@mikeywith I can't thank you enough. I tried the option 2 and now both run with the same speed and not noisy at all (however I still hear a muffled whistling sound on the new one). I had to set the RPM to 30% in order to get to the same speed on the old S9J !!!
the whistling sound has to do with the fan brand/type, if you want to get rid of it, you need to find the exact fan on your 1st miner and install it on the second miner, the whistling sound seems appear at certain RPMs , so you can alter the RPM slowly till it "might" just disappear.
Now the question is, is there any way to modify the firmware files to get to a desired speed without setting a fixed RPM or losing the auto-tune feature ?
there must be away, there is a temp to rpm equation/code and it's different from a firmware to another, notice that i have never attempted looking it , but the logic states that it has to be there, but i doubt it's an easy job to do, an alternative option would be using something like awesome miner, you can have it change the miner frequency/rpm when the temp get to x degrees.
tho i don't think that's important, as long as your temps are good you can just keep the fixed rpm , it will be saved even after power disconnect, so you only need to do it once , if they get hot, you can reduce the frequency , and most importantly make sure you enable the temp safety by doing this
1- while on your miner setting tab, right click and hit "Inspect"
2- Type the word (display) in the search box
you will get this.
whenever you find (:none) just delete it and hit enter , you will unlock a few good stuff, including frequency,temp protection, fan control etc.