Can I use DC adapter for AC device

I got some speakers calls Creative Gigawork T20 I got from my sister but one of her 10 cats has chew up the cable on the power adapter so I just took a quick look on it rated 12v - 2.9 amper so I took one of my spare power adapter rated 12v - 2 amper and use it for a few weeks I was waiting for the heat shrink to arrive so I begin to repair the old one to use that one instead of the spare one so i found out its a AC adapter but the funny thing is i use DC adapter on it with no issues I was thinking that's pretty weird

so my question is can devices require AC can i use DC without taking damage on the devices I know it sounds pretty stupid but most of my spare ones is DC adapter I don't want to see huge cloud of smoke or explosive

sorry about that here's the pictures of it

^its output AC testing with multimeter

the other two make DC testing with multimeter

I also use this one for fun