Hi, Uncle John,
So I bought a SoundTouch Wireless Link Adapter and two SoundTouch 10 speakers. The adapter (LecternR001) takes an "aux in" signal and transmits it to both SoundTouch 10 speakers (Cry Room and Foyer).
This setup works well except for one problem, the two speakers lag the adapter by about 3 seconds.
How can this be remedied?
I just set up a SoundTouch Wireless Adapter and some remote speakers to replicate your set up.
Unfortunately, using the Bose SoundTouch Wireless Link Adapter Aux input introduces the lag (latency) between the sound source presented to Aux input and loudspeakers connected locally or in your case remotely. This happens as the signal sent to the SoundTouch Wireless Link Adapter audio output is synchronized with the external loudspeakers connected over the wireless network.
This latency is not noticeable for recorded music (this is the intended purpose of the Aux Input).
For live sound applications, you will notice the latency when you can hear both the live sound source (e.g., a talker at the lectern) immediately, and the remote sound (e.g., Cry Room and Foyer). You probably won't notice the latency if you can't see or hear the talker at the lectern. If you can isolate the rooms (close the doors), the latency should be less noticeable.
I'm sorry there isn't an all Bose solution for the latency. Any other approach that comes to mind would likely be more expensive.
Bose S1 Pro systems for the Cry Room and Foyer
You would also need low-latency receivers
Instead of using the Bose SoundLink Wireless Adapter, you would need a different kind of transmitter to connect to the low-latency receivers in the Cry Room and Foyer.
The kinds of transmitters and receivers I'm thinking of here are relatively new in the market (last year or two) that operate in the 2.4 GHz frequency range. Some people are pleased. See Wireless transmitter/receiver to use with two S1 pro speakers. Others have reported latency issues.
Another approach is to use different wireless broadcast technologies with greater range and more channels. Here is a link to some systems from Shure.