Unfortunately, even a $500 scope will typically almost bottom out with good-ish yet audibly different amplifiers, even with averaging.
These tend to do -100 to -106 dB or so.
The calibrated microphone is good for correcting some rough low frequency room reflections and frequency response unevenness and measuring spatial response, but not really measuring other distortion and noise. It's only typically -60 to -80 dB SNR. Even though distortion adds, it'll end up in the noise, and cheap ADC plus microphone preamplifier are typically not as high quality as DAC and speaker amplifier either adding its own cruft.
The headphone measurement couplers are more of an art than science for the moment. You can, in fact, make a decent-ish rig for a thousand or so, but MiniDSP one is not it. For plain equalization I'd trust your own ears with sine tones and some bandlimited noise instead. For measurements, it's just poor.
Klippel NFS is something I have personally seen exactly once, and I cannot attest the quality of its measurements (esp. room subtraction) personally. Almost nobody has it.
The calibrated microphone is good for correcting some rough low frequency room reflections and frequency response unevenness and measuring spatial response, but not really measuring other distortion and noise. It's only typically -60 to -80 dB SNR. Even though distortion adds, it'll end up in the noise, and cheap ADC plus microphone preamplifier are typically not as high quality as DAC and speaker amplifier either adding its own cruft.
The headphone measurement couplers are more of an art than science for the moment. You can, in fact, make a decent-ish rig for a thousand or so, but MiniDSP one is not it. For plain equalization I'd trust your own ears with sine tones and some bandlimited noise instead. For measurements, it's just poor.
Klippel NFS is something I have personally seen exactly once, and I cannot attest the quality of its measurements (esp. room subtraction) personally. Almost nobody has it.