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Help identifying some Heresy speakers

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I found speakers advertised on CL as Heresys (didn't say I, II or III), but the prior owner painted them black, put plastic corner guards on them and put a pair of handles on the side.  I might buy them if I can find out more about their origin.


The serial numbers are 158Y728 and 158Y746.  I found something about the code used and from interpreting that I think the 158 means first day (or first month) of the year 85.  


Or that might be completely wrong and it could be the codes used for speakers from '62 to '83 using the letter format.

 1962-1983 Letter format

A=62 F=67 K=72 R=77 X=82
B=63 G=68 L=73 S=78 Y=83
C=64 H=69 M=74 T=79
D=65 I=70 N=75 U=80
E=66 J=71 P=76 W=81


In that case could it mean the 158th day of 1983 (hence the Y)?


Anyone know what the serial number means?



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1983. Heresy # 157,728 and # 157,746



1. Based upon additional information related to the use of letters starting in 1955, the 1962-1983 coding has been modified to reflect that information.

2. The serial number was written on the paper serial tags and die stamped on the back edge of the top panel (inside top portion in LS). This practice was not used on later "MDF" cabinets for Heresy's, etc. Serial numbers can often be found written in pencil on the inside of some of the Heritage series, most notably Klipschorn's and Belle's.

3. While the 1946-1961 manufacturing dates can only be found in the Engineering Library in Indianapolis, accurate specific dates for the day of manufacture may also be found by close examination of the interior of the speaker cabinets. As an example there were often small inspection tags stapled inside the cabinets and penciled notations with dates inside the cabinets. An example of the production inspection stickers was the use of "PRIDE" stickers inside some models. These were used in the early through mid-1980's.

4. Additional letters stamped in the edges of Heritage series made from birch plywood, and on the poplar and ash "lumber core" as the substrate, were "USA" and/or the cabinet builder's and final sander's initial(s). For reasons of protecting their right to privacy, I have not identified the names of those superb craftsmen (and women).


1946-1947 ### 001-020 (ending at #20)

1. 1946 & 1947 Klipschorn serials #002 - #013 were made by Baldwin Piano.

2. Serial numbers #14-20 were made for purchasers in Paul Klipsch's "tin shack", before the move to the newly built factory. There are no Klipschorn's with a serial number between 21 and 120.


1948-1961 #### (starting #0121)

From 1948 though 1961, Klipschorn's had the serial number stamped into the tailboard, woofer access door, or inside the woofer chamber.

3. The number Klipschorns produced in 1948 is unknown; a total of 26 were made in 1949


1955-1983 ##letter#### 20Y1234

1. Letters that look like numbers (e.g. I, O, Q, V) were not used. "S" is frequently misread as a "5" and Y has been confused with an X on occasion.

2. July 29, 1955 was the last day for the four digit serials (i.e. 1811). After that the "number- letter-serial" system went into effect (2 August 1955). The first "number-letter-serial" speaker was produced on the 2nd of August 1955; that serial number was 1A812.

3. In the 1955-1983 serial method the first, or prefix "digit(s)" before the year letter represents the sequence of production for each 1000 units. The suffix digits after the letter code will always be three digits - 001 through 999. For example 1C999 would be the 999th unit built, and 2C999 would be the 1999th built in 1965 C = 1965).

4. These digits before & after the year code apply only to that type of speaker.

5. The year code letter only identifies the year in which that number occurred.

6. As an example, if you have a pair of Klipschorn's and one of the serial numbers is 15T252, then by 1979 there had been 14,151 Klipschorn's made (Klipschorn's made in 1946-1947 were serial numbered from 1 to 20, and in 1948 started with #121, skipping #21 through #120).

7. For a pair of 1979 La Scala's, with serial number 22T403, it means there were 21,403 La Scala's made to that point.

8. Another example: A pair of Belles from 1979 has the serial number 3T242 and 243. This means that in 1979 these Klipsch Belles, the 2,242nd & 2,243rd, were made.


A = 1955-63* F = 1968 L = 1973 S = 1978

B = 1963-64* G = 1969 M = 1974 T = 1979

C = 1965 H = 1970 N = 1975 U = 1980

D = 1966 J = 1971 P = 1976 W = 1981

E = 1967 K = 1972 R = 1977 X = 1982

Y = 1983

* Cornwall's & La Scala's used "A" 1963 and "B" for 1964; the first Cornwall to use a letter code was 3A09, shipped in August of 1963.


1984-1989 YYWW#### 89261234

1. YY = year (e.g. 89 = 1989)

2. WW = week of the year (e.g. 26= last week in June)

3. The WW can also be a single digit for weeks 01 through 09; e.g. 877#### (mid February 1987)

4. In the early-mid 80's (generally starting in 1984), Klipschorn's had two serial numbers assigned to each speaker; one for the bass bin and one for the top section. The bass bin had an "L/F" at the end of the "type code" (see further below) and the top section had an "H/F" at the end of the type code.

5. This coding was is used on Chorus, Forte & Academy

Edited by mungkiman

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Heresy I




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.

Edited by mungkiman

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If they have the K-701 composite horn and K-53-K midrange driver, some would call them Heresy 1.5

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Thanks for the info.  This would mean that they were among the last Heresys made before the Heresy II came out.  I think I'll take a flyer and buy them.  I won't be able to know about the mid driver until I get them.

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Thanks for the info.  This would mean that they were among the last Heresys made before the Heresy II came out.  I think I'll take a flyer and buy them.  I won't be able to know about the mid driver until I get them.

the heresy 11's came out in late 1985 and the Y stands for 1983 in the ones your talking about

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