During normal day to day stuff, this rig can happily sit at 0dB above ambient noise with no running fans or other moving parts.
I just spent the last 12 out of 14 months underway on a Navy warship. I had over 60,000 horsepower worth of gas turbines within a few dozen feet from where I slept. Ambient noise was ~85 decibels while trying to sleep (Measured with a calibrated OSHA approve decibel meter). If you want to know what this is like, turn on your vacuum cleaner. Keep your vacuum cleaner running 24/7/365 and no more than a few feet away from you the entire time. As such, I wanted some peace and quiet now that I'm home for awhile. Silence, and single monitor performance for Star Citizen were my only concerns.
Right now is kind of a stupid time to go all out on a monster gaming rig with Skylake/big Maxwell/1ms GSYNC IPS panels on the very near horizon.
I needed a new desktop, as I've been nursing my tired old Alienware M17x R3 3D along as my one and only PC since early 2011. It's been drug through every time zone on the planet, boarded pirate ships with me, interfaced with UNIX based navigation computers that only speak German, and has picked up almost 50,000 miles of travel. It's time to retire it to comfortable reddit surfing on the couch duties.
I felt like buying a new desktop right now would be kind of silly with so much new hotness on the horizon (as I try and futureproof my rigs as much as possible), so I decided on a compromise.
Once I retire this thing in a year (Because srsly, CV1 Oculus with what Star Citizen has on the horizon is going need way more than what a single 970 can push) it will find a home in the living room as a silent HTPC. I already tried pushing (downscaled) 4K video content through it, and it was still able to survice at < 60C across the board without any fan usage.
It's probably going to be at least 10 years before I start looking beyond 4K content. With no moving parts and the build quality of these components, this rig will probably last at least that long in my living room. With 8 SATA ports and a solid RAID controller, I can continue adding storage for a good many years.
Using the audio tools app on my phone I did some noise testing, The phone was placed about 12" off the ground, 18" away from the front of the case. I had an audio engineer friend tell me that while absolute dB values aren't very accurate with this app, relative values are accurate enough for my purposes.
I recorded ambient noise in the room to be ~57 dB in the evening with light traffic outside. This seems high. My house is pretty well insulated, and I live at the end of a cul-de-sac right next to a lake. A calibrated meter would probably read much lower.
At idle during web browsing, I recorded ~1dB above ambient. My spec-an showed the increased noise was at 60hz, so this is probably a bit of noise from the transformer in the power supply.
I wasn't able to find a DX9 game that pushed the system hard enough for the fans to come on (CPU is set at 55c, and GPU at 66) at 1080p frame locked to 60FPS (Waiting for the 1440p, 144hz 1mS IPS Gysync monitors to drop before I upgrade beyond a 60hz panel).
Dragging my mouse across the desk, or breathing brought readings up to ~3dB above ambient
With the HVAC in my house running (all other tests were taken with the HVAC off for reference), noise was measured at ~5dB above ambient.
Running the Heaven/firestrike benchmarks saw ~7dB above ambient.
Star Citizen saw ~10dB above ambient during an extended play session against bots (to push the CPU/GPU as hard as possible).
A 24 hour prime-95 burn in test saw 21 dB over ambient (With all fans going at 100%).
Temperatures held steady at 80C @ 4.2ghz and stock voltages. I'm going to do some tinkering to see if I can maintain that same overclock at a lower voltage, then see how far I can push it at lower voltages keeping the thermals below 80C. I might be able to hit 4.4. We'll see.
Even at 21dB above ambient during full load, this is still by far, the quietest computer I have ever personally used in 25 years of building rigs. With my Sennheiser HD558's on (over the ear, open design) and nothing playing, I still REALLY have to struggle to hear this thing running, even with all the fans at 100%.
GPU was pushed to 1470mhz on the core, and 8ghz on the memory. Temps never got above 70C, even with none of the case fans running.
So, I spent way more on this than I needed to, but I stand by all of my decisions. Example: $150 for a 520W power supply is insane... but it has no fans.
The motherboard was stupid expensive for an mATX unit, but offered more PWM fan outputs and a few other features that no other MOBO in the mATX form factor did.
$100 for an mATX case is also expensive, but I couldn't find another case on the market that I didn't hate the visuals on, that also had a thermal layout appropriate for 100% passive cooling. The Arc Mini R2 has vents/fan openings in both top and bottom AND has filters everywhere. This allows cool air to be drawn in through the bottom and hot air to be expelled through the top of the case through pure convection.
Initial thoughts: The ROG front base is ******* AWESOME for what I need it for. I can play with all sorts of undervolting/overclocking parameters and monitor everything right through the front panel in real time. When this thing moves to the living room, it will be nice to tell at a glance how the hardware is doing.
I don't care what all of the haters say. The 970 strix is an amazing card. Silence performance for the vast majority of the time, with the horsepower to push Star Citizen on my 1600 x 1200 monitor past 60FPS.
I didn't go with the 980/4790 combo, as the idle/load power consumption was quite a bit higher, which is very important for the silent goals of this build.
If there is enough interest, I'll post some results on just how far I can push this rig without thermals getting to where fans are needed. Even when pushing this thing to the limit on Star Citizen, all of the fans stay below 50% duty cycle (which is still EXTREMELY quiet on the fans I chose).
I still have a tiny bit of cable management to clean up, and I'm debating de-soldering the white LEDs on the GPU/MOBO and replacing them with red ones (I do component level repairs on bajillion dollar military radars for my day job, a single LED isn't too tough). I may de-lid the CPU and go direct to die to increase the thermal gradient with the heat sink (which will improve passive convective cooling). I think I did OK in the silicon lottery. I am definitely thermally limited right now. A de-lid direct to die setup should help with this quite a bit.