KLIPSCHORN LOUDSPEAKER

Manufacturer's Specifications System Type: Three-way horn-loaded, for corner placement. Drivers: 15-inch woofer, 2-inch midrange, and 1-inch tweeter. Frequency Range: 35 Hz to 17 kHz, dB. Sensitivity: 104 dB SPL at 1 meter for 1 watt input. Crossover Frequencies: 400 Hz and 6 kHz. Impedance: 8 ohms nominal, 4 ohms minimum. Recommended Amplifier Power: 20 watts minimum. Dimensions: 52 in. H x 31 in. W x 29 in. D (132 cm x 79 cm x 74 cm). Weight: 165 Ibs. (74.9 kg). Price: $1.499 each. Company Address: Klipsch, P.O. Box 688, Hope, Ark. 71801. For literature, circle No. 90
A legitimate Golden Oldie, now well into its fourth decade, the Klipschorn, along with its designer, Paul Klipsch, are true legends in the field of high-fidelity sound. Nothing I could write would do complete justice to its description, so let me quote the words of a dear friend, long past, Howard Tremaine, who many years ago described the Klipschorn in his Audio Cyclopedia (Howard W. Sams & Co., 1959) as follows: "The enclosure is a low-frequency horn so folded that it may be placed in a room corner to utilize reflections from the floor and walls to improve the impedance match at the mouth of the horn and thus increase the response at low frequencies." Continuing Tremaine's description: "One advantage of using a horn at the low frequencies, compared to the use of a direct radiator mounted in a flat baffle, is that the horn efficiency is 10 to 50 times greater; and because of the acoustic loading, a given acoustic power may be generated with considerablv less excursion of the louds~eaker diaphragm, thus reducing harmonic and intermodulation distortion." The low-frequency horn is substantially exponential in its expansion rate and thus would have an acoustic path length of about 8 feet if unfolded. This horn is intended to cover the lower four octaves of the audible range, from about 32 Hz to 400 Hz, where the folded horn is crossed over to a midrange "squawker" that carries the range up to 6 kHz, where the response passes to a tweeter. Midrange and tweeter are also horn loudspeakers, and both are mounted behind a grille assembly placed on top of the folded bass horn. The system is heavy. Oh, my, it is heavy. And it is big. But there is a reason for its size, and the reason is acoustic efficiency. Ten watts of music into this speaker will part your hair if you stand too close. One is soon reminded of the old horsepower adage: There's no substitute for cubic inches. Because the Klipschorn uses the corner and floor of the
patient editor should ever be forced to wait for a review) and then decided to resort to computer software and physics. b r s must be placed in the corners for best reproduction. If Figure 4 shows the measured free-field amplitude of e listening room does not have available corners or is very in my opinion, purchase of a Klipschorn system sound pressure as a function of frequency for a constant t be contemplated. It simply needs room to sing. drive voltage corresponding to 1 average watt into 4 ohms. e of its bulk, the Klipschorn comes in two pieces, The plot is corrected for an equivalent distance of 1 meter horn and the midrangeltweeter unit. The instruc- on axis relative to the front of the enclosure, although the clear, and no difficulty should be experienced in actual measuring distance is 3% meters. Figure 5, the free-field phase response, is plotted in two or hookup. There are no controls or switches, and onnection is made to two well-marked terminals sections. The midrange phase plot is corrected for a time delay of 11,980 FS, and the tweeter phase plot is corrected !on the rear of the enclosure. Because of the extreme efficiency of these speakers, you for a time delay of 10,308 FS. The 1.672-mS time' difference 'will not need a large power amplifier; 100 watts IS more than is caused by the physical offset between. the tweeter and adequate, and most listening will probably be done at levels midrange. The free-field sound is reasonably uniform from a lower below 5 watts. But the amplifier must be of high quality and have low noise. If it should have any hiss or hum, you will cutoff of around 38 Hz to an upper cutoff of around 18 kHz. The irregularities both above and below the acoustic crosshear it with these speakers. over at 6 kHz are caused by internal acoustic reflections from the drivers, horns, and grille assembly. The system is Measurements The measured magnitude of impedance which the Klip- incredibly sensitive, producing well over 98 dB per watt at 1 schorn presents to an amplifier is shown in Fig. 1. The lowest meter. It is easy to see why the suggested amplifier rating is value within the audio range is 4.5 ohms and occurs at 55 only 20 watts per channel. This system really will give the Hz, while the highest value is almost 10 times that amount, rated 104 dB SPL at a distance of 4 feet into a room. One 42.3 ohms, at 2,155 Hz. The peak lies above the limits of the watt into a Klipschorn will produce the sound level that 30 plot of Fig. 1, which is scajed to show the details of imped- watts produces with many smaller loudspeakers. If one were to use the full 100 watts of drive for which the Klipsch ance throughout most of the audio range. From the standpoint of amplifier drive requirements, a is rated, the sound level would soar to migraine limits. worst-case frequency appears to be around 5,200 Hz, Dropping a stylus on a record might break a lease, as well where the phase angle lags by 70, although the magnitude as some crockery. of impedance is 11 ohms. This can be seen in the complex The low-frequency response has some interesting surimpedance plot of Fig. 2. The many pig-tails in this plot are prises. A measured low-frequency roll-off below 38 Hz does due to local impedance resonances. With the exception of not seem impressive; there are many smaller enclosures the major bass resonance at 37 Hz, the majority of pig-tails which measure as well. But something happens when this are probably caused by acoustic reflections which occur in low frequency comes as a large-area wavefront whose.the bass, midrange, and tweeter horns. Figure 3 shows the boundaries are the walls of the room, rather than as a complex impedance rescaled to show the midrange imped- wavefront expanding spherically from a position in front of a ance peak at 2,155 Hz. This peak is not a smooth loop, but wall. For one thing, the first impression one has is that the itself has several minor deviations in its peak range. low end is deficient, because the low-frequency rumbling Fortunately, from the standpoint of amplifier drive require- and grumbling of most systems, which many people associate with low-end reproduction, just isn't there. However, as one begins to really listen to the music and sound, one

