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15th May 2013, 05:26 AM  #1 
diyAudio Member
Join Date: Mar 2013
Location: Atlanta, TX

Marshall 1960 Celestion G12t75 ohm?
I own a Marshall 1960 cabinet which comes stock with Celestion G12T75 speakers but it doesn't show what ohm the speakers are. I use the cab on the 4 ohm setting. I did a little research and found out that you can only buy those celestions in 8 or 16 ohms. I want to buy a Marshall MG cabinet which only has one input and need to know how to wire the speakers to 4 ohms for the input. Which ohm speaker would I buy to do this? and how would I go about doing this? I'm kinda new to wiring speakers.

15th May 2013, 06:58 AM  #2 
diyAudio Member
Join Date: Sep 2004
Location: Lansing, Michigan

Unless you wire them in stereo...
To wire four speakers in one cabinet, you have two real choices. One. You can simply run them in parallel, and the total will be 1/4 what one is. In other words if you use 16 ohm speakers, four in parallel makes 4 ohms. (1/4 x 16) A parallel cab will most likely use 16 ohm speakers. If you wire a parallel cab with 4 ohm speakers, you get a 1 ohm cab. Two. You can wire them in series/parallel, in which case the four speakers will total the same as one of them. So 16 ohm speakers will make a 16 ohm cab, 4 ohm speakers will make a 4 ohm cab, and 8 ohm speakers will make an 8 ohm cab. You could also wire them all in series, but that would be pointless. Four 16 ohm speakers in series would result in a 64 ohm cab. There is no way to wire four 8 ohm speakers to make 4 ohms or 16 ohms. SO you would want to get four 16 ohm speakers and wire them in parallel. 
15th May 2013, 10:22 PM  #3 
diyAudio Member
Join Date: Mar 2009
Location: Buenos Aires  Argentina

Agree and add: very different cabinets.
1960 use 16 ohm speakers and straight descend from the very first Marshall Cabinets which were single input, 16 ohms only. And use best speakers available. Which are available by themselves, are in the catalog, you have all kinds of info .... and are relatively expensive MG 4x12" use the cheapest of the cheap, which do not appear in any catalog or Web page, there's absolutely no data (I managed to grab a picture or two, nothing else) and Celestion acts as if they were embarrased about having made them (which is understandable). It's 8 ohms so all speakers must be individual 8 ohms too, so you can't. Even if you could , you would spend your money much better by buying spare good speakers in the impedance you need ad mount them in any suitable cabinet. 
16th May 2013, 05:32 AM  #4 
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Join Date: Mar 2013
Location: Atlanta, TX

Thank you Enzo. My question now is how would I wire them in parallel? As I said, I'm new to this. I know that each speaker has 4 prongs on it. Which would I wire it to?

16th May 2013, 11:16 PM  #5 
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Join Date: Sep 2004
Location: Lansing, Michigan


17th May 2013, 01:58 AM  #6 
Banned
Join Date: Oct 2012

the g12t75s are decent speakers pretty aggressive but tad bit harsh on the top end, I always liked the g1265 waaaay more much more richer mids and smoother highs to me they sound closer to a hotrodded higher powered greenback which was the intended idea I believe? While guys still rave about the Vintage 30s those will always have an ugly mid hump/spike and again kinda piercing highs.

17th May 2013, 11:29 AM  #7 
diyAudio Member
Join Date: Oct 2011
Location: Tauberbischofsheim, Germany

You probably own a cabinet with 16 ohms speakers. Do you have a digital multimeter? If not so, please buy one, a cheap one will do. Measure the DC resistance of one speaker. If it reads somewhat of about 1215 ohms, it's impedance is 16 ohms. If it reads about 67 ohms, impedance value is 8 ohms.
Next, connect the red marked terminals of two speakers, then the black marked ones. Do the same with the remaining two speakers. This gives you two arrangements with half the impedance of one speaker each. If you then connect both arrangements in parallel (i.e. all red and all black terminals together), the resulting impedance will be a quarter of each speaker's impedance (i.e. 16 ohms > 4 ohms or 8 ohms > 2 ohms, respectively). If you connect both arrangements in series, i.e. the red terminals of the first to the black terminals of the second arrangement, the resulting impedance will be equal to a single speaker's impedance. Note: These considerations solely are applicable, if all four speakers are of the same impedance! Best regards! 
17th May 2013, 12:48 PM  #8 
diyAudio Member
Join Date: Mar 2009
Location: Buenos Aires  Argentina

Agree and add.
Celestion G1275 are the most popular ones, and available in different impedances .... but not for the end user For 1960 4x12" cabinets or tube (JCM800 for example) 2x12" combos or 2x12" closed cabinets (1936): 16 ohms each. For SS combos (Valvestate 8080): 8 ohms (single speaker) For SS *stereo* combos, such as Valvestate Stereo Chorus 8240 (2 x TDA1514 40W/4 ohms chipamps) : 4 ohms each (1 speaker per channel) . Available only to OEM So as you see, if you have an original speaker in a cabinet, you already know , but if you buy a used one at, say, EBay or Craigslist, always check as suggested above. 
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