1960A vs 1960B - Noticing huge difference in sound -

[jagrenet]

Hello Gurus !!

I have an interesting situation, with a 2 part question. I'll try to be as clear as I can.

First part -
I just bought and received a 1960B cabinet to compliment my 1960A and ultimately, to "complete" a stack. First thing I did upon unboxing was to plug in and test.
All 4 speakers are working. Mono "mode" works great(4 speakers) - Stereo "mode" works great(2 speakers). The problem is, when I have it set to Mono ....... It sounds more like an AM Radio than a good, solid 1960(x) cabinet should. In Stereo mode, it sounds nice, full and rich .... the way it should.
For a bit of context here ... and all things being equal, - Same amp, same speaker cable, same power feed, 8 Ohm tap - the 1960A sounds nice, full and rich ...... regardless which mode I select or which jack I am connected to.
What am I missing ?????

Second part -
As I mentioned, these 2 cabinets will ultimately end up as a stack configuration, supporting various different heads.
'79 JMP 2203
'91 JCM900 2100 (non-reverb model)
6100 LM 30th Anniversary
JVM410H
Up to this point, I have never had a stack and have always utilized 1 of my (4) 1960A's, to get the job done, always using the 8 Ohm output.
When I stack these .... which output do I need to use to prevent damage occurring to any of the equipment - 4, 8, 16 ???

If this has been covered before, I apologize for being redundant. I'm just new to running a stack and don't know. Likewise, I would prefer not to run a stack, if the bottom cabinet is going to degrade the luscious sound of these remarkable heads, and the tone they deliver.

Thanks in advance !!

 

[RLW59]

First part, it's possible the 2 pairs of speakers are out of phase. Perhaps a previous owner swapped out the stock speakers and put the originals back in when he sold it, and messed up the wiring.

It's also possible the switching jackplate has developed one of the notorious failures and is only working properly in the stereo mode.

Second part, why are you using the 8 ohm output on the amp with single 1960's? Running all 4 speakers in a 1960 is either 4 ohms or 16 ohms. The only time a 1960 is 8 ohms is when you're only using 2 of the 4 speakers.

To use 2 1960's together (all 8 speakers), you have to run them in the 16 ohm mode. 2 16 ohm cabinets are 8 ohms together in parallel, so you'd use the amp's 8 ohm setting.

(There were some Canadian and Scandinavian market 1960's that were 8 ohm, but they didn't have switching jackplates.)

 

[Deftone]

FWIW: I'd get an A/B box and run your signal into two heads, one on each cab. Like the 2203 and the 2100. You can run efx through the loop on the 2100 (MKIII I assume? Nice!)

That's how I roll. True stereo (I think?) and it sounds awesome.

I tried running two heads through one cab in stereo and didn't like it.

 

[jagrenet]

First part, it's possible the 2 pairs of speakers are out of phase. Perhaps a previous owner swapped out the stock speakers and put the originals back in when he sold it, and messed up the wiring.

It's also possible the switching jackplate has developed one of the notorious failures and is only working properly in the stereo mode.

Second part, why are you using the 8 ohm output on the amp with single 1960's? Running all 4 speakers in a 1960 is either 4 ohms or 16 ohms. The only time a 1960 is 8 ohms is when you're only using 2 of the 4 speakers.

To use 2 1960's together (all 8 speakers), you have to run them in the 16 ohm mode. 2 16 ohm cabinets are 8 ohms together in parallel, so you'd use the amp's 8 ohm setting.

(There were some Canadian and Scandinavian market 1960's that were 8 ohm, but they didn't have switching jackplates.)

I am/was using the 8 Ohm output because of my ignorance. I haven't ever had a problem and it always sounds great - (the no problem thing is probably due to blind luck) -
I attached a picture of the wiring, hoping it is clear enough to determine if they are wired correctly. Again, I don't know if they are or not. I switched the output of the amp to 16 Ohms .... no change in sound. Plugged in the 1960A and it is as beefy as it always is. - Thank you for the input -

 

[Dogs of Doom]

I am/was using the 8 Ohm output because of my ignorance. I haven't ever had a problem and it always sounds great - (the no problem thing is probably due to blind luck) -
I attached a picture of the wiring, hoping it is clear enough to determine if they are wired correctly. Again, I don't know if they are or not. I switched the output of the amp to 16 Ohms .... no change in sound. Plugged in the 1960A and it is as beefy as it always is. - Thank you for the input -

looks out-of-phase to me...

 

[jagrenet]

FWIW: I'd get an A/B box and run your signal into two heads, one on each cab. Like the 2203 and the 2100. You can run efx through the loop on the 2100 (MKIII I assume? Nice!)

That's how I roll. True stereo (I think?) and it sounds awesome.

I tried running two heads through one cab in stereo and didn't like it.

