Vox AC30: the Celestion alnico blue
Alnico magnet, effectively a Celestion CT 3757 with a bell-shaped magnet cover.
This page will be updated as dateable examples come to light.
A page from the JMI booklet produced in early 1961 to advertise the new split front AC30s.
As is well known, Celestion kept a log book recording the introduction of new models and special orders. The book was generally known as the "T Numbers" book.
The entry for the T530 is something of a patchwork. The model was basically a species of G12, sub-type CT3757 - "- G12 - As CT.3757. Sprayed Oyster. Fitted with cone H.1668." - "oyster" being the name for the hammertone finish. "Sprayed Oyster" was later over-written in the book with "Blue" and "COLOUR No. M104 (AZURE BLUE)".
For examples of the CT3757 and other speakers used in AC30s before 1961, see this page.
No date is given against the entry, nor against the additions made in different handwritings.
In a second register though, the T530 is recorded as being "blue" in a batch of entries added on 19th January. So we have, thanks to Jim Elyea, who looked closely at the Celestion records, a sort of "terminus ante quem".
Since the preceding set of entries, in which the "blue" does not figure, was made on 24th November 1960, it is clear that this version of the T530 came into being at some point during that period - between late November 1960 and mid January 1961.
Whether the parallel presented by the T1088 (the "alnico silver") is of any help here is an open question. The T1088 was recorded in the Celestion registers on 27th May 1964. There are, however, surviving examples with date codes in early April.
Thanks to Robert Valentine, who worked for JMI from 1959 to 1964, a detail from a photograph taken at 115 Dartford Road around July 1964 - a Celestion box, probably for a 15" speaker (for a Vox T60 or 2x15" speaker cabinet), on one of the benches. Celestion blues and silvers - T530 and T1088 - are likely to have come in similar outer boxes. Only the inner packaging is known at present - see the picture further below.
Advert for the Celestion stand at the Russell Hotel Audio Fair, early August 1963.
As with many other types of Celestion speaker, "blues" can only really be dated effectively by the date code stamped on the speaker's cork gasket - the part that makes contact with the cabinet's baffle board.
The date code has two figures, and two letters. The two figures are the day number, the first letter represents the month, the second the year. For the month the sequence is "A-M" where "A" is January and so on, and "I" is omitted. In terms of the second letter: "E" is 1960, "F" is 1961, "G" is 1962, "H" is 1963, and "J" is 1964.
A detail of the gasket of a "blue". The model designation "T530" is at right. To the left is the date code "14EG" = 14th May, 1962.
For the most part, the speakers that find their way into the open are from 1963 and 1964. Occasionally there are exceptions, some of which will be assembled below.
An overview of RIC cone codes can be found on this page.
Earliest Celestion blue currently known
12th February 1961 (12BF), recorded by Jim Elyea. The earliest single-speaker AC15 that has come to light so far with a blue (rather than a Hammertone T530/CT3757) is serial number 4433N.
Serial number 4478 - currently in Germany and the UK
The chassis is now separated from its original cabinet. Both speakers have the date code: "15EF" = 15th May 1961. Thanks to Marc for the pictures.
A detail of the cone code of one of the drivers: "RIC 1 UJ"
Serial number 4606 - currently in the USA
The cone code is "RIC 1YG"
Date codes "16FF" and "29FF" = 16th and 29th June, 1961.
One of a pair
"11GF" - 11th July 1961, no note of the RIC cone code. The date code of the speaker to the right is illegible unfortunately.
A single speaker
Sold as a "1965" blue. The date code however is "18KF" = 18th October 1961.
Serial number 5002 - currently in the UK
AC30 Super Twin serial number 5002N. Both Celestions have cones RIC 1 DJ, and date codes "22FM", one of those instances where the letters for month and year are given in reverse. The date envisaged is 22nd December 1961. "M" as the year makes no sense at all where Celestion blues are concerned. The amplifier section has components with 1961 date codes.
A Super Twin speaker cabinet (with changes) - currently in the USA
A Super Twin speaker cabinet, original grille cloth and vinyl replaced. The Celestion has the same cone code as the cab above - RIC 1 DJ.
A beige Super Twin cabinet from the second half of 1962, exterior painted black. The date code for both speakers is "14EG" = 14th May 1962.
Black panel AC30/6 chassis and speakers
Speakers accompanying a black panel AC30/6 chassis - date codes 24EG and 25EG = 24th and 25th May 1962, and cone code RIC 1 JB. It seems unlikely however that these blues belonged originally to the cabinet that housed the chassis.
Serial number 6097 N - currently in the USA
The date codes on the Celestions are "31KG" and "08LG" = 31st November and 8th December 1962.
Serial number 6364 B - currently in South Africa
Date codes 04MG and 18MG = 4th and 18th December, 1962. Pulsonic cone, code: 71 H 1777.
A stray pair
Date codes "11AH" and "15AH" = 11th and 15th January, 1963. Pulsonic cone, code: 71 H 1777.
Serial number 6529 N - currently in the UK
Date codes unknown. Probably mid 1963. Cone codes are "RIC 2 TO" and "RIC 2 TP".
Serial number 9434 N - currently in the UK
Date codes "07LH" = 7th December, 1963. Pulsonic cone, code: 10 H 1777.
Late blues - sometimes classed as T1088s
A strange pair of blues, repaired in 1971. The one on the right - date code "10GH" = August 1963 - has an unused set of holes for solder terminals in its frame. The one on the left - a T1088, date code "30MJ" = 30th Dec. 1964 - has an added terminal strip.
Below, an example with the date code "18JJ" = 18th September 1964.