I use Subsonic specifically because my library is too large for Sonos to handle. The library currently shows -
Media collection 1,611 artists
4,855 albums
69,886 songs
Sonos is hard coded to not see anything greater than 65000 I believe.
If I use this url against one of my Sonos speakers to see what is sees (
http://speaker_ip:1400/status/tracks_summary) it shows -
Title
MAX 65000
COUNT 65000
I can't browse my artists either. Sonos times out. I can browse the Albums though and can certainly search everything. How many albums do you have? My library has around 4671. Sonos has a hard 20 second timeout to get a response from the server. I wish it were configurable as then I'm sure I could list the Artists if I increased it a little.
None of this answers your question but I just wanted to let you know it should work, at least, more should work than what you describe.
It's tough to do if you are not familiar with the logs but maybe try and do the search in the Sonos controller and then open the subsonic.log and find that search string you sent and verify that the server received it and see what, if anything, it did with it.
Good luck.
billraff