Hi, I'm getting an extension cab for my DSL401 combo. It has two outputs for extension cabs, one being used by the internal 16 ohm speaker. When I get my extension, can I use both the internal speaker in the combo and the extension cab at the same time? Or would it change the impedance seeing as there are 3 speakers in the circuit?
Cheers, David

Oh and just to check, two 8ohm speakers in series would make 16ohms wouldn't it? Never used an extension cab before so hopeless with all the technical side of it haha
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just downloaded the manual from the marshall site.

yeah from the looks of it you have the option of running the internal speaker alongside an external cabinet, or you can run the external cabinet alone.

if you want to run both together i'd want the external cabinet to be 16 ohms so it matches the internal speaker. odds are (contact marshall to be sure) the speaker jack sockets are wired in parallel so you'd set the impedance to 8 ohms.

to run both together you'd (presumably) just plug the internal speaker into one of the jack sockets and the external cabinet into the other.

bear in mind that doing it this way, half the power will go to the internal speaker and half to the external cabinet. which is probably fine (since the internal speaker can handle the combo's full wattage alone) but if your external cabinet has multiple speakers each of those speakers won't be driven as hard as the internal speaker.

to run the external cabinet alone you'd unplug the internal speaker and just plug in the external cabinet (and set the impedance to 16 ohms).
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Yes you can use both at once, but you need to have a 16ohm cab to add to it. This along with your 16ohm internal speaker will make a 8ohm load total. So you would switch to 8ohms on the amp and plug the internal speaker and the external cab in.

Yes 2 8ohm speakers in series is 16 ohms.
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