Klipsch Forte III--Pleasantly Surprised

From Klipsch : 
 

X. HERITAGE PRODUCTION NOTES & TIME LINES:

1. HERESY:

• 1957: The Heresy is introduced as a center channel for the Klipschorn. It is the first Klipsch speaker that does not require corner placement. This model utilized the K-1000 midrange horn. These are rare, and one example in the Museum in Hope is the rarest of all the Klipsch Heritage speakers.
• 1957 - 1959: Both 8" and 12" woofer versions were produced during this period.
• 1967 - The H-700 is introduced in the now familiar format using a 12" K-22 woofer (There were several variants used E, EF, K) K-700 horn; K-55-V mid-range and the K-77 (T-35 type Alnico magnet) tweeter.
• From this date through the end of the model run in 1985, various networks were used: Type C, Type E and Type E-2. All were variations on the same design.
• 1972-1973: The Heresy's name is changed from H-700 to Heresy.
• 1983-1984: The K-24 woofer is substituted for the K-22, and during the last production of the Heresy-I, the midrange K-53/701 is substituted for the K-55/700.
• 1985: The Heresy II is introduced using a mid-range and tweeter driver set that, for the first time since the introduction of the H-700 differed from that of the Klipschorn. Component designations were: Woofer K-24-K, Midrange K-701 horn and K-52 driver (the mid range assembly was also stamped K-53 on the driver). The tweeter is K-75-K horn and K-76 driver. This was the first Heresy model to discontinue the use the traditional alpha numeric network designations (Type E-2). All of the drivers in the Heresy II were front mounted to reduce the diffraction effects caused by rear mounting and firing through the motor board.
• May 2001: Finish, grill and riser variant options are reduced from nearly 100 to 10.
• Sept 29, 2005: The Heresy III is introduced featuring increased sensitivity (3dB), Titanium mid-range and tweeter diaphragms, Tractrix tweeter horn and bi-wire inputs. Component designations are: Woofer K-28-E, Midrange K-53-Ti (K-701 horn and K-53-Ti driver), Tweeter K-107-Ti (K-79-T horn and K-100-Ti driver). Finish, grille and riser variations are further reduced from 10 to 3.
• May 2006: The Heresy III midrange compression driver is sourced to a new supplier and the network is revised to compensate for the change.
• 2008+: There have been a number of improvements produced, and Klipsch has transitioned the crossovers to a more modern design. For information on the recent changes, please go to the website (Klipsch.com) for product information.

2. CORNWALL:

• Oct 1959: The Cornwall is introduced as the world's second commercially produced center speaker. A speaker with higher output capability than the Heresy was needed when used in three speaker arrays between Klipschorn’s. Component designations: Woofer EV 15WK, Midrange K-1000 Horn and University SAHF Driver, Tweeter K-77
• Late 1959: Transition to the K-33-J Woofer (Jensen)
• 1959 - 1961: Sporadic transition to the K-55-V mid-range driver (Atlas)
• Jan 1963: The K-1000 diffraction type midrange horn was replaced with the exponential K-600 horn with a lower (600 Hz) cutoff.
• Sept 1967: Transition to the K-33-M. The records are not clear as to the origin of this driver but it is believed to be an Eminence driver with an Alnico magnet.
• Jan 1968: Transition to The K-33-P Woofer (CTS Paducah KY)
• 1974: The horizontal version of the Cornwall is discontinued
• 1974: K-56 mid-range driver (Electrovoice 1828) is used for a short period as a temporary replacement as the supply of K-55-V drivers was interrupted.
• 1975: Transition to The K-33-B Woofer (CTS Brownsville TX)
• 1975-1979: K-33-E and the K-33-B were used interchangeably.
• 1979: The Eminence K-33-E woofer is used exclusively
• June 1981: The updated B2 network, with steeper crossover slopes is phased in with no changes to the K-33-E, K-55-V and K-77-M drivers.
• Oct 1981 - March 1983: The transition between four different iterations of the midrange driver from revolving sources occurs during this period. The original K-55-V was changed to a K-51-V (10/19/81) This marked the first time in the Cornwall's history that it used a driver set that differed from that of the Klipschorn. The K-51-V was then changed to the K-55-G (essentially a ceramic magnet version of the Atlas Alnico K-55-V). The K-55-G was then changed to the Hepner built K-52-H and finally the Klipsch built K-52-K.
• Mar 1983: The B-3 network and the K-52 midrange driver starts to be used in this model.  Component designations were: Woofer Eminence K-33-E, Midrange K-57-K (K-600 Aluminum horn and K-52-K driver with the threaded snout), Tweeter K-77-M and B-3 network.
• Jan 1986: The Cornwall II is introduced featuring front mounted drivers to reduce baffle induced diffraction effects. Component designations were: Woofer Eminence K-34-E (K-33-E with a dressy pad ring), Midrange K-57-K (K-601 plastic horn and K-52-K driver), Tweeter K-79-K (K-75-K horn and K-79 driver) and CW II network.
• 1990: The Cornwall II is discontinued
• Mar 2006: The Cornwall III is introduced marking the end of the Cornwall's 15 year absence from the market. This version utilizes the Klipschorn woofer, the horn and driver set from the Heresy III (featuring Titanium diaphragms and a Tractrix® tweeter horn) and bi-wire inputs. Component designations are: Woofer K-33-E, Midrange K-53-Ti (K-701 horn and K-53-Ti driver), Tweeter K-107-Ti (K-79-T horn and K-100-Ti driver).
• 2008+: There have been a number of newer models produced, and Klipsch has transitioned the crossovers to a more modern design. For information on the recent changes, please go to the website (Klipsch.com) for product information.

