Turning Wireless Sennheiser Headphones into Wired

[Bryan Sepkowski]

Hey guys,

I have a pair of wireless Sennheiser RS120's that I use to listen to my TV at night. To use them, I have to heave the wireless receiver plugged into the wall for power and into my TV using Red/White for audio. What I'd like to do is implement a headphone jack between the speakers and the wireless transceiver so, with the flip of a switch, I can go from wireless to wired mode, which I would use with a standard auxiliary cable. Can anyone help me with this?

 

[Blueteeth]

Not entirely sure what you mean.

Wireless headphones are one way transmission so the 'receiver' is your headphones. The red/white are phono plugs, for which you can easily get adapters to/from 3.5mm (1/8") stereo jacks/sockets used as a standard headphone connection.

Do you want to add a socket to your headphones, so you can plug in a 3.5mm cable, that will 'bypass' the wireless part, meaning the headphones speakers are driven directly by the signal coming form that cable? Thats doable, although will void your warranty Perhaps I have misunderstood.

Do you want this switch to change the sound from 'tv speakers' to 'headphones' ? Or to just change the headphones from being wireless, to wired?

 

[Bryan Sepkowski]

Do you want to add a socket to your headphones, so you can plug in a 3.5mm cable, that will 'bypass' the wireless part, meaning the headphones speakers are driven directly by the signal coming form that cable? Thats doable, although will void your warranty Perhaps I have misunderstood.

This is exactly what I want I'm pretty sure I've figured it out by now, but I have a couple questions.

Firstly, how do you wire a TRRS jack?
Second, do the Ground wire and Audio wire both get connected to the same conductor on the TRRS jack?

 

[Blueteeth]

Well, the good news is that, providing you can fit a small TRS socket into your headphones - they are often 'switched'. That is, when nothing is plugged in, the pins that are normally connected to the plugs tip and ring, are connected to two other pins. That was used for a long time on tv's with a headphone socket, or in small portable audio system. So as soon as you plugged in your headphones, the speakers would go silent - because their signal would now go through the socket, into the headphones. This would negate the need for an actual 'switch'. However, if you can't find a 'switched socket', then a simple 2-pole switch will do, be it a toggle or a slide switch.

So you would have to wire the wireless part to these two switch pins (getting polarity correct, left/right). When nothing is plugged in, the audio from the wireless circuit/headphone drivers will go straight through the socket, and it will behave as normal.
When you plug in a stereo plug (TRS 3.5mm) it will disconnect the audio signal from the wireless part, and connect direct to the plug. As to what the other end of this cable plugs into - that is up to you. I am assuming that the speakers in your headphones are standard 16/32Ohm types here. Often the red/white phono jacks are 'line out' and may not be able to drive the speakers in the headphones. (note, the 'line out' on soundcards has a built in driver so it can power headphones direct)

As for the ground wire, I don't see any problem connecting the ground wire permanently to the ground of the TRS socket. Each of the headphones speakers ground wires will most likely be connected together at the circuit board of the wireless part anyway. Just tap that and that is the ground of the TRS.

I can't find a decent picture of a socket... but one like this is fully switched, small, and would work:
**broken link removed**

here's another one with a small schematic showing the switching
**broken link removed**

Sorry for spamming links.

There are so many types of socket, PCB mount, panel mount, solder tabs etc... all depends on what you can get hold of, or where you would prefer to get one.. ebay, mouser, etc..

So, two options:
1. Standard 3.5mm socket (preferably panel mount so you can mount it with a hole in the headphones). With 3 pins, tip, ring, and GND. Use a 2-pole (DPDT) switch that will switch both the left and right from the wireless part, to the socket.
GND/ground can just be wired to the common ground of the speakers. I can provide a crude diagram if you wish

2. Switched 3.5mm socket. This will have 5 pins. tip, ring, tip-switch, ring-switch, and ground. Slightly more complicated, but only one part. The trouble with this is, only way to 'switch' between wired, and wireless signals is by physically unplugging the cable. The first option might be better if you have the cable from your headphones plugged into one thing, and the wireless part in another - flick of a toggle switch and you can switch between those two inputs.

