I hear ya @esadreb
This is frustrating because this thread / issue has been around for ages. I am experiencing exactly the same as you. I have even removed the -3dB attenuation that UE4 applies by default for headroom purposes (set in the Windows config file if you are on PC). I’m seeing a loss of -6.3dB on tests that I am running whereby I am playing a 2D sound from UE4 and comparing it to the level of the source.
More worrying is the loss of bottom end. You are right, under 200Hz it starts to fall away considerably. I haven’t been using UE4 audio for long enough to know if this has always been the case but it has been an issue for at least the last year. It’s a pretty serious problem as far as I’m concerned.
This has nothing to do with 3D sound settings, air absorption, Soundclass settings, compression settings. I have been running tests simply by playing back a 2D sound in both the content browser and in a packaged game.
I am using the new audio engine and 48khz source assets.
Hopefully this will get fixed soon. In the mean time I will log these issues on UDN.
Cheers.