3. LASCALA:

• 1963: The La Scala is designed as a portable version of the Klipschorn to be used as a P.A. system for Winthrop Rockefeller's Arkansas gubernatorial campaign. Component designations were: Woofer K-33-J (Jensen), Midrange K-400 horn and K-55-V driver (Atlas), Tweeter K-77 (Electrovoice).
• 1966: The designation for the Type 1RC crossover network was changed to Type A.
• Sept 1967: Transition to the K-33-M. The records are not clear as to the origin of this driver but it is believed to be an Eminence driver with an Alnico magnet.
• Jan 1968: Transition to The K-33-P Woofer (CTS Paducah KY)
• 1971: The Type AA crossover network was introduced featuring Sneer diode tweeter protection.
• 1974: K-56 mid-range driver (Electrovoice 1828) is used for a short period as a temporary replacement as the supply of K-55-V drivers was interrupted.
• 1975: Transition to The K-33-B Woofer (CTS Brownsville TX)
• 1975? - 1979: K-33-E (Eminence) and the K-33-B were used interchangeably.
• 1979: The Eminence K-33-E woofer is used exclusively.
• 1983: The Type AL crossover network was introduced incorporating steeper filter slopes for enhanced tweeter protection and smoother response in the crossover regions.
• 1983: The Type AL-2 network was introduced to accommodate the new K-55-M mid-range driver. This Electrovoice sourced driver was essentially the same as the previous K-55-V with a smoother response.
• 1987: The aluminum K-400 horn was replaced with the K-401 structural foam horn resulting in slightly improved distortion figures.
• 1989: The AL-3 network was introduced to correct for a shift in the output of the K-55-M mid-range driver.
• 2000: Electrovoice ceases production of the K-77-M and K-55-M tweeter and mid-range drivers. The search for replacement drivers and the acquisition of the EV tooling is sought. Very limited production of a few pairs occurs at the end of 2000 and the early months of 2001 using existing part stocks
• May 2001: The Atlas PD-5VH (Current version of the previous K-55-V) is modified slightly and christened the K-55-X. The various components of the K-77-M tweeter are either retooled or sourced from the new owners of the tooling and assembled by a third party. This variant of the tweeter is designated the K-77-F. An entirely new network (AL-4) was created to accommodate these driver changes. Fusing is eliminated in favor of a polyswitch for tweeter protection. The tweeter on the La Scala was flush mounted for the first time using "Z" brackets. A metal input panel with binding posts in a bi-wire configuration replaced the traditional screw type barrier block.
• Dec 2005: The La Scala II debuted as the first "finished" version of this model featuring a two piece veneered cabinet utilizing 1" MDF instead of the traditional 3/4" plywood. The AL-5 network was introduced to compensate for the improvement in low frequency response resulting from the change in cabinet construction. The HF and LF cabinets stacked together using thick rubber isolating spacers. Finish variants were reduced from 6 to 3.
• April 2006: The horn portion of the K-77-F tweeter was re-tooled to include a recessed flange eliminating the need for the separate "Z" bracket and attachment rivets, the new designation is the K-77-D. This also allowed the updating of pre-Z bracket La Scala’s (prior to May 2001) to flush tweeter status without motor board modification.
• 2008+: There have been a number of new versions produced, and Klipsch has transitioned the crossovers to a more modern design. For information on the recent changes, please go to the website (Klipsch.com) for product information.

