Today’s article is intended to show how a reasonably reliable measurement of very different transducers can be achieved with the resources of a normal editorial office, although of course one quickly comes up against certain limits. This is mainly due to the fact that you would actually need three optimized and standardized couplers, since a distinction is made between in-ear, on-ear and over-ear headphones. And it was exactly this challenge that really appealed to me, because I wanted to combine three measurement setups in a single device. And I almost felt like MacGyver when finding ideas, as I strolled through the hardware store looking for something or searched relevant websites for inspiration. Because you already need a bright idea for the rededication of purchasable products for your own purpose.
What I do not want to provide here in the article is an exact rebuild instruction. The competitors are welcome to become active themselves and to acquire the necessary basic knowledge if required, and they are also welcome to tinker with the practical implementation themselves. Otherwise the fun of such a challenge would be lost. But I will provide enough transparency to understand and evaluate my solution. Then the step to your own solution is only a small one.
The investment including all parts and calibration/comparison measurement with two reference platforms including service is a good 1000 euros. That may sound like a lot, but considering the prices for ready-made solutions, it’s almost a gift. Of course, it would have been much cheaper to save a little on the microphone (I bought used, professional technology here) and leave out the services. We can see in the picture a ready-made solution for in-ears (only that alone would be a mere 1/3 solution for the earplugs) and two very well replicated “rubber ears” made of silicone, the size of which was chosen to be average and should also fit under all the over-ears to be tested. In addition, there was a measurement protocol and a calibration file, I own Arta as a measurement program anyway.
Of course, this alone is not a complete measurement setup for everything, but it is a good basis. And so my thanks also go to the community for the many comments, suggestions and restrictions, which makes many a “gold standard” look a little different in practice. And I can already spoil that I will measure the over-ears even with 2 methods, because ear canal is not equal to ear canal. But let’s get back to the starting point and the three different measurement setups together with their justification and the underlying principles.
Three principles, one problem
In general, to measure the transmission behavior of headphones, one uses so-called couplers with clearly defined volumes and fixed, cleanly calibrated measurement microphones. There are two internationally standardized couplers for plug-in earphones (in-ears) and small earphones (e.g. from hearing aids). There we have the very simply constructed 2-cm³ coupler (lEC 126) and the technically clearly better simulator for the closed auditory canal according to IEC 711, as I will also use it.
Simpler headphones and headsets as so-called on-ears (see above the Beyerdynamic on the left in the picture) are also called headphones with supraaural cushions. For such headphones (on-ear) there are now two internationally standardized coupler forms, the very simple 6 cm³ coupler (lEC 303) and the “artificial ear” according to lEC 318, which is much better in terms of its technology. The ear thing is good, but it’s also very special. Later, I can compare the results very well with my reconstructed “artificial ear” or with a soft plate. So why I will measure twice here or even have to measure, I’ll explain in detail in a moment.
The thick over-ears, i.e. circumaural or ear-enclosing headphones, are virtually the top of the class when it comes to measurement and, above all, reproducibility. This is precisely why there are no standardized couplers yet. The reasons for this are due to difficulties in measurement technology and the many influencing factors that make reliable reproducibility almost impossible. Therefore, such circumaural headphones are predominantly measured with appropriately modified couplers for supraaural headphones by additionally using a flat and damping plate as a support for the circumaural cushion.
Of course, I had to experiment a lot with the choice of materials, but I was quite satisfied with the results later. Since various vibrations and resonances quickly turned me away from an initial setup made of wood, I came up with a very solid solution made of steel in combination with well-damping soft materials for the support. How I then solved everything in detail, I’ll show you of course in a moment. Please turn the page once!
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