The miniDSP EARS is multiple uses. It can certainly be used to create EQ profiles with a miniDSP box, but it also a more broadly applicable tool for measuring headphones and IEMs.
It has some latent limitations, a few oddities, and a quirk or two, but it is easy to use, comparatively inexpensive, and seems quite repeatable between different copies. It’s worth a separate discussion.
Beyond that … in general … and at a very high level that I (and I’m sure others) will delve into in more detail …
Taking measurements, and production graphs or charts from them, require several things:
First, the item to be measured … generally referred to as the “Device Under Test” (DUT). This might be a headphone, an amplifier, a DAC or some other widget.
Next you need a way to take a measurement. This varies with what you’re measuring. For headphones or speakers you need a microphone (calibrated, ideally), some way of capturing the output from that microphone (which could be a dedicated audio interface, or something as simple as a mic-input on a sound card or phone), and a way to get that information into a measurement device (usually done with an analog-to-digital converter or ADC).
If you’re measuring a DAC or amplifier, then a microphone would not be necessary and instead you’d connect your ADC to the output of the DAC or amp in question.
Then you need a signal generator, which can be a dedicated piece of hardware or it can be software. If it is software, then it’s going to have to feed something that can turn the generated signal into an analog form - so typically this is a DAC (digital to analog converter).
Finally you need software (or hardware) that can drive and synchronize all of this, so that it knows what it is supposed to be measuring relative to the signal is being generated. Capture the data, and present it in a suitable form.
You can do all of this with the built-in audio hardware in almost any PC, laptop, and a good number of tablets and phones. This might take the form of a dedicated tool for audio analysis or it could be a more general-purpose signal-generator/virtual scope arrangement.
Often a better approach is to use an external audio interface, such as the Focusrite Scarlett Solo (about $99 and has DAC, ADC, mic-input/amp and a headphone output … which covers the vast majority of what you want to measure) and suitable software (e.g. Room EQ Wizard or ARTA).
Beyond that are dedicated audio-analyzers that typically offer much better performance (lower noise, better resolution, more automation, higher accuracy, greater consistency/repeatability) but at rapidly increasing costs. Something basic like the QuantAsylum QA401 can be had for about $449, and you can spend thousands upwards from there on tools like the PicoScope III or the APx555.
So that’s a bit on tools … and I’ll post a lot more here as I have time.
Technique and measurement regimen is at least, probably more, important as your tools. It is trivially easy to completely bork measurements, especially when dealing with signals at -120 dB, simply by running an AC cable too close to a signal cable, or taking a measurement when your refrigerator’s compressor is running etc.
After I get my next review published, I’ll do a couple or so posts to illustrate the specific tools and approach to do some simple things like measuring the frequency response and jitter for a DAC, and getting a basic response profile for a pair of headphones or speakers.