Plantronics M2500 Bluetooth headset review
Even though the M2500 does not sport DSP, I found the sound quality to be excellent when you are in a quiet environment. The voices reproduced by the headset's earpiece are clear with their full tonal range, and just need to be a little louder. When listening to someone using the M2500, again the voice sounds loud and clear. As with other wireless headsets without DSP, the boom mic picks up some of the surrounding noises. If the headset had DSP, then usually the ambient sounds are muffled.
Almost all of the today's Bluetooth headsets are rated for operation of up to 30 feet (10 meters). In my subjective testing, the M2500 performed as expected excellent sound to about 20 feet (line of sign no obstacles). There were some crackling sounds noticed between 20 and 30 feet, which increased substantially after 30 feet. But please keep in mind that the ideology behind bluetooth is to provide connectivity only in very short proximity.
In our outdoor/wind simulation, the M2500 failed awfully (as excepted). Since it does not utilize DSP or any other special mechanism to cancel the wind interference, I could not hear myself when I put our test fan about 9 inches (25sm) away from my face. Other headsets like Logitech Freedom or Scale 500 use special foam-like encapsulation of the microphone which absorbs the wind interference.
The M2500 is rated for up to 5 hours of continuous talk time, but in our tests we able to get only about 250 minutes, which is about 4h and 10 minutes. The headset's stand-by time is rated to 120 hours.