Wow, I fixed it!
I went to Al Lowe's Troubleshooting page to see if I could get a clue as to what might be wrong.
http://www.allowe.com/Larry/troubleshooting.htm
Looking at his section about the new collection, I noticed he has some instructions on copying the LSL6CD and LSL7 to the hard drive. It replaces the LSL6 installed by the collection done that way. I prefer to keep both so I'm glad you include the option of installing those versions in your updater/installer.
But the key was checking my resources.cfg in the LSL6CD folder. It did not have any resAUD or resSFX lines in it. I gave it a shot and added them, figuring the game might not be finding something it needs for the voices.
I added:
resAUD = .\AUD
resSFX = .\SFX
I typed it in with the big spaces around the = just so it fit in with the rest of the file, and put the folders in those caps since the folders appear capitalized like that in the folder.
Sure enough the game's next run had all the voices. It must be easier to find the music when left to itself but not the voices.
RESOURCE.AUD is in the AUD folder and you're right about that being a big file. Same size as on the cd so I think it's okay.
I had some fun initially installing this stuff. The first time I installed properly the latest DOSBox into C:\Program Files\DOSBox but left the big TM at the end of Sierra's install folder. Then when your installer requested a folder I just let it go since I saw it had C:\Sierra\Leisure Suit Larry Collection. Arrgh! No TM! Heh. So I had to uninstall your installer and uninstall the collection, the next time removing the stupid TM from the end of the folder name.
It's been a long time since playing these. I have the rest of the Sierra new collections as well and really have never played any of those, though I've played through and completed all the Larry games several times over the years (even that Magna C Laudy thing). I used to enjoy the Vivendi Sierra forums and have been using your installers for the other games. In the past I've just installed my Larry games from the Collection Series or Pleasure Pack (they're the same), but since you pre-patch the games now I figured this time on my new Windows 7 installation I'd go ahead and check out the Vivendi/Sierra version of the collection.
Another reason I've used the older installation media for Larry is that I've been using DOSBox on Linux a lot and haven't been using Windows for quite a while. Now, with Windows 7, it's something new to play with and experiment on.
I don't know if something went weird in the installation that caused those lines pointing to the aud and sfx folders not to appear in resource.cfg or whether they just won't appear unless actually running the original installer from the cd. Perhaps in another version you may want to script those lines into resource.cfg? Either that or just change the readme to include the suggestion to add those lines manually if there's a problem with the voices in LSL6CD?
In any case, you're doing a great service for old time gamer types like me!

So I do want to say thank you for this great site, all the installers and troubleshooting help, forums, etc, etc.
Actually I'm not too sure I'm much of a gamer anymore. In the old days it was part of the fun of discovering computers for me, just figuring out how to get games and other software to work and then playing through the games and, in the case of the LSL series, laughing and enjoying every minute of it! Nowadays I've been more interested in watching Linux grow and change (I use Debian testing these days). I was a big Nintendo addict too, and play the old stuff on emulators now when I do want to do a little gaming. I can't see buying the newer consoles as I already have more games (PC too) than I'll ever devote the time to play.
Thanks for keeping the Sierra experience alive!