Acho Reviews - Measurements

English | Español

Note: This post is out of date, to see the current information, visit this page: https://espanol.achoreviews.com/p/solospec.html

As I post measurements of IEMs that I review, I think that it is important to share how I measure the IEMs and why it is important to not compare these to measurements performed on any other system.

Let me start off by saying that my measurement set up is based on the MiniDSP EARS system. Anyone who has had experience with this system knows that it is pretty much invalid for measuring IEMs.

Part of the problem is that the silicone fake ears have a single straight tube from the point of insertion to the microphone which is inside. This does not correlate with the anatomy of the human ear and does not provide a measurement that matches a real life experience.

Unfortunately, without creating a more realistic ear canal, this is something that cannot be resolved. I do not have the means to create a realistic ear canal and therefore my system does not provide realistic measurements that match up to real life experiences. This means that the graphs can only be used to compare how two different IEMs compare on the EARS system.

And that brings us to issue number two, which is in my opinion even more of a problem, getting consistent measurements that can be repeated over and over again.

As the faux ears on the EARS system are made of a soft silicone, when pushing an IEM into the opening, this causes friction and makes the tip of the IEM move or even crunch up (for lack of a more technical term), this makes it very difficult to get a good seal and almost impossible to get the same seal an placement repeatedly.

I found that taking 10 measurements of the same IEM, removing and reinserting the IEM each time, would result in 10 different measurements. This is frustrating as you never know which of the 10 is the one you should focus on. It also means that when you swap to another IEM, it is impossible to know if the seal and placement is the same, resulting in measurements that cannot be compared even against themselves.

I found that using foam tips made this slightly easier, but was again almost impossible to repeat the measurement results after removing and reinserting, at least not without multiple trial and error.

I decided that this is something that I could remedy and by doing so would at least give me measurements that could be compared against each other.

To solve this issue, I removed the silicone ear pad from one side of the EARS, leaving the microphone exposed.

Using trial and error, with much patience, I created a simple tube like support that fits around the microphone and is made of a much stiffer rubber. The tube itself is made up of various rubber grommet washers, that have been glued together while inserted over a rod in order to guarantee the correct placement of each washer. I then covered the inside of the washers (once glued together) with more glue to form a smooth surface and avoid and (very) small imperfections between washers.

I played around with different lengths before deciding on this one as it was the one that gave results with the frequency dips in the most similar places as the measurements by others with much better set ups.

This system does not solve the issue of not corresponding to the human ear but it does result in a system that provides the same measurements over and over again.

While trying out the system, I took dozens of measurements of the same IEMs over and over again, removing and reinserting them, going on to other IEMs and returning, etc. and the results matched every time (except for cases of human error).

So, this is the system I use, now, how do I use it?

For IEMs, I always use the Shanling M2X DAP as a DAC, connected to a PC running REW.

In order for the only difference between IEMs to be the actual IEM itself, I always use an NiceHCK balanced cable (except for the cases where the cable is non removable) and I use NewBee foam tips.

My choice of foam tips is partly due to the fact that it makes it easier to guarantee the same fit every time, but also because foam is my preferred tip and what I listen to.

With each IEM I take 5 measurements of each side, making sure that each measurement matches the others, I will then take an average of the 5 measurements, which, as long as everything has gone well, literally lays on top of all the other results.

Finally, I take an average of the AVG left and AVG right (except for cases where the two channels have a clear imbalance) and smooth that to 1/48.

One last thing to point out is that I use the RAW calibration file from my unit from MiniDSP, and only use the left channel of the EARS to create IEM measurements.

The result is that every one of my IEM measurements uses the same tip, the same cable (except for non removable cables), the same microphone on the EARS, the same calibration file and has the same insertion depth and seal of the foam tip on each measurement.

Again, although these measurements can be compared amongst themselves, this is by no means an industry standard measurement, nor is my system calibrated to be compared against any other system that is used by many reviewers on the web.

If you are in need of measurements that are closer matched to reality and are calibrated correctly, I suggest you check out some of the webs that are dedicated to posting measurements. In the case of IEM measurements, Crinacle (https://crinacle.com) is a highly recommended starting point.