Celestion G12M-55 (1970s)
The Celestion G12M-55 — also sold and referred to as the G12M "Blackback" — is a 12" guitar speaker from the 1970s, a period variation of the more famous G12M Greenback family. The "55" in the name refers to the 55 Hz cone, a Pulsonic cone design that gives this variant its distinct voice. The Blackback name comes from the speaker's visual appearance: apart from the black plastic magnet cover, these are essentially the same speakers as the Greenbacks of the same era.
The record on this model is thin in places, but what survives is consistent. The G12M-55 was rated at 25 watts and was produced in multiple impedance versions — dated examples from the 1970s show 8-ohm and 16-ohm units, and current reissues are listed in 8-ohm and 15-ohm versions at Finnish retailers. A 1977 example found on craigslist carried the model number T1871 and a date code of KK19, which the seller interpreted as October 19, 1977. Other dated examples include a 1970 unit with its original 55Hz Pulsonic cone and a 1976 Rola-built example with Kurt Mueller cones, identified by the "444" stamp near the voice coil. The 1978/79 examples appear in a YouTube comparison video.
The G12M-55 is perhaps best known for its association with Marshall amplification. One owner on The Les Paul Forum describes a mid-70s 50-watt Marshall combo loaded with two G12M Blackbacks that has held up well over decades of use. A Gear Page user running a 55Hz example with a Swart STR-Tremolo reports it works very well — though he notes the speaker's 25-watt rating when considering a higher-powered head. A YouTube comparison describes the Blackbacks as "basically not any different from Greenbacks except the plastic covers' color."
One caution for collectors: a single Reverb listing for a 1970 G12M notes that the label says "75Hz" while the seller identifies it as a 55Hz Pulsonic cone speaker, suggesting some 55Hz-coned speakers may have left the factory with 75Hz labels. This is one source's claim, but worth knowing if you're hunting for a specific cone.
- 12" guitar speaker, 25-watt rating
- 55 Hz Pulsonic cone; some examples stamped "444" (Kurt Mueller cones)
- Known impedance versions: 8Ω, 15Ω (reissue), 16Ω
- Dated examples: 1970, 1976, 1977 (date code KK19), 1978/79
- Current reissues listed as "G12M (55) Blackback" at €145
No production years, sensitivity ratings, frequency response data, or original pricing are documented. The Heritage Series G12M (55) is a current reissue of this design, but its specifications are not separately documented here.
Similar items on eBay
No exact Celestion G12M-55 listings are live right now — these searches show current Celestion and similar vintage audio gear on eBay:
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.
Related Models
- Celestion 3 (1989)
- Celestion 7000 (1978)
- Celestion 700SE
- Celestion A4
- Celestion COUNTY (1978)
- Braun AUDIO-1 (1965)
- Braun AUDIO-250 (1965)
- Magnavox Component Systems (1972)
- Acoustic Research AR (1967-1976)
- Acoustic Research 11