Jamo PP3000 Speaker System Review

Jamo’s “Push-Pull” speakers are named for the configuration of their twin “subwoofers.” These deep-bass drivers are mounted face to face in a separate enclosure at the bottom of the cabinet and radiate through a 3-inch-high slot around the periphery of the speaker base.

In the four-way PP3000, the top of the Push-Pull line, the two 10-inch deep-bass drivers cross over at 180 Hz to a forward-facing 8-inch cone driver. This “woofer” operates up to 850 Hz, and its enclosure is vented through a port in the rear of the cabinet. Above the 8-inch bass driver is a 5-inch cone midrange driver for frequencies up to 4,500 Hz, where it crosses over to a 1-inch dome tweeter.

The arrangement of the deep-bass drivers in the PP3000 is said to enable them to reproduce the lowest musical notes as well as a 15-inch driver in a cabinet four times as large. The 10-inch and 8-inch bass drivers are constructed as matched, parallel-connected bass-reflex systems with complementary impedance characteristics. Otherwise unavoidable impedance variations are said to be practically neutralized, enabling the amplifier to deliver its full power to the bass units. Rated overall system impedance is 8 ohms.

Unsnapping the cloth grille covering the forward-facing drivers in the PP3000 reveals a cross-hatch-patterned front panel and flush-mounted control knobs next to the midrange and tweeter. The controls permit continuous adjustment of these drivers’ response over a ±4-dB range. Next to the treble control is a red overload light; the tweeter is protected by an automatic-reset system, and the light flashes when the input level is excessive.

The insulated connectors recessed into the rear of the cabinet accept the stripped ends of speaker wires but not any of the other types of speaker-terminal connectors. Other specifications for the PP3000 include a sensitivity of 92.8 dB sound-pressure level at 1 meter with a 1-watt input and a maximum power input of 200 watts (380 watts of music program).

The wooden cabinet of the Jamo PP3000 is finished in dark rosewood and measures 45-1/2 inches high, 13-1/2 inches wide, and 12-1/4 inches deep. Each system weighs about 68 pounds. Price: $499.95 each.

Lab Tests

Our live-room frequency-response measurements, whether made with a frequency sweep of a warbling sine wave or an FFT computer analysis of the speaker’s pulse response, do not unambiguously show a speaker’s response in the bass range or its correct relationship to the response at higher frequencies. Indeed, there can be no one “correct” overall response specification for any speaker since actual response is influenced so profoundly by the room in which a speaker is located.

Nonetheless, the FFT response of the Jamo PP3000, measured either 1 or 2 meters away from the speaker, varied only about ±3 or 4 dB from 200 to 15,000 Hz. The most prominent and consistent variation was an upward “jog” of about 4 dB around 5,000 Hz, which was possibly due to a crossover anomaly between the midrange and the tweeter. The averaged room response showed the usual amplitude irregularities but maintained a reasonably uniform average level from a few hundred hertz to 20,000 Hz. It also showed some evidence of a 5,000-Hz peak, though at a much lower level than in the quasi-anechoic FFT response.

These measurements were made with the balance controls centered. The midrange control varied the output by up to ±4 dB between 600 and 7,000 Hz, and the treble control had a range of +4 to — 9 dB and affected frequencies above 2,000 Hz. The speaker output was relatively directional in the horizontal plane, with an angular change of 45 degrees having an appreciable effect on the response above 3,000 Hz. This effect is consistent with Jamo’s use of a fairly large (5-inch) cone driver over much of the high-frequency range.

Normally we measure the response of a woofer with a close-up microphone to eliminate room effects, summing the result with a measurement made at the port (if any) after scaling for the relative areas of the cone and port. That technique was only partially successful with the Jamo PP3000. The inclusion of two separate and quite different bass systems, each having its own port and particular phase relationship with the other, made it impractical to combine our measurements of them into a single bass frequency-response curve. We were able to deal with the forward-facing woofer in our usual manner, and its response could be combined with the higher-frequency curve to form a single frequency-response curve whose shape was generally consistent with what we heard from the speaker. The measured subwoofer response, however, consisted principally of a peak at 70 Hz, with its port radiating a flat output response down to at least 25 Hz about 10 dB below the maximum at 70 Hz.

The same factors affected our bass distortion measurements, since we obtained different readings from each source (two drivers and two ports) at each frequency. Fortunately, our ears told us that the low-bass output was strong and clean, once more emphasizing the superiority of the human ear to laboratory measurements for determining how something sounds'.

As claimed, the speaker’s actual impedance was very uniform over the frequency range, averaging about 7 to 8 ohms, with a minimum reading of 5 ohms at 150 Hz and a maximum of 11 ohms at 500 Hz. The short-term power-handling capability of the PP3000 was measured with tone bursts of 3 or 4 cycles, the level of which was increased until distortion was apparent either in the speaker’s acoustic output or in the amplifier’s electrical output. At 100 Hz there was an audible rasp when the input reached 40 watts. Since this is a relatively sensitive speaker, the 40-watt input produced a very high sound level (well over 100 dB). At 1,000 Hz the speaker did not distort until we applied a 535-watt burst.

Comments

Listening to a pair of Jamo PP3000’s, we found the most obvious characteristic of their sound to be an unusually powerful bass. Although by no means “tubby,” the bass was certainly heavier than we are accustomed to hearing. And the effect was no psychoacoustic illusion, since at reasonably high listening levels the speakers induced mistracking in a Compact Disc player elsewhere in the room! (The effect is similar to acoustic feedback in an analog turntable.) Perhaps this was a byproduct of the speakers’ apparent peak around 60 to 70 Hz. In any case, while we would expect the low-bass response to be somewhat room-dependent, Jamo’s Push-Pull driver system certainly seems to do what is claimed for it.

Bass aside, the PP3000 system sounded very smooth and well balanced with its midrange and treble controls centered. Adjusting these controls could make a distinct change in the sound character of the speaker, but it was gratifying to find that their indicated center positions gave both the flattest overall measured response and the most pleasing sound. It would not surprise us if these speakers were a first-rate solution for a thin-sounding listening room. Their size and weight discouraged us, however, from any thought of moving them around the house to verify that supposition.

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