How to detune 1936 cab to 1x12 G12M

Marco Disseldorp

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Hi

I need some help detuning my 1936 cab. Going through a bit of a learning curve as I’m new to this. I’ll first explain the current 2x12 config of the second hand cab I bought which seemed to have had one speaker replaced. Next, I’ll go through the desired 1x12 config.

Current config
  • 2x12 cab
  • Standard jack plate with red wires going to positives, black wires to negatives
  • 1 x Celestion Gold back, 16 ohm
  • 1x Celestion, G12T-75, 16 ohm
Question 1: Measuring the right jack labeled 8 ohm/mono, I measure around 12,7 ohm. If the right jack wiring typically is parallel, shouldn’t this be 8 ohm with measurements like 7,2 ohm? If my thinking is correct, what was done with the wiring to achieve this (from the looks of it the wiring looks untampered and feels intact).
1936 jackplate.png 1936 jackplate back.png Goldback.png G12T-75.png

Desired config:
  • Detuned cab 1x12
  • Standard jack plate, red wire goes to positive, black wire to negative
  • 1x Celestion, Heritage Series G12M, 8 ohm
Question 2: How do I achieve this? Here’s my thinking. 1. Use right jack labeled 8 ohm/mono for input from head (head set for 8 ohm output). 2 Only wire red/black from right input jack to G12M positive/negative respectively. 3. Leave wires from left input jack disconnected (don’t use any input for left jack, obviously).

Thanks for your thoughts
 

Geeze

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Personally I would remove both jacks, put in a new mono jack for the single speaker and plug the unused hole. No chance of hardware failure or you plugging into the wrong hole. Mark the resistance at the jack.

If you're getting 12.7 ohm what the jack is connected to is 16 ohm - a clear indicator that something was changed inside.

Russ
 

Marco Disseldorp

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Thanks, that's helpful advice. I'll try this replacement jack from tube amp doctor

can't seem to post links as i'm below 5 posts, so here's a pic of part number CO1030

CO1030 TAD.png
 

Marco Disseldorp

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Cheers!

There’s a couple of things that made me interested in trying this. I have a 4x12 425A cab which has great sounding G12C’s, but it takes space. I wanted to have a smaller cab that could still hold my 2204 head without sticking out on the sides. The 1936 is sized just right for this. Next, I also wanted to keep it light and having just one speaker obviously helps. Re sound, I wanted try for something different both by switching speakers and to learn what detuning could bring to the ear. Especially curious to hear what one speaker hole left open could do the frequencies, making the mid’s perhaps warmer and the bass tighter. Perhaps I'll add another unused speaker back in to see what that does to the sound.

I actually did a quick rewiring job reusing the existing mono jack. This ended up measuring 7.2 ohms, so that’s fit for purpose. Maybe the second jack was wired faulty. Who knows. I btw ended up ordering some replacement jacks from Cliff, which seem to be the original parts. But most importantly for now, everything works so it's listening time how the new G12M breaks in.
 

GIBSON67

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My thoughts...detuning a 2x12 by removing one speaker will not yield good results like detuning a quad the same way. You will lose bass if one hole is open.

I'd go with a dual jack system, one for each speaker...you will get better results than removing a speaker. If you are worried about weight then go with a couple of neo's.
 

Marco Disseldorp

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I like that thought - thanks man. Bonus indeed to have two single speakers ready to rock any time. I'll compare anyway to hear what the open hole does to the sound.

Thanks as well for pointing out the neodymium's. It's putting Jensen back on the radar. Ultimately though lightweight is nice, but tone remains king. My back however disagrees.
 

GIBSON67

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Celestion Vintage Neos are top notch and I liked them very much...even in a 1x12 combo cab. I had a Jensen Neo at one time and I did not like it one bit...M2C again.
 


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