How to turn off captions/subtitles by default?

Hi,

I've noticed that for some time subtitles have been automatically enabled on each video. Since I usually have no problem understanding what it is said in the video, I always turn off the subtitles. However, turning off subtitles on each video separately has gotten very tedious and annoying, so I was wondering if there's a way to turn them off by default?

I'm posting this here because I believe that this is a setting on the Khanacademy website, since on youtube captions are turned off by default.

Please note, that I would like to continue watching videos embedded on the Khanacademy's website.