Pinnacle PN5+ Speaker System Review

The Pinnacle PN5+ is a miniature bookshelf loudspeaker that employs a proprietary Diaduct port design to extend its bass response. The optimum duct length and port diameter for a given bass response are critically related to the bass drivers’s characteristics and the enclosure’s volume. According to Pinnacle, the use of an angled duct tube terminating in an oval port on the rear panel permits a bass response not otherwise obtainable in a fourth-order vented enclosure of the PN5+’s size using the same drivers. The PN5+’s cabinet depth from speakerboard to the slightly recessed rear panel is only 6 inches, which obviously could not accommodate the required 6-inch-long duct in a conventional design. Angling the 1-1/2-inch-diameter tube at 40 degrees to the rear panel enables its length to be increased without obstructing the internal duct opening and the external port to be increased to a 1-1/2 x 2-3/8-inch oval.

The PN5 + is a two-way system whose driver complement consists of a 5-1/4-inch polycarbonate-cone woofer and a 3/4-inch polycarbonate-dome tweeter cooled and damped with ferrofluid. The crossover frequency is 5,000 Hz, and the rated frequency response is 50 to 21,000 Hz. The nominal impedance of the system is 6 ohms, and its rated sensitivity is 86 dB sound-pressure level (SPL) at 1 meter with a 1-watt input.

The PN5+’s cabinet measures only 11-1/4 inches high, 6-3/4 inches wide, and 7 inches deep including the removable black cloth grille. It is solidly constructed of half-inch particle board covered in walnut-grain vinyl veneer. Weight is 8-1/4 pounds. The spring-loaded terminals, which accept the stripped ends of the speaker wires, are recessed slightly into the back of the cabinet. The speaker is recommended for use with amplifiers delivering between 10 and 50 watts per channel. Price: $149 a pair.

Lab Tests

The averaged room response of the Pinnacle PN5+ speakers was relatively smooth, with less than the usual amount of low-frequency room interaction, possibly because of their inherently limited low-bass response. We mounted the speakers on pedestals about 26 inches from the floor and well away from any walls for our measurements. The most obvious feature of the response curve was a midrange depression, the output in the 1,000- to 2,000-hz range being about 5 dB less than at lower and higher frequencies. Of course, the same characteristic could also be interpreted, subjectively, as a slightly emphasized bass and treble response relative to the midrange reference level. The output also rose at the highest frequencies; the octave from 10,000 to 20,000 Hz was about 5 dB higher in level than any other portion of the audio spectrum.

The close-miked woofer response reached its maximum at 130 Hz, falling off at 18 dB per octave at lower frequencies and at 6 dB per octave at higher frequencies. The effective crossover from the woofer’s cone to its port radiation was at 80 Hz. When we spliced the woofer curve to the room curve, the resulting composite frequency-response plot had a swaybacked shape. There were approximately equal maximum outputs at 130 and 15,000 Hz and a 9-dB dip to the minimum at 1,300 Hz.

The quasi-anechoic response measurements made with our IQS FFT analyzer confirmed most of the room measurements, showing a moderate number of irregularities and an overall variation of about ± 5 dB from below 100 Hz to almost 20.000 Hz. The horizontal dispersion was good, the response curves on-axis and 45 degrees off-axis diverging only above 10,000 Hz. The group-delay variation was only ±0.2 millisecond from 500 to 18.000 Hz.

The system’s impedance reached a minimum of 4.5 ohms at 220 Hz and maxima of about 18 ohms at 36, 110, and 2,300 Hz. The 6-ohm rating appeared to be reasonable for the variations we measured. The sensitivity was somewhat less than rated, a rather low 83-dB SPL at 1 meter with a 2.83-volt input of pink noise.

Measured with a 6.3-volt input (equivalent to a 90-dB midrange SPL), the bass distortion was high, as would be expected from such a small woofer. From 4.5 percent at 100 Hz, distortion increased rapidly to 15 percent at 70 Hz and 22 percent at 40 Hz. At a reduced input of 2.83 volts, the distortion rise was less steep, increasing from 1.5 percent at 100 Hz to 10 percent at 40 Hz. In our pulse-power tests, the woofer rattled at a 100-Hz input of 168 watts into its 12-ohm impedance, and the amplifier clipped at 650 watts into 11 ohms at 1,000 Hz. At 10,000 Hz, the amplifier clipped at 1,040 watts into the tweeter’s 7.5-ohm impedance.

Comments

Having listened to the Pinnacle PN5+ speakers for some time before making any measurements, we found it difficult to reconcile our test data with what we had heard.

At reasonable volume levels, the PN5 + simply did not sound like a minispeaker. It had a smooth spectral balance, without boom or sizzle, and certainly without a seriously depressed midrange. As might be expected, the speakers could not be played at very high levels without sounding strained, but at lower levels their sound character was amazingly close to that of our reference speakers, which cost nearly twenty times as much!

I am not saying that the PN5+’s sounded like our reference speakers, since they could not produce really low bass (below 50 Hz) at any usable level. But their octave-to-octave energy balance from, say, 100 to 10,000 Hz was closer to the balance of our reference speakers than has been that of many other speakers we have tested over the years.

We also placed the PN5+ speakers on a low shelf a couple of inches from the wall, with very similar results. Their imaging and general sense of space were best in a freestanding position, but they were relatively insensitive to room placement. Wherever situated, they also conveyed an impression of bass response an octave or so lower than they can really deliver. This effect may well have been a benefit of the relatively high harmonic distortion from the small woofer in the range below 100 Hz. Distortion consisting mostly of second and third harmonics can give an artificial sense of lower bass when only the harmonics, not the fundamentals, are present (in reasonable amounts).

In any event, no one would choose these speakers as part of a primary music system with the expectation that they could reproduce the full audible spectrum, though I imagine a pair would make fine satellite speakers along with a subwoofer. According to Pinnacle, “The . . . sound of the PN5+ is often mistaken for that of a much larger, more costly speaker,” and our experience confirmed that claim. Quite remarkable from a box displacing about one-sixth of a cubic foot!

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