4. BELLE KLIPSCH:

• 1971: Belle Klipsch was introduced as a more elegant or finished version of the La Scala. Component designations were: Woofer K-33-P (CTS, Paducah KY), Midrange K-500 horn and K-55-V driver (Atlas), Tweeter K-77 (Electrovoice).
• July 1971: The Type AA crossover network was introduced featuring Zener diode tweeter protection.
• 1974: K-56 mid-range driver (Electrovoice 1828) is used for a short period as a temporary replacement as the supply of K-55-V drivers was interrupted.
• 1975: Transition to The K-33-B Woofer (CTS Brownsville TX)
• 1975? - 1979: K-33-E (Eminence) and the K-33-B were used interchangeably.
• 1979: The Eminence K-33-E woofer is used exclusively
• Feb 1983: The Type-AB crossover network was introduced incorporating steeper filter slopes for enhanced tweeter protection and smoother response in the crossover regions.
• Oct 1983: The Type AB-2 network was introduced to accommodate the new K-55-M mid-range driver. This Electrovoice sourced driver was essentially the same as the previous K-55-V with a smoother response.
• 2000: Electrovoice ceases production of the K-77-M and K-55-M tweeter and mid-range drivers. The search for replacement drivers and the acquisition of the EV tooling is sought. Very limited production of a few pairs occurs at the end of 2000 and the early months of 2001 using existing part stocks
• May 2001: The Atlas PD-5VH (Current version of the previous K-55-V) is modified slightly and christened the K-55-X. The various components of the K-77-M tweeter are either retooled or sourced from the new owners of the tooling and assembled by a third party. This variant of the tweeter is designated the K-77-F. An entirely new network (AB-3) was created to accommodate these driver changes. Fusing is eliminated in favor of a polyswitch for tweeter protection. A metal input panel with binding posts in a bi-wire configuration replaced the traditional screw type barrier block.
• Late 2005 - Early 2006: The Belle Klipsch is phased out of production as parts are used up.

