Klipsch KG4 Floor standing speakers
The Klipsch kg4 is a two-way floor-standing speaker system featuring unusually high efficiency (for a home speaker) combined with an extended, smooth frequency response. Its handsomely finished oak-veneer enclosure is 24-1/4 inches high, 15-3/4 inches wide, and 10-3/4 inches deep, and the system weighs 45 pounds. The dark brown, wood-framed cloth grille is retained by strong plastic fasteners and requires considerable effort for removal.
The front panel of the kg4 contains two white plastic-cone woofers, one above the other, with a nominal diameter of 8 inches. At the top of the panel is a horn-loaded tweeter-a device unusual in home speakers-with mouth dimensions of 8-1/2 x 3 inches. The crossover frequency is 1,800 Hz. On the rear panel of the enclosure is a 12-inch passive cone radiator that extends the low-frequency response limits of the smaller bass drivers. The binding-post terminals, recessed into the rear of the cabinet, accept banana plugs, including dual plugs on 3/4-inch centers, as well as wires. There are no external controls or adjustments. Price: $520 per pair.
Lab Tests
Since no specific suggestions for room placement were supplied with our samples of the Klipsch kg4, we tried them first about 1 foot from the rear wall and moved them through a range sufficient to establish that the speaker-to-wall spacing was not at all critical. The 1-foot distance was used for our room-response measurements. Our FFT quasi-anechoic measurements were made with the speaker standing in the clear, as far as possible from any walls.
Bass response was measured separately for the driven woofers and the passive cone. For these tests we used close microphone spacing and combined the two curves with allowance for the radiating areas of the different sources. The bass curve was spliced to the smoothed room-response curve (made with a sweeping warble-tone sine wave), which had been corrected above 10.000 Hz for the known absorption characteristics of the room. The resulting overall composite frequency-response curve confirmed our earlier subjective impressions, and we consider it to be a reasonably valid description of the performance of this speaker in a listening room of average size and acoustic properties.
The overall response thus derived was very flat, ±3.5 dB from 30 to 20.000 Hz, making the kg4 rank very high among the speakers we have tested in respect to the range and smoothness of its frequency response. There were several minor ripples in the curve between 1,000 and 6,000 Hz, but their peak-to-peak amplitude did not exceed 5 dB. In general, the output showed a broad maximum between 50 and 400 Hz, and on average it was slightly elevated in the range from 5.000 to 7.000 Hz as well as above 13.000 Hz. The low-bass output decreased at about 6 dB per octave below 60 Hz (the effective crossover frequency from the driven cones to the passive radiator) and was down only 10 dB at 20 Hz.
The sensitivity of the kg4 measured a high 93 dB when it was driven by 2.83 volts of noise (equivalent to 1 watt into 8 ohms) in an octave band centered at 1,000 Hz. The kg4 is about 6 dB more sensitive than most speakers of its size that we have tested, which means that it needs only a quarter as much input power to deliver the same sound-pressure level (SPL).
The minimum measured impedance of the kg4 was 4 ohms between 150 and 300 Hz, with maximum readings of 25 ohms at 67 Hz and 38 ohms at 2,900 Hz. The average impedance over the audio range was from 6 to 7 ohms, making the speaker's nominal 4-ohm rating reasonable as well as consistent with industry practice. We measured the bass distortion at a constant drive level of 2 volts, the voltage needed to produce a 90-dB SPL at 1,000 Hz. Close-miked readings were taken separately at the driven cones and the passive cone at several frequencies from 100 to 20 Hz. To calculate the distortion we used readings at a driven cone above 60 Hz and the passive-cone readings in the range below that frequency, where its output was dominant. The Klipsch kg4 had some of the lowest overall bass distortion we have yet measured: 0.2 to 0.4 percent from 100 to 80 Hz, about 2 percent down to 40 Hz, and only 5 percent at 20 Hz.
The FFT measurements showed that the group delay of the kg4 was within a 0.8-millisecond range from 3,000 to 20,000 Hz. Our measurements of the horizontal polar response showed little difference between the on-axis and 45-degree off-axis response other than some apparent cancellations in the vicinity of 11,000 Hz.
The power-handling ability of the speaker was measured with short tone bursts (2 cycles on, 128 cycles off) at frequencies of 100, 1,000, and 10.000 Hz. The electrical drive waveform and the acoustic waveform, sensed by a microphone in front of the speaker, were displayed simultaneously on an oscilloscope, and the drive level was increased until waveform distortion became visible on one of the signals. At 100 Hz the speaker absorbed 200 watts (based on its 6-ohm impedance at that frequency) before its output distorted visibly. At 1,000 Hz the maximum power was 80 watts. At 10.000 Hz the acoustic output burst became clipped on one side at rather low levels (7 to 12 watts, depending on how much clipping was deemed acceptable), while the other peak of the signal did not clip until the power reached about 35 or 40 watts. We do not feel that any conclusive judgment about the tweeter's power-handling ability can be drawn from this test.
Comments
In our room the Klipsch kg4 sounded very much the way its frequency-response measurements would suggest: smooth and clean with a slight but definite emphasis (warmth, rather than heaviness) in the upper bass. The sound was fully integrated, giving no clue to the number or types of drivers. In fact, it was not until after we pried off the grille that we realized it had a horn tweeter. So much for the so-called "horn sound"!
The high sensitivity of this speaker was unmistakable in A/B comparisons with other speakers. Few speakers intended for home use can match the combination of high sensitivity and excellent overall frequency response of the kg4. In itself, this says nothing about the sonic properties of the speaker, but since its high sensitivity, compared with typical box speakers in its price and size class, has the effect of quadrupling the available amplifier power, this factor cannot be ignored. Moreover, the measured bass distortion of the kg4 is exceptionally low, which is hardly to be disregarded, even though whether a modern loudspeaker has a low level or a moderate level of bass distortion is usually not immediately apparent to the ear.
No two speakers sound alike, and the Klipsch kg4 did not sound exactly like our regular reference speakers or any others to which we compared them. However, it was plain from the start that the kg4 is a truly excellent speaker that we could live with and enjoy without going through a "sonic familiarization" process. It is also among the more attractive box-type speakers we have seen and therefore offers an unusual combination of desirable aesthetic and electroacoustical qualities at an equally attractive price.