med at such distance, and I have chosen 3% meters, this is the distance at which I listened to these units.

Fig. 1-Magnitude

impedance.

FI;EQL>EF;S't

A~DIO/NOVEMBER986 i
The Klipschdrn is heavy! And big! But there is a reason-acoustic efficiency. Just watts will. part. your hair at close range.
realizes that the deep bass is actually there and that i
ed ETC of the free-field response of Fig. 7 is shown as 8. This departs from our conventional review format, w
1 near the rear of the enclosure. Believe it or not, the

RESISTANCE

the midrange horn, whose compression driver lies
broad peak at 17.7 mS is the sound from the bass d which carries the frequencies below 300 Hz. Now con
Fig. 2-Complex Impedance; see also Fig. 3 for the range from 1 to 5 kHz.
several milliseconds later. Fortunately, the left and channels are symmetric in this sound, since it is caus the geometry of walls, ceiling and floor. In my earlier
heavily carpeted floor. There is another obvious item related to due this time to the geometry of mounting t
167 pS with a decay rate of about 9 dB per period. causes the irregularities in free-field sound around 6 which is evident in Fig. 4. Since this frequency coinc

RESISTCNCE - OHMS

Fig. 3-Complex impedance. Note the rescaling from Fig. 2.
Measured "free-field" using computer software, the K-horn is reasonably uniform from around 38 Hz t o upper cutoff at 18 kHz.
sure reflections occur after about 6 mS. The first sound from the woofer is not on this measurement since it arrives about 8.4 mS after the sound from the tweeter. What does it. mean? A loss of clarity for those sounds which contain significant energy around 6 kHz, such as higher register female vocals and piano, but clean transient sound for both mid-register and extreme upper-register instruments such as some horns and triangle. The 3-meter room response (which, for this speaker only. was actually measured at 3% meters) is shown in Fig. 9. 1
measured only the on-axis response, not only since this the recommended listening position, but also because a 3 off-axis response does not make much sense for a corn
of the spectrum is quite good. Only the time of arrival IJ

FREQLiENCY

Fig. 4--Free-field sound pressure level for a constant voltage drive corresponding to 1 average watt into 4 ohms.
polar energy response. Even if I had the services of King Kong to move the speaker. I would still need to rotate the, whole room, walls and all. However. I was able to verify, by selected close-up microphone measurements, that the horizontal and vertical polar energy response was essentially smooth within 15" of the normal listening position. This agreed with my earlier listening impressions; I was able to walk around the room, over a significant range, without. change in the level or tonal balance of the sound. Measured harmonic distortion for the frequencies of 41.2 Hz, 110 Hz, and 262 Hz is shown in Fig. 10. These frequencies correspond to the musical tones of E,, AP, and middle C, respectively. I chose middle C rather than A (440 Hz) , because the actual acoustic crossover from woofer to midrange is slightly above 250 Hz, and I wanted to measure the distortion for the same driver at all frequencies. Low bass (El) harmonic distortion progresses smoothly from a few tenths of a percent at 100 mW drive upward to near 10% at 60 average watts, with second harmonic slightly above third harmonic throughout the whole range. Mid-bass harmonic

FREQUENCY

Fig. 5-Free-field phase response at 3%meters. The midrange response is corrected for 11,980-pS time delay, while the tweeter response is corrected for 10,308-FS time delay.

