Vox AC30: Pulsonic H1777 cones in Celestion blues
1962-1964
Pulsonic cone code 71H1777, Celestion blue, December 1962.
A provisional note on Celestion blues with Pulsonic cones (H1777). The page on Celestion blues with RIC cones can be found here.
Pulsonic Limited was brought into being in July 1961 by Derritron Limited and Darlington Chemicals to develop and specialise in ultrasonic welding. That at least seems to have been its initial brief. There were two factories: one in Bishop Auckland (county Durham), the other in Sands, High Wycombe (Buckinghamshire).
At some point in 1962, Pulsonic evidently branched out into making speaker cones. These were made at the High Wycombe factory. So far as one can tell Celestion placed its first orders for "Pulsonics" in autumn, perhaps having played some part in their development (though that is not known for certain). Up to that point, Celestion had mostly produced and used its own cones (stamped with RIC codes). Increasing demand naturally gave rise to the need for another line of production.
Overview of codes
1962 apparently has its own scheme, the (prefatory) numbers relatively high towards the end of the year. In 1963 (at some point) the sequence appears to start again. 1964 seems to be a continuation of 1963.
Charting these numbers with a view to divining the "system" may be a fool's errand. But it is probably worth collecting and collating the evidence as it arises.
As for what the prefatory numbers may be: probably week of production, week 1 notionally being the first week of business after July 1961. So by late November / December 1962, we are at week 71, the production of cones having begun somewhere around week 60, say, in September 1962. In some weeks, it seems that no cones were produced.
It is worth saying that there will naturally have been some interval between the manufacture and stamping of a cone and its incorporation by Celestion in a speaker - in other words, a gap between the week of manufacture of the cone and the date stamp on the speaker's gasket (recording date of final assembly).
Whether 1H1777 and 9H1777 (February and March 1964) are mistakes or simply indications of something else at work is unknown at present. The tabulation for the time being is confined simply to Celestion date codes and H1777 cone stampings. Representative pictures will be added later. A good number of the speakers listed below are no longer in the AC30s to which they were originally fitted.
1962
20JG and 21JG - 20th and 21st September 1962 - 49H1777.
21JG - 21st September 1962 - 50H1777.
27JG - 27th September 1962 - 54H1777.
18KG - 18th October 1962 - 65H1777.
19KG - 19th October 1962 - 64H1777.
28KG - 28th October 1962 - 65 or 68H1777.
08LG - 8th November 1962 - 68H1777.
04MG - 4th December 1962 - 71H1777.
18MG - 18th December 1962 - 71H1777.
1963
10AH - 10th January 1963 - 71H1777.
08BH - 8th February 1963 - ?51H1777.
09DH - 9th April 1963 - 9H1777.
22DH - 22nd April 1963 - 54H1777.
25DH - 25th April 1963 - 54H1777.
25DH - 25th April 1963 - 8H1777.
08EH and 09EH - 8th and 9th May 1963 - 15H1777.
15GH - 15th July 1963 - 18 or 19H1777.
26GH - 26th July 1963 - 19H1777.
12HH - 12th August 1963 - 18H1777.
16HH - 16th August 1963 - 18H1777.
26HH - 26th August 1963 - 18H1777.
02JH - 2nd September 1963 - 18H1777.
25JH - 25th September 1963 - 34H1777.
02KH and 08KH - 2nd and 8th October 1963 - 34H1777.
29KH - 29th October 1963 - 40H1777 and 41H1777.
07LH - 7th November 1963 - 40H1777.
29LH - 29th November 1963 - 41H1777.
02MH - 2nd December 1963 - 41H1777.
04MH - 4th December 1963 - 41H1777.
07MH - 7th December 1963 - 41H1777.
1964
14AJ - 14th January 1964 - 41H1777.
25AJ - 25th January 1964 - 51H1777.
29AJ - 29th January 1964 - 53H1777.
18BJ - 18th February 1964 - 52H1777.
20BJ - 20th February 1964 - 52H1777.
21BJ - 21st February 1964 - 1H1777.
02CJ - 2nd March 1964 - 51H1777 (originally stamped 51 102 003).
03CJ - 3rd March 1964 - 52H1777 (originally stamped 51 102 003).
17CJ - 17th March 1964 - 52H1777.
25CJ - 25th March 1964 - 1H1777.
31CJ - 31st March 1964 - 52H1777.
20DJ and 22DJ - 20th and 22nd April 1964 - 1H1777.
05EJ - 5th May 1964 - 9H1777.
06EJ - 6th May 1964 - 9H1777.
11EJ - 11th May 1964 - 53H1777.
Celestion silvers (From May 1964)
02FJ - 2nd June 1964 - 10H1777.
17FJ - 17th June 1964 - 10H1777.
13HJ - 13th August 1965 - 21H1777.
23JJ - 23rd September 1964 - 22H1777.
08KJ - 8th October 1964 - 26H1777.
09KJ - 9th October 1964 - 27H1777.
11MJ - 11th December 1964 - 43H1777.
Celestion silvers - 1965
02CK - 2nd March 1965 - 7H1777.
31CK - 31st March 1965 - 7H1777.
20DK - 20th April 1965 - 10H1777.
10EK - 10th May 1965 - 8H1777.
03FK - 3rd June 1965 - 8H1777.
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