SB X-Fi 5.1 output noob ??

**BigJPDC** · **08-06-08, 05:51 PM**

Greetings. New to all this stuff I guess. Brought home the SB X-Fi Surround 5.1 USB sound card from Circuit City today ($59) to give this a try.

Running Vista on my laptop, connected the device and it was immediately detected and installed. Installed REW, hooked up the Radio Shack SPL and that also calibrated just fine, so in under five minutes I was ready to roll.

I am using the digital optical out into my B&K preamp, and ran a couple of test sweeps which look right on with what I've gotten by doing the realtraps tones (in one-millionith of the time), but I see that the output only comes from teh center channel.

Am I missing something somewhere which makes the REW output respect the B&K settings for output channels. Does optical not work with REW? I just hope the answer isn't to install a bunch of SB software, everything else is just working fine without any effort.

thanks, I have some hommade traps I am waiting for baselines to throw up.
jp

**JohnM** · **08-06-08, 06:13 PM**

The signal from REW is the same on left and right channels. If you have any surround mode active on your processor it will typically route the signal to the center. To get it going to left and right set the mode to "stereo" or "direct" or the equivalent and then disconnect the channel you are don't want to measure. If you are mainly interested in measuring the sub you can leave things as they are, make sure the centre is set as "small" and disconnect it so the low frequency will be redirected to your sub.

The disadvantage of using the optical output is you cannot easily calibrate out the effects of the soundcard. The soundcard roll-off is typically fairly modest on a good soundcard, so that's not a show stopper.

**BigJPDC** · **08-06-08, 06:48 PM**

Thank you John for the prompt reply; REW looks amazingly comprehensive. My primary goals here are to test sub placement and accoustic treatments so I was thinking that I would have to activate as many speaks as possible for the fullest sound at the listening position.

The SB card has analog left and right outputs - would it be better to use those, a seperate preamp input and 3ch audio for my testing?

jp

**brucek** · **08-06-08, 07:14 PM**

Quote:

The SB card has analog left and right outputs - would it be better to use those, a seperate preamp input and 3ch audio for my testing

Use the single analog right channel of the soundcard for all your testing.

You use analog line-out right and analog line-in right to first calibrate the soundcard with a loopback cable, then you remove that cable and use that channel for measuring..

Feed the right line-out output to your receiver AUX or CD analog input (with a splitter if you like) and put the receiver in stereo mode (with crossover selected) and disconnect your mains.

Now you will be sweeping the subwoofer only.

Please see the REW HELP FILES and the REW Connection Basics thread..

brucek

**BigJPDC** · **08-06-08, 08:32 PM**

ugh. I don't have an RCA single to double cable to allow the splitting of the right channel into my preamps' left and right inputs. This seems kind of silly to me.

**salvasol** · **08-06-08, 09:07 PM**

Quote:

BigJPDC wrote:

ugh. I don't have an RCA single to double cable to allow the splitting of the right channel into my preamps' left and right inputs. This seems kind of silly to me.

What about using a "Y" cable (1/8" to RCA) ...

I don't know if you can use/or have the option on your pre-amp to run the "stereo for all channels"

**BigJPDC** · **08-06-08, 09:23 PM**

Quote:

salvasol wrote:

What about using a "Y" cable (1/8" to RCA) ...

I don't know if you can use/or have the option on your pre-amp to run the "stereo for all channels"

the XFi has RCA left-right, not a 1/8" out.

**JohnM** · **08-07-08, 04:04 AM**

You can also simply connect one analog output of the soundcard to the power amp input for each channel you want to measure if you have a separate PA, or to the 7.1 analog inputs of your processor if it has them. You will almost always want to measure one channel at a time, it is only when looking at the integration between sub and L/C/R that it makes sense to have both the sub and a main channel running.

**BigJPDC** · **08-07-08, 07:37 AM**

Quote:

JohnM wrote:

You can also simply connect one analog output of the soundcard to the power amp input for each channel you want to measure if you have a separate PA, or to the 7.1 analog inputs of your processor if it has them. You will almost always want to measure one channel at a time, it is only when looking at the integration between sub and L/C/R that it makes sense to have both the sub and a main channel running.

That sounds like something fun to do someday, but even the REW interconnect diagrams have both fronts and sub in the picture. I would think it would be trivial to add functionality in REW to accomodate newer soundcards with actual RCA connections.

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