Nov 6, 2019 at 11:50 AM
I'm currently using a UMIK-1 + 711 for measurements. The mic actually fits pretty perfectly into the coupler; however, the silicone o-ring in the coupler doesn't seem to be enough to seal in all the energy. I was getting a massive dip at around 7K and some roll-off at 50 and 14K.Wow.
The amount of information in your very first post is both stunning and incredible. Amazing work, and I'm really loving the level of dedication you guys have to headphone measurements. I stumbled in here as I was trying to learn more about accurately measuring headphones for a review I'm working on, of the AirPods Pro vs other well known wireless earbuds.
I'm considering going with an IEC 711 adapter + UMIK1 for measurements, as apparently the THD of these mics is far lower, and allows for proper measurement of stuff like ANC. Do any of you foresee any issues with this?
It turned out that the cutouts at the tip of the mic was responsible for the leakage. I tried different ways of sealing off the leakage, and finally found a stainless steel flat washer that had the perfect inside and outside diameters. I'm still getting a little bit of roll-off at the low and high ends, but everything in between is fine. I am sure that if you remove the tip and use epoxy to seal the mic to the coupler, like the example given by @csglinux, that there would be no issues. However, you lose the ability to remove the coupler if you want to use the UMIK for room measurements. For instance, I recently used the UMIK to EQ my car.
Ultimately, the UMIK + Steel Washer + 711 is accurate enough for my purposes and really easy to use. I usually leave it plugged into my desktop, but can take it and make measurements on my phone with just a USB cable swap. If you try it out, I can send you a few of the steel washers that I got, and I would also love to see what you come up with get a good seal.