6. KLIPSCHORN:

• 1930: While working In Chile, S.A. PWK was an amateur radio enthusiast. Comparing various types of radio speakers, he recognized the superior efficiency of horns.
• 1933: Back in the U.S. at Stanford University, PWK made note of a classmates comment that "speakers sound better in a corner".
• 1934: Still at Stanford, PWK read the Symposium on Auditory Perspective by Bell Telephone Laboratories.
• 1939-41: The above mentioned facts were blended into a design philosophy. PWK drew pictures and built paper models that were to become the "Klipschorn".
• Feb 1940: Paul Klipsch applies for a patent on his first prototype cornerhorn, the X-1.  It was during patent "negotiations" that he first learned of prior art cornerhorns. There were several such designs.
• 1941: While stationed at the Aberdeen Proving Grounds, PWK reviewed and corrected his first manuscript on corner horns. Note: A second design was prototyped as X-2, but was destroyed by termites before meaningful measurements could be made.
• May 1942: The first successful prototype (X-3) was built in Paul Klipsch's garage using only hand tools. This basic corner woofer has changed little over the years. This was serial number 1.
• Oct 1942: Paul Klipsch applied for a patent on X3.
• Feb 1943: Paul received a patent on his first (unsuccessful) prototype, the X-1.
• April 1945: A patent was granted for the third prototype (X3) which was to become the Klipschorn.
• June 1945: Another patent was applied for describing Paul's second high frequency horn (X-5). This later became the K-5-H horn.
• 1946: Klipsch and Associates was incorporated.
• Early 1947: The first production run of 12 units, serial numbers 2-13 were built to Paul's specifications by the Baldwin Piano & Organ Company of Cincinnati Ohio.  The high frequency driver in these was the WE713A. At least one of the woofers was a JBL.
• Late 1947 - Early 1948: Seven more serial numbers 14-20 were built by hand in a local cabinet shop. Paul Klipsch recalled that no more than two were alike. It was during these "experiments" that the LF horn's "sinus" cavities were added to the woofer's back air chamber to maximize acoustic capacitance. Component Designations: High frequency Western Electric 713A, Woofer unknown.
• June 1948: The first Klipschorn to be built in the first actual Klipsch factory was S/N 121. The building was formerly the telephone exchange building for the Southwest Proving Grounds and is currently the Klipsch Museum of Audio History. Component Designations: The early production logs (1949) first make reference to the use of the Jensen P-15-LL woofer. The production log makes reference to a total of 26 Klipschorn’s built this year.
• 1949: The Stephens P52LX2 becomes the primary woofer. This driver is used through August of 1953 when the transition to the Stephens 103LX2 was made. The Stephens P15 High frequency driver starts appearing in the logbook.
• Aug 1950: The Electrovoice EV 15WK woofer is first referenced in the production logs and is used interchangeably with both of the Stephens woofers and the early K-33-J woofers until March of 1961
• 1951: The University SAHF replaces the Stephens P15 as the primary high frequency driver.
• June 1951: The first three-way Klipschorn incorporated a Jensen RP203 tweeter. This tweeter came from the famous Jensen G-610 Triaxial 15" driver and required considerable negotiations with Jensen. It was not until mid-1952 that all Klipschorn’s were three-way. A two-way Klipschorn with response to 12Khz was generally adequate for program material up to that time. The University MID-T-4401 replaced the Jensen unit as the tweeter of choice later in 1951.
• July 1952: The original K-5-H high frequency horn of the patent was modified to become the K-5-J. This involved changing the vertical taper so that the dividers ("boats") could be removed. This resulted in a production cost savings, not an acoustical improvement.
• Sept 1952: A cardboard shipping container was used for the first time. Prior to this all Klipschorn’s® were shipped in wooden crates. The last wood crate was used on S/N 912 on June 13, 1955
• Aug 1953: The Stephens 103LX2 Woofer starts to be used
• 1955: K-500 / 5000 network phased out in favor of the 1 RC (Type A network)
• Nov 1957 - May 5, 1958: This was the transition period between the University 4401 tweeter and the Electrovoice Alnico magnet T-35 (K-77) which yielded substantially flat response to 17Khz
• Aug 1959: The first shipment of Electrovoice T-35 tweeters designated as K-77 is received. The K-77 is first used in S/N 1445 on Oct 15,1959
• Nov 1958: Driver polarities were first observed and made consistent. This practice was initiated due to marginal improvements noted during listening tests.
• Apr 1960: Transition to the K-33-J Woofer (Jensen) from the EV 15WK began. And University SAHF mid-range drivers started to be designated and labeled as K-55
• May - Sept 1961: This was the transition period between the 6" high woofer horn throat and the current 3" high throat. This boosted output in the 400 - 500 Hz range further smoothing the response. Multi-tapered wedges were also added to the woofer throat (opposite side of the motor board from the driver) to further improve the response in this region. The use of these wedges was soon abandoned but the smaller throat dimensions were retained and are in use today.
