Sit down, have a cuppa and hopefully the reader will find this description of benefit in deciding if these headphones might suit their needs
HISTORY:
In the world of professional audio, Sennheiser is a well known and respected designer and manufacturer of audio products for the recording industry.
This wireless headphone is one of their forays into the consumer market, intended for the home user. Sennheiser's inital offerings in the world of wireless headphones were quite frankly, not good. They were based on infra-red communications which means you could only use them in the same room together (the transmitter and receiver (the headphones) had to be within sight of each other because they used Infra Red light to communicate)
Fortunately, Sennheiser moved on and redesigned their wireless consumer products and this RS 120 II system was one of their offerings. Not based on Infra Red but true Wireless using radio waves which means that you have far more flexibility of where you can listen using the headphones in relation to the transmitter.
These wireless headphones are not a new product, we bought a couple of these "sets" back in 2015, so the product has been around in the market for about 10 years. The original price we paid back then was A$249 per set.
The audio quality is very good, although it can be "fiddly" to set up. The worst thing about this system is the terrible "no real information here" user instruction booklet! Woeful is my best description. I aim to correct this lack of information in the detailed description below ...
Here is a "general" video from a UK guy, not really great on the technical "actual use" side of information but it may help people understand or confirm what I am saying below ... this guy is not very technical e.g the noise at turn on is NOT feedback but in fact White noise!
SENNHEISER - Wireless Headphones
Designed in Germany
Manufactured in China
Release date around 2015
I believe the production of these RS 120 II's have now (2024) been discontinued.
Australian market product (beware of SENNHEISER RS 120 II's intended for other parts of the world, they use different frequencies and may not be legal to use in Australia)
Technology used: Radio Frequency using FM in the range 925~926MHz (UHF)
Think of these as your personal FM stereo radio station, the base (with the Chrome headphone stand) being the transmitter and the headphones, the receiver.
Aural coupling (how the sound is transferred to your ears) Open type, meaning the muffs sit ON the ears but do not cup them.
The complete system is called the RS 120 II
The individual components are:
HDR 120 II Wireless Headphones (Receiver)
TR 120 II Wireless Transmitter (Sender)
Accessories supplied:
2x NiMH 1.2V rechargeable batteries (for the headphones)
1x SENNHEISER NT9-3A Australian plug pack (for the transmitter) NOT a 3rd party substitute!
1x RCA 2 port to 3.5mm stereo plug (useful, depending upon the sound system or television that the transmitter is being connected to)
Basic technical information
22 ~ 19500Hz frequency response (3dB points)
Maximum THD (distortion) <0.7% at 100dB SPL (VERY loud)
Maximum SPL 106dB
Signal to Noise ratio (Receiver - headphones) >65dBA
Reliable operating time is 20 hours when the batteries in the headphones are fully charged
How it all works (personal experiences)
Once setup, these wireless headphones are truly very good audibly. The sound quality is very good and that's what these headphones are all about after all.
Being of the "open ear" type of headphones, it is not a good idea to use these while exercising, dancing etc! Even sitting down while listening to some great metal music would not be a good idea if you are into "head banging" they will probably fall off your ears ... if however you just want to chill out in the lounge chair or even outside on a lovely summer's day, these work a treat in those situations.
Setting up is a little fiddly and there are some tricks which the pathetic manual does not give you information on ...
When you first plug the transmitter power pack into the wall, the ON light (Green) does NOT light up! What The ...? The secret is that the transmitter ONLY comes alive when audio is going into the unit from your sound source, usually a home entertainment system or the television. If using the latter, remember that the audio output from the television needs to be analog, not optical. If it is optical then you will need a converter = spending more money.
On the headphones side of things, the ear muff covers are very easy to open up (small twist and they will release), it is necessary to remove these to 1) fit the two batteries and 2) clean the muffs when required.
When you first turn on the headphones (switch on one side of them), you will most likely hear a rushing sound (White noise) so do not have the volume turned up too loud initially! Now just below the Volume knob (rotating type) is another knob called TUNING.
The Tuning knob is critical to have your setup working correctly. Think of it as a "fine tuning" control. When you are tuned into the transmitter, that rushing sound will disappear (called fully quieting) and you may or may not hear the audio signal that is going into the transmitter. Tune around a little (it's a little touchy but not too bad) and you will hear different things happening as you tune "across" the transmitted audio. In one position of the tuning knob you may hear great sound but only from one channel ... tune a bit more and suddenly a full stereo signal is heard ... tune a bit past this point and again you hear great audio but this time from the other ear. If you don't like a fiddle or two, then perhaps this type of headphone system is not for you!
