Since 1956, all Celestion chassis drivers have been stamped with a date code (2 numbers and 2 letters), denoting the exact date of manufacture. The codes are added on the production line and are placed on the speaker's housing leg or the magnet edge. The following lists provide an accurate record of the date codes used.

1956 - 1962

1956 A   January A
1957 B   February B
1958 C   March C
1959 D   April  D
1960 E   May E
1961 F   June F
1962 G   July G
      August  H
      September I
      October J
      November  K
      December L

The datecodes from 1956 to 1962 are written in the form: Day, Month, Year. For example: 15DE = 15th April 1960

1963 - 1967

1963 H   January A
1964 J   February B
1965 K   March C
1966 L   April  D
1967 M   May E
      June F
      July G
      August  H
      September J
      October K
      November  L
      December M

Note the loss of the 'I' from the month codes. The date codes from 1963 to 1967 are written in the form: Day, Month, Year. For example: 19MK = 19th December 1965

1968 - 1991

1968 A   January A
1969 B   February B
1970 C   March C
1971 D   April  D
1972 R   May E
1973 F   June F
1974 G   July G
1975 H   August  H
1976 J   September J
1977 K   October K
1978 L   November  L
1979 M   December M
1980 N      
1981 P      
1982 Q      
1983 R      
1984 S      
1985 T      
1986 U      
1987 V      
1988 W      
1989 X      
1990 Y      
1991 Z/A      

The date codes from 1968 to 1991 are written in the form: Month, Year, Day. For example: KH7 = 7th October 1975

1992 -

1992 B   January A
1992 V   February B
1993 D   March C
1995 E   April  D
1996 F   May E
1997 G   June F
1998 H   July G
1999 J   August  H
2000 K   September J
2001 L   October K
2002 M   November  L
2003 N   December M
2004 P      
2005 Q      

The date codes from 1992 are written in the form: Day, Month, Year. For example: 29EJ = 29th May 1999


JBL: JBL speakers were optional (at additional cost) for nearly all models from 1960 to about 1980. JBL D-series speakers had orange baskets and Fender by JBL labels in the 1970s. JBL D-series speakers can generally handle upwards of 60 watts each. A pair of JBL D-120Fs in a Twin Reverb are only seeing about 40-watts each (no sweat), but remember that no speaker likes to see square waveforms. So, driving the Twin with any amount of distortion lowers the power handling capacity of the speaker, which makes any speaker more susceptible to damage; even a high-wattage type like the JBL. 

Jensen: Jensen was the prevalent stock speaker in Fender amps from 1946 through about 1961. As the story goes, Leo Fender wanted Jensen to make some changes to speakers and either the speaker couldn't (price constraints?) or wouldn't do so. That's when ol' Leo switched over to Oxford as the standard speaker (though Jensens were still used from time to time). Just conjecture, but the lack of orders from Fender from 1962 - 65 must have hurt Jensen's pocketbook so they hit up the new owners of Fender (CBS) for some business. These Jensens wear brown and gold Fender by Jensen label and were put into Fender amps beginning in late 1965 through about mid-1967. Some amp geeks don't like the way these Fender label Jensens sound, but let your ears be your guide. I think they sound just spiffy.

Jensen Vibranto LI and MI series speakers (alnico magnets) and Jensen EM-series speakers (ceramic magnets), while excellent, were not used by Fender. I have included them here because I get a lot of questions about them. They are were often sold as replacements for blown speakers which is probably one reason why the ended up in more than a few Fenders. The Vibranto LI series speakers had a lifetime warranty and it seems that Jensen went out of the musical instrument speaker business just in time to avoid the claims. All speakers can and will fail eventually (just like the hard disk on your computer); remember that.

Jensen speaker models denote their approximate power handling capacity and magnet type. The actual power ratings have been published in several books so I'll discuss them in general terms here.
The R, S, and T suffixes denote a low power rating: good for Princetons and Champs, but the R is barely able to handle the power of a Deluxe. The Q and P suffixes denote a medium power rating. These are especially good for multi-speaker amps up to 40-watts since multiple speakers divide the amp's total output power between them. For this reason, the P10Q is the speaker to have in the 5F6-A Bassman. Note that it does not appear that Fender used the "P" rated speakers very often. The N and LL suffixes denote a high power rating, with "high power" being a relative term. The P12N, on a good day, can handle 20 watts. It's no wonder that 80-watt Twins easily shredded a pair of them. Note that Fender did not use the "L" rated speakers (but Ampeg and Leslie did).