AUDIOINOVEMBER

Because the listening room is part of the low-bass reproducing system, the K-horn requires a t least. four feet of side walls in the listening room.
Fig. G E T C of the Klipschorn including early reflections from the room.
Fig. 7-ETC of Fig. 6 minus the room reflections.

TWEETER

r MIDRANGE
timbre as the sound pressure rises to high levels. Th measurement also indicates that no discernible lateral sh of stereo image should occur with changes in drive The same exemplary performance is maintained second musical tone is added to an existing to means that stereo imaging should remain steady, instrumental wander caused by changes in musical ics throughout the useful intensity range of the reproducer. In short, the Klipsch stays together re of what happens in the music.
Use and Listening Tests A stereo Klipschorn reproducing system requires a with two good corners. Period! If your listening room not have left-channel and right-channel walls which out in an uninterrupted fashion for at least 1% meter their respective corners, then forget it. I am fortunate in that I have two such corners in

TlME - mS

Fig. &ETC of Fig. 7 with an expanded time scale and corrected for a 1-meter measurement position.
wall to rear wall. The reason for all this fussiness bec evident when you begin to listen to the system: The list sures 12.88% and has picked up a phase modulation of 6" room is part of the low-bass reproducing system. peak-to-peak on middle C, in addition to about 8% peak-toAs mentioned above, the first impression one has is th peak amplitude modulation. The result of the crescendo test is also impressively good. In this test, the ratio of sound pressure level to drive power is measured for selected musical tones. Perfection occurs when the SPL precisely tracks the drive power. In the case of the Klipsch, the tone of El (41.2 Hz) slowly drops in relative SPL with drive power such that a 63-watt test level is 0.5 dB below the level which represents perfection, relative to a starting power level of 100 mW. The tone of A2 (high-quality condenser Hz) drops in a similar manner by 1.2 dB from a startin a location where I coul reference,of 100 mW to a 63-watt maximum test level, whil while viewing the Sam middle C slowly drops by 0.7 dB over the same range. Th net effect will be an extremely mild softening of instrumenta

AUDIOINOVEMBER 1

Overall, the Klipschorn
demands a great deal of respect as an accurate reproducer, surviving modern recording and electronic technology well.

POWER - W A T T S

Fig. 9-Three-meter room response; see text.

Fig. 11-IM of middle C (262 Hz) caused by mixing with El (41.2 Hz) at equal levels. Fig. 10Harmonic distortion for the test tones of E, or 41.2 Hz, A2 or 110 Hz, and C4 (middle C) or 262 Hz.
Orchestral balance is also quite accurate; horns and strings stay put and are accurately placed on the st stage. Brass is brilliant and accurate on this system, these instruments are so well placed that I felt I could directly at each instrument. On the down side, to my vocals, particularly female ones, seemed strident, could not get an accurate sonic illusion of piano, w The usable listening area extends over much of the listening room, and one can move about freely without losing stereo balance as long as the speakers are at least 3 meters from your listening location. It takes a pretty good-sized. room to get a good sound from the Klipsch system; a small,. room will probably produce sonic disappointment. This is not a speaker system you haul to a dormitory. The Klipsch system has two additional sonic characteristics which warrant discussion. First, it is one of the few sound-reproducing systems which sound natural when on walks into an adjacent room. This is an interesting subjec tive illusion, one which I cannot explain. However, we hav all had the experience of hearing a live musical instrument being played in an adjacent room; it still sounds natural we can readily tell that it is not artificially reproduced piano recordings with which I had had trouble while i listening room actually sounded "live in the next room" I was in a room adjacent to the listening area. While o may disagree, that is the illusion I experience. The second characteristic is'the maintenance of tim balance even when the sound is reproduced at substant1 lower sound levels than would be normal for a given piece material. Again, this is my personal opinion, and others m disagree. Overall, the Klipschorn is a Golden Oldie that surviv modern recording and electronic technology very well. A jagged in the midrange, it still demands a great deal Richard C. HeYS resDect as an accurate reDroducer.
and listening, then walking inside and listening to compare the reproduced sound with reality. I could also switch between the K-horns and a pair of excellent speakers whose bass could shake the house on pipe organ; they made the K-horns sound thin by comparison. Then a funny thing happened. The sound of a slammed car door sounded like a slammed car door on the K-horns, but sounded like muffled "whumps" on the "wider range" system. The same with helicopter fly-overs (quite frequent where I used to live) and with the sound of distant traffic. I never forgot that experiment nor its ear-opening ramifications with regard to sonic accuracy versus measurement. Quite true, I have listened to many excellent subwoofers that could shake the walls at 10 Hz, while the K-horn produced little sound pressure even an octave above that frequency. But in my per-