Moblie bluetooth speaker unsmarting

Hi all! I'd like to make a wired multiroom sound system with base speaker at bathroom, wc, etc. a mobile bluetooth JBL Go (design/price/quality). Connection would be through 3.5 jack aux, power would be wired. It should be modified as killing the on off pushbutton and its auto power off. My ideas: 1. making a hardware modification 2.buy a cheap PC speaker and use its amplfier. 1. would be the real soulution as remaining volume control and bluetooth function. At 1. I have measured onn VCC when power on +4 volt, when power off, 0 volt. On bat+ (with ext.power, without battery) constant +4 volt. So I wired these two, but nothing happened. This is the status. On the enclosed picture up-left is the on off button, left is the passive speaker out, right bottom is the mic, right up is the battery. At 2. I am afraid of the background noises (now it is fully cut). Any ideas? Thank you in advance.