>>7967341japanese sound effects libraries from the 90's/2000's are pretty hard to find as they came only on CDs and usually didn't get much use in the western world. look up E&M Planning Center, they worked on so many animated features.
libraries that are easier to find and have that kind of sound would be Sound Ideas and Hollywood Edge libraries from the late 80's and 90's (especially Martial Arts, Premiere Edition, The Edge Edition, Series 1000/2000) which were very much used in the anime market as well. soundeffects wiki is a good place to start looking for references, Taira Komori has an interesting free library on his website and you can find many sound effects ripped clean(ish) from anime online, especially from 5.1 releases.
anyway, about the audio processing. you have to consider what they were editing on and what they were printing on. the mixing on hentai was usually done for home video (vhs, laserdisc, dvd) and I'd guess not with the sound quality's best interests in mind. for analog releases the sound had to be at least loud enough so that the quieter parts didn't get drowned in noise. if you want to recreate that sound try putting a hard limiter at -8 dBFS on the mix bus (it's an old standard for tv mixing) and generally cut your mix around 10-12 kHz with a 24db (or steeper) lowpass filter. tape simulation / saturation to taste. the overall track levels should be such that the slightly louder parts of the dialogue and sfx bump into the limiter a bit (3 to 6 dB reduction is fine but you can push it more for a stylized effect). in the loudest scenes you'll hear the girl getting fucked screaming, and the music, and the sfx fighting against the limiter in a very messy uncontrolled way. master your files to no more than 44.1kHz 16bit (maybe even 12-14bit) with some old style shitty digital dithering for a slightly crunchy noise floor.
t. film re-recording mixer
