jbl boombox

Hi, I've a one question. When I connect my JBL to PC it sounds way louder than on my phone (SG A6 Android 8.0). I've turned every EQ and bluetooth BS on my phone off. When I compare the difference, 50% volume on my phone is equal to 15% on pc. Why? I bought Boombox for loud parties not casual...

I'm going to buy a good portable speaker but I don't have enough ideas which one to choose. The best for me is Marshall Kilburn II, Harman/Kardon Go Play, JBL Boombox. I often leave the city and for me is really important the quality and max. volume of the speaker. I have been listening both...