HHi Joe:
The BTP 525 is a closed system. It features an internal two-channel stereo amp in the primary Patio speaker. One channel connects to the internal speaker, and the second channel is hard-wired to the second channel of the satellite speaker using the two conductor speaker wire that is supplied in the kit. Adding the two speakers to this speaker connection would cause a harmful load to the internal amp.THe BTP525 features the new Bluetooth version 5.0, so you can sync up to another pair of BTP525 as long as you have an Android smartphone. Apple products will allow you to sync up to two pairs of Apple-branded products like two AirPods or Bluetooth Beats headphones. It will sync up with two BTP525 but only allow you to play one or the other, not both simultaneously.
TimL/7-18-2022