Dan Clark: "At MrSpeakers, we started as modifiers of closed headphones so I thought it fun to create a closed can from the ground up. When we started the project, there were no high-end closed planars to market. I thought people might really connect if I could improve on current ergonomics and deliver a different take on a high-end closed planar both sonically and aesthetically.  Early experiments convinced me that I might be able achieve a closed loading that would really sound open so we began designing a driver and researched different magnet and motor configurations. The project was code-named Dreadnought after the Theta Dreadnought 5-channel home theatre amp I use to this day. It made for a nifty code name.  Along the way we were doing research on driver behaviour in closed cups and I came across a knurled planar-driver patent by Bruce Thigpen. I called him to ask if he thought it’d apply for our use. He thought it might and suggested we try  It helped but not enough to solve the problem we had. Bruce’s knurling technology basically creased the driver panel to reduce surface oscillations which can cause nonlinear response and distortions.  We discovered that if we took the process a lot further by using a deeper form of knurling that permanently deforms and textures the driver surface, we reduced distortion, improved dynamics and extended response at both ends of the spectrum. 

"We called it V-Planar and released it with an update to the Alpha Dog we called Alpha Prime, which was really well received. By late last year we had working Dreadnought prototypes and were getting some good early feedback but I was finding it really hard to make progress voicing that sealed headphone. I wasn’t satisfied. In other words, I was stuck. So we switched gears to focus on an open variant instead. Things clicked and Ether was born. The core driver work had already been finished for Dreadnought so it was more an optimization process than ground-up struggle to create the open-backed version. As soon as I sat back down afterwards to try the closed form, the mental bits I'd been stuck on came unstuck in essentially one day. Gotta love perspective!"

Here’s what I don’t understand. I get that conventional planar membranes are edge-clamped. They have to bow in the middle because they can’t do the pistonic balanced-armature thing. Pleating around the edges will add a quasi surround, hence increased excursion where it’s usually restricted. But what does that do to membrane tension? After all, planar membranes aren't stiff like paper or plastic cones. Or are they? With the innate elasticity or expansion potential of a pleated membrane, don’t you increase bowing in the middle to lose not gain control?

Ether launch at the 2015 Tokyo headfi fest, photo compliments of John Darko [www.digitalaudioreview.net]

"Most planar diaphragms are made of Kapton, Mylar or PET. These are all relatively inelastic materials which must be put under light tension much like a drum head. The motor force then works against a tensioned surface that doesn’t particularly want to stretch. But if the surface is loose, applying force is like pushing a string. Tension is critical. In point of fact, it is one of the trickier things in creating a planar headphone to ensure that its drivers have consistent tension. Tension affects many operational parameters. If you can’t control tension, you get unit-to-unit variations. Here V-Planar does two things. It permanently stretches the substrate while creating an opposing spring force through the traces to take up slack and give the surface shape. This maintains a light tension on the driver and prevents it from returning to its default flat form.

"The main benefit? It's now easier for the motor to 'flatten' these creases than to stretch the entire inelastic substrate. Compliance increases and goodness ensues. Visualize breaking up the driver into rectangular segments with a V shape. Under load, each V is subjected to approximately the same tension and motor force. As the driver goes through large excursions, the Vs flatten out. Each small section behaves like a pleat in a window shade that is getting slightly shallower as the diaphragm extends. Now aggregate lots of small sections in parallel and you can visualize the effect on the surface more clearly. The effects are additive across the surface. After processing the surface of the driver, we apply a secondary tensioning operation followed by initial burn-in of the drivers and matching." [At left, Evalucon's SN range of connectors of which Dan Clark uses the 4-pin version as my favourite locking headfi plug, better than what the HD800 and D1000 use, better than the 2.5mm mono plugs of the HE1000.]

3D printing factored big and in obvious ways with the Alpha Prime. Your new baffles are aluminium. The C cup is Carbon fibre. How does 3D printing still factor with the two Ether models?
"There are certain internal parts which we still make with 3D printers. What I love about 3D printers is that they allow us to think about problem solving very differently once we consider printers as production tools in their own right, not just for prototyping injection, casting and machining parts etc. Each manufacturing process has things it can and cannot do. If you think about what 3D printing can do which other approaches can't, you solve problems in very unique ways. 3D printing as a prototyping system for molded plastic or metal parts is very productive and also reduces risk. But the real benefit to using 3D printing is leveraging how printers generate solutions to problems that would be much harder to implement with conventional molding, casting and machining processes, say making the double-walled headphone cups for our Alpha models.

