I own a pair of IEMs (Westone 4R). I wanted to know what I could do to further augment the sound of these IEMs. . I assume additional hardware could help, but I figured software is a cheap, convenient fix, and thus a great first stop. . Audio Sources: . I use the following as audio sources: Laptop: Macbook Pro (Early 2015) Phone: LG Nexus 5 mp3 Player: iPod Shuffle (4th Generation - Late 2012) . Equalization: . I don't think anything can be done with the iPod alone, but an equalizer could be applied to the laptop and/or phone output. . IEM Characterization: . These particular IEMs have been characterized on: InnerFidelity GoldenEars . Desired Response: . Should my goal be to make corrections to the frequency response based on the difference between the measured frequency response and a universal desired frequency response? . InnerFidelity and GoldenEars both offer tips on the desired frequency response: InnerFidelity GoldenEars . Either site provides a different desired response. What is the reason, is one preferred, or is it purely subjective? . Corrective Method: . In the case of InnerFidelity, do I simply come up with my own corrective equalization curve which adds 0 dB where no correction is needed and +/- dB at frequencies which do not enter the regions Tyrll specifies (such as the desired +10-12 dB at 3 [kHz])? . In the case of GoldenEars' graphs, I can't tell if the modified (blue) curve on the IEM characterization page is the equalization to incorporate or the final result. (Do I set the equalizer to look like the blue or do I set the equalizer to the difference between the green to the blue?) Why doesn't it look like the desired response, which has boost in the bass? . Is there anything else to consider when making the equalizer corrections? Step response, impulse response, impedance, phase, etcetera? . Equalization Software: . What should I use to perform the equalization on macOS? Should I use itunes' equalizer, or find software which operates at the OS level? . What should I use to perform the equalization on Android? [GoldenEars offers the Accudio app, but that's iOS only.] . I hear that I should use something at the OS level. (The phone is rooted so this should not be an issue.) I hear that parametric equalizer software at the OS level does not exist; but a 10 band equalizer (Equalizer Pro app) is the next best thing. (I have not yet tested it.) . Digital Amplifier: . I'm considering purchasing a digital amplifier (SMSL AD18). I'm going to use it to drive speakers for which measured data does not exist (cheaply crafted by a friend : j ). . It has a headphone jack also though. Will using the amplifier affect the use of the equalizer? Is there anything to take into consideration for it? .