OK Here goes:
I have a stock Linksys WAG54g, which provides my WAN connectivity. The wifi from this is extended onto a Linksys WRT54g, (running third party SVEASOFT firmware,) into which my Wintel server and NSLU2's are plugged, (I have two NSLU2's, one stock, the other configured for Twonky with uNSLUng.)
For players, I'm using two identical Pinnacle SoundBridge's, (OEM Roku devices.)
As identified above, I'm running Twonky on an NSLU2 to serve music to the SoundBridges.
To enable multiroom capabilities I've had to implement a third party application Cidero (
http://www.cidero.com) which acts as a uPnP media controller.
In addition to standard upnp controller functionality, Cidero includes the ability to synch multiple players, (I don't know if this will work with more than two,) for which it uses it's own software proxy which seems to be some kind of software upnp render device.
(I currently have the proxy installed on my Wintel server, but would like to run it directly on the slug alongside Twonky.)
Still with me?
Right, now it gets fun:
With both my players switched on and connected, I fire up the Cidero Media controller on my laptop. Confirm that all settings are correct, and chain the two players together.
Then it's just a question of selecting traks to add to the playlist and hitting the play button:
Out of both players I get perfectly synched music playback!
I have a friend with a similar setup, (same audio players, same media server setup) who can also manage multiroom, but has had more issues with synch and playback, (his house is bigger and his wifi setup, (Netgear,) doesn't have the extended range of mine.)
it seems to me that the Cidero controller is telling Twonky to stream the requested audio to the proxy, and directing both the players to receive the stream from there,
almost as if it were an internet radio station.
It's a shame that the dev team have given up on this functionality, as it's a killer feature and much sought after. I've read a lot of the associated posts in this forum and most of those who attempted multiroom seemed to have had totally unrealistic setups. Most people seemed to expect that Twonky should successfully synch the hotch-potch of kit they had connected to their network ,and screamed blue murder when it didn't work.
If I can find an old NSLU2 compiled version of Twonky that supports the multiroom function I'll maybe give it a whirl.
Hope that helps