REW Cabling and Connection Basics

**jaypeecee** · **03-04-09, 10:14 AM**

Hi Folks,

In the above thread for the ECM8000/Xenyx 802 combo, I am intrigued that both input and output connections to the PC sound card are on the RH channel. Whilst I can understand this for the input, I would have expected the PC sound card output to be on the LH channel, which was then split between the LH channel and RH channel on the line input to the power amplifier. I should point out that I do not have a home theatre setup - I want to use REW purely for stereo Hi-Fi.

I'm not questioning that your diagram is incorrect - it obviously isn't. It's just that I can't understand the setup. Presumably, I'm correct in thinking that the output from the sound card feeds test tones (pink noise, etc.) into the amplifier and thus through the connected loudspeakers? The resultant sound is then picked up by the ECM8000 and amplified by the Xenyx 802 before being fed into the sound card. So, is the LH channel of the sound card never used - either input or output?

Please clarify.

JPC

**brucek** · **03-04-09, 10:34 AM**

I'm not really understanding your question.

REW creates a mono signal that is picked up by a mono mic and fed to a single channel of the soundcard.

One of the channels (line-in and line-out) is never used.

Many people split the line-out at the receivers input with a Y-splitter (as shown in the diagram) to feed the mono signal to both the receivers right and left channels, allowing the user to test both right and left or both mains.

brucek

**jaypeecee** · **03-04-09, 10:50 AM**

Bruce,

Apologies for not making myself clear. I was thinking of the sound card as a duplex device whereby you've got record and play going on simultaneously. In this sense, record is equivalent to the sound card line in and play is equivalent to line out. I just can't understand how record and play are occurring simultaneously on the same (i.e. right) channel. After all, what is fed into the RH channel input of the sound card will appear at the RH channel output - is that not correct? So, that would mean that the amplified ECM8000 signal would be fed into the receiver/amplifier and that doesn't make sense. Surely, the test signal (pink noise, etc.) is the only signal you want on the sound card output? I guess the answer lies in the REW software.

If I haven't made things any clearer, I'll try again.

JPC

**brucek** · **03-04-09, 01:31 PM**

Quote:

After all, what is fed into the RH channel input of the sound card will appear at the RH channel output - is that not correct?

Absolutely not. In fact, that's a mode called monitor, that has to be shut off in the soundcards application or Windows mixer, or REW will not operate without feedback. That's a mode that you would use (for example) to listen to a CD while you're ripping it.

Quote:

I just can't understand how record and play are occurring simultaneously on the same (i.e. right) channel.

That is indeed how it works...

brucek

**jaypeecee** · **03-04-09, 02:23 PM**

Bruce,

Thanks for answering my questions. I guess it just means that I have a lot to learn about REW and the whole business of carrying out measurements of this kind! Would you please confirm that I am correct in saying that the RH channel output from the PC sound card is what feeds the test tones from REW into the receiver/power amplifier (and thus the loudspeakers)?

One final question - do you still recommend the Behringer ECM8000 and Xenyx 802 as your preferred mic/preamp combination (particularly in the light of recent threads talking about defective ECM8000s)?

JPC

**brucek** · **03-04-09, 03:02 PM**

Quote:

the RH channel output from the PC sound card is what feeds the test tones from REW into the receiver/power amplifier (and thus the loudspeakers)?

You have the option to select either the right or left channel for use with REW. Once the channel is selected, that is indeed the channel that feeds the signal from REW to the receiver.

Quote:

do you still recommend the Behringer ECM8000 and Xenyx 802 as your preferred mic/preamp combination (particularly in the light of recent threads talking about defective ECM8000s)?

Yes, the ECM8000 is perfect for measuring your system.

Hopefully, you have read and become familiar with the REW HELP files.

brucek

**Wayne A. Pflughaupt** · **03-04-09, 07:58 PM**

Quote:

jaypeecee wrote:

I was thinking of the sound card as a duplex device whereby you've got record and play going on simultaneously. In this sense, record is equivalent to the sound card line in and play is equivalent to line out. I just can't understand how record and play are occurring simultaneously on the same (i.e. right) channel. After all, what is fed into the RH channel input of the sound card will appear at the RH channel output - is that not correct?

To expound a bit on what brucek said, the soundcard output feeds REW’s signals to the receiver, while the input feeds what the measurement mic picks up to the computer for REW to process. These things occur at the same time, which is why the sound card must be duplex.

Quote:

do you still recommend the Behringer ECM8000 and Xenyx 802 as your preferred mic/preamp combination (particularly in the light of recent threads talking about defective ECM8000s)?

The ECM/802 combo is only necessary if you want full range measurements. If all you’re wanting is subwoofer measurements, a Radio Shack SPL meter is all you need.

Regards,
Wayne

**jaypeecee** · **03-05-09, 07:05 AM**

Thanks guys,

The sound card that I'm using is the Edirol UA-1EX, which is full duplex with REC SOURCE switch = ANALOG (except for 96kHz setting) and this is the switch setting that I am using. Wayne, I want to do full-range (not just LF) measurements so it looks like the ECM8000/Xenyx 802 is the way forward. Bruce, I have familiarised myself with the REW Help Files and have successfully completed the first six steps.

Thanks again.

JPC

**jaypeecee** · **03-05-09, 10:21 AM**

Bruce,

I just spotted what I believe to be an error on the ECM8000/Xenyx 802 connection details. The sentence immediately following the layout diagram states "The output of the XENYX 802 preamp is a balanced line level from a 1/4" TRS phone jack". Shouldn't this read "The output of the XENYX 802 preamp is an unbalanced line level from a 1/4" TS phone jack"?

Sorry if it appears that I'm being pedantic - that's not my intention.

JPC

**brucek** · **03-05-09, 11:20 AM**

Yeah, I never updated that when they brought the XENYX out. It was from when it was written for the UB802 that had a typo in the manual (long story - very boring).
Actually, I don't thing Behringer ever uses a TS connector, they just use all TRS and wire them to suit. But anyway, I will change the guide to say unbalanced and TS.....

brucek

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