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Discussion Starter #1
I've Emu 0404 USB soundcard attached to my laptop. I use XLR cable to connect the ECM8000 mic to sound card.
Now the 0404 has both 1/4" single output as well as stereo 3.5mm output. What should i connect?
I tried both and the curve are very different. the Single connect gives output about -10db lower then stereo output.

Here is the link to the image of emu
http://www.emu.com/products/zoom/15185.html

Can somebody please help?
 

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I tried both and the curve are very different
Can you elaborate? The first thing you must do before you do any measuring is to create the soundcard calibration file. For this you have to connect a loopback from line-out right to line-in right. What connection did you use for this? Can we see your soundcard calibration graph?

brucek
 

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Discussion Starter #3 (Edited)
Can you elaborate? The first thing you must do before you do any measuring is to create the soundcard calibration file. For this you have to connect a loopback from line-out right to line-in right. What connection did you use for this? Can we see your soundcard calibration graph?
brucek
Bruce,
I already calibrated the soundcard using a 1/4" loopback cable from the Mic input B to the 1/4" Right output. Unfortunately i'm at work & i don't have access to cal file. I'll attach that when i get home. But the graph is flat from 15Hz-20KHz. I also loaded the ECM8000 calibration file.
I did check levels using RS meter at 75db and did "Calibrate SPL". The "Calibrate SPL" level is spot on 75db. I used the technique you suggested by holding the RS meter close to the mic.

When i take measurement using single 1/4" R output from the sound card to Dual RCA the SPL is very low from 20Hz - 100 Hz.
But when i take measurement using main output 3.5mm stereo jack to dual RCA the measurement is close to 75db line.

here is the link to 1/4" to Dual RCA cable that i used
http://www.musiciansfriend.com/document?base_pid=331067&cpd=0OEY&doc_id=99371&index=0


My confusion :confused: comes from the connection diagram on REW help file where its told to connect only single output from soundcard to splitter RCA connect into AV processer. If i do that i don't get a good graph.:gah:

I tried searching for an answer but could not find one.:sad2:
 

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I already calibrated the soundcard using a 1/4" loopback cable from the Mic input B to the 1/4" Right output.
Generally, connecting a line level to a mic level input isn't advised unless you fabricate a resistive pad to attenuate the signal so as not to clip the mic input. Usually the loopback is connected from 1/4" line-out right to 1/4" line-in right. Yes, this bypasses the small mic preamp, but experience shows the effect is minimal.

When i take measurement using single 1/4" R output from the sound card to Y Splitter RCA the SPL is very low from 20Hz - 100 Hz.
Can you explain what you mean? Do you mean you can't get enough level out of the soundcard feeding the receiver that you can't turn it up to achieve 75dBSPL at the listening position?

But when i take measurement using main output 3.5mm stereo jack....
I would use the same output used in the soundcard calibration routine.....

My confusion comes from the connection diagram on REW help file where its told to connect only single output from soundcard to splitter RCA connect into AV processor. If i do that i don't get a good graph
Again you'll have to explain this.

Basically, you first create a soundcard cal file with the 1/4" right line-out to right line-in. Then, with the loopback still in place, you take a measurement from 0Hz-20000Hz of that cable with the soundcard file in place (and no mic file loaded). The result should be a perfect flat line (if the soundcard file is correct).

Then remove the loopback and hook up the mic to the right channel mic-in and the receiver to the right line-out. Load the mic cal file and do the Check Levels and the Calibrate routine and Measure..

brucek
 

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Discussion Starter #5 (Edited)
Generally, connecting a line level to a mic level input isn't advised unless you fabricate a resistive pad to attenuate the signal so as not to clip the mic input. Usually the loopback is connected from 1/4" line-out right to 1/4" line-in right. Yes, this bypasses the small mic preamp, but experience shows the effect is minimal.
I guess if you look at the Emu 0404 front panel the Mic input is a neturik connector that will take both XLR and 1/4" line level. This is the only input type that's available on this soundcard.
Here is the link to the soundcard http://www.emu.com/products/zoom/15185.html

Can you explain what you mean? Do you mean you can't get enough level out of the soundcard feeding the receiver that you can't turn it up to achieve 75dBSPL at the listening position?
No this is not the problem. I do "check level" and get 75db SPL on RS meter and line in level is good between -18db to -15db

I would use the same output used in the soundcard calibration routine.....
Yes I use the same input called "B Hi-Z/Line Mic" that outputs to the 1/4" Right channel on the soundcard.

Basically, you first create a soundcard cal file with the 1/4" right line-out to right line-in. Then, with the loopback still in place, you take a measurement from 0Hz-20000Hz of that cable with the soundcard file in place (and no mic file loaded). The result should be a perfect flat line (if the soundcard file is correct).
Then remove the loopback and hook up the mic to the right channel mic-in and the receiver to the right line-out. Load the mic cal file and do the Check Levels and the Calibrate routine and Measure..
Expect for the measurement from 0Hz-2kHz I did what you said.
The output is hooked up as follows.
I use 1/4" to Dual RCA patch cable to connect the right 1/4" output of the soundcard to receiver Left & right RCA inputs (AUX inputs). This is where i'm :confused:. This gives me a very low SPL on the graph.
Now when I connect only one speaker using 1/4" to single RCA then the SPL seems resonable. Which to my understanding is incorrect as per the REW help file that suggests to connect both L&R speaker using splitter cable. I need clarification on this please.:dontknow:
 

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I use 1/4" to Dual RCA patch cable to connect the right 1/4" output of the soundcard to receiver Left & right RCA inputs (AUX inputs). This is where i'm . This gives me a very low SPL on the graph.
But when you run Check Levels, you set the receiver volume to receive 75dBSPL at the listening position.
Then you run the Calibrate routine and match the REW SPL meter to read 75dBSPL.
Then you run Measure.
The result can only be at 75dBSPL - it cannot be low on the graph if you've done all this.

the REW help file that suggests to connect both L&R speaker using splitter cable. I need clarification on this please.
You can connect to the right or left or right and left. It's up to you. It's only a suggestion to use a splitter to connect both right and left as a matter of convenience, since it makes no difference in levels and it allows you to check one or both speakers.
You're doing something wrong if it alters your levels after you've set them to 75dB.

brucek
 

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Discussion Starter #7
Bruce,
I found the problem. It was in 1/4" jack to RCA cable. The problem is 1/4" jack is stereo plug and not mono so when i was connect it i was loosing some SPL.
When I connected 1/4" mono to single RCA adapter and then used the splitter to connect to L & R inputs to the AV it worked.

BTW i've attached the graphs for loopback measurement. The 2nd Graph shows the problem i was having.
The 3rd graph was taken using 3.5 mm output of the sound card and
The 4th graph was taken using mono plug.
The 5th graph has all the measurements
 

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Looks good now.

Try and remember to always use the LOG mode and not the LIN mode for your plots. (The button to switch between the two is in the top right corner of REW called Freq Axis). :)

brucek
 

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Discussion Starter #9
Thanks Bruce for your help and walking me thru.

The real fun begins now:). Now i have to think of ways :scratchhead: to tame those peaks and dips. I've SVS AS-EQ1 on preorder and i'm anxiously waiting for it to see how this will help smoothen out the lower end response.
 
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