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An Afternoon With

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					                                                                    An Afternoon With

                                                           TheJoumal is pleased to publish another in this
                                                           series of interviews conducted by the AES
                                                           Los Angeles Section. These "Afternoon with ..."
                                                           encounters offer spontaneous conversational
                                                           portrayals of the careers and experiences of major
                                                           figures in audio history, followed by informal,
                                                           open-ended exchange with attending guests.
                                                             On May 4, 1980, Peter Sutheim moderated
                                                           this dialogue with Paul Klipsch. Mr. Klipsch,
                                                           born in 1904 in Elkhart, Indiana, has written papers
                                                           and holds patents in fields as diverse as geophysics,
                                                           acoustics, and firearms. He is the recipient of the
                                                           Audio Engineering Society Silver Medal (1978) for his
                                                           contributions to loudspeaker design and for the
                                                           measurement of distortion. In this excerpt from the
                                                           transcript, Mr. Klipsch offers a retrospective glimpse
                                                           of a profound, enduring, and distinctive audio career.


         utheim: Welcome to Paul              S: Thereby proving himself one of the          old telephone b u ~ l d ~ n g the Prov~ng
                                                                                                                       at
         Klipsch, president of Klipsch        first audiophiles.                             Ground, wh~chhad about 3000 square
         and Associates in Hope.                                                             feet of space. The basement was 12 feet
         Arkansas, manufacturers of           K: Yes, indeed. He had a TRF tuner                   so
                                                                                             h~gh, we had plenty of room to swlng
loudspeakers. Paul is,a Fellow of the         feeding an M I 4 Jensen loudspeaker in         an e~ght-foot   board around or feed ~t
AES and the IEEE. a member of the             a real baffle-strange beast in those           through a saw. Lloqd used to put thrngs
Acoustical Society of America and of          days. It sounded less like a radio than I      together, and I tned to be a salesman In
Tau Beta Pi and Sigma XI. and he is. list-    had. ever heard before. The symphony            1948, we produced 26 Kl~pschhorns.
ed in Wlo's Who it? Et1gincri.iizg. Paul is   was plkying that aftemobn. I had never         one every two weeks. In 1978, some-
well known for his classic folded horn        heard symphonic music, but I decided I         thrng over 2000 Khpsch horn4 were pro-
loudspeaker, for research in the acous-       liked it, and I put together some boards       duced, and that accounted for only ten
tics of loudspeaker radiation. for driver     and a 12-inch loudspeaker fed by a re-         percent of our total volume. We had
design, and for AES publications on           built radio.                                   many other products-the Heresy, for
modulation distortion in loudspeakers.           Much later, in Houston. my wife said.       example. u h ~ c htooh care of almost 50
He is an advocate.of comer placement          "You've been wanting to build loud-            percent of our dollar volume.
of loudspeakers and the use of a derived      speakers. Why don't you use the back
center channel for center fill.               room for a laboratory?"-words like a           S: Paul, how did the Heresy get its
   Paul, can you tell us how you became       red flag to a bull. and the beginning of       name?
interested in loudspeakers'?                  the end, I guess. I began with an X-l
                                              woofer and an X-2 squawker. World              K: Back in 1955, I wanted to revive the
Klipsch: I was a radio bug in 1920. My        War I1 came, Uncle Sam punched my              Bell Telephone Laboratory idea of a
first loudspeaker was a cardboard tube        ticket. and I went off to the Southwest        bridged center speaker. We were mak-
attached to a Brandes earphone. It didn't      Proving Ground.                               ing only corner loudspeakers, and we
work very well: it was years later that I        After the war. 1 rented a little tin shed   needed a noncomer speaker. I was sit-
found out about exponential horns. At         behind the laundry where I learned to          ting there drawing pictures on the backs
Stanford University one of my class-           mold parts vie no longer make-the X-5         of envelopes, and my then Philadelphia
mates invited me to his house one Sun-         and X-5 horns-and hired my first em-          sales rep, leaning over my shoulder,
day afternoon, and he said, "You want          ployee in 1948. One of us had to back         said, "That's not a comer speaker. Paul."
to hear the radio?" I said no, and he          out of that barn before the other could       I said no, and told him why. He shook
turned in on anyway.. .                        tum around. But we moved out to the           his head and said. "Paul. coming from

                                                                                                 J Audio Eng. Soc., Vcl. 40. No. 6, 1992 June
An Afternoon With Paul Klipsch

you that would be heresy." The lights                                                       K: If you want another dB or two of
came on and I said, "That's what we'll                                                      power output, I guess that is the way to
call it."                                                                                   go. But I still like passive crossovers.

