Ear cushions like a dream
I had already teased it: The ear pads of the Sendy Audio Aiva have a very unique, but really ergonomic shape. What looks more like a children’s bathtub here is characterized by the lowering of the narrower side walls towards the top. According to the manufacturer, a data analysis of different head shapes was used as a basis, but you can actually come up with that as well. At least it saves the usual pressure points in the memory foam, and we now know why I had advised the optional rotation of these pads until perfection was achieved.
But you are also rewarded, because such a good contact without excessive pressure is really rare to find. In direct comparison, the velours of the old T1 are just undifferentiated sofa cushions. No, they aren’t bad either, but after an hour at the latest, the temple of the glasses was always in ouch mode. That’s exactly what I don’t have with the Sendy Audio Aiva. Thanks for that. The outer cover is made of perforated protein leather (usually made of 80% rayon and 20% nylon) and the surfaces resting on the head are made of a velvety soft yet breathable fabric cover.
We can also see an intermediate textile layer in the ear pad (pictured above), in addition to the fabric covering the large drivers under the retaining ring in the ear cup (pictured below).
What is a magnetostatic transducer?
So, and now we finally come to the magnetostatic or planar transducer, where, in contrast to the familiar plunger coil, a wafer-thin membrane foil oscillates, which is located in a magnetic DC field generated by powerful permanent magnets. A meandering conductor loop is then vapor-deposited onto the wafer-thin membrane foil, which in the case of the test sample measures 97 by 76 mm and is therefore oval (only 3 µm thick in this case), through which the actual signal current then flows.
This then creates an alternating magnetic field (proportional to this signal current), which interacts with the permanent magnetic field (DC field) to cause the membrane to oscillate almost without delay. The real advantage of the magnetostatic principle over conventional plunger coils, however, is that the driving forces act uniformly over the entire diaphragm surface. And yet, despite all the euphoria in theory, there are also various problems in real implementation.
Since it is a multilayer structure, it is necessary to ensure good sound transmission through the magnet construction so that the radiation is not negatively affected. The permanent DC field must be as homogeneous as possible and the mass of the foil as low as possible. Otherwise, the good impulse behavior will be lost. We will see later in the diagrams that the transient response of the Sendy Audio Aiva is exemplary, but at some frequencies there are very slight “lags”, i.e. minimal delays (“resonance”). By the way, magnetostatic transducers radiate the front and rear sound in antiphase, which makes them more susceptible to acoustic short circuits in open systems than in closed plunger coil systems, And yet this disadvantage is also an advantage, if the shell takes this into account in the size and the ear pads are any good.
Since the conductor path on the membrane foil can be arranged in a meandering (rather than a spiral) pattern, the magnetic field lines of the adjacent conductor paths compensate for each other almost completely. The result is a very low voice coil inductance and thus an almost straight impedance curve, which allows the amplifier to operate without reactance. This is then rather uncritical as a circuit and one can also generously disregard the gladly taken 1/8 rule for the output impedance of an amplifier. However, the amplifier should not be too weak, because the characteristic sound pressure level of magnetostats is rather low. So you need proper electric propulsion, which almost completely rules out onboard solutions or mobile devices.
You can go deeper into the topic of processing the zebra wood for the shells of the ear cups on the homepage, but I don’t want to insert any flowery marketing translations from the homepage at this point, even if it would be obvious in view of the high-quality results. The picture above shows the inside of the still unprocessed shell, the final product will not look much different. And since there are no other electronics to marvel at, I’ll leave off disassembling my expensive headphones this time. I know what’s in it (or what’s not).
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