Planar Headphones Sound Reality
History of creation
My acquaintance with planar headphones began with the purchase back in 1985 Electronica TDC-5М. At that time, they were one of the best in terms of sound quality in the post-Soviet space; and their design was completely copied from the Yamaha YH-1000 headphones. Then, compared to everything else that could be purchased, it was something fantastic in terms of sound!
Many years have passed, but planar headphones still have a number of advantages over the dynamic ones. Despite the significant development of both types of drivers (dynamic and planar), the audience of connoisseurs of high-resolution sound from planar headphones is constantly growing.
I returned to the topic of planar headphones and to listening to music on headphones, in general, a while ago, in response to the demands of my clients. To get the desired result, I had to seriously immerse into the topic so to understand the specifics of all components and their compatibility. And the goal was to reach the highest sound resolution along with the most comfortable fit of the headphones on the head.
I wasn't required to "reinvent the wheel." It was enough to think of the essential components that determine the driver's capacity to reproduce the most realistic audio picture:
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Membrane weight. Previously, membranes were made from Kapton, now they are made from Mylar. Mylar is lighter, thinner and more elastic, so it can have a greater amplitude of the membrane shift.
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Membrane area: the larger the better. The larger the membrane area, the greater the sensitivity of the driver. Also with a larger membrane area, the frequency range can be significantly expanded in the low-frequency zone.
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Interaction of magnetic fluxes of a 'permanent magnet' and an alternating electromagnetic field formed by the inductance of a conductor on the surface of the membrane. The better the interaction, the higher the output efficiency of the driver. And this is determined only by the power of the installed magnets and the density of the tracks on the surface of the membrane.
The most specific thing in the production of planar drivers is the production of membranes with applied current-carrying conductors. The most effective material for current-carrying paths is thin aluminum foil. There are several unique people here in Ukraine who have managed to produce quite good membranes with tracks applied to them almost at home.
However, after studying the topic further, I was able to find a manufacturer who has good industrial equipment and who can produce much more high-tech membranes with conductors on the surface, according to the technical specifications provided.
This became the starting point for bringing to life some of my technical and creative ideas for building planar headphones of my own design.
Approach to implementation
Drivers
Engineers typically consider the so-called piston mode of operation in standard versions of planar drivers, in which the membrane moves up and down like a piston.
I also explored the formation of a sound wave across the full surface of the membrane, which occurs when a wave-like 'jitter' of the membrane is created throughout the entire plane, allowing for better microdynamic elaboration of the audio signal. This is the so-called 'wave' mode of the driver's operation. As a result, the driver operates in both modes - 'wave' and 'piston' - at the same time.
For this purpose, the idea of filling the entire surface area of the mylar membrane as densely as possible with conductors of the smallest cross-section was implemented. Thus, we achieve significantly better elaboration of the microdynamic vibrations of the membrane in one plane. And, as a result, we get higher resolution in the reproduced audio image over the entire frequency range.
This strategy perfectly justified itself - the advantage in the resolution of such drivers proved to be significant.
Acoustic design of the eadphone housings
Planar-type drivers perform best in the open-back acoustic design of the headphones' housings.
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Housings for drivers are made from fiberglass, since it has perhaps the best ratio of firmness and light weight.
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The same headband arcs with height adjustment and axis shift mechanisms are used as in the Denon D-9200 headphones. This headband design proved to be the most comfortable of the various options we explored.
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Ear pads are made of very soft small-cell siliconized foam rubber, which is covered with thin eco-leather. In the higher class versions of the headphones, the ear pads are covered with perforated eco-leather, thanks to which they 'breathe' better. Such ear pads are more expensive to manufacture, so they are used only in higher class models
The range
From the beginning, I intended to build a range of headphones that would be identical in design and construction principles, yet weighed as little as feasible.
Understanding that people's financial capabilities differ significantly, the ideas of three models, which differ sound-wise and price-wise correspondingly, are currently being implemented.
The designs of the headphone housings and the headbands are absolutely identical. The models differ only at the level of the drivers.
Duet
Resistance: 100 ohm
Membrane weight: 56 mg
Sensitivity: 100 dB
Weight: 319 g
The first model in the range. Dense filling the surface of the membrane with current-carrying tracks allows to achieve a higher resolution of this model compared to the well-known headphones "HiFiman Ananda"
Trio
Resistance: 470 ohm
Membrane weight: 56 mg
Sensitivity: 100 dB
Weight: 319 g
Filling the membrane with tracks is denser vs. the 'Duet'. The section of the tracks decreases as their number increases. Thus, the effect of the so-called 'wave' mode of membrane operation is achieved more efficiently than in the 'Duet'
Orchestra
Resistance: 1000 ohm
Membrane weight: 56 mg
Sensitivity: 103 dB
Weight: 319 g
The area of the membrane filled with tracks is significantly larger. Moreover, the weight of the membrane is the same as that of the two previous models. Although the length of the track has almost doubled, the section of the track has been reduced. Magnetic system used is of maximum possible reinforced type
When testing this model, my wife said: "Enough experiments! I'm already getting scared..."
But I still have a few ideas to implement :) Maybe later, when...