Questions on PC audio calibration

Seeing as lower/higher frequencies change their impact disproportionally depending on the volume, I would like to boost lower frequencies when playing music quietly, and reduce when playing loudly. Now, this would be a very crude way to go about it, so is there any software that could do it automatically (and more importantly, more precisely) across the whole frequency range?

Preferably for foobar, but if you know of anything that can do this - I'd be interested to know.

Maybe some eq calibration software similar to what some home theathres have?

I have a decent microphone and a cheap sound level meter - am I right that the former would be more suitable for something like this? Are there any rules of thumb or a reliable method to do this manually 'by ear'?

While at it, is there anything that can switch eq/preset depending on the output device as well?

Study up on Fletcher Munson Curve.
This caught my interest even though I had no direct experience, so I had to go on a google chase.  I could not find much, but I did find one discussion:

It looks like WOK VST plugin + Foobar2000 VST 2.4 adapter might be the easy way to go.  Otherwise, you could custom code some DSP modifications as discussed.
I run my PC audio: mini rca headphone out, to my sound system. That allows an intermediary hardware device to automatically apply a loudness curve for low volume.

Chase RLC-1 Remote Line Controller does what you want:

Adds wireless remote control to any non remote equipped stereo receiver or preamp. controls volume, balance, mute, power on/off, bass and treble and input switching for up to 4 line level sources.

No noise or distortion 105db S/N RATIO 0.05% THD & IM

rare new open box

other used ones are out there, make sure it has the remote, you cannot use it without the remote.

I have used them in my systems for many years, and tried hard to detect any detriment to having it in or out of the system. It simply does it’s job undetected.


the new open box I linked is a darn good price, is FREE RETURN 30 days, you have nothing to lose trying it. 
What you need is a Dynamic EQ after your volume control which you would adjust to your taste.