Who is saying ? I didn't quote anyone. ''D5 pumps are capable and flow restriction doesn't matter'' this is just a thinking i often see in watercooling circles.I think what hes saying is that even with todays cpu and gpu blocks the restrictions are so little that a d5 can overcome it easily and still maintain an ideal 1gpm. Thats what reviewers shoot for when they set up the test beds. So adding blocks wont make a difference for their testing purposes.
Unfortunately d5s are a hit or miss proposition. Some are whisper quiet, while some are loud as hell! I have 3 of them and they all have their own tone at 100%. So i naturally chose the 2 that are as close to silent as possible at 60-70. The way that you mount them can have alot to do with the amount of noise they generate as well. If possible try to use gel pads or rubber washers rather than hard mounting them to your case.
If its still under warranty ek is really good about taking care of loud pumps so dont just suffer in silence if its under warranty.
100% pump speed in furmark 305W load: 56C core - 42C water = 14C delta
40% pump speed in furmark 305W load: 60C core - 40C water = 20C delta
Components: Legit D5, low restriction cpu+gpu block, low restriction PE360 rad and high restriction gts 360 rad. Soft tubing without bends.
You can see the difference. It's not the end of the world but if we don't wanna optimize our systems why we are even bothering testing 1C difference between rads, waterblocks, thermal pastes, coolers etc.
I think 100% pump speed never gonna be silent. 40%-60%-70% depends on times of day, ambient noise. I opened and cleaned the pump over the years, everything looks ok. 2 year warranty is ended anyway.