"Here being a smaller company has distinct advantages. One is that we can easily use printers to manufacture parts in volumes that meet our needs but wouldn’t work for large-scale commodity production lines. For Ether, we solved two specific challenges by using 3D printed parts. We also used them for the painted retaining rings to keep the 'family look' with Alpha. This time 3D-printed solid cups simply weren't a good solution. They might have sounded really great but were too heavy. So we went with Carbon fibre for its sonic performance of not storing energy; and to minimize bulk and keep weight to a minimum. Our carbon cups are very light, extremely rigid and very well damped. We get great performance but without the weight." [At right, Zortrax M200 printer as used by MrSpeaker.]

MrSpeakers digs on 3366 Kurtz Street in San Diego

One would assume that using the same driver in an open and sealed enclosure would require some serious retuning. What can you tell us about that?
"Some aspects, such as knurling and tensioning, are pretty much identical for both. But after that it’s the difference between creating a sealed loudspeaker or a dipole. Pretty much everything about how the driver is loaded changes. One must deal with stored versus distributed energy. I can unequivocally say that closed headphones are much harder to design properly. Everything matters. Everything is coupled to where tuning and voicing become extremely difficult when correcting one issue usually creates two new ones. Designing the open-backed Ether was far more straightforward as there was so little to worry about energy storage."   

How did you increase efficiency to 96dB? Usually that’s a combined function of magnetic field strength and moving mass so, stronger magnets plus lighter membrane?
"The math behind driver force is straight algebra of F=BIL. We increased the strength 'B' of the magnets, decreased resistance to increase 'I' and really packed in the traces to increase 'L'. There are ~28 feet of trace on each driver. Our traces are ~0.009" wide (or narrow if you’re a glass half-full type). I’m not aware of any other driver with so much trace density. The substrate is also quite thin. So are the traces. Hence moving mass decreased greatly. These wonderful attributes more than offset the loss of 50% of motor force when we decided to go single-ended. With a symmetrical driver, I think we probably would be over 100dB efficiency. That, I might argue, would be too efficient relative to noisier tube gear. In the end, we felt that the single-ended motor sounded way better and measured better too. It’s important to stress that this is for our implementation, with our driver. I’m not trying to imply that my single-ended drivers are generically better than double-sided variants. There are too many variables at work. The choice of asymmetrical or symmetrical motors remains application specific."

V-Planar driver surface.

With a dipole or omni speaker, the room returns the rear radiation. This adds 3dB or more output over a monopole version of that same speaker. With an open-backed headphone, the rear-firing energy simply dissipates. It never returns to the listener. Why then is the Ether C 4dB less efficient? Unless its cups were 100% absorptive to truly kill off all reflected energies, wouldn't one expect the C to be slightly more efficient in fact? Is this difference down to the tuning changes that were necessary to adapt the driver to the sealed environment?
"The C is 3-4dB less efficient because the tuning and damping schema are different on several key levels. One of those is that we actually do some tuning also on the ear side which reduces output. We even supply a packet of 'tuners' by way of six discs which may be inserted into the ear pad's ear hole. No tools are required. It takes 3-4 seconds and the pads stay on. These enable four different tuning levels for the Ether C and will ship to all owners who bought C before we introduced these pads. The tone of each tuning progressively darkens from bright and lively—really nice with a lot of classical—to a dark chocolate voicing with incredible bass. The latter really delivers with electronica. It’s our take on a bass-head tuning and a ton of fun. This graph shows the effect of our tunings. Each progressive step reduces output by ~1dB above 3KHz as measured on our G.R.A.S. 45CA in open office space.

"THD below 100Hz shows incorrect in this next graph because our test environment has a lot of vibration which creates THD. It’s usually better when I measure on weekends. Note that the THD in the critical midrange is exceptionally low for all tunings."