Preface: my PC is not a display peice. See my sig.
After weeks of bleeding ears, I decided to do what I could with what little I had lying around. I played around with fans hanging in free air, no grills, using a small 12v power wart for quietude. Found out that
anything anywhere near intake(more) or outlet(less) makes noise. Noise we don't need. Answer: skip the grills - don't need them.
- First I yanked the cheapass PSU, and cut out the grill. Wide open round hole. The PSU fan is slow enough not cut even a baby's finger, and nobody's back there anyways. Result: much quieter; much better airflow.
- Second, I yanked the stock 60x10mm screamer fan off my Arkua cooler. Built a square 80->60mm duct using thick felt (about same as white synthetic felt shoe insoles), hot-melt glued at corners, and hot-melt glued to plastic flange that screws to top of HS. Use a Thermaltake 80mm thermal controlled fan, sinched in with string. Again, no grill, the case is closed anyways. Result: quieter but TT fan is still loud; much cooler than screamin' stock 60mm.
My ears don't bleed
quite so much now

but my panaflos are on the way

As for filters, I only run the PSU fan for case venting, so the less air restriction the better.