As with all older measurements, a Beyerdynamic A 20 and a USB Box S+ as DAC are used for the output, as well as a separate, very low-noise USB interface in the form of the Steinberg UR22C with phantom power switched off and XLR adapter for the microphone input. I use the A 20 because the output is once again decoupled with serial 100 Ohm resistors and I can use it to control all headphones up to 600 Ohm cleanly and without distortion. The software used is Arta.
Now we come to the measurement setup and the mechanical implementation. I quickly parted with the principle of the bracket suspension again, the effort would have been disproportionately higher if I had not implemented this in wood. After all, I want to connect three test setups in one and there is nothing worse than crashing in-ears or slipping headphones. I already wrote at the beginning that reproducibility is an extremely big problem. Since I only want to measure one channel (you can also make two individual measurements for left and right), I preferred the horizontal measurement to the hanging one.
In order to get a safe stand and a really solid and mechanically stable construction for the support and the clamping, I purchased a smaller, but still quite heavy (because massive) drill stand and modified it accordingly for my needs. The picture below shows quasi the naked stand, but already with the permanently mounted unit for earplug measurement according to IEC 711.
But back to the big headphones, because that’s where we have to tinker now. Normally, one uses an angle of 4.5 degrees each and orients oneself to a head thickness of 140 mm between the ears in order to realize a sit-on setup with the ear cups aligned almost vertically, but also slightly angled. My first wooden setup also corresponded to this, but the reproducibility was not given at all because of the constantly slipping listeners. There are also countless test reports from relevant institutes, all of which came to the conclusion that it is extremely time-consuming to impossible to achieve this in a truly reproducible manner.
The next picture shows an intermediate step, where I use the largest headphone from my collection as a template for the initial sizing, to later cut (and string) the necessary pads. Because without this cushion will not work. On the stand, you can also see a second, height-adjustable support for the other, unused ear cup to correct the distance. In addition, I can also set an inclination of up to 9 degrees here, which also results in 2x 4.5 degrees, if you really want it.
I’ll skip the following steps now, because I’ll keep a few secrets for myself after all. Of course, all spacing and fitting the silicone ear with the simulated ear canal according to the standards are important, as well as covering the foam pads with thin leather to simulate the skin. I have deliberately dispensed with rubber, because such skin does not exist. The picture is a bit deceiving from the perspective, because even the fattest pads in my not small collection still lie cleanly.
However, I deliberately chose the distance between the stand and the ear to be as small as possible, because it will later be an ideal orientation aid and quasi “resting edge” for the auricles. This also applies to the other two sides for the top and bottom of the ear. Here it is really easy to readjust (reproducibility). The fact that it really works well is shown later by the measurement with four runs after a completely new placement of the earpiece.
With this, we have dealt with the basic information about the structure transparently enough and I think everyone can live with that. Those who are familiar with the matter know about the necessary compromises of such setups, but here the listening experience and measurement also subjectively fit together perfectly. The most important thing for the future will be the comparability of the tests with each other, because it is almost impossible to copy other setups 1:1. It is important to work out the weaknesses and merits of headphones and not to insist on the sole valid, best and ideal measurement curve. These do not exist at all in circumaural headphones.
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