S: The current preference for direct-radi-                                                  Q: Doesn't that c h o i c e also have
ator loudspeakers seems to have                                                             something to do with intermodulation
eclipsed the horn approach except where                                                     distortion?
very large sound pressures are needed.
I'm curious to know the reasons behind                                                      K: Yes, but with present amplifiers, I
that drift away from horns. Vented box-                                                     think overall intermodulation is going to
es have come back in the last five years                                                    be well below audibility as long as you
or so, but horns are not popular for                                                        stay below clipping. We do it. We don't
home use.                                                                                   offer biamplification as an option, but
                                                                                            the customer can buy our professional
K: True, they never will be. But the                                                        models without crossover networks and
trend is toward horns. not away from                                                        biamplify or triamplify as he chooses.
them. We are growing faster than many        The legendary "Heresy" loudspeaker,
of the other manufacturers. We are one       designed in 1955 by Paul Klipsch.              S: Could we talk for a moment about
of the few manufacturers of ham-loaded                                                      comer placement and your reasons for
treble systems.                               Doppler effect and was reminded that it       it? That recommendation puts you at
                                              might occur in loudspeakers. I made an        odds with the advice of other manufac-
S: I'd like to know more about frequen-       eccentric capstan for an old tape ma-         turers. The standard nowadays is up off
cy-modulation distortion, an aspect that      chine. It produced about one percent          the floor and away from the walls.
you seem to have pursued more or less         peak FM, and with a 2 kHz tone made
alone. Occasionally I talk to designers of    an odd sound. So I knew that FM could         K: Let's look at a comer speaker, l ~ o t
direct-radiator systems, and they tend to     produce audible effects. Beers and Belar      necessarily a comer design, just a speak-
pooh-pooh its importance. It's an acous-      had published their 1943 paper on FM          er in a comer. We have three mirror im-
tical phenomenon, not an electrical one,      distortion in loudspeakers, and their         ages, and if we rub out the walls and re-
and if it is indeed audible-in music,         comment was that the distortion was           place each image with a real speaker,
say-is there any way around it? Is horn       hard to describe.                             then as far as frequency response is con-
loading the only way to prevent it? I            One commentator said that it doesn't       cerned, there is no difference between
know it shows up in your measure-             exist. and even if it did, it wouldn't be     this array and the one vpeaker in the cor-
ments. but how audible is it*?                audible. I think it is hard to identify the   ner. For all the frequencies for which
                                              particular oddity of sound from a n           these are good walls, the efficiency dif-
K: Perhaps the first coaxial speaker was     .overloaded direct radiator a s d u e          ference between the comer speaker and
described in Elec.tronic,s, about 1938.       specifically to FM or AM distortion.          the four-speaker, no-wall array, will be
The objective was to make the woofer          But if you listen to a typical 12-inch di-    very small. I have found, as I've put it
and tweeter sounds coincident, as nearly     'tect r5diator at 100 d B SPL and com-         before, that bass response can be im-
as possible. We rigged one of our speak-      pare it with a good horn at the same          proved out to 10000 Hz. If you analyze
ers with a tweeter mounted in the hollow      output level but with a tenth of the          it this way, the comer begins to make
of the woofer cone. The tweeter was fed       power input, there is a recognizable          sense, and the folks opposed to it appear
a little over 9000 Hz, the woofer 50 Hz.      cleanness in the horn. In our measure-        to be a little prejudiced. If you don't be-
Someone said, "They are different dia-        ments, we find that AM distortion usu-        lieve the comer will help a box loud-
phragms; why should any modulation            ally exceeds FM in direct radiators. In       speaker, try it and see. You may have to
distortion show up'?" Think about it. The     horns, the FM distortion predominates,        tum the bass down to get it back in bal-
woofer sound pressure forces the tweet-       but it's an order of magnitude lower          ance. but you w ~ l l then find the distor-
er diaphragm, perhaps generating a little     than in direct radiators. I haven't found     tion down by about the same amount.
cross-modulation there. And the tweeter       out how to conduct a satisfactory listen-
sound diffracts around the edges of its       ing test to correlate listening impres-       Q: When you have two corner loud-
motor and bounces off the moving              sions with measurements. In other             speakers and the third speaker halfway
woofer: you could expect frequency            words, I cannot really answer your            between. ir it fed the sum of the two
modulation, and we found some, down           question. I do know that there is some        channels or the difference'?
27 dB. Next, we moved the tweeter to          sort of correlation. and people who lis-
its normal location, about a foot away        ten to good sound over horns recognize        K: The sum. In 1957 1published a paper
from the woofer center, and the distor-       the difference.                               where I said it made no difference. I
tion dropped 13 dB.                                                                         now have to disagree with the author.
   In the 1950s I was trying to fasten on    Question: What is your feeling about           The program material I had played up to
why the horn sounded better than the di-     multiamplification compared with pas-          that time didn't make a difference. But
rect radiator, and I knew about the          sive dividing networks?                        then I got a particular Nat King Cole

                                                                                               J. Audto Eng. Soc., Vol. 40. No. 6, 1992 June
four-track. On one side, the three-speak-      300, 600, 1000 watts input. It's output      is polar pattern. There are times when
er setup sounded just fine. Playing the        that matters. Bragging about input pow-      you want to project the sound tightly,
other side, the soloist in the center disap-   er is a little like bragging about how       but usually you want to cover a fairly
peared. Obviously, phases were differ-         much gasoline your car can bum. The          wide area. Last in importance is ampli-
ent on the two sides.                          second important characteristic is distor-   tude-frequency response.
                                               tion. The two go together; distortion (to
M: Any parting advice?                         a first approximation) is proportional to    John Prose: Ixt me introduce myself. I
                                               power input in any loudspeaker. It fol-      am chairman of the section, and I want
K: When you buy a loudspeaker, it is           lows that distortion is inversely propor-    to thank you very much for coming and
supposed to put out acoustic power.            tional to efficiency. Horn speakers are      for this particular opportunity we have
Speakers are advertised that will handle       inherently more efficient. And the third     had to be with you.

				
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