You wouldn't be far off base if you thought the Plantronics Discovery 665 was an update from the Discovery 655 Bluetooth headset, as it looks and feels very much like its predecessor. It even comes with a similar-looking charging pocket and also comes in a silver and black finish. However, though the Discovery 665 has improved audio quality, we can't recommend it over the 655 due to its lack of charging options. The Discovery 665 will retail for $149.99.
The Discovery 665 is slimmer and more tapered than its predecessor at 0.4x0.5x2.0 inches (the 655 measures 0.6x0.5x2.0 inches), and it weighs less than 0.3 ounce. Even though it also comes in a silver and black finish, the color scheme is reversed when compared to the Discovery 655. Everything else about the Discovery 665 headset remains the same: three different rubberized ear gel pieces for your comfort, an optional flexible ear hook for more security, a simple square multifunction button on the front, as well as two tiny rubberized buttons for the volume controls underneath. As with the 655, we weren't too fond of the tiny buttons. Though they are raised from the surface of the headset, they still proved a bit tricky to press when the headset was worn on our ear.
As with the 655, the Discovery 665 headset also comes with a carrying case that doubles as a charger. It has a clip on the back in case you want to attach it to a shirt pocket. If the headset is in the charging case when there's an incoming call, it will vibrate as well as light up. This is especially useful when in the car, since it provides a visual indicator for an incoming call. Taking the headset out of the case will automatically answer the call. Unlike its predecessor, the Discovery 665 has only two charging options: a vehicle-charging adapter and a USB adapter. While we understand the 665 is supposed to be for drivers, we would still like to have additional charging options included in the package. The 655 on the other hand, comes with an AC adapter as well as an AAA-battery charging unit.
The most exciting upgrade to the Plantronics Discovery 665 is its AudioIQ sound-processing technology that optimizes sound quality on both sides of every call. We tried it out in an isolated booth with some piped in sound, and we tested the headset with and without the AudioIQ technology. With the AudioIQ turned on, calls sounded clearer without the need to increase the headset's volume.
We tested the Plantronics Discovery 665 with the T-Mobile Sidekick 3 and the LG CU400. We managed to pair the headset with both phones without a problem. The audio quality was excellent, thanks to the AudioIQ technology mentioned. Features of the Discovery 665 include a battery strength indicator; the ability to answer, end, make, and reject calls; call mute; last-number redial; power-saving mode (this disables the AudioIQ/DSP technology); voice dialing, and the ability to switch a call from the headset to the phone and vice versa. The Discovery 665 headset has a rated talk time of up to 3.5 hours and a rated standby time of three days.