With dozens if not hundreds of different options now on the market, iPhone-compatible monaural Bluetooth headsets can be understood as compromises of five essential components: ear-sized speaker, microphone, battery, enclosure, and miniature computer chips. Historically, the smaller and lighter these parts have become, the less you could expect from them in performance, and the more you can expect to pay for the miniaturization.

Left to right: Argard M10, Voyager 520, Discovery 665, Apple Bluetooth Headset
Three new Bluetooth headsets we’ve been testing generally follow the historic rule, but also interestingly diverge enough from it to be worthy of any iPhone owner’s attention. Two are from Plantronics—the brand new Voyager 520 ($100) is an improved sequel to the company’s popular mid-range Voyager 510, while the Discovery 665 ($150) is a smaller and lighter alternative at the top of the Plantronics lineup. The other is Argard’s M10 ($149), which is size of a stack of watch batteries with a silicone-tipped earbud attached. It’s around a third the 665’s size, and similarly under half the size of Apple’s own iPhone Bluetooth Headset (iLounge rating: B); weighing 5 grams and measuring 23mm by 22mm by 31.5mm, M10’s the very smallest Bluetooth headset we’ve seen.
If you start from the historic premise—smaller sounds worse and is more expensive—you’ll be part of the way to understanding these three new headsets. Using Apple’s good but not spectacular iPhone Bluetooth Headset as a common reference point for sound, we found that callers preferred the way we sounded through the less expensive, larger Voyager 520, found the Discovery 665 essentially equivalent, and found Argard’s M10 a small step below Apple’s and the 665’s mark.
In other words, if sound quality is most important to you, stop reading now and find a way to test the Voyager 520 for yourself: it’s not small or sexy, but as we’ll explain below, it’s a very strong performer overall.
Sound quality, however, isn’t the only factor in Bluetooth headsets; size and looks are becoming increasingly important. Here, M10 is a surprisingly strong contender: using your choice of either silver or titanium-colored metallic plastic shells, plus matching A-shaped charging docks, M10 fits wholly inside your outer ear, and unlike all other Bluetooth headsets we’ve tested, it doesn’t jut out beyond that. Three silicone tips in small, medium, and large sizes can be swapped to make M10 sit comfortably inside your ear canal; we had no problem placing it or keeping it in place. All of these components are packaged in a deluxe black compartmented box that looks gift-worthy.
A thin ring of blue or red light signals connection or disconnection from iPhone, and three buttons—two on the top for volume, one on the outside edge for power and pairing—blend right in with the rest of the casing. M10’s design is nearly as neutral as Apple’s, but with the volume controls the iPhone Bluetooth Headset lacks. Similarly, given past experience, we would have expected that M10’s microphone would suffer tremendously given how far it is from one’s mouth, but that’s not the case—it’s an inch or so further from your lips than the Apple headset, but callers routinely told us that the sound difference between them was “small.” M10 picks up a bit more ambient noise, but not enough to make a huge difference; neither unit comes close in wind or noise filtering to Aliph’s optimized Jawbone, but they’re also both a lot smaller.
As with all of the Bluetooth headsets we’ve tested with iPhone, M10 had no problems initially pairing with the iPhone, or maintaining connections within its 10-meter (30-foot) range. That said, it suffered from even more static interference than Apple’s headset when we separated the devices by 10 feet, becoming basically unusable by the end of the 30-foot distance.
Callers couldn’t hear us and we couldn’t hear them; Apple’s headset asymmetrically sounded better to callers, but not to us, at similar distances.
A brief note on the Bluetooth technology inside these headsets is also warranted. Both of the Plantronics earpieces include Bluetooth 2.0 technology that’s compatible with newer phones and computers, and each pairs especially quickly with iPhone once the headset’s turned on. By contrast, M10 uses older Bluetooth 1.2 technology, and doesn’t auto-pair as quickly, but it worked just fine with the Bluetooth 2.0-capable iPhone in most of our tests. When flipping back and forth between headsets, we once heard M10’s audio become screechy on both ends, but we attributed the issue to our unusual Bluetooth toggling rather than a problem with M10, and it went away when we hung up and then resumed our phone call.
There are more substantial differences between the various headsets’ bundles. The Plantronics 520 and Argard M10 each come with a wall charger and a desktop dock—nothing else—but the Plantronics dock is almost tacky in its cheapness, while the M10 dock is stylish and sophisticated. The 665 is the best-appointed of this bunch: it lacks a wall charger, but includes a USB charger, a car charger, and a shirt-clipped wearable charging sleeve that you must dock 665 in to refresh its battery. You’ll need to decide whether the absence of a wall adapter is important to you, but we find computer recharging to be sufficient, especially when a car charger is included in the package.
The one final offset to these devices is their differing battery lives.