Sony MDR-RF925RK Wireless Headphones

Sony MDR-RF925RK/RF970RK Stereo Headphone System  (Updated 9-1-2011 to add range and listening information)

This interesting component was purchased in order to modernize our Home Audio System; the principal difference between old and new being the latest wireless design. I had not experienced any difficulty with the stereo cords except for the length; which, at 10' was usually too short to reach my easy chair. Making do with a 20' extension cord solved the distance but not the nuisance. With this new equipment I am able to enjoy the desired freedom of movement around the house.


In the Carton: Headphones and Transmitter, AC Power Adapter, Rechargeable NiMH Battery, and 1 six foot stereo audio cord with RCA Plugs. Also, operating instructions in a dozen languages.


DESCRIPTION:
The System consists of two Major Components* with different Model Numbers:


MDR-RF925R Cradle/Transmitter/Charger Unit
Wireless Channel selector switch (3 Positions)
Connectivity Center:
DC IN 12V, RCA Stereo Jacks (Red Right, White Left), "B" Mini Stereo Input from LINE OUT or REC out on other components.
Battery Charging & Earphone Storage Receptacles


The headphones fit readily into the cradle, fitting two ways: 1. Wrong; and, 2. Correct. Small triangles are placed on both components, when both triangles are matched, the process of charging begins. No power switch is needed, an automatic shutoff circuits monitor the battery charge and charging stops when a full charge is detected. An LED indicator shows Red or Green depending on the status of the charge. If no signal is being received, The RF Signal is stopped while charging. FM Stereo varies with signal strength and geographic location of the Radio Station Towers.


MDR-RF970R Headphones Unit
Over the head, whole ear covering, with built-in wireless antenna receiver. Vertical alignment is achieved with a self-adjusting separate flexible plastic Band that keeps the antenna strap away from the head. The Band and the Ear Pads are nicely covered with a cloth material that appears to be a solution to the checking of the foam pad cover on older models. There is about an inch of play in every direction which allows adjustments to the wearer's satisfaction.


L Earphone: What appears to be a decorative medallion is actually a removable cover. While looking right at the L Earphone, there is, at the 135 degree or 4:30 analog clock position on the rim a 1/2" by 3/16" button that is marked "PUSH". That pressure on a hidden latch releases the cover on your side (but may trigger the opposite one first). DO NOT FORCE it. It is laughably easy when the cover is off because the numbers 1 and 2 mark those latches and the sequence needed to replace that cover.


The cover protects the battery compartment where two Ni-Mh rechargeable cells assembled into a battery module are to be installed.
(Sony P/N BP-HP550-11 2.4V, 550 mAh; which is a proprietary part.)
Even so, it is OK to replace this assembly/battery with any two AAA dry cells (properly polarized).
There is also a shielded ceramic magnet located next to the battery assembly. That makes possible the electromagnetic induction that charges the battery when the Earphones are returned to the cradle.


When the Band is pulled upward as in putting on the earphones, it engages an on-off switch concealed in the L Earphone that turns the sound on. When the headphones are removed and just set down, that switch has already cut the power to decrease the drain on the the battery charge. Power is indicated by an LED pilot lamp located over on the...


... R Earphone: This is the business side; where the Pilot Light and Three Controls are located around the bottom edge. Arranged Counterclockwise are the VOLUME CONTROL and the TUNING button.
Volume is adjusted by moving a knurled wheel - turning controls both earphones. Range is about nil to earsplitting, depending upon the source signal strength.
Tuning is done by sliding the 3 position button so marked. It is awkward but can be done using both hands. (My unit worked only in position 3.)



SPECIFICATIONS:
Carrier Frequency: 915.5-916.5 MHz
CH1, CH2, CH3
Modulation: FM Stereo
Audio Frenquency Response: 20 - 20,000 Hz

OPERATIONS and PERFORMANCE


All told, I spent half a day wearing Sony's MDR-RF970RK headphone set and comparing its performance to that of my old 2005 era SONY MDR CD350 Digital Reference headphones. All testing was done using a Sony STR-DG510 AV Receiver. Thanks to the recent relocation of the local FM station transmitters in our San Francisco Bay region, we do have FM reception but our "Box Canyon" locale still causes trouble and interference. Our favorite stations sound like the old short-wave stations; with some hiss in the background. 

Both the headset and the cradle are efficient antennae that are highly directional. Headphone reception can be improved by turning one's head slightly or, rotating the cradle slightly. In some cases, switching the channel may improve reception.
In the Cradle, Audio frequency signals received from a tuner or television are compressed and converted to Radio Frequency (RF) FM Stereo and broadcast to the headphones. The latter reverses the conversion back to audio and decompresses it. This process, it is claimed, reduces noise picked up during transmission. There was no 60 cycle AC hum detected.  


RANGE: Supposedly 150 feet, practical testing suggests no more than 50 feet for clear reception. That test was made through a picture window out onto the driveway. Reception through interior walls was satisfactory if the cradle were aimed properly; which is the long dimension at right angles to the easy chair. This house is a wood frame balloon structure with sheet rock screws and nails securing the finish wallboard. If the wall contains steel studs, reception will be severely limited (as demonstrated with cellphones used in commercial buildings). 
Comparing new to old revealed a wide difference in power being delivered to the different sets of headphones. Comfort of the new model was better thanks to softer padding.


I was concerned about negative reviews of these Headphones and poor quality audio reproduction. I have no idea what standard was being applied; there seems to be a highly subjective and selective preference at work here.
Seeking a decent, repeatable measure led me to listen to a special Compact Disc performance of a work* I first heard in a Music Appreciation class in the 7th Grade.
The composition is 16 Minutes long, features highly trained performers playing every imaginable kind of instrument, sounds range the audible scale from Piccolo to Bass Drum. 

My hearing is still relatively keen* and this CD can shake the house if I am allowed to crank it up on the right equipment.        

In comparison to other sources including live performances in some of the best theaters out West; this is one of the best; delivering rich, clear, fine fidelity that I am used to. Rather than the 'surround' sounds that enrich the speaker manufacturers, one's ears are simply flooded with descrete musical entertainment. Seeking perfection in the effort to simulate a theater environment is fatuous. In life, the orchestra never flies around the building nor does the audience invade the stage.  


RECOMMENDED


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NOTES:


The Sony Catalog is specific but the components carry intermixed Part Numbers. The Epinions Data Base carries both numbers and reviews have been submitted using either or both numbers. As in "Gilbert & Sullivan" or "Rogers and Hammerstein", you can't have one without the other.


"Young Person's Guide to the Orchestra", 1946, by Benjamin Britten (1913-1976), English Symphony Orchestra, Nimbus NI7017, DDD 1994, SKU 0-710357-701726 (No spoken dialog)


My "Laboratory" is a vintage Sony RDR-VX555 CD/DVD player. The headphones have both mini and standard audio plugs; which were attached to a Sony AV Receiver STR-DG510.
  Those amongst us who are familiar with the M-1 Rifle will appreciate the damage done out on the firing range to the right eardrum by the blast from the chamber as the spent brass is ejected. I had to do that 4 times in as many military training schools during the late 1950's. The first round always rendered me deaf for a week afterward. (No sissy ear muff protection used in those days.)   I was a Navy Electronics Technician but one never knows when pirates might board a ship. 
A long-time critic of excess in anything, I can still detect which side of the orchestra holds the strings.