Once setup, I found the settings to be very stable and I didn't need to readjust the tuning control. I even went up to the transmitter and tried to "influence" the transmitted signal but I had no effect at all.
The audio quality is very good and there is good presentation of both the "highs" and "lows", particularly the lows - great for music with a thumping Bass line but also just as good if listening to a concerto from Beethoven! That said though, these headphones are for entertainment use, not critical listening situations where high quality wired headphones are much more suited or just use a decent pair of near-field monitors!
This system works great for around 50 metres or so distance, yes the manual says something like 120 metres but once you get too far away, the White noise begins to become apparent again - the weaker the signal from the transmitter then the higher will be the White noise heard in the headphones.
At the front of the transmitter unit is a tiny switch which is intended to select a channel, 3 options are available. I never used to change this - no need. It is intended to be used in situations where "other" equipment could be causing radio interference or (extraordinarily rare) if your neighbour is using the same system! Common things like WiFi are not an issue (the frequency is much higher than this system "listens" on) but older (I mean really old) wireless telephone handsets can cause issues with interference because they also used very similar frequencies to this 900MHz system. These old telephone handsets are not common these days and it is unlikely most people would have one. As I say, I/we used these headphones (two sets of the RS 120 II's on different channels) for around 8 years and never had these interference issues and certainly none from our 2.4GHz WiFi equipment.
Another interesting thing about this system is that when you pump "too much" audio into the transmitter, it doesn't all fall apart and become distorted. It seems there is audio limiting built in and as the input to the transmitter is increased, the received volume increases until it reaches a certain point and it increases no more ... this was useful when changing sound sources of different levels as it saved our ears from any sudden explosive increases in volume (and the resulting distortion) - nice!
I didn't notice any compression of the audio signal, the dynamic range is very good.
Nice visual design of the system and it does have a practical purpose! While the headphones are sitting on that top Chrome section, the batteries will be charged - this is indicated by a Red LED on the front of the transmitter. Lift the headphones off this stand and of course, no more charging. A full charge using completely discharged batteries can take about 15 hours so overnight charging is a sensible idea - this is not a rapid charger.
I found the contact between the headphones and the Chrome part of the transmitter stand to be reliable and not difficult to use at all - just don't go placing "stickers" on the Chrome areas otherwise the charging will stop working!
Not much more to say about the operation, it is in reality pretty easy to setup but that tuning part needs to be done right or you will not be happy Jan!
Headphone comfort
Not much good having a good sound in your ears if your head hurts! Personally I didn't have any issues wearing these headphones for an extended period of time, sometimes even fell asleep in the recliner with them still on!
Total weight of the headphones, with the two batteries installed, is 225g. In my opinion not heavy at all but not featherweight either. The headphones are weight balanced Left to Right so they don't make your head lean to one side with resulting neck aches.
The headband is comfortable and provides a positive grip to the head, of course it is also adjustable on either side. The foam padding on the muffs and the underside of the headband is sufficient to ensure comfort while wearing these. If you are unfortunate enough to have some sort of ear "leakage" problem, the muff coverings are easy to remove and clean. I think that Sennheiser USED to supply replacement pads too but I don't know if they are still available. A good brush or even a gentle wash will clean up most dirt buildup anyway.
I did also notice however (a design flaw) that it is unfortunate that the Volume and Tuning knobs are so close to each other - sometimes I would want to adjust the Volume and accidentally end up changing the tuning! A little more thought could have gone into this by Sennheiser.
COSMETIC CONDITION:
USED
These are just on 10 years old now but they look "like new" - no children have been bashing these around and I always took good care of them.
NO plastic is cracked, broken or even discoloured.
NO damage to the headphone structure itself
The padding and foam coverings of the muffs have no holes or discolourations - very nice and clean.
The audio lead (permanently fixed to the transmitter unit) is undamaged in any way
The power pack and audio adapter are also undamaged
I have taken a few pictures (including INSIDE the transmitter unit, it's a "techie thing" as I like to see what is 'under the hood' in my equipment). Inside there is the usual single SMD board with a completely sealed RF section in the centre and also the internal antenna is clearly visible. I was dismayed to find that the wire leads taken out to the front panel LEDs were a bit sad looking, as the insulation had sort of flaked off each wire where the lead is soldered to the PCB. I have remade those joints, it just didn't look good previously!
Each item has now been packed into individual sealed clear plastic packets and then the whole system has, once again, been completely sealed in clear plastic so that the current condition is maintained.
NOTE: The two rechargeable batteries ARE supplied but packed separately from the headphones - this is because Australia Post does not like shipping any equipment with the batteries installed and any batteries must be in their own sealed pack(s) - in case they start a fire etc ...
