Over the weekend I discovered some delay problems whenever there are more than 20 or so sources playing at around the same time in the Helicopter demo applet I wrote some time ago. I spent a great deal of time looking into the issue.
I haven't been able to solve this problem yet, but I have discovered a couple of interesting things. Firstly, the problem only appears when running jPCT via the LWJGL Applet Loader, and only for the LibraryLWJGLOpenAL plug-in (LibraryJavaSound works fine, even when loaded via the Applet Loader). In other words, I can only replicate the problem when mixing the LibraryLWJGLOpenAL plug-in with jPCT in an applet. Since jPCT relies on the LWJGL, as does the LibraryLWJGLOpenAL plug-in, I suspect there is a thread synchronization problem in my code related to the LWJGL that is conflicting with jPCT. The confusing thing is that the problem only appears in applets and not applications (due to limited resources, perhaps?)
I am currently working on porting the helicopter demo applet to the JMonkey Engine so I can mix OpenAL and OpenGL in an applet without the LWJGL Applet Loader. This should either strengthen or refute my theory that the problem is a thread synchronization issue related to the LWJGL. If the problem exists there as well, then I will start looking at other possible causes, such as memory leaks and the like. I will post further information as I progress.