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Old 11-29-2017, 03:43 PM   #1
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Default Will this setup work?

I have a Marshall JCM 800 4210 and a Marshall MA50C. I want to use the speaker in the JCM along with the MA as an extension cabinet. I've included a pdf file for you to see. Will this setup work?

Thanks.
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Old 11-29-2017, 05:40 PM   #2
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I have a Marshall JCM 800 4210 and a Marshall MA50C. I want to use the speaker in the JCM along with the MA as an extension cabinet. I've included a pdf file for you to see. Will this setup work?

Thanks.
It will work, but it depends on the ohm resistance of the speakers as to whether it will work CORRECTLY, and not damage your JCM800.

If the stock speaker in the JCM is 8 ohm, and the speaker in the MA50 is 8 ohm, and you have the amps ohm output selector on the JCM set to 4 ohm, it will work fine.
Same thing if both speakers are 16 ohm and the amps output selector switch is set to 8 ohm... no problem.

You're gonna run into a problem is if the speakers in those amps ohm resistance is mismatched.

Ex: If there is an 8 ohm speaker in the JCM and 16 ohm in the MA50. Then its not gonna work properly. In that case, the 8 ohm speaker will not only be louder, but you will also have a total speaker resistance that the amp does not have an output setting for. Some amps can tolerate a speaker ohm resistance that differs from the amps setting, and some amps cannot tolerate that mismatch.

If you know the speakers ohm resistance (it should be listed on either the speakers label, or on a small tag somewhere on the speaker frame), it will make answering your question way easier.
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Old 11-29-2017, 08:46 PM   #3
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You pay attention to what StFill said. He's pointing you in the right direction and as he said, some amps can tolerate a wide impedance variance, others can't. If you use a low ohm speaker and a high ohm speaker in parallel, they will act a bit like a passive crossover network and the higher impedance speaker will block the really low frequencies and tend to pass the mids and highs while the lower impedance speaker will try to pass every frequency. Just do your best to match your speakers.
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Old 11-29-2017, 09:30 PM   #4
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It will work, but it depends on the ohm resistance of the speakers as to whether it will work CORRECTLY, and not damage your JCM800.

If the stock speaker in the JCM is 8 ohm, and the speaker in the MA50 is 8 ohm, and you have the amps ohm output selector on the JCM set to 4 ohm, it will work fine.
Same thing if both speakers are 16 ohm and the amps output selector switch is set to 8 ohm... no problem.
Ya I just checked. The JCM speaker is 16 ohms and so is the MA50C speaker. So I could connect the speaker of the MA50C to the other jack on the JCM and then turn the selector to 8 ohms.
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Old 11-29-2017, 11:38 PM   #5
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Ya I just checked. The JCM speaker is 16 ohms and so is the MA50C speaker. So I could connect the speaker of the MA50C to the other jack on the JCM and then turn the selector to 8 ohms.
Yep, that'll work fine as long as the JCM800's output is set to 8 ohms. You might even like the JCM's tone better with an 8 ohm total speaker load than the 16 ohm load it has with the stock speaker.

PK and I discussed this in a PM when I was setting up a cab for a Mesa Roadster I got recently, and his advice was right on the money... sometimes an 8 ohm load will actually sound better than a 16 ohm load. I've always gone by the dictate that if an amps max ohm setting was 16 ohms, then try to use a 16 ohm speaker load.

In actual practice, it doesnt always work that way. The Mesa rig I set up DOES sound less muddy and have better note attack and definition with an 8 ohm load than it did with a 16 ohm load.

Just dont forget to switch the JCM back to 16 ohms if you disconnect the MA50's speaker.
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Old 11-30-2017, 01:35 AM   #6
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Yep, that'll work fine as long as the JCM800's output is set to 8 ohms. You might even like the JCM's tone better with an 8 ohm total speaker load than the 16 ohm load it has with the stock speaker.

PK and I discussed this in a PM when I was setting up a cab for a Mesa Roadster I got recently, and his advice was right on the money... sometimes an 8 ohm load will actually sound better than a 16 ohm load. I've always gone by the dictate that if an amps max ohm setting was 16 ohms, then try to use a 16 ohm speaker load.

In actual practice, it doesnt always work that way. The Mesa rig I set up DOES sound less muddy and have better note attack and definition with an 8 ohm load than it did with a 16 ohm load.

Just dont forget to switch the JCM back to 16 ohms if you disconnect the MA50's speaker.
Excellent! This is good to know. Thanks for your help and advice!
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Old 11-30-2017, 03:48 AM   #7
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Excellent! This is good to know. Thanks for your help and advice!
My pleasure!!

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