Equipment Review No. 2 March 2002
Amphony 2.4 GHz Wireless Headphone
Operating time: max. 100 hrs on two AA batteries
Freq. Response: 20 Hz - 24KHz
Max. Sound pressure level: 113 dB
Transmission method: 2.4 Ghz digital signal
S/N ratio, A-weighted: typically 93 dB
Dynamic range: typ. 93 dB
Channel separation: typ. 91 dB
Harmonic distortion: typ. -88 dB
Audio sampling method: 64 times oversampling
Transmitted data rate: > 3 Mbps
Data also available at high-speed data port
Max. Transmitter output power: 1 mW
Operating range: max. 200 ft. line of sight, 50 ft. thru walls and ceilings
10179 Berlin, Germany
U.S. Rep: Amphony Corp.l
1006 S. Raven Rd.
Shorewood, IL 60431
The Amphony is claimed to be the worlds first 2.4 gig digital wireless headphone and was first introduced at CES 2002. Wireless headphones have used infrared, FM, and 900 MHz signals in the effort to free the user from long cables. Few have matched the sonic quality of a set of wired high end phones, and many of the approaches suffered from various interference problems. Amphony has developed a proprietary technology using a 2.4 gig signal that transmits the stereo audio in a digital format. They say that solves the drawbacks of the other systems in that noise and audio distortion are absent from the digital transmission. Also, since the unit transmits at a data rate over 3 Mbps there is no need to use compression on the signal, and an intelligent error correction circuit can be used to correct transmission errors under difficult conditions.
Since the unit transmits digitally and is identified as a Digital Wireless Headphone I had expected the input on the transmitter to offer a coaxial or TosLink digital jack to feed it directly from a CD player or computer without having to go thru another D/A and then A/D process. But there are only L & R line-level input jacks on the transmitter - the digital conversion occurs before the transmission. The headphones are large but not heavy; they are sleek-looking but press rather hard against ones head - perhaps with use that will subside. I didnt want to risk breaking the headphone by bending it. A second self-adjusting headband at the top fits them to anyones head. There are only two controls on the phones themselves: the on/off switch on the left earpiece and the level control on the right earpiece. The soft ear cushions cover some of the left and right sides of the circular earpieces, giving the shape of the pupilof a cats eye. The drivers are about half the diameter of the ear pieces.
I tried several CDs, SACDs and DVD soundtracks via the Amphonys, with the Sony player feeding directly from its output jacks to the input jacks of the transmitter. Their quality was excellent, though I didnt hear the sort of high end extension that would seem to be indicated by the specs of up to 24 KHz range. I found their timbre rather similar to many Koss headphones - rich and bass-heavy. On Paul Chambers bass solos on Kind of Blue there was a loose sort of exaggerated bass extension, while on my Sennheisers and Grados the bass was more solid and taut-sounding. However, the Amphonys imparted more depth and dimension to many recordings than the other headphones did. It almost seemed they were extracting more L - R difference information from the stereo signal than normal wired headphones were capable of.
Some reviewers have reported that they couldnt find any spot in their house where the headphones didnt work. My experiences suggest they must live in houses without any inside walls. I found that the blocking of just one wall between the transmitter and headphones caused loud putt-putting distortion much like serious ignition noise with a car audio radio or player. I was looking forward to being able to audition stereo SACDs and binaural CDs from my Big Rig while working in my office, but though it is only about 30 feet distance, two walls intervene and the continuous distortion to the signal made it impossible to listen to. Even out in the open on a balcony just above the transmitter I still got the heavy putt-putt sound; I finally figured out it was due to the narrow slats in the balcony railing - when I stood with my head just above the railing the signal became excellent again. However, I found that when within direct sight of the transmitter, moving your hands, reading the paper or changing position slightly didnt muck up the sound - as occurs with my present infrared wireless phones.
So if you have clear line of sight from your transmitter to your head, and require the freedom of wireless, the Amphony will probably give you the best wireless sound you can get for the money. They surpassed other wireless phones I have tried, and the two AA batteries give very long life and seem a better solution than the rechargeable batteries of some other wireless phones. For watching video and DVDs without bothering others in the house or risking anyone tripping over your headphone cable and strangling you in the process, wireless phones cant be beat. If you have a newer component with the Dolby Headphone feature, you can feed the transmitter from that phone jack and experience surround effects on your Amphonys.
- John Sunier
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