Two unusual problems there.
Well, vibration/echo is sort of usual, but more commonly with HDDs and cheap cases.
No HDDs now. All drive bays removed also. The case is a fairly large midi tower with a now-empty front, so it's pretty hollow. It wasn't cheap, but Enthoo Pro is more solid value range than enthusiast range. The front and top surfaces on which founts are mounted aren't rigid (aluminium sort-of-wings rather than the steel case frame). I decided to use Noctua's rubber bolts rather than screwing the fans tightly (overtightening the screws tended to work better for me than rubber pads some 10–15 years ago).
Part of the problem with vibrations is that there's a heckton of them coming from the outside (think municipal works at night, like plumbing fixes or whatever) and my relatively small room (<12 sqm) on the 11th floor seems to pick up sounds from the outside or even amplify them. Sitting near the window you can sometimes hear conversations from the outside quite clearly. Much of the time ugly sounds feel like they're coming exactly from the PC case under the desk, though the real source is outside, which you only find out by shutting down or hybernating the computer (at which point the sound is still there but as if less prominent). The PC itself stands on a thick anti-vibration rubber mat, so it probably shouldn't be quick to catch vibrations from the outside.
Other than vibrations, it's generally coarse motor/bearing sounds, such as on my Silent Wings 3 hi-speed when pulling through mesh+filter as front intakes. They were audible around 550rpm and problematic from 600 up. At 800 the problem was big. As CPU fans, 900 is or borders on inaudible. Or clicks, if a fan develops them, such as the original 200mm from Phanteks.
Other with audible air flow. Too much air flow.
Could both be linked to those massive 230mm fans? Turn them off?
A bunch of 500rpm fans tends to make things audible for me. I keep case fans off for work and light gaming. IIRC they won't start until CPU hits 60C, at which point they run 300-ish (500–600 tops) and the CPU fan runs 600-ish. In Prime 95 this isn't sufficient, or rather the mobo does a vdroop throttle, Asus-style (Z370-H), as soon as the VRMs reach 75C or Watt output reaches 125. Then, the CPU frequency doesn't seem to change and voltage seems to change only slightly, but wattage seems to be intent on going from 125 to 95, reducing in a huge temp drop, then the cycle starts again. This is the behaviour on my cheap mobo that serves as a temporary replacement for my Aorus Pro Z390.
And coming back to first reaction. You don't need many fans at all.
Plan A:
Slap a big heavy cooler (can recommend Scythe Ninja, wide fin spacing good for low rpm) on CPU.
Add 1 (one) sub 800 rpm exhaust fan somewhere. Let GPU manage its own ****. Done.
The case sits in the exact corner of the room, under the desk. Rear exhaust is 140mm, very close to the wall. Top exhaust is 1x200 or 2x140 (or 1x230 ghetto), often not as close to the desk as the rear is to the wall. Would you suggest rotating the CPU cooler 900 degrees?
As for GPU, I've recently realized that while the air movements are inaudible at 1000-ish rpm, the bearings make a nasty vibration-like contribution to the unsettling sorta-silence-but-something-feels-off overall acoustic impression.
Plan B if fancy overclocking:
Add intake fans blowing cool air into CPU and GPU coolers. Done.
Yes, well, there's a lot of empty space in the case front right now. This is probably what leads to the audibility/echo, and is also what makes me think that this works kinda like a modular/two-chamber case, where you could put bottom intakes opposite of top-front AIO rad exhausts with nothing in between them, somewhat far away from the mobo. (The added length of the removed bays as compared to a modern bayless case.)
In the AIO variant, I would have:
A. CPU top 360 AIO exhaust, GPU front 280 AIO intake, bottom 140 intake, rear 140 exhaust.
B. Top-rear 140 exhaust, CPU front-top 280 AIO exhaust, rest as above.
C. GPU 240 bottom intake.
D. CPU 280 front, GPU top (280+140 fan or 360 rad).
E. Normal fan intakes, GPU with Morpheus/Accelero.
Everything else is just to have fun tinkering, no real benefit.
There's a promo at a retailer's nearby, with Liquid Freezers 280 actually cheaper than D15 or LGMRT. Does this change anything?
