Pinnacle PN8+ Speaker System Review

Pinnacle’s inexpensive and compact loudspeakers feature the company’s patented Diaduct venting system, which was developed to solve the problem of fitting a duct tube of the required length and diameter for a given low-frequency response limit into a box of small size and attractive proportions. The depth of a typical speaker enclosure limits the maximum length of a conventional duct to the distance between the front and rear panels (bending the duct can introduce undesirable air turbulence). A short duct, however, must be relatively small in diameter and port-opening area for correct box tuning, reducing the system’s low-frequency output capability.

The Diaduct system uses an internal tube installed at an angle to achieve the longest possible acoustic path for a box of given size. In addition, the port is elliptical, rather than circular, to increase its area. The result is a deeper bass response than could otherwise be realized from the same driver in an enclosure of the same size.

Pinnacle’s design goals are to achieve high sound quality from small, affordable speakers. In our review of the company’s first speaker, the PN5 +, we commented on its smooth, uncolored sound, which was comparable to that of far more expensive speakers. The line has grown since then to five full-range two-way speakers and a subwoofer. This time we tested the top-of-the-line PN8 + .

The PN8 + ’s 8-inch woofer operates in a fourth-order vented enclosure. It has two Diaduct tubes, both opening on the front panel. The woofer cone, formed of mineral-filled polypropylene, has a 1 >/2-inch voice coil and a butyl surround. There is a first-order (6-dB-per-octave) crossover at 2,200 Hz to a 1-inch dome tweeter, whose double internal tuned cavity is said to extend its response an octave below that of conventional drivers of the same size.

The nominal system impedance is 6 ohms, and sensitivity is rated as 88 dB sound-pressure level (spl) at 1 meter with an input of 2.83 volts. The system’s recommended operating-power range is 20 to 125 watts (375 watts peak), and its frequency response is given as 30 to 21,000 Hz. The cabinet, finished in black, measures 19-1/2 inches high, 11-3/8 inches wide, and 11-3/4 inches deep, including the removable black grille. Twin binding-post terminals, which accept dual banana plugs or stripped wires, are recessed into the rear panel. The bottom front portion of the enclosure, below the grille, has an oak-finished trim strip. Each PN8+ speaker weighs 36 pounds. Price: $399 a pair.

Lab Tests

Except for a couple of minor “bumps” at 300 and 900 Hz, the averaged room response of the left and right Pinnacle PN8+ speakers was very smooth and uniform, varying only ± 3 dB from about 100 to 20,000 Hz. When the outputs of the two ports were combined with the close-miked woofer response, the bass response was within ±1.5 dB from 30 to 500 Hz. The composite response curve formed by combining the bass response with the room curve was a remarkable ±2.5 dB from 25 to 20,000 Hz.

It is possible to obtain such a response curve from a vented speaker whose low-bass output is actually more limited, since the curve is created by combining separate measurements of the cone and port outputs. A small port diameter may appear to give a strong low-bass output yet be unable to create a useful sound level under actual listening conditions.

Listening tests with sine-wave signals confirmed, however, that the PN8+ actually delivers a strong, audible bass output down to at least 30 Hz. That is uncommon performance for any speaker of this one’s size and especially for one of its modest price. We also found an output peak (about 20 dB in amplitude) at 540 Hz at the port opening, but the port’s overall response was down so far at this frequency that the peak barely reached the level of the output from the cone. And since the peak was rather narrow, with a “Q” of approximately 10, it had no discernible audible effect.

The smoothness of the PN8 + ’s midrange and high-frequency output was equally impressive. Its horizontal dispersion was good, with little difference between the on-axis and 45-degree off-axis response curves at frequencies below 10,000 Hz. Phase linearity was very good in the tweeter’s range, as evidenced by a group-delay variation of less than ±0.2 millisecond from 2,000 to beyond 20,000 Hz.

The sensitivity of the PN8+ was very high, producing a 92-dB SPL at 1 meter with a pink-noise input of 2.83 volts. We measured low-frequency distortion at a 2.25-volt input (which would yield a 90-dB SPL output in the sensitivity measurement). In the cone output, the distortion was 0.8 percent at 60 Hz and 0.3 to 0.5 percent from 80 to 2,000 Hz (except for a rise to 1 percent at 90 Hz). The port output dominated below 60 Hz; its distortion measured 2.5 percent at 60 Hz, 4 percent at 40 Hz, and 6 to 7 percent from 30 to 20 Hz.

The system’s impedance peaked at 13 ohms at 25 and 70 Hz and reached 15 ohms at 2,200 Hz. Its minimum of 4.2 ohms occurred at 160 Hz. The impedance phase angle remained within ± 30 degrees from 20 to 20,000 Hz.

The speaker’s power-handling ability was very good. With a single-cycle tone burst at 100 Hz, the amplifier clipped at 985 watts into the 7-ohm load without reaching the woofer’s limit. At 1,000 Hz, where the speaker impedance was 5 ohms, the amplifier clipped at 1,200 watts, and at 10,000 Hz it clipped at 1,150 watts into 6 ohms. Of course, any speaker, and especially a vented system, can easily be overloaded at extremely low frequencies, but the PN8+ clearly demonstrated its dynamic capability (and ruggedness) over our standard test range.

Comments

Loudspeaker frequency-response measurements, no matter how they are made, seldom correlate well with a listener’s perception of the system’s sound. There are many reasons for this, which we cannot go into here. But sometimes a speaker sounds very much the way its response curve suggests, and the Pinnacle PN8+ was one of those rare exceptions.

It was unusually free of such common colorations as upper-bass emphasis (evidenced as an unnaturally heavy or tubby sound, especially on male voices). On the other hand, unlike some speakers that avoid such emphasis simply by not reproducing frequencies below 60 to 70 Hz at a useful level, the PN8+ went down another octave, and with low distortion.

Similarly, the high frequencies, up to and beyond the limits of hearing, were reproduced smoothly, at a useful level, and with enough horizontal coverage to be appreciated over a typical listening area.

To be sure, there is no such thing as “everyman’s” speaker, since individual taste varies widely. Nevertheless, the Pinnacle PN8+ (like the smaller PN5 + ) manages to break the rules. A system using a modest box and a pair of outwardly conventional drivers, without benefit of unusually rugged construction or exotic materials, and selling for about $400 a pair is not supposed to sound as good as this one. Very few systems meeting that description do. Hear the PN8+ if you can— especially if you are looking for an exceptional value in a speaker.

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