magnets in headphones… would this calibration method work?

[DQCarder]

I just got a pair of Sennheiser HD 558s, which are full-sized headphones. I was told by a fellow iRacer that headphones can cause drift with the DK1, and he wasn't kidding. It's bad enough that after a few minutes in a demo I'll be almost 45° off-center.

I took the headphones off and tried moving them around my head and in front of the Rift. Sure enough, as I moved the headphones, my view in the Rift moved. I'm talking about a range of 20° or so — very obvious and I can repeat it over and over again and it's very consistent.

So… I really want to be able to wear these headphones with my Rift, but I don't know much about the technical aspects of the Rift. If were to put the Rift and the headphones on, say, a mannequin head (or something roughly the size and shape of my head), and secured the Rift/headphones into place, and did the magnetometer calibration with the dummy head instead of with just the Rift, would this fix the issue?

I tried doing the calibration while wearing the Rift and the headphones, but I wasn't able to give it enough data for the calibration to succeed. Maybe even if I'm not wearing it and I can move it 360° in every direction it still won't work because the magnets in the headphones might be so strong that they're "diluting" the magnetic signals? Like I said, I don't know how this stuff works.

Any ideas? I can't find anyone talking about issues with headphones and the Rift, but it's really really bad. The drift is consistent and fast enough that you can easily see it moving. For demos this is annoying, but for racing in a cockpit that's built to the exact scale/shape of the virtual cockpit, it's pretty much a dealbreaker. I know this will be fixed for DK2.

[ThreeEyes]

I was going to post a link to one of the makers of compass ICs because if big magnets are placed too near at least some of the compass ICs, it can semi-permanently bias the compass IC. Unfortunately, Google warned that their site had been compromised and someone had inserted links to malware. The Google synopsis I had found that looked like it discussed the strong magnet issue also had the warning. I would bet other sites would discuss the effect too but I'm on tablet right now.

As a side note, it's kind of cool if you haven't seen it. Just Google "compass IC magneticsensors.com" and check the results for "This site may harm your computer" then look at the explanation of why they are alerting - but don't go to the site itself unless ye are brave and willing to risk it.

Anyway, if you get a strong magnet too close to at least some of the sensors, it can add an offset to the signals until it is specifically reset or possibly permanently. I first heard about this over in the multicopter forums with the flight controllers with compass ICs in them too. Get them too close to strong magnets and they can't be re calibrated.

I don't know if it is all compass ICs or just some of them, but without knowing which IC Oculus uses, we can't check the data sheet or application notes to know.

I only bring this up so people won't put strong magnets near their DK1 and cause possibly ruin the tracking.

At least some of the ICs have special circuits built in to degauss the IC but those have to be commanded on to do it.

If anyone does know the IC markings, could you post them? It's probably a square and unusually tall IC that isn't too big. I don't have a DK1 or else I could find it.

And if Oculus is listening, if the IC you use has degauss capability, do you expose that where the chip can be degaussed in the calibration software? Or does anyone else know?

[CaliberMengsk]

I just checked by placing some of my disk magnets on the top of the back of my chair (right behind my head) and trying recalibrating the rift's mag sensor, and it seemed to pass every time this time, so theory checks out, as long as you have a good enough magnet. These are about the size, and I think strength (I bought them a while ago, and just don't remember for sure, but I'm fairly certain they were n45's.) Only difference is that the link doesn't have a hole in the center like mine does.
http://www.ebay.com/itm/Neodymium-Disk-Magnet-1-75-x-0-25-Very-Strong-N45-NdFeB-Rare-Earth-Magnet-/1...

I can't promise the quality or if it will work in your particular setup. I can say that setting the magnets on my desk did not work, but having it on the back of the chair at head level, holding the rift at head level worked for me. Hope this helps you some.

This one should also probably work, and if you have a harbor freight near you, you can just go and pick it up probably. http://www.harborfreight.com/66mm-round-magnet-96650.html

More weight it can lift the better the magnetic field. Just be aware that you don't want it to be so massive that it messes with things like hard drives 😛 (pretty sure mine are the 45lb ones.) Main difference between the two is the top is a neodymium earth magnet (natural magnet) and the second is a manufactured magnet. Difference being that the second one is more likely to loose magnetism when placed inside of another magnetic field.

Enjoy.

[enilcleahcim]

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[DQCarder]

Thank you so much for testing that out CaliberMengsk! 🙂 When I got back home I asked my roommates if they had any magnets, and one of them had a bunch of small neodymium magnets. I tried using them to calibrate to no avail (although they definitely were showing up on the calibration tool readings), but we do have a Harbor Freight nearby and that eBay magnet is cheap too, so I'll try one or both of those out when I get a chance and report back.

[ElectricMucus]

Perhaps are Bone Conduction Headphones a solution?
http://www.wired.com/2012/05/aftershokz/

Some use piezoelectric transducers which wouldn't give off a magnetic field.

[DQCarder]

"ElectricMucus" wrote:
Perhaps are Bone Conduction Headphones a solution?

Not for an audiophile. With DK2 this won't be an issue anyway as the camera will prevent drift.