When you connect an external cab to a combo using the external speaker output, is the output of the internal speaker reduced, or does it remain the same?

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Current Rig:
-Guitar: 72 Tele Custom Reissue
-Amp: Peavey Prowler 45w Tube Combo (6L6's)
-Effects: Boss TU-2 > Boss Blues Driver > Boss OD-3 > FX loop: Guyatone Slow Volume > Boss GE-7 > Boss BF-2 Japan > Ernie Ball Jr. VP > Ibanez DE7 > Boss DD-5 > Digiverb