• Nov 1961: The Atlas K-55-V Alnico magnet mid-range driver is introduced. This driver was patterned after the famous Western Electric 555-W.
• 1963 - May 1964: The K-5-J mid-range horn was replaced with the K-400 resulting in a flatter overall spectral balance, particularly in both crossover regions.
• Oct. 24, 1966: The designation for the Type 1RC crossover network was changed to Type A.
• Sept 1967: Transition to the K-33-M.
• Jan 1968: Transition to The K-33-P Woofer (CTS Paducah KY)
• July 1971: The Type AA crossover network was introduced featuring Zener diode tweeter protection.
• 1975: Transition to The K-33-B Woofer (CTS Brownsville TX)
• 1975-1979: K-33-E (Eminence) and the K-33-B were used interchangeably. The records are not specific about the actual start date for the K-33-E but it is believed to be in the early to mid 1970's
• 1979: The Eminence K-33-E woofer is used exclusively
• Feb 1, 1983: The two piece Type-AK crossover network was introduced incorporating fusing and steeper filter slopes for enhanced tweeter protection and smoother response in the crossover regions. Heavy gauge (10 AWG) internal wiring was used throughout and binding posts replaced the traditional screw type barrier block as input terminals. The tweeter was flush mounted in the baffle using "Z" brackets. Rubber wall gaskets were added to the sides of the tailboard to improve the seal to less than perfect wall surfaces.
• Oct 1983: The Type AK-2 network was introduced to accommodate the new Ceramic Magnet K-55-M mid-range driver. This Electrovoice sourced driver was essentially the same as the previous K-55-V with a ceramic magnet and a smoother response
• Apr 1987: The "D" style decorator cabinet (no cosmetic panels or grilles) was discontinued.
• Nov 1987: The Aluminum K-400 horn was replaced with the K-401 structural foam horn resulting in slightly improved distortion figures.
• Oct 1989: The AK-3 network was introduced to correct for a shift in the output of the K-55-M mid-range driver.
• 1995: A limited edition of the Klipschorn is produced to mark the 50th anniversary of the company and the Klipschorn. A total of 150 pairs were offered in three different finishes but less than 50 pairs total were sold. The only changes to this model were cosmetic.
• Aug 1995: The "C" style cabinet (no intermediate collar or kick plate) was discontinued
• 2000: Electrovoice ceases production of the K-77-M and K-55-M tweeter and mid-range drivers. The search for replacement drivers and the acquisition of the EV tooling is sought. Very limited production of a few pairs occurs at the end of 2000 and the early months of 2001 using existing part stocks
• May 2001: The Atlas PD-5VH (Current version of the previous K-55-V) is modified slightly and christened the K-55-X. The various components of the K-77-M tweeter are either retooled or sourced from the new owners of the tooling and assembled by a third party. This variant of the tweeter is designated the K-77-F. An entirely new one piece network, located on the woofer door, (AK-4) was created to accommodate these driver changes. Fusing is eliminated in favor of a Polyswitch for tweeter protection and a trap circuit was added to tame the longstanding response peak in the middle of the woofer's pass band, resulting in an improved spectral balance. The number of variants available was reduced by the elimination of the Brown and Cane grille cloths and oil finishes.
• Dec 2005: The Type AK-5 network was introduced to compensate for the improvement in low frequency response resulting from the addition of a horizontal wall seal to the top of the low frequency cabinet. The style "B" cabinet was discontinued by the elimination of the inset "intermediate collar" and visible "woofer top" panel in favor of a 3/8" gap between the cabinets. The long standing angle brackets, hanger bolts and wing nuts used to attach the HF and LF cabinets together were replaced with thick rubber spacers, on the LF cabinet, indexed into recesses on the HF cabinet.
• April 2006: The horn portion of the K-77-F tweeter was re-tooled to include a recessed flange eliminating the need for the separate "Z" bracket and attachment rivets. This also allowed the updating of pre-Z bracket Klipschorn’s (prior to Feb 1,1983) to flush tweeter status without motor board modification. This variant was designated as the K-77-D
• April 2006: A special limited edition Klipschorn was produced to commemorate the 60th anniversary of the company and the speaker itself. Low frequency response was enhanced with the addition of rear low frequency horn panels. This eliminated the need for a tight fit into the corner and permitted toe-in and toe-out flexibility for the first time. Additional upgrades were made to the binding posts, internal wiring, and network component specifications. Aesthetic enhancements included a Lacewood veneer finish on the LF cabinet and a high gloss Black finish on the HF cabinet. The traditional wood kick plate was replaced with a machined and anodized Aluminum version containing a Silver finish PWK logo containing a real diamond. The rear of the HF cabinet was totally enclosed with finished panels featuring display windows for a commemorative numbered plaque and the HF network. 200 pairs were produced

2008+: There have been a number of “special editions” produced, and Klipsch has transitioned the crossovers to a more modern design. For information on the recent changes, please go to the website (Klipsch.com) for product information.