Overlay stereo with mono, without losing stereo?

[grimerking]

Hi,

I'm planning to modify a set of headphones to create an Xbox 360 gaming headset. I found this guide.

However, there is a problem with the design - i.e. the 'game chat' will only be output from one headphone speaker. I'd really like it to be output from both speakers, but wiring in the Xbox headset audio into both headphone speakers will 'short' the stereo signal.

Is it possible to splice the xbox headset mono signal into both headphone speakers using diodes? If so, what type would I need?

If diodes aren't suitable, can anybody suggest an alternate method?

Thanks in advance,

Rob

 

[DUG]

Diodes will not work.

If you are working with only line level signals there are (at least) two ways to mix what you need.

Transformer mixing...feeds amplifier for headphones...passive...no power supply needed...I have used this to mix two "ipod" signals to feed an amplifier. I haven't tried at pure speaker level but with lower impedance transformers it should work.

Active mixer using operational amplifier...full audio bandwidth...lower distortion...thousands of this circuit in use.

 

[grimerking]

Hi Dug,

Thanks for the diagrams. Unfortunately, I have no idea how to convert that into wiring!

Am I right in thinking the passive solution consists of:

• A 600 ohm in-line resistor fitted to the positive wire of the left speaker.
• A 600 ohm in-line resistor fitted to the positive wire of the xbox headset, which then connects to the positive terminal of both the left and right speaker.
• A 600 ohm in-line resistor fitted to the positive wire of the right speaker.

I'm not that hot with electronics. Isn't 600 ohms quite a large resistance?

 

[DUG]

The solutions I suggested are more for inputs to an amplifier.

Yes you could use resistors but I think that 50R to 100R resistors would would be better if your headphones are in the 24R to 50R range.

Xbox headphone impedance (google search) is 32R

 

[Pano]

I'm confused, but I know nothing about X-Box audio.
The idea is to make a stereo headphone with a boom mic?

Is the game audio coming from left and right but the voice is only in one channel? It's isn't mixed to center by the X-Box?

 

[dheming]

There are three options when it comes to Xbox voice chat: output to headset, output to speakers or output to both. The reason why it would only be one channel the way he's talking about hooking it up is because the Xbox headset only has one speaker.

I'm thinking it would just be easier to only hook up the mic to the headphones and then have the voice channel come out stereo with the game audio by selecting the send to speakers option. This way you still have mic function, but the voice chat will automatically be in stereo as well as adjustable in level via the menu option.

I've done something similar with my Xbox rig. The headset goes around my neck and I angle the mic up to be close to my mouth. I removed the single speaker and in its place soldered a six foot cable with a 1/4" TS connector on the other end. This then goes into a spare channel on the mixer that sits on my desk. The reason I did this is so I can quickly adjust voice volume without having to go into the multiple layers of menus to make a simple change. Also my mixer has a built in compressor on the first 6 channels and I have it maxed out on the voice channel. This is great for when people yell late at night. So on my Yamaha my mixer I have: music from computer on two channels, voice on one channel (panned to center) and game audio on another stereo channel. I like to turn off game audio between matches and just listen to the music and my crew talking. The versatility of this system is pretty great actually.

 

[grimerking]

Thanks for the replies so far.

Pano Said:

I'm confused, but I know nothing about X-Box audio.
The idea is to make a stereo headphone with a boom mic?

Is the game audio coming from left and right but the voice is only in one channel?

That is exactly the issue. The Xbox 360 headset only has one speaker, so the voice chat is in mono. I'd like to link up the mono source to a set of stereo speakers (headphones) without breaking the stereo separation.

Dug said:

I'm thinking it would just be easier to only hook up the mic to the headphones and then have the voice channel come out stereo with the game audio by selecting the send to speakers option. This way you still have mic function, but the voice chat will automatically be in stereo as well as adjustable in level via the menu option.

I did consider this option, but I'd really like to maintain the in-line volume control function. If I need to adjust the volume quickly, I don't want to have to mess around with menus.

As I've said, my knowledge of electronics is quite limited. Would you be able to provide a simple wiring diagram that shows how to wire up the headphones, headset mic/speaker wires and any necessary resistors/components to get this working?

 

[sofaspud]

I too know nothing about XBox audio, but from keeping up with the thread it seems like an external box to receive and manipulate all the signals would be the easiest route.

 

[grimerking]

I too know nothing about XBox audio, but from keeping up with the thread it seems like an external box to receive and manipulate all the signals would be the easiest route.

Any suggestions?

 

[dheming]

I too know nothing about XBox audio, but from keeping up with the thread it seems like an external box to receive and manipulate all the signals would be the easiest route.

Indeed, I think a cheap little mixer like the Mackie 402-VLZ3 would be the easiest and much more versatile solution. They are made for doing exactly this kind of thing. Also they have headphone amps built into them as well. Another nice thing is that since they have gain you can boost the chat signal by quite a bit if need be. This comes in handy for games like Halo Reach where there are no volume sliders in game and you can't hear your friends over the music when it ramps up, even with the chat slider on max. Also sometimes people talk quiet or have their mics far away from their faces.

 

[grimerking]

To be honest, one of the reasons I'm doing this DIY solution is to get a decent quality headset for 'free'. I already own some headphones and an Xbox 360 headset. I was hoping to integrate them without too much additional cost. That Mackie mixer is $140 in the UK, so it is way too expensive for this project.

Thanks anyway.

 

[dheming]

Okay, so plan B would be to just build a simple mixer circuit. Splitting mono into stereo is the easy part, but combining that with a pre-existing stereo signal is a bit more involved. You say you're not that hot with electronics. Have you considered just buying a simple audio mixer kit you can put together yourself, such as this one: 4 Channel Mono Mixer Module (CPM010)

 

[grimerking]

I can solder and am comfortable following instructions - e.g. 'add xR in-line resistor to positive cable of x'. I just don't know what components I would need to buy.

If you could provide a circuit diagram that explains what components are needed, I think I could follow it.

 

[dheming]

There are tons of simple passive mixer circuits out there for line level signals. These are designed to work with the typical output and input impedances found in audio electronics from a few kΩ to 10's of kΩ range. I'm not sure how the values of the resistors would need to be modified to work with the impedance range of headphone drivers which are usually in the 24Ω to 300Ω range. Not to mention the issue of how to prevent crosstalk between the L and R channels when you split the mono signal across them.

I'm thinking this would be better done with an active circuit, but then it would need power and a little circuit board. So it wouldn't be easy to incorporate that into the headphone itself.