Found this Deal on Harman Kardon website, from $699 to $10 is can transform any on Wireless speaker system to wireless or multiroom system. i have 2x of the older version at home (non Chromecast version) and they have worked well. Spec are below,
"CITATION ADAPT is intended to be used for streaming music. A consumer can stream Bluetooth audio to the speaker. A consumer can connect their speaker to the localWi-Fi Network and stream music with Google Chromecast. In addition, the speaker will work with Google Home. This product is designed to be instantly on and ready to play music at a moment's notice, therefore, the Bluetooth andWi-Fi connection must remain active at all times to ensure proper operation. CITATION ADAPT is in compliance with the European Union energy legislation. CITATION ADAPT will enter into sleep mode (networked standby) after 20 minutes without operation, after which it can be re-activated via Bluetooth or Wi-Fi. "
Power supply 100-240v ~ 50/60Hz
Wireless network 802.11a/b/g/n/ac (2.4GHz/5GHz)
2.4G Wi-Fi transmitter frequency range 2412 – 2472MHz (2.4GHz ISM Band, USA 11 Channels, Europe and others 13 Channels)
2.4G Wi-Fi transmitter power <20dBm
2.4G Wi-Fi modulation DBPSK, DQPSK, CCK, QPSK,BPSK,16QAM,64QAM
5G WISA transmitter power <14dBm
5G WISA modulation OFDM, BPSK, QPSK, 16QAM
5G WISA transmitter frequency range 5.15 - 5.35GHz, 5.470 - 5.725GHz, 5.725 - 5.825GHz
Power consumption in sleep mode <2.0Watts
Buy now, think later. Thanks OP.