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Review: AL13 raises the bar for iPhone bumper design

Cell Reception

AL13 is beautiful and functional, but there is one caveat. Because the bumper is made from aluminum, it blocks radio signals. In our testing, we found a decrease in reception strength of about -20 dBm, depending on proximity to the nearest cell tower. This can bring overall reception down to around two or three bars as represented by iOS "signal bar" mapping.

While the iPhone 5 is honed from similar aluminum billet, the handset has four breaks, or "windows," in its unibody chassis, through which radio waves can pass. These are filled with a dielectric material, like plastic, which is non-conductive and allows for the phone's dynamic two-antenna setup to communicate effectively.

AL13 masks these windows somewhat, but doesn't create a conductive bridge over the gap thanks to the rubber lining. If it did, reception would be much worse.

AL13 Lining

Mapp said that preliminary testing found signal loss of 5 to 10 percent; not enough to cause dropped calls. Investigation into new materials is already underway, with an ultimate goal of making the bumper, as well as future designs, radio transparent.

We didn't experience dropped calls, but battery life was impacted slightly. Our guess is the iPhone has to boost power to the radio module in order to maintain acceptable signal strength. Though not unacceptable, some power users who are already teetering on the edge of running their iPhones dry in less than a day may find the added burden worrisome.

That said, we believe the flaw would go largely unnoticed by the average consumer. In some cases, especially with the iPhone 4, the bumper may actually increase reception. As seen in the notorious "antennagate" fiasco, putting a finger over the dielectric filled gap can drop reception down to nil.

Bottom line

With a product like AL13, it's difficult to attach a star rating. The bumper is beautifully designed and executed, but the hit to cell reception is definitely a problem. In the end, we based the final score on attributes a well implemented bumper should display: protection, aesthetics and ease of use.

As a majority of readers will have trouble seeing the difference in cell reception and battery life, only one half star was deducted from the final tally. It should be noted, however, that more discerning users may need to look elsewhere, beyond wraparound aluminum bumper designs.

AL13 lives in that intersection where beauty and function meet. It takes special attention to detail and knowledge of craft to end up with a product like this.

Bottom line: many accessory makers never even reach the level at which Designed by m started with AL13.

AL13 Hand

At a price of $79.99, AL13 is expensive, but some will find it worth the premium. Those interested can pick one up at Designed by m's website.

Score: 4 out of 5

  • Incredible, lightweight design
  • Exacting fit and finish
  • Low tolerance build, high quality materials

  • Causes reception/battery drain issues
  • Expensive for some