Oxford: Oxford speakers codes work in a similar fashion, but it is the letter that denotes power handling. The higher the letter, the higher the power rating. I found an Oxford ad in a 1960s trade magazine with the peak power ratings of some speakers: K = 25 watts, L = 30 watts, M = 40 watts, and T = 45 watts (12" speaker) or 60 watts (15" speaker). It is important to note that these are peak power ratings, not RMS power. The RMS rating is more realistic and is usually about half of the peak rating so use that as a rough guide.

The "J" rated speakers are usually found on 12-watt Princetons. The "K" rated speakers are found in reverb and non-reverb Deluxes and in multi-speaker amps up to 40-watts such as the Tremolux and Concert. The "L" rated speakers are found in reverb and non-reverb Deluxes, some Tremolux amps, and multi-speaker amps like the blackface Concert, Super Reverb and Vibrolux Reverb. The "M" rated speakers had good service life in the piggyback Bassman and Bandmaster amps, but were easily blown in blonde Twins. The "T" rated speakers were standard in Twin Reverbs, but like the Jensen C12Ns, they often had a short service life.

Many amp geeks don't like Oxford speakers found in Fender amps from 1965 through the 1970s. The gap distance was increased in the Oxfords that Fender used later in the decade and this reduced their efficiency (and they were cheaper to make this way). Again, I say let your ears be your guide. I've heard many great sounding Fender amps with Oxfords. I will admit that I prefer Jensens, but I've never let an Oxford speaker sway my decision from owning a Fender amp. Additionally, the Oxfords from early '60s generally sound very good. According to noted vintage amp specialist Gregg Hopkins, these early Oxfords were constructed similarly to Jensens from that period with respect to materials and voice coil gap. That could explain why they sound good.

CTS: CTS (Chicago Telephone Supply!) speakers were used occasionally in Fender amps until the mid-1960s. These are good quality speakers that tonally lie between Jensens and Oxfords. The alnico 10-inch CTS speaker was the most prevalent speaker in Super Reverbs from the mid-1960s through the 1970s.

Utah: Fender didn't use Utah speakers very much until the 1970s. The Utah speakers from the '50s sound very good and I've heard a killer '66 Super Reverb that was equipped with factory original Utahs. Generally, the Utah speakers of the '70s weren't as great sounding as their predecessors, but again let your ears be your guide. If you like the way your '75 Twin Reverb sounds with its Utah speakers, just leave it alone and go right on playing. Utah went on to become Pyle of Radio Shack and car audio fame.

Eminence: Eminence has its roots in CTS (Mr. Gault left CTS to found Eminence) and many of the early Eminence designs are similar or identical to CTS speakers (good examples of the similarities can be found in mid-1970s Ampegs). Fender began using Eminence speakers as standard in nearly all of its tube amps beginning in the early 1980s. These are generally made to Fender's specifications and in some cases, such as the reissue '65 Twin Reverb, the speakers were designed to emulate the Jensen C12N speakers which were often found in the original '65 Twin.

Rola: Yet another speaker that Fender used in the mid to late 1970s was Rola.

So in technical terms, why don't the non-Jensen speakers from the mid-1960s through the 1970s sound as good as Jensen speakers? Speaker guru Ted Weber explains:
"Utah, CTS, Oxford, etc. simply copied the Jensen designs and started competing for Fender's business. As a result of the price wars, they had figure out how to make the speakers produceable with a very low reject rate as well as use less expensive parts, i.e. smaller magnets. So, they widened the gaps to make them easier to throw together on a fast assembly line. This lowered the energy, so the voice coils were shortened to compensate. The companies also needed to produce speakers with long term reliability, so they doped the surrounds. The end result is that with some of these speakers you get a relatively sensitive driver that sounds great at lower volumes, but falls apart when you push it -- flabby on the low end and/or harsh on the high end."
Replacement speakers: It is very common to find non-original speakers in Fender amps made up through about 1980. Because reconing wasn't a common option until the 1970s, players simply replaced the speakers if they blew up. In some cases, such as Altec and JBL, the factory would recone a speaker. Today, reconing is a very popular option for players to keep their amp's speakers original. Reconing must be done correctly and with the right parts so stick with a reputable reconing service that offers a warranty. In most cases, the reconed speaker will sound nearly as good or as good as the original. In some cases, the speaker will sound even better. The reconed Oxford 12K5 in my Deluxe Reverb sounds better than any original cone 12K5 I've heard. 

There is a strong market for used speakers. Many times a player can find an original speaker to replace the non-original speaker. Another option is to install vintage style speakers. Jensen has reissued the C10Q, P10R and P12N and WeberVST makes many models of Jensen-style alnico and ceramic speakers.

One final note before you scope out the speaker chart -- there are exceptions to every rule and this especially applies to Fender! So, if you see a factory stock P12P in a tweed Deluxe, don't be overly surprised. 

