The Sony R10 - as good as its reputation?

You can't really liken the damping papers used in the fostexen or the ZMF designs to the Sony. Once the backwave leaves the driver, it never crosses paths with it again. The Fostex designs actually reflect the backwave back at the driver and the ear side volume to create a phase delay and increase the bass response slightly. The R10 deletes the backwave entirely.

 

I can't say I've seen that, but my goodness I would love to see someone try!!

 

If you're claiming that no reflected sound reaches the ear, that's simply not true. There is cup effect at play - that energy does reach the ear, and may or may not be phase-sync'd with the direct frontwave signal. CSD measurement would confirm.

How can there both be cup decay but also no backwave reflection? That's a contradictory statement. In a closed headphone, that energy goes somewhere. It isn't just deleted by a clever baffle porting design. Maybe I'm just misunderstanding what you're saying or what the underside of the baffles look like. If anything, the extensive backwave reflections are what suck all the bass out of the response, whereas a solid baffle would likely have much better extension.

Or are you just referring to the slanted depth of the cups? Still wouldn't account for reflection of erroneous distorted signals and partials from a far-from-perfect driver.

...is it some type of acoustic labyrinth? Now that would be really cool to explore in a headphone, and something laser cutting and 3D printing would make possible.

 

Yes it is! Sony calculated the trajectory and shape of the backwave from the driver, and CNC'd the interior of the wood earcups to reflect the wave back at itself over and over again, effectively cancelling it out and removing it from the equation. As for whether it is perfectly accurate or not, well, measurements will be needed to be sure.

There is some baffle venting which sends the frontwave of the driver into the cups, as well, but this should be mostly irrelevant after losing it's energy in the baffle tape, foam, and finally the cavity damping in the rear volume.

 

@takato14 Do you have a source for that? The cancelling of the backwave with its own reflection doesn't really make sense to me. At which frequency is that supposed to work? At a different frequency you'd have constructive instead of destructive interference.
I think the idea is rather spreading the resonances that occur (lowering their Q), sort of like a much more advanced version of the concave glass of the HD820. By doing that you'd more or less cancel the effect the cups have on the FR. But Bill-P's measurements on changstar did show some effects that I think are due to cup interactions.
I also guess that thinking in terms of "reflections" within the cups doesn't really make sense for audio frequencies. For ultrasonics with much shorter wavelengths where the driver is much more beamy it might, though. But for the audio band I guess you more or less just want to avoid nasty resonances. I think many closed headphones are designed for such a goal. (I wonder what the Focal Stellia cups look like as that has a nicely even and smooth FR.)

 

Pretty sure wavelength doesnt affect directionality? just what it passes through and what it doesnt... the shape of the wavefront will be determined entirely by the objects in front of it -- IE, the coil, magnet, and basket assembly behind the diaphragm -- as it leaves the driver...

 

That's still a matter of passing through something though. I'm only talking about the trajectory of the soundwave. Obviously lower frequencies will pass out of the earcups... but, the R10 driver hardly responds below 100Hz in the first place.

 

How in the world is passing through something the same as which direction it's heading???

 

I didn't say "directionally", I said directionality.

From Merriam Webster, directionality - the property of being directional or maintaining a direction

I'm talking about which direction the wave is headed. The vector on which the wavefront travels.

Let's take a sine wave at say, 1kHz. It exits the driver's rear port at an angle perpendicular to the surface of the diaphragm, headed towards the earcups.

It hits the earcups on one of the angled interior surfaces, and reflects off of it at an angle.

Then, this reflected wave hits _another_ surface of the driver's earcup, again at an angle, but this time it's being reflected backwards because of the shape of the latticing.

This process repeats over and over again until the wave has lost all of it's energy via transfer to the housing.

The actual math required for something like this is considerably complex, as fluid dynamics does not operate in a manner entirely the same as this, but this is the general idea I'm trying to convey.

 

It passes through the walls of the earcups.

The theory at the time was that spatial information was mostly contained in the upper registers -- that's where the R10's cup design operates. To my understanding, the cups are rather thick.

 

No existing headphone measurement coupler can reliably measure the frequencies in which this design would operate. It's at least >10kHz and probably even higher than that based off the wavelength charts you can find on google. But, that doesn't mean it's incorrect/doesn't work.

I was just trying to demonstrate the principle quickly...? It's like 1 AM, I drew the diagram on my phone. I'm not deliberately "omitting" anything.

I really just want people to understand the unique principle of the headphone's design -- this type of stuff is my passion.

 

I'm just trying to explain what sony was going for with the design. Whether it works or not is left up to the measurements. Guess the answer is no. That's not depressing at all.

Can you direct me to a walkthrough of bill's coupler?

 

Think of the frequency vs "directionality" idea like a ball bouncing on a surface. Take a wall with a bunch of triangular slots cut into it, say the slots are 2" wide. If you throw a golf ball, of course it's going to bounce out at a different angle. Throw a baseball, and probably the same thing except sometimes it hit in just the right spot and bounced like it hit a flat wall. What about a basketball? or a beachball? The larger we get, the less meaningful those slots become when determining how the ball bounces because it just smooshes against the peaks and doesn't see the angles below... at least from a macroscopic/reflection point of view. Does it bounce as well as if it hit a flat wall though? That's a much more interesting question.

Does something happen right at the surface? the boundary layer/interaction? Intuitively you want to say yes, but there you're into particle theory rather than wave theory and other fun stuff. Wave theory is often a "zoomed out" view, the particle stuff up close (I'm simplifying obviously), and there's that annoying middling middle ground which is maybe where some of the headphone voodoo lies. It may be worth exploring how acoustic impedance is affected by such surfaces, if at all (it might be a red herring, I haven't read up on that particular topic).

A factor people often neglect when looking at these things is friction. Acoustic/air/whatever friction is a thing. Wibbly wobbly surfaces have a greater surface area than flat ones; more boundary interaction; yadda yadda.

I have a wibbling theory that wobbly surfaces increase the effectiveness of filler/damping materials by allowing wavefronts greater depths of penetration into the wall and prolonging boundary layer effects within the dampening material, but I would need to blow smoke out my arse plus a schlieren machine to study it.