There are no licenses and/or frequency coordination to be concerned with; D1 systems use the 2.4 GHz Band (2,400 to 2,483.5 MHz), which is license-free worldwide for low power devices. Sennheiser will supply the appropriately powered D1 system depending on the country of planned operation. In the USA and Canada, Sennheiser has fitted its evolution wireless D1 systems with adaptive transmission power, with up to 100-mW of power ensuring an extra-reliable link and extended range.

-- Sennheiser evolution wireless D1 Vocal SKM

To allow co-existence with Wi-Fi, Bluetooth and other 2.4 GHz systems, the D1 receiver continuously scans the band and seamlessly hops to another frequency if it detects potential sources of interference. This process is inaudible--there are two channels are always available: the actual audio transmission channel plus a redundant back-up channel.

So I wanted to check how easy and simple using the new D1 systems actually is. I got the ew D1-835 Vocal Set and I was surprised to find that the one-sheet instruction was almost not needed! From the moment I put the two AA batteries (supplied) into the SKM D1 handheld mic with Sennheiser e835 dynamic capsule and plugged in the wall-wart power supply for the EM D1 digital receiver, I was already paired and feeding audio over the receiver's XLR output to my Sunset Sound S1P Mic Pre and onto Pro Tools 12 at a good level.

For a test of range, I was able to walk down my street two doors down--about 250-feet away and at all times I was transmitting crystal-clear sound. Using a 24-bit/48-kHz sample rate audio stream transmitted in TDMA (Time-division, Multiple-Access) along with the fast-switching antennas (diversity) back on the EM D1 receiver insured that audio was always there at all times while in range.

I learned that the receiver continuously sends data to the transmitter about how much RF output power is actually needed for a stable signal. The transmitter adapts accordingly and transmits at the requested power. This feature also extends the transmitter's battery life by reducing power to absolute minimum when close to the receiver.

Unlike analog or some other digital systems, there was no fade out or noise build-up at the fringes of the coverage area. If I wondered out of range, my audio just went mute without any static. Awesome!

-- Sennheiser evolution wireless D1 Kit

Audio quality is excellent--exactly how the e835 wired mic sounds due to the aptX Live® codec built-in. Overall latency is 3.9 milliseconds, which is ideal if wireless monitors are to be used (Which also can add latency).

Lastly, the D1 system can be controlled and configured by Apple® or Android® devices using a dedicated app by plugging in a network cable going from the EM D1 receiver to your router. Besides the vocal and instrument systems, there are other D1 series systems that use the EM D1 receiver with the ME 3 headset mic, or the ME 2 lavaliere mic, or the SK D1 belt-pack transmitter for guitars.

The D1 kits each come in a handsome traveling case that includes everything you need to go wireless anywhere in the world. Much more at: www.sennheiser-d1.com.