# Marshall speaker problem.



## Moosehead (Jan 6, 2011)

I was playing at a house party last night and all of a sudden my amp went silent.

No smoke or lightning, tubes were still glowing but no sound.

At first I grabbed another head, impedance matched up but no sound.

Plugged into a cab and voila, sound. So the speaker died. Speaker cable looked good and connections were fine.

What would cause the speaker to just up and die like that? I was only playing on 3-4 on the master vol. 

Amp is a 2204 50w jcm800 combo. Never had as much as a crackle from the speaker or speaker cable in the last 3 yrs.

What would be a good replacement? Speaker is the original celestion g12m-70.


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## Wild Bill (May 3, 2006)

Moosehead said:


> I was playing at a house party last night and all of a sudden my amp went silent.
> 
> No smoke or lightning, tubes were still glowing but no sound.
> 
> ...


Most likely something died in the voice coil winding. It doesn't sound like you put so much power into it that it burned out. More likely, it just got old!

Before I gave up on it, I would take a soldering iron or gun and reheat the connections at the output terminal strip. If you look close you will see that the voice coil is connected from the cone to the terminal strip by short lengths of flexible wire, which are soldered to the bottom of the terminals. That connection might "go bad" over the years. Reheating the connections just might bring the speaker "back from the dead".

As for a replacement, you can still buy Celestion speakers, as far as I know.

At my shop, I supply Eminence speakers and my customers are very happy with them. To match the Celestion sound, I would try a Wizard model. It's rated at 75 watts and has the Celestion brightness, with a tone bang on for classic rock.

Wild Bill/Busen Amps


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## dcole (Oct 8, 2008)

I have also seen the connection break at where the voice coil wires meet the connection wires that are glued into the cone.


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## Moosehead (Jan 6, 2011)

Thanks for the responses guys, going to pull the speaker and see if I can salvage it.


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## LydianGuitars (Apr 18, 2013)

What kind of cab was it? 1x12, 2x12, 4x12?


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## Moosehead (Jan 6, 2011)

1x12 combo

Speaker salvage didn't work out. 

Looking for a replacement... im thinking greenback flavoured but curious to hear what other folks like with this amp.


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## nonreverb (Sep 19, 2006)

Greenback flavoured perhaps, but not an actual Greenback as you'll quickly be back to where you are now. Greenback is only rated for 25watts.


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## LydianGuitars (Apr 18, 2013)

The G12M-70 is no great loss. I would try to figure out why it blew though. Check the grounding, bias, coupling caps and filter caps to ensure they're all in top shape.


I would suggest a G12-65, one of the best speakers for that amp IMO, or perhaps even one of the newer 65w Celestion Creambacks 

http://celestion.com/product/26/heritage_series_g1265/

http://celestion.com/product/123/g12m65_creamback/


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## nonreverb (Sep 19, 2006)

Age.....and volume. The greatest killer of speakers. Bias , coupling caps, filter caps etc. are all isolated from the speaker via the output transformer. The only way that a speaker can be blown in a tube amp is by square waving it to the point where it overheats, although most speakers can handle a fair amount providing they're not under powered. A breach in the output transformer where the B+ arcs over to the secondary (although this is an exceedingly rare occurrence) or age. Age is one of the greatest killers of speakers. As they age, the paper, glue and windings begin to get brittle. In the case of a single Celestion in a 50 watt Marshall tube amp that's probably been blasted for the last 30 years...it's only a matter of time...


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## LydianGuitars (Apr 18, 2013)

I didn't want to imply that coupling caps, bias and those things could have caused the speaker to blow - its just good maintenance for an older tube amp. As long as you're in there fixing it up, you might as well give it a full checkup. Of course, at the speaker, any DC offset that would be present on the primary winding would not be present on the secondary.


One thing that can cause speaker failure, among other things, is parasitic oscillations that you can't hear. Putting the amp on a scope and checking the output signal would be a wise thing to do IMO.

"nonreverb" makes a good point though. Maybe the speaker was just tried and the windings were on their last legs.


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## nonreverb (Sep 19, 2006)

Although theoretically possible in high power amps, I've heard of the problem with a Marshall Major taking out a speaker with parasitic oscillation, speaker destruction from oscillation it's not common. Even at full volume oscillation, at say 50Khz a 50watt amp can only deliver 50watts and the reactance of the speaker changes and the resulting impedance increases. The oscillation amplitude can vary widely from one example to another as well.

The greater danger to the amp is the power tubes. They'll be in far worse shape than the speaker in no time as they'll be dissipating oodles of power.
Usually there are indicators as well forwarning you of the impending doom as the sound will get fuzzy or there will be a distinct hum due to the tubes running hard.


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## Moosehead (Jan 6, 2011)

The amp has been running strong for the last 3 years I've owned it. Maybe its time it saw a tech... or at least had new(backup) power tubes.

BUT it sounds like its working properly so I dont think the amp did it. I've been playing it through my cab and had no problems.


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## nonreverb (Sep 19, 2006)

I've had to replace many blown/ loose/ separated speakers in old/vintage amps over the years. It's a common problem.
The JCM800, as Wild Bill states, was the last of the well built Marshalls. They rarely have serious problems and with ocasional service, will continue to run reliably.
Furthermore, the Canadian version probably has about as many fuses as the average car so the chance of something going catastrophic is almost nil....except for the speaker:food-smiley-004:


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