In the following question:

Dual output speakers and headset

I wanted to output to multiple sources simultaneously. I was instructed that this isn't possible. HOWEVER - I have a sound card that has dolby digital 5.1 surround sound - a Soundblaster X-Fi. It has two outputs which I can get to work - i.e. a center channel and rear channel (it also has a sub channel I think, but this isn't probably useful for this discussion).

What I've tried doing is connecting my external recorder to the rear channel, enabling the "quadraphonic" (4 speaker) setting, and then trying to record. Unfortunately, unless the software is actively sending a signal to the rear channel, it doesn't record anything.

What I'd like to do is be able to send the SAME signal to both center and rear channels. Is this possible with the soundblaster card I have?

  • What operating system are you running? – ctrl-alt-delor Sep 17 '12 at 14:48
  • Microsoft Windows 7 – jwir3 Sep 17 '12 at 17:01
  • I know you can do it on Gnu/Linux in the layer between the applications and the hardware drivers (the sound system, it is not part of the OS). But have no idea on Microsoft Windows, but would hope you can do the same. – ctrl-alt-delor Sep 18 '12 at 9:43


A 5.1 audio system usually has the following outputs

  • subwoofer
  • front left
  • front center
  • front right
  • rear left
  • rear right

So far as I know, when playing a stereo signal, this gets routed to front left and front right outputs. A mono signal is lekely to be routed to both front-left and front-right. Some sound systems give you limited control over what (if anything) gets routed to the other channels. Some systems can synthesize signals for other channels to give a pseudo surround-sound effect but this isn't a simple duplication of the front signals. I expect the front-center and subwoofer signals may be synthesized by mixing and applying a low-pass-filter.

Speaker electrical outputs are a bad source for recording from, normally you want line-out signal levels and impedances. You can buy a DI box for this purpose.

Recording speaker output

To record what you are listening to,

  • You can use a software solution (e.g. if your soundcard drivers allow for a "wave-out mix" or equivalent source. Alternatively you can use a third-part product like Virtual Audio Cable "VAC is useful to record application's audio output in real time"

  • You can feed line-out to an external hardware audio-mixer then feed that signal from the mixer both to monitors (powered speakers) and to a recording device.

    • the recording device could probably be your PC's line-in connection so long as you have audio monitoring off (which feeds inputs back to your outputs again)

Details depend on audio hardware and drivers

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