Hello everyone, Couple of weeks ago I decided it's time to make a measurement rig, which I did. But I can't make it work properly for some reason - I've tried different things, read those forums and it still doesn't work the way it should, details below. In advance I'd like to apologize for the the mess and chaos in this post, I didn't know how to tackle it, and I'm a bit tired and angry that it doesn't work... First, about the rig: Microphones are WM61As from ebay. Mics are connected to a circuit board with capacitors, resistors, etc. (pic below) Casing is made from plumbing pipe and plywood. On the inside of the plumbing pipe I've put a bitumen mat for damping (but that proved to be useless) As for the microphone housing, I've tried few different ones, but none of them seemed to work properly. Rig is connected to the Scarlett 2i2 through XLR connectors. Ok, so what's the problem? I compared my FR graphs to those from Innerfidelity and other people, and they don't look similar, there's either too much bass, or a massive drop in the mids, or there are too much highs, depending on mic housing I use. For the needs of this post I used B&O Beoplay H6 headphones and compared them to Innerfidelity graphs: http://www.innerfidelity.com/images/BangOlufsenH6.pdf Let's start: First, I put the microphones in the wooden tubes I made and attached them to CDs padded with PVC foam Excuse the "ear", didn't work out the way I planned, but it seems to have very little influence on the measurements anyway. Inside of the rig. With this setup, FR graph looks most similar to Tyll's, but there's way too much bass: So I figured I'll add more damping to tame the bass and I put this synthetic wool. Which had little influence on the graph. There's still too much bass. So I went on to add soft memory foam inside for some more damping. But that only bumped the mids a bit and had no effect on the mighty bass. So I figured that the problem must lay in the wooden housing, and binned it. Instead I went for a soft memory foam circle with pvc dense foam glued to it on both sides to stiffen it up. And that did make a significant change to the FR graph. As you can see, bass is now tamed and more in level with higher frequencies, but I get a massive drop around 200Hz, which definitely shouldn't be there (or at least shouldn't be that visible). So I continued to tinker with that and put the synthetic wool back in, which did help a bit to get rid of that drop, but boosted bass again Lastly, I figured I'll try just memory foam, without any stiffening, but that didn't help me much either: Graph for this: It tamed the bass as I wanted, but the drop is still there + highs are messed up now as well. I tried few different sources and headphones, recalibrated everything numerous times in ARTA and results are always skewed in a similar way, so it's either ARTAs fault (which I find doubtful), or my faulty rig design, or the materials I used. I ran out of ideas and I hope for your insight super best audio friends. As you probably figured out by now, I'm totally new to all this, so please don't be too hard on me. Thank you everyone for reading and your (future) input.