How-To: Build a MMM rig for RTA purposes for $25 or less.

erinh

This is my second video and I'm learning.  It isn't perfect (I need better garage lighting and a better mic) but it's the journey, right?...

Anyway, in this video I'll teach you how to DIY your own Moving Microphone Measurement (MMM) setup to use with an RTA system to EQ your stereo system's response.

Due to the reflective nature of car and home stereos it is often recommended users take multiple RTA measurements of their system in the "head space" (where they sit and listen).  To do this you are left with two options: 1) Place the mic at different locations, measure and then average all the results together.  However, this can be time-consuming and not very repeatable.  2) Sit in the listening position and hold the microphone in front of you while moving the mic around the head area.  This is complicated by your own body's influence (even your hand can change the result).  This is especially detrimental if you are trying to use a "target curve".

Therefore, I am providing a low-cost alternative: an oscillating fan to move the microphone.  I am definitely not the first person to do something like this and I'm not pretending to be.  Also, while not perfect, this solves the above two issues of time and in-accuracy and will be an improvement over the typical methods we use.

Make sure to watch the entire video for some tips on things I learned when building mine.  I tried to answer all questions in advance so don't tell on yourself by asking something until you've watched.  

JasonP

This is great!

I actually have a project on my "wishlist" (it is a long list, so who knows if I'll ever get to it) that is a stepper motor controlled mic holder than can move 250mm x 250mm in 2 dimensions. The idea being, you'd script it so it would move, record a measurement, and repeat. Then you could average them all in the end.

erinh

That could work.  

The only downside to doing averages, though, is you have to stop the measurement to take the average, then EQ "offline", then re-measure and re-average.  I like the idea of a constantly-moving mic because you can make changes in real time without ever stopping anything in the process.  

I have some ideas how to make this at least 2-axis but I would love to have something that can move in a sphere-like pattern.  But, like you said with your wish list, it's a long wish list and I may never get to it, either.