Development Update #5: Tweaking and Tuning

July 29, 2014
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We’ve been making some steady progress these past 2 weeks on mechanical, EE, and firmware design, including the various adjustments we mentioned in the first update!

There is now a small recess around the audio jack port, to make the Arc compatible with as many third-party cables as possible. You can see a render of the new shape here:

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Thankfully, this doesn’t affect the appearance of the headphones from profile or side angles (collective sigh of relief).

During the latest rounds of user testing, we also garnered some feedback about weight being a little heavy. We took to the kitchen scales, and found that Arc weighs in at roughly 280g, compared to 150-200g for non-Bluetooth headphones (e.g. Urbanears Plattan, Beats Mixr) and 250-275g for Bluetooth models (e.g. Beats Wireless, Parrot Zik)

To cut Arc’s weight down closer to a target 250g, we’ve shortened the overall shape of the headphones by about 10cm, which will reduce plastic and steel mass. This also solves another issue we’ve had with Arc being too large for smaller heads. The new batch of samples with these changes will be ready in the next week or two!

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On the EE front, our intern Sunny has been hard at work rerouting the PCB to his satisfaction, and simulating various Bluetooth antenna designs to find the most efficient shape. So far we’ve been able to achieve at least 85% efficiency (i.e. how much energy is actually transmitted, relative to how much is input from the Bluetooth IC) with a peak of about 95% at 2.45GHz, taking into account interference from the casing and human head. This weekend Sunny will be heading back to Shanghai ahead of schedule, to actually produce, test, and tune the various antenna designs with a network analyzer.

We’ve also started experimenting with various ways of representing audio with the LED ring (until now, they’ve simply pulsed according to bass amplitude) and making sure it shows up well under different lighting conditions. The glow looks great indoors, but is hard to see in direct sunlight. We’ve updated the shape and material of the ring to transmit light more efficiently (including removal of screws that block the path of light rays)

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In the next engineering update, we’ll go in depth on firmware development and also show you some brand new packaging designs!

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