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Discussion Starter #1
I recently purchased a TASCAM 144 usb preamp and ECM8000 mic to use with REQW. Am trying to calibrate my soundcard, but don't think I'm getting acceptable results. Performed the loopback calibration and then a loopback measurement, see attached graph. Are these result OK? They are more variable than what is shown in the REQW Help file.

A long time ago I uninstalled all the Creative Labs software that came with the SB Audigy sound card because I believed it was interfering with iTunes streaming music wirelessly to AirPort Expresses. So, the only control I have over the soundcard is via the simple Control Panel functions.

Are the problems I'm seeing in the graph due to "monitoring" being active on the soundcard? If yes, guess I'll have to reinstall the Creative Labs software to fix it.
 

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Discussion Starter #3
Already did that, didn't see any place to turn off record monitoring. Got the same results as shown above.
 

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Already did that, didn't see any place to turn off record monitoring
Well, if you're using the Tascam 144 USb card, then the monitor is the MON MIX dial. It must be all the way clockwise to turn off monitoring.
Be sure to use the right channel and be sure to have the mic/line-guitar switch in the mic/line position.

Be sure to unbalance the line-in jack with an adapter or TS connector.

brucek
 

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Here's why I think I've got a problem. Am trying to use REW to measure full range frequency response on a two channel Hi-Fi system. The mic set at 3' on axis with the speaker tweeter. As you can see in this graph, the spread is +/- 15 dB, higher than expected.

I think the graph is incorrect because the same speaker can be measured using individual test tones from 20 Hz to 20,000 Hz and an SPL meter. I tried to upload a graph of these results in a Word document, but the file was to big. So, you'll have to take my word for it.....the frequency response is much smoother and has a am smaller spread, approximately +/- 10 db.
 

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Here's why I think I've got a problem.
I'm afraid I can't agree with you. You don't have a valid soundcard calibration file yet, as shown in your upper posts. There's really no use proceeding to the measuring phase until that's complete.

brucek
 

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Discussion Starter #7
Bruce,

I am using a stereo 1/8" patch cord for the soundcard loopback measurement. Might that be the problem with the calibration?
 

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Can you tell me the jacks you are using for your loopback connection and the cable terminations you're using for each.

Hopefully we're talking about a Tascam US-144 USB soundcard. You have the title of your thread listed as SoundBlaster Audigy, yet you say you have the Tascam US-144. So, I am quite confused about your thread.

Tell me the type of soundcard you're using and the type of loopback cable including terminations, and what jacks you're plugging it into.

brucek
 

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Discussion Starter #9
My PC has a Sound Blaster Audigy 4 card installed in it. All soundcard calibrations have been done looping the output of the card back to the Line-in input using a stereo 1/8" patch cord.

I'm using a Behringer ECM8000 mic, so need phantom power. To meet this need, I purchased a TASCAM US-144 standalone box. The mic is going to the front MIC IN R input. The TASCAM output if via the USB out to my a PC USB input.

The Audigy 4 output is going to a Denon AVR 3600. The AVR 3600 is driving a single full range speaker. My objective is to measure the full range frequency response of various vintage speakers.

Thanks much for your patience and help.
 

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Wow, what an arrangement. I guess you know that the usual setup is to use the line-in and line-out of a single soundcard.

I'm not sure that REW will recognize the line-out of one soundcard and the line-in from an external USB soundcard.

Why would you purchase an external USB soundcard simply for its phantom power preamp abilities, and not a conventional XENYX 802 mixer?

Either way, I would forget about the Sound Blaster Audigy 4 card for REW measurements and only use the Tascam. This way you use its line-out and the mic in ports. To do a Tascam soundcard calibration, you use its line-out to line-in.

brucek
 

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Guess I'm just an idiot following another idiot's advice (the guy who told me to buy the TASCAM US-144) on another forum. :coocoo:
 

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The Tascam will certainly work to do your REW work on its own, and then when complete you can use the SoundBlaster for your regular computers sound duties.

Simply set the Tascam up as the default sound device and do a soundcard calibration and you're ready to go. If you have any trouble, let us know and I'm sure we can sort out any problems...

brucek
 

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Now I am starting to understand. Didn't know the TASCAM US-144 could be used as a soundcard. Thought it was just for ECM8000 phantom power.

Here's my current connection set-up. The TASCAM USB output is connect to the PC's USB input. The line out right is going to my AVR. The ECM8000 is going to the Mic In right. Input R dial is set to MIC. Line out dial set to maximum. Mon Mix dial set to Computer.

Here's what the loopback calibration looks like. The black dashed line is the TASCAM calibration. The solid black line is the mic/meter calibration (downloaded for the ECM8000 from this web site).

Am I headed in the right direction now?
 

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Am I headed in the right direction now?
Absolutely....

Here's a quick and dirty full range F.R. measurement on a small bookshelf speaker.
Good job. But, try and use the standard we recommend here for graph scaling.
For subwoofers use a Vertical graph axis of (45dB - 105dB) and the Horizontal graph axis of (15Hz - 200Hz) using the Graph Limits button in the top right corner of REW. Use a measurement start frequency of 0Hz and an end frequency of 200Hz.

For full range, use the standard Vertical graph axis of (45dB - 105dB) and the Horizontal graph axis of (15Hz - upper limits you desire, i.e. 1KHz -20KHz - certainly no higher than your soundcard can extend).
For full range only, enable smoothing to eliminate the comb filtering. Use a 1/3 octave smoothing.

brucek
 
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