Running A Marshall 1960 Av 412 With Only 2 Speakers?

[Faraz]

Hi there,
I have a Marshall 1960 AV cab, that is wired at 16 ohm series parallel. A year ago i just switched the two (bottom and top) speakers with 2 celestion greenbacks (16 ohms) . Just for the sake of pure greenback sound I have been running the cab in stereo mode with only the left side of two speakers (Greenbacks) working at 8 ohms.

The right side has had Celestion G12 vintage, which recently i just sold. Now the cab only has two Greenbacks in the left side (bottom and top). My question is, until i receive the two Celestion Evh Greenbacks, Can i have the same series parallel wiring, swtich to stereo mode and run the two greenbacks by them selves without having any other speakers connected in the other side?

I am running it through a Evh Lbx 15 watt head, so wattage wont be an issue.
Thanks...

 

[KraftyBob]

I'm not sure how the switch works on the back of the cab and what difference, if any, removing two right speakers will have on it in stereo mode. I would suspect that when you're in stereo mode the two sides are independent of one another. A quick check would be to plug in your speaker cable into the left input and check the ohm rating at the tip & ring. 8 ohms should measure between 6-7 ohms on your multi-meter.

 

[JohnH]

good advice above ^

If its going to be a while, you might like it better with both speakers at the top or in an X pattern. Also, if theres nothing in the other holes, bass is totally different/reduced.

I ran by valvestate cab for years with 2 in the top and the others closed off with 9mm ply.

 

[KraftyBob]

good advice above ^

If its going to be a while, you might like it better with both speakers at the top or in an X pattern. Also, if theres nothing in the other holes, bass is totally different/reduced.

I ran by valvestate cab for years with 2 in the top and the others closed off with 9mm ply.

Look up "detuned" cab. It's best described as sounding like an open back cab but the fullness coming from the front. Some people love it, others meh.

I considered this with my cabinet rebuild project. I'm converting a 2x12 into a 1x12 and building a new baffle for it. I thought about leaving the 2x12 baffle with only one speaker but ultimately decided just to build the 1x12 baffle.

 

[Faraz]

I'm not sure how the switch works on the back of the cab and what difference, if any, removing two right speakers will have on it in stereo mode. I would suspect that when you're in stereo mode the two sides are independent of one another. A quick check would be to plug in your speaker cable into the left input and check the ohm rating at the tip & ring. 8 ohms should measure between 6-7 ohms on your multi-meter.

Yeah KraftyBob, Im gonna grab my multi-meter and check the Ohms with 2 speakers only and switched to stereo mode. If it still gives me 6 to 7 Ohm reading then i suppose we are good.

 

[KraftyBob]

Yeah KraftyBob, Im gonna grab my multi-meter and check the Ohms with 2 speakers only and switched to stereo mode. If it still gives me 6 to 7 Ohm reading then i suppose we are good.

Let us know what you find out.

 

[Faraz]

Let us know what you find out.

Well, I have tried measuring the Ohms reading with only those two greenbacks Installed and the stereo mode on, The speaker cable is going into stereo left side and the reading which i am getting is around 7.6 to 7.9 Ohms, which is what is should give on each side,once switched to stereo.

So it shows the reading is good, all thats left now is for me to turn the amp on with impedance switched to 8 ohms and check to see if the speakers are working fine, I'm a bit afraid of blowing out the speakers or the amp or something. But lets see what happens.

 

[KraftyBob]

I'm surprised to see the reading so close to the actual speaker rating. It's typically a little lower but perhaps the cable and your switching input jack is adding some resistance? In any case, it's not 16 or 4 ohms, and when you run it in stereo the two sides have to be isolated otherwise it would mess up the impedance so you should be good to go!

Jam away!