Looking at the 4 series it seems like they only have a gaping grill but no pre-filter? Won't that kill the HEPA filter in no time? My Samsung AX90 pre-filters collect an entire layer every few months that can be cleaned instead of piling onto the expensive replacable filter, need something smaller but hesitating to get the 4s cos of this.
Edit: And I just realised the air reaches the fan first in these before going through the filters so that's another thing to clean, wow thereare so many ways you can mess up such a simple machine
I've read some people add their own