Back around 2010, I grabbed a—then new—Bogner 4x12 with Chinese, 16-ohm G12M-25. It sounded fantastic. I got ride of it for some reason years ago. Now I want to grab a quad of Greenbacks for a new cab. But I don't know which version to get. I see they're now made in the U.K. since 2018 or something like that? I guess that's my only option for new Greenbacks? But what are the various iterations of this speaker? Cone codes, T-blah-blah-blah codes, etc.?
I see a quad of Greenies with 6402 cones for sale, but not sure what these are all about.
In my experience.....
Older are always better. Nothing wrong with the newer ones, but the earlier you go the more 'complex' the tone, 3D if you will, with some differences that may make you value one version vs the others.
Pulsonics-
These are otherwise known as 'pre Rola' speakers, made in the Pulsonic factory(cones only) up until the fire in 1973/4 took the formula away for making those great speaker cones. From the early 60s up until then, every British speaker pretty much used the Pulsonic cones..Celestion, Fane, etc. The 'pre Rola' thing is really only about the cone stamps...most people think it's the sticker on the back of the magnet but Rola started appearing in the early 70s on the stickers yet the cones were still the sought after Pulsonics. The stamps will be 003, 3, 004, 4, 14 to mention a few. I've had 1 intact 1972 cab with Pulsonic M25s and the midrange is very creamy, smooth if a tad loose in the lows. Very addictive speakers.
After the fire, Celestion started using RIC cones which are a tad more aggressive and tighter in the lows. This change coincided with the cream back mag covers being used. These can be found in cabs from 1974-75. These speakers are what you hear in Ted's cabs. I had a 74 cab with them, killer cab.
Then, in 75 you could find grey, and black mag covers on the M25s and now Celestion were mostly using the Kurt Mueller cones with either 1777 or 444 stamps. The 1777 are 75hz lead cones, which are the most common, and 444 are the bass cones which are a little mid scooped in comparison. The Mueller cones need a little more vol to come alive, but sound incredible when you hit them hard. More aggressive yet than even the RIC cones, and definitely more aggressive than the Pulsonics.
From 1976 on, all M25s used black mag covers, hence the term Blackbacks. Still a greenback but with black covers. These lasted until 1981 when the JCM 800 line came out, no more M25s to be made until 1989 when Marshall introduced the 1960 Classic cab, with the GB reissues that have the 6402 cone codes.
I haven't owned an early cab with these 6402s but I have some from the mid 90s-2000, and they are very good, sound better at low vol than some vintage GBs but don't seem to have the same aggressiveness as the vintage BBs, or RIC cones from the 70s. The 6402s sound better to my ears than the Chinese reissues. But that's just my opinion.
The 'King' of all GBs is the original Pulsonic G12M20s, only made from 1966-early 1968, had paper voice coils that made them sound amazing but also made them burn up under heavy use/wattage. This is why Celestion changed to Nylon(I think?) voice coils in 1968 so the speakers would take more volume without going up in smoke. These are super rare these days, and IF you find them they'll run 6-800 per speaker.
The H30 greenback is another version that has the same history as the above ^^ M25s, but I'm not a fan as they have extended highs and hollow mids to my ears. Many swear by the H30 Anniversary from the 90s, similarly the 6402s but I personally just don't jive with the H mag speakers. Other than the G12 80s.
I'd personally look for a good 70s BB cab, with the 55hz T1511 for example as they are more aggressive than any version greenback imo. Pulsonics are killer but are a touch 'softer' sounding than the RIC cream backs or Kurt Mueller black backs.
