Jvm 205c With 2x12

[Ryan500mtm]

Hi everyone. I'm newish to the forum. After doing tons of research I have finally bought my first Marshall. Thanks mostly to the advice on these forums.

I just purchased a JVM205c with Mercury Magnetics mod and upgraded speakers with Eminence 50w Red Fang and 50w Private Jack speakers. I also have the MX212 cabinet. Will this cab work with this amp? If so, which speaker outputs do I need to use.

Thanks for your help!

 

[MonstersOfTheMidway]

Hello.
Congratulations on the JVM205C. I, too, own a JVM for a little over 10 years now; they're a lot of fun to play, so I'll hope you'll enjoy yours for many years to come.

In regards to the MX212 cabinet. According to the specs (assuming the MX212 you have is stock), the MX212 is rated as 160watts, which makes it more than capable of handling the 50watt output of the JVM205C.
https://www.sweetwater.com/store/detail/MX212

The MX212 cabinet has a single 8ohm mono input. Quite simply, would plug a speaker cable from the MX212 input into the JVM205C speaker output labeled "1x8 ohm" because you are only using 1 cabinet rated at 8ohm.

In the diagram below, 1x8 ohm output is directly above the words "1x8 ohm"

Hope this helps. Let us know how it sounds.

 

[Ryan500mtm]

Thanks MonstersOfTheMidway! Just to confirm, would I leave the combo speakers plugged into the 1x16ohm output? Pictured below.

 

[JCarno]

No! You cannot (should not) use a single 16ohm and single 8ohm. If your 2x12 cab was 16ohm, then you would plug into the 2x16ohm.
Pretty sure 4K was assuming you were just going to use the 2x12 and not the internal speaker.

 

[John BNY]

Unplug the combo speaker. Plug a speaker cable (not instrument cable) into the 1x8 ohm on the amp and into the cabinet.

 

[Ryan500mtm]

So there's no way to run the combo speakers and the mx212 together?

That's a bummer. Oh well. Thanks everyone for the info.

 

[JCarno]

So there's no way to run the combo speakers and the mx212 together?

That's a bummer. Oh well. Thanks everyone for the info.

You can, but you'd have to put an 8ohm speaker in the combo and use the 2x8ohm connection.

 

[Ryan500mtm]

You can, but you'd have to put an 8ohm speaker in the combo and use the 2x8ohm connection.

The combo has two 8ohm speakers in it already.

 

[John BNY]

Someone more knowledgeable should chime in, but if you have two 8 ohm speakers in your amp, then I would think they should be connected into 4 ohm on the amp.

 

[Ryan500mtm]

Someone more knowledgeable should chime in, but if you have two 8 ohm speakers in your amp, then I would think they should be connected into 4 ohm on the amp.

From the factory, this amp comes plugged into the 1x16ohm output as pictured above. I just assumed this was correct. Sheesh, impedance is confusing.

 

[John BNY]

My 1936 cab as well as my JCM 900 combo each come with two 16 ohm speakers. When properly wired, the two 16 ohm speakers should connect to 8 ohm jack on the amp. Similarly, a 4x12 cab with four 16 ohm speakers gets connected to the 16 ohm jack on the amp. If your amp has two 8 ohm speakers, then I think it should connect with the 4 ohm jack on the amp.

BUT, I suggest you not do anything until someone more knowledgeable gives you proper guidance.

 

[BanditPanda]

My 1936 cab as well as my JCM 900 combo each come with two 16 ohm speakers. When properly wired, the two 16 ohm speakers should connect to 8 ohm jack on the amp. Similarly, a 4x12 cab with four 16 ohm speakers gets connected to the 16 ohm jack on the amp. If your amp has two 8 ohm speakers, then I think it should connect with the 4 ohm jack on the amp.

BUT, I suggest you not do anything until someone more knowledgeable gives you proper guidance.

John, you're certainly correct about waiting for a more knowledgeable person to chime in.
I went on line but couldn 't find an answer to the OPs specific question.
However if 8ohm / 2 speakers = 4 ohm why would 16 ohm / 4 speakers = 16 ohm? Would it not also = 4 ohms?
It probably comes down to a question of wiring i.e. Parallel vs Series.
In Ryan's case both the combo and the extension should be both wired in parallel which is the most common type when it comes to guitar related amps and speakers.
Now if, as 4K says "....The MX212 ext cabinet has a single 8ohm mono input " which leads me to believe that it holds 2 x 16 ohm speakers( 16/2 = 8) then now I think we need to know the ohms of the speakers in the combo.
Ryan what do those combo speakers show as ohms?
BP

 

[JCarno]

The combo has two 8ohm speakers in it already.

Ok, sorry, I thought it was a 1x12. That doesn't change the fact that you shouldn't use the 16 and 8ohm at the same time.

