Hi guys, I've have some rare stuff going here today, let me explain

I got one rar I compressed time ago, a pack of samples, typical uncompresed wavs 16/44.1 stereo. I've been using the rar compression with rar v4, best compression, max dictionary size and in advanced compression I choose Force Audio compression with channels to 0 (I've tested with channel to 2, but usually found files to be larger with this). This usually beats 7z's size (tested various methods). I know I could compress first with flac, but I want to be simple here

The story is today I got the same rar in some random web, and it was smaller than mine. Mine is 462MB compressed in the way above, and this is 437MB. So, i did some research, I listed the files with 7z l -slt command, in the new file the method used was m3:22 (AFAIK this means is using normal compression and dictionary size 4096KB (2^22). My files are compressed with m5:22 method.

So I compressed mine also to m3:22, fail, the new file is smaller. No files are using solid method.

What I am missing here? It's there any other data i could look in the new file to guess how it was compressed?