at 15,000 Hz.

Comments

The excellent measured performance of the JBL L100T came as no surprise. We listened to the speakers for some time before making any tests, and it was obvious from our first hearing that these were exceptional speakers. Their balance, smoothness, and extended response at both ends of the audio spectrum were all striking, and a pair of speakers we had previously favored always came off as second-best in A/B comparisons with the L100T’s.

A total lack of mid-bass boominess on male voices set the L100T apart from most other speakers— and they are few in number—that share its ability to generate clean, deep bass down to 20 Hz. Similarly, the clarity and transparency of its high-end response were distinctly superior to what we have heard from most competitively priced speakers, as well as some far more expensive models. Yet, because of its flat response, which extends well beyond the audio range, it never had a trace of “edginess” or “bite.”

Although our tests showed that the L100T can handle very large peak-power inputs without damage or obvious distortion, it is considerably more sensitive than most speakers of comparable quality and can be driven to very high volume levels with any good 80-watt amplifier. As with any speaker whose woofer operates in a vented enclosure, it is advisable to limit the infrasonic output of the amplifier used with the L100T (although you are unlikely to damage this speaker with any signal that your hearing can tolerate).

Our recent experience with speakers in the $500 to $600 range indicates that there are a number of superior-sounding models in that price bracket, which seems to offer the highest ratio of sonic performance to price available to serious audiophiles. Without attempting to make any specific comparisons, we can state that the JBL L100T is one of the star performers in its price range. We find it strange, however, that the speaker’s model designation conveys the impression of a relationship with the L100 series that JBL manufactured for many years. One could not imagine two more different-sounding speakers, to say nothing of the differences in size and price between them. The L100T is something wholly new, and it should carve out its own reputation in the marketplace with no difficulty.

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