This is certainly an odd issue. Sorry to hear about it, but let's get it figured out for you. I have a few questions to start off:
I just want to confirm: even with with Wi-Fi disabled on the SoundTouch 300, your devices get disconnected from your network?
Your Airport Express, is it a newer one with 2.4 and 5ghz wireless? If so, have you tried both wireless bands?
Is the Airport Express the only wireless router in your home? No other extenders or routers provided by your ISP?
Nov 19, 2016
I fixed it for you guys.
*sigh* Why am I doing your job? 🙂
I reckon try different channels first...(Wifi channels)
This fixed it. Thanks. I read in the manual the Bose uses 5150 to 5250mhz (I assume for it's additional speakers and subwoofer connection), I changed the Apple Airport's 5ghz network from Automatic to channel 149, which is well above 5250mhz (can wikipedia this stuff) and so far no issues. I'm surprised the Apple didn't adjust automatically but nothing is perfect.
Jan 9, 2017
Just picked up a SoundTouch 300 and it's killing all of my Apple products too. Most importantly, it's rendering my AppleTV useless.
I don't really undersatnd the fix though. I rent a Verizon FiOS Router. How am I supposed to change the channels?
Any help and guideance on the fix would be great.
Would really hate to have to return the SoundBar.
Sep 20, 2017
Oct 18, 2017
I have exctactly the same problem, SoundTouch kills my wifi (Apple TC), unfortunatelly I cannot move my router to channel 149 because in Europe we have only 36-40-44-48, means 5170-5250MHz.
Is there any solution for this problem? Can we change the channel to the SoundTouch?
Sorry to hear about the issues. Is the Soundbar interfering with just 5 GHz or also 2.4?
What is the distance from the router to the Soundbar?
Do you have the AM300 subwoofer as well?
Dec 18, 2017
Just bought soundtouch 300 and subwoofer, unable to use my wifi connection after plug in soundtouch 300, like everyone saying BOSE soundtouch with subwoofer is interupting WIFI signal, im gonna have to return this item.