Sorry for a long post, sometimes even simple idea's can balloon with options, plus I prefer to explain things thoroughly, don't be put off!! I just repeat myself lots.

 

[Bryan Sepkowski]

I ordered this from Sparkfun to put in my headphones : https://www.sparkfun.com/products/11570
I figured I can just wire that directly to the speakers inide the headphones, bypassing whatever other components there are. That way, I can plug one end of the male-to-male cable into the headphones and the other into whatever it needs to be plugged in to, and have it output sound. With this, I could turn ON the headphones to use the wireless portion, or leave them OFF to use the wired portion

This would work, right?

 

[Blueteeth]

Pretty much! Providing the headphones have a power switch on them, and there may be some other caveats

As you're wiring the socket in parallel with whatever circuit is in there, if your headphones are on, and you have a source plugged into the socket - they will be in parallel, and so you have two drivers working against eachother. *may* cause damage to either the wireless circuit or the input source, unlikely but could happen. Secondly, even when the wireless circuit is off, the input form your cable will be driving that circuit as well as a speakers, which, depending on how the internal wireless headphones drivers work, could load the input signal making it very low volume.

With that said, you could just try it An actual 'switch' to switch the headphone speakers between the socket and the wireless circuit would completely isolate the two, but would be more work.

Tip is 'left', Ring is 'right' and sleeve is ground. The one you linked has an extra sleeve, like those 4-conductor plugs used for phones with a mic attached, but you can just ignore that pin.

 

[Bryan Sepkowski]

I'm going to wire in a microphone so I can use it with my phone and stuff if I need to, so which ring is right and which ring is left (According to the piece I bought- ring1 or ring2)?

 

[Blueteeth]

The tip is left channel, the first ring is 'right' channel, and the second ring I believe is for microphone - most likely the hot side of a small electret capsule.

As to how well the mic will pick up your voice if its mounted inside the headphones, I do not know, often its just mounted in the cable itself.

This one shows the wiring for a standard stereo headphones:
https://2.bp.blogspot.com/-Z12CRxrAmys/T_RT2HgwVFI/AAAAAAAAAfM/qR4j_NTzwdg/s1600/IMAG0092.jpg
From this site:
https://leon-hacks.blogspot.co.uk/2012/07/sennheiser-35mm-connector-repair.html

I know thats a plug, not a socket, but you can work out the pinout of the socket from that (the sparkfun socket all the pins are aligned, so its tip, ring 1, ring 2, sleeve, from left to right)

If you use a 4 connector plug, I suspect the second ring would be the mic.

That said, apple always likes to be different [rant] like customers to only buy their products at a marked up price [/rant], and their pinout is this:
https://lh4.googleusercontent.com/-.../s603/4-pin%203.5mm%20headset%20connector.png

Some stereo sockets will 'ground' the 2nd ring, so will plug into standard stereo audio jacks (for headphones only) as well as the iphone connector, but that depends on the socket. Although there are standards, in the phone industry, these are relatively slack.

A cheap way to add a mic is to buy a cheap Chinese knock-off hands free set, with an inline mic. Chop off the crappy earphones, and those are your connectors to the speakers, which you can wire a 3-pin 3.5mm plug to - to plug into your headphones.
So you can use that for your phone, or a standard stereo 3.5mm plug-to-plug cable for just headphones into normal audio equipment.

 

[Bryan Sepkowski]

That's what I heard about Apple, and it sucks. I plan to use this with my iPhone and my Xbox One Headset Adapter, which I don't know the pinout of. So, just for the sake of future-proofing it, is there a way of having both pinouts?

Also, is there a way to tell which wire is the ground wire and which is the audio wire? Off each speaker, there is a blue cable and a white one and I wan't to make sure I wire them correctly to the jack


That's actually exactly what I did for the microphone. Found an old 2.5mm one-ear earphone and lopped everything off except the microphone Also, this had a green cable and a white, so how can I tell which is the ground cable for this?