 

[John BNY]

John, you're certainly correct about waiting for a more knowledgeable person to chime in.
I went on line but couldn 't find an answer to the OPs specific question.
However if 8ohm / 2 speakers = 4 ohm why would 16 ohm / 4 speakers = 16 ohm? Would it not also = 4 ohms?
It probably comes down to a question of wiring i.e. Parallel vs Series.
In Ryan's case both the combo and the extension should be both wired in parallel which is the most common type when it comes to guitar related amps and speakers.
Now if, as 4K says "....The MX212 ext cabinet has a single 8ohm mono input " which leads me to believe that it holds 2 x 16 ohm speakers( 16/2 = 8) then now I think we need to know the ohms of the speakers in the combo.
Ryan what do those combo speakers show as ohms?
BP

I don't know enough about electronics to answer why a cab with four 16 ohm speakers should be connected to the 16 ohm jack in the amp. But, if I look at the back of the 1936 cab, it says 8 ohms for mono. Similarly, with my 1960 cab, it has a jack for 16 ohm mono, which gets connected to the 16 ohm jack on my amp. I know someone here can explain why this is so.

 

[BanditPanda]

ok as per Ryan's info "....The combo has two 8ohm speakers in it already " and he stated that the amp came from the factory with them connected to the amps 16 ohm out.
This means the speakers are wired in series.
When wired in series you add the number of ohms per speaker together.
When is parallel you divide the number of speakers in to the ohms.
It means that Ryan has 1 pair of speakers with an 8 ohm input ( MX ) and one pair of speakers with 16 ohm input (m 205c )
So one cab = series wiring and one cab = parallel wiring.
And in exceptionally simplified terms that is how a 4 x 12 @ 16 ohm can produce a 16 ohm out.
One set of 12's is in series and the other in parallel.
Again I am just trying to understand this and in no way shape or form do I know anything about the subject matter at hand lol.
BP
p.s. I think there is a way for Ryan to run the combo and the ext at the same time however a wiring change would have to take place on one of the cabs.?????

 

[Ryan500mtm]

ok as per Ryan's info "....The combo has two 8ohm speakers in it already " and he stated that the amp came from the factory with them connected to the amps 16 ohm out.
This means the speakers are wired in series.
When wired in series you add the number of ohms per speaker together.
When is parallel you divide the number of speakers in to the ohms.
It means that Ryan has 1 pair of speakers with an 8 ohm input ( MX ) and one pair of speakers with 16 ohm input (m 205c )
So one cab = series wiring and one cab = parallel wiring.
And in exceptionally simplified terms this is how a 4 x 12 @ 16 ohm can produce a 16 ohm out.
One set of 12's is in series and the other in parallel.
Again I am just trying to understand this and in no way shape or form do I know anything about the subject matter at hand lol.
BP
p.s. I think there is a way for Ryan to run the combo and the ext at the same time however a wiring change would have to take place on one of the cabs.?????

I'm with you brother. Now that we've gone down this rabbit hole I need to see it through. I've emailed Sweetwater to see what they say. I'll let you know!

 

[JLBIII]

Here's a quote from the "old" JVM forum:

Yeah, even Santiago said this in the JVM forum!!
Here's the link to the thread:
JVM Forum • View topic - Can I run a 16 or 4 Ohm cab + an 8 Ohm cab?

"There won't be a mismatch if you plug the 8ohm cabinet into the 1x4ohm output and the 16ohm cabinet into the 1x8ohm output. Everything will be perfectly matched and the power splitted equally into both cabinets.

Santiago"

 

[Ryan500mtm]

Here's a quote from the "old" JVM forum:

Yeah, even Santiago said this in the JVM forum!!
Here's the link to the thread:

"There won't be a mismatch if you plug the 8ohm cabinet into the 1x4ohm output and the 16ohm cabinet into the 1x8ohm output. Everything will be perfectly matched and the power splitted equally into both cabinets.

Santiago"

Thanks for sharing JLBill!

 

[Ryan500mtm]

Here's some good info in case someone else has a similar question.

 

[MonstersOfTheMidway]

Hello Ryan500.
Sorry for the confusion. In my first post above, I thought you initial post was written with the intention of using the cabinet and disconnecting the combo speakers. If you are just going to use the cabinet and not the combo speaker, then you can hook things up as I described above.

If you want to run the combo speakers and the cabinet speakers, then you'd probably be running in a mismatch. Some mismatches are "safe" but you need to look at the internal wiring of the speakers to be sure. But it looks like in your #19 post in this thread you found a source of information. To be honest, I never ran any of my amps in a mismatch, so I'm can't tell you that the results will be positive or that your gear will suffer no harm. I've certainly heard of people running their amps and cabs in a mismatch, but it's not something I have ever done.

The safest way I know to use the cabinet with the combo is to unplug the combo speakers from the amp and then plug in the combo into the amp.

I'm not sure if your looking for a different sound, more power, or a desire to spread the sound. With the speaker output options on the 205C, you certainly have plenty of good options.

Good luck with the gear.