I like that idea and have thought about that. (A/B box) Except, I was thinking of using the JMP for solos and the MKIII for Rhythm. Yes, ... it is a MKIII - and I'm not sure why other people complain about "fizzy" Gain. I have my Gain maxed out - Gain AND Pre are maxed - I get no "fizz" whatsoever. In fact, it sounds REALLY good !!!

 

[jagrenet]

looks out-of-phase to me...

What is the proper wiring configuration as in, what do I change ??

 

[Dogs of Doom]

What is the proper wiring configuration as in, what do I change ??

well, just the obvious, if red wires are all positive, you have ½ of them hooked up to the negative terminals on the speakers...



the image is not a mirror image left/right. If you spin the speakers around to the same orientation, the wires are backwards to each other...

Who knows how the jackplate PCB assembly is wired up though, as that's part of the equation...

 

[jagrenet]

well, just the obvious, if red wires are all positive, you have ½ of them hooked up to the negative terminals on the speakers...

View attachment 126192

the image is not a mirror image left/right. If you spin the speakers around to the same orientation, the wires are backwards to each other...

Who knows how the jackplate PCB assembly is wired up though, as that's part of the equation...

So, based on your arrows, I need to swap those two ???? - Attached is the Jack Plate

 

[Dogs of Doom]

you need to make sure that + is + (red) & - is - (black) on all speakers main connections, otherwise, even if you get this cab in-phase w/ it's self, it will be out-of-phase w/ the other cabinet & you'll suffer the same problem when you run the cab's in tandem...

If the connections are all correct, then you have that issue, then the other cab may be backwards polarity & will need to be made correct...

 

[jagrenet]

well, just the obvious, if red wires are all positive, you have ½ of them hooked up to the negative terminals on the speakers...

View attachment 126192

the image is not a mirror image left/right. If you spin the speakers around to the same orientation, the wires are backwards to each other...

Who knows how the jackplate PCB assembly is wired up though, as that's part of the equation...

I don't mean to sound completely inept, I just don't want to damage anything by making the wrong move.

 

[jagrenet]

you need to make sure that + is + (red) & - is - (black) on all speakers main connections, otherwise, even if you get this cab in-phase w/ it's self, it will be out-of-phase w/ the other cabinet & you'll suffer the same problem when you run the cab's in tandem...

If the connections are all correct, then you have that issue, then the other cab may be backwards polarity & will need to be made correct...

Understood. I am going to open the "A" cab and do a stare and compare. Why that didn't dawn on me in the first place is totally unknown.

 

[Dogs of Doom]

 

[jagrenet]

Understood. I am going to open the "A" cab and do a stare and compare. Why that didn't dawn on me in the first place is totally unknown.

Stare and compare absolutely supports your arrow guidance. Made the swap and SHAZAM - There's that wonderful beefy sound - No more AM Radio. Dogs of Doom ..... thank you kindly for being patient with me and illustrating the obvious. I do appreciate your help !!! - A kind thanks to everyone else who chimed in and lent support as well. Gotta love this Forum - I know I do. Tonight, the stack comes to life. @ 16 Ohms - Rock forth Gentlemen -

 

[jagrenet]

View attachment 126194

That helps tremendously - Thanks !!! - I got it re-wired - Good to go. Many thanks !!

 

[Dogs of Doom]

just make sure, that, when you run 2- 16 ohm cab's, you hook them up to your amp at 8 ohm out.

8 ohm output to 2 x 16 ohm cabinets...

since you are dividing the load between 2 cab's ~ 16 ohm ÷ 2 = 8 ohm...

 

[PowerTube44]

If you're going to go in and fix this problem, you may as well hardwire it for 16 ohms while you're at it. Those switches are notorious for failing and they can take your amp head with them.

 

[jagrenet]

just make sure, that, when you run 2- 16 ohm cab's, you hook them up to your amp at 8 ohm out.

8 ohm output to 2 x 16 ohm cabinets...

since you are dividing the load between 2 cab's ~ 16 ohm ÷ 2 = 8 ohm...

I will for sure. I appreciate that. While I am by no means an electronics master, .. I have performed many many modifications to my amps - all of them. However, the speaker/ohm load thing is something I have not fully grasped along the way. You have seriously helped illuminate that concept for me. Thanks man -

 

[jagrenet]

If you're going to go in and fix this problem, you may as well hardwire it for 16 ohms while you're at it. Those switches are notorious for failing and they can take your amp head with them.

I have considered that . and may end up implementing it in the near future. I have read and learned about many issues being cause by that switch/PCB failing. Don't want to find out the hard way.

 

[Dogs of Doom]

I will for sure. I appreciate that. While I am by no means an electronics master, .. I have performed many many modifications to my amps - all of them. However, the speaker/ohm load thing is something I have not fully grasped along the way. You have seriously helped illuminate that concept for me. Thanks man -

sure, no problem... that's what the forum is about!