im in the process of building a little self contained spectral analyzer consisting of an arduino due, a lcd and a mic/preamp circuit. i wanted to get thoughts about something i cant quite decide on.... in the spirt of creating a meter as acurate as possible, does anyone think there would be a need to incorporate a small multi band eq circuit into my design to counteract any fluctuations in the frequency response of what ever mic i end up using. i was considering working in like a 5 or 7 band eq with trim pots that i would only need to access once when i figure out what microphone i want to use. also had the idea to add several different ports and jacks on to the "box" so i could say, use a XLR port for a standalone mic with the preamp circuit or remove that and use it as a XLR line level in, with a mic/line switch of course. but also having a way to bypass the eq circuit thats there for the mic. Or do you think the minor fluctuations in a microphones frequency response wouldn't have much of an impact on the outcome of the FFT computations? hope all that makes sense and let me know what your thoughts are on the whole idea
I would do the equalization/calibration in software.
i wasnt aware that you could do that. is that something that varies based on the specific fft library i decide to use? ive got some experience with writing code for arduino but nothing remotely near the complexity of the fft library i plan on using so im not entirely sure what it can do lol
The FFT converts your data from time domain to frequency domain. What you do with it after that is up to you. You can subtract constants from each frequency band or multiply each band by a constant (or both!). How you come up with the constants is up to you.
Or do you think the minor fluctuations in a microphones frequency response wouldn't have much of an impact on the outcome of the FFT computations?
It could make a BIG difference! Every mic sounds different, and that's mostly because of frequency response variations. Recording engineers use different mics for each application (vocals, acoustic guitar, electric guitar, horns, etc.). They might even prefer a different vocal mic for each singer. If you were making a spectrum analyzer "effect", I wouldn't worry about it,. But, since you are making a measurement instrument you need to take it into account.
For measurements, normally a (non-directional) calibrated "instrumentation mic" or "measurement mic" is used. [u]This[/u] is the cheapest one I know of.
You have to be careful with directional mics. At very-short distances you get bass boost (proximity effect) and the off-axis frequency response is usually much worse than on-axis response, which means refelected sounds won't get measured accurately.
thats pretty much what i was thinking (by the way, i just started at the conservatory of recording arts and sciences in phoenix) after my audio recording class pertaining to microphones. im having one hell of a debate with myself about this issue lol. the way i see it, if i went with a hardware eq, i would be able to adjust the eq, if needed, on the spot buy sweeping a sine wave and watching the frequency bands and tuneing accordingly, but that wouldnt give me the best resolution. if i went with the code route, i could get much better accuracy but wouldnt be able to change it in the studio or whereever i may be, but it would be easier to work in a bypass option for when i run line level through it. the mic i planned on using the one i got when i started at the school which is a Sennheiser e815 s-x. still have no idea why the hell im so determained to build this damn thing tho other than i love watching those bars jump to music lol. not entirely sure it will prove to be much use to me tho but oh well 