Alnico vs. Ceramic Magnets

Alnico magnets possess a certain buzz in the speaker world (and also in the world of guitar pickups), and are considered to be a more “musical magnet” that’s revered for sweetness and dynamics. Alnico is an alloy of aluminum, nickel, and cobalt (blended with a quantity of iron). Thanks to the relative scarcity and expense of cobalt, it’s an expensive alternative to the ceramic magnets that are also employed in speaker manufacturing, and alnico was all but dropped from use in the 1970s and ’80s. While this description of alnico implies a certain superiority, be aware that several classic speakers—even many vintage models, and those that remain the driver of choice for countless major players and tonehounds—were (and continue to be) made with ceramic magnets. Celestion’s G12M Greenback and G12H-30 are both ceramic speakers, as are plenty of great units from Eminence and revered early to mid-’60s Jensens.

Speaker Distortion

When we talk of speaker distortion, we mean a form of distortion—distinct from amplifier distortion—that is generated when a driver is pushed near its operating limits. The voice coil and paper cone begin to fail to translate the electrical signal cleanly, and, as a result, produce a somewhat (or, sometimes, severely) distorted performance. Put simply, the voice coil begins to saturate, the paper cone begins to flap and vibrate beyond its capacity, the magnet’s performance compresses, and the entire electro-mechanical network that makes up a speaker cooperates to bring its own degree of fuzz to the brew. The concept of such distortion is sometimes confusing, because it often occurs on top of any distortion the amplifier itself is producing. The distortion produced by a high-gain preamp stage—or a floored output stage—can occasionally be heard on its own when an amp is played through high-powered speakers that refuse to distort (or distort very little), even under high-output conditions. In most cases, when an amp is raging, you’re hearing a little of both.


Code formats were not completely standardized, but a little deciphering will generally yield the info of interest. Note that many makers also stamped OEM (Original Eqipment Manufacturer) part numbers above or below the EIA code, in some cases parts makers or the customer elected not to include the EIA codes, so not all parts have them.
They generally follow the following format: (example)
322 5904
where 322 is the manufacturer code (in this case Tungsol), 59 is the year (1959), and 04 is the week.
One alternate scheme is:
274 940
274 is the EIA code (RCA) 9 is the last digit of the year (in this case 1949). Usually single digit date codes are from the 1940's, but have on occasion shown up in later decades, even up to the 1970's. If one has a general idea of the age of the piece in question, usually the decade can be divined from that.
Another alternate is in the format following:
188-5 69 32
188 is General Electric. 5 is the plant code (in this case, Owensboro, Kentucky). 69 32 is 1969, 32nd week.
And another is like this:
322 6104-1
322 is Tungsol, 6104 is 1961, 4th week, 1 is the shift code (1 would probably be the day shift)
After about 1960, many tube manufacturers went to encrypted alphabetical date codes., such as:
The reason was purportedly to allow factories to track the dates of manufacture of defective tubes (especially important in the case of OEM customers that might send back entire batches of tubes), but avoid possible consumer complaints about "stale" tubes. This sounds perhaps a little silly since the shelf life of tubes is decades, at least (indefinite in practical terms), but some OEM's might have beenn a bit irritated by occasional consumer complaints such as "my 1961 model TV has 1959 model tubes in it!"

Tubes made for the US military, or certain OEMs (such as some test equipment manufacturers) that requested it, continued to carry numerical date codes.

In years past, EIA (Electronic Industries Association) also went by the name of RETMA, and the original acronym of RMA (Radio Manufacturer's Association).
EIA Code Lists for:
Potentiometers (controls) & Resistors
Other Manufacturers

