I find myself in the position of having to consider a new casing, and looking at current designs, it seems bottom mounted PSUs are now quite popular. Most other places on the web cover top vs bottom mounting as a cooling issue, but I'm curious as to where the SPCR crowd stands on the issue from the silence perspective.
Google leads me to this tread
and this article
, though both are over a year old.
Seems to me that in the case of a passive PSU, we would have to mount it vent side up (as per the Seasonic passive X instructions) regardless of whether it's top or bottom mounted. The top mount position then requires a top blowhole, and it has the advantage of being a relatively "closed system" to the rest of the case. Bottom mounting it I suspect the issue is whether or not the case is running at a positive pressure.
With a fan-equipped PSU... well, I'm quite lost. At either top or bottom, if the PSU is fan side up, then I would think the fan would outweigh any convection. Bottom mounting the PSU and a positive pressure case would help here. But if there's a fairly hot GPU above it would that cause the PSU fan to ramp up early?
Fan side down - bottom mounting the PSU makes it a closed system. But there's the issue of ground clearance and dust intake. Top mounted the PSU then sees all the hot air rising in the case, again leading to the PSU fan ramping up. Would a case exhaust fan by the CPU help here?
And I haven't even considered whether a "normal" (CPU above GPU) or "flipped" (GPU above CPU) placement would have an effect on deciding where and how it'd be better to place the PSU. Admittedly, at that point this might be a better post for the Cases and Damping forum. Thoughts?