Tubes and CRT's EIA code
Amperex (USA) 111
Bendix 125
DuMont 158
Eimac (Eitel-McCullough, Inc) 162
Electronic Tube Corp 169
General Electric Co (USA) 188
Hytron (CBS-Hytron) 210
Machlett 231
RCA (Radio Corp of America) 274
Raytheon 280
Superior Tube Co 310
Sylvania (Hygrade Sylvania Corp) 312
Tung-Sol 322
United Electronics 323
Western Electric 336
Westinghouse 337
Zenith Radio Corp (CRT's) 343
Nortn American Philips Corp 423
Taylor (aka Cetron-Taylor) 713
Lewis & Kaufman 738
National Electronics (also Cetron) 749
Penta Laboratories 771
Vacuum Tube Products 781
Varian Associates 809
Litton Industries 879
Electrons, Inc 935
Capacitors EIA code
Aerovox Corp 102
American Condensor 109
Centralab 134
Chicago Condensor 135
Aerovox Hi-Q Division 163
John E Fast 178
General Electric 188
Mallory 235
Micamold 240
Millen 242
Radio Condensor Company 273
Solar 296
Sprague 303
Gudeman 438
Good-All 446
Barker & Wiiliamson 461
Pyramid 472
United Condensor 516
Electrical Utilities Corp 569
Illinois Capacitor (Condensor) 616
American Radionic 648
Sangamo 658
Ajax 705
Standard Condensor 710
RMC (Radio Materials Corp) 732
Condensor Manufacturers 885
Transformers & Coils EIA code
Stancor (Chicago-Standard) 138
Coil Engineering 141
Ensign Coil 172
Freed 183
General Radio 194
Jefferson Electric 218
Thordarsen-Meissner 238
Merit Coil & Transformer 239
Standard Coil 305
Essex (Transformer Division) 352
New York Transformer 366
Altec Lansing-Peerless 391
Foster Transformer 394
General Transformer 412
United Transformer Corp (UTC) 418
Radio-Television Products Corp 489
Empire Coil 452
Caledonia 503
Triwec Transformer 524
Midwest Coil & Transformer 549
Standard Winding Co 550
F & V Coil Winding 572
Woodward-Schumacher 606
Central Coil 637
Electrical Windings 682
Grand Transformers 757
Forest Electric 773
Ogden Coil & Transformer 776
Triad 830
Better Coil & Transformer 831
Acro Products (Acrosound) 878
Mohawk 883
American Transformer 892
Tresco 897
Coilcraft 906
Aerocoil 908
Acme Coil & Transformer 928
Magnetic Coil Mfring 933
Northlake 1005
Pacific 1052

Resistor & Potentiometers EIA code
Allen-Bradley 106
Centralab 134
CTS (Chicago Telephone Supply) 137
Clarostat 140
Erie 173
IRC (International Resistance Co) 214
Mallory 235
Muter 244
Ohmite 251
Speer 300
Stackpole 304
Ward Leonard 532
Milwaukee Resistor 722
Dale 816
Atlas 932
Speakers (Drivers only, not cabinets) EIA Code
CTS (Chicago Telephone Supply) 137
Jensen 220
Magnavox 232
DuKane (Operadio Corp) 252
Quam (Quam-Nichols) 270
Rola 285
Utah 328
Western Electric 336
Altec Lansing Corp 391
North American Philips (Norelco) 423
Oxford 465
Waldom Electronics 555
Electro-Voice 649
Russell Speaker Co 748
Quincy Speaker Mfr Corp 767
Klipsch 843
University 847
Oaktron 934

Other commonly seen manufacturers

Company Product Code
Admiral Corp TV's, Radios 101
Alpha Wire 733
Amphenol Sockets, plugs 554
ATR Vibrators 551
Anaconda Wire 547
Arvin Sears radios & TV's 248
Astatic Phono cartridges 345
Belden Wire 579
Bell Amps 708
Bogen Amps 589
BIC British imports 409
Cannon Connectors 440
Cinch Sockets, connectors 139
Collins Radio gear 439
Connector Corp Sockets, connectors 888
Consolidated Wire 607
Crosley Radios 152
Drake RF gear 851
DuKane (Operadio) Amps 252
Eby Sockets 160
Empire Phono cartridges 452
Essex Wire 175
Gates RF gear 187
General Cement Adhesives, Testor's paint 396
General Radio Test Equip 194
Hallicrafters Ham & SW gear 199
Hammarlund Ham & SW gear 201
Harmon-Kardon Hi-fi gear 794
Hickok Test Equip 508
International Rectifier Semiconductors 845
Jackson Tube Testers 216
E F Johnson Sockets, ham xcvrs 222
Kester Solder 224
Keystone Hardware 699
Lenz Wire 228
Littelfuse Fuses 230
McIntosh Hifi gear 793
Methode Connectors 720
James Millen Sockets 242
Muntz Cheap TV's 772
National Co Ham & SW gear, hifi 245
Newcomb Amps 437
Packard Bell TV's radios computers 254
Philco Radios & TV's 260
Philmore Hardware 262
Pickering (Stanton) Phono cartridges 631
Pilot Hifi tuners & amps 264
Pioneer Cheap recievers 706
Precision (Grommes) Hifi & PA amps 871
Radio Craftsmen Hifi gear 275
J P Seeburg Jukeboxes 289
Shure Brothers Phono carts, mics 590
Mark Simpson (MASCO) PA Amps 295
Simpson Electric Meters 614
Sonotone Phono cartridges 787
Tetrad Phono cartridges 842
Triplett Test equipment 321
Wells-Gardner Monkey Wards radios 334
Weston Test Equipment 338
Zenith Radios & TV's 343



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