# Problems with measured levels



## mstailey (Jan 2, 2007)

Why is the measured response so high (spl) after carefully setting levels? The SPL calibration is 75.x spl, the check levels is way within limits and after running set target level (which is 75.x spl) the measured response is way high. Running find peaks, the program goes nuts. 

What am I doing wrong?


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## brucek (Apr 11, 2006)

You forgot to run the CALIBRATE SPL routine..................


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## Wayne A. Pflughaupt (Apr 13, 2006)

Here’s a cut-and-paste from my “REW quick instructions” note that I refer to when I use REW (I tend to forget the details when I don’t run it for months at a time). Comparing the settings in the pictures you provided to my notes, I’ve bolded a couple of things I see that are different. Try these changes and see if it helps.

_Set the Wave Volume at 1.000 and the *Output Volume about ~0.500.* 

Adjust your receivers volume control so the actual standalone Radio Shack SPL meter reads ~75db at the listening position.

*Then adjust REW Input Volume to end up with -12dB on the REW input VU meter (i.e., matches the Output meter).*_

Regards,
Wayne


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## mstailey (Jan 2, 2007)

Hi Ken,
I did calibrate SPL, right after I checked levels (did not post that in original post - sorry) and it was set to 75 db. I did the calibration with the RS meter right next to the ECM8000. Note I'm doing this thru my AV unit not directly connected to the sub meaning I've pre-set the sub volume to 75db then when setting levels and calibrating REW I'm using the master volume on the AV unit.

I'm getting 75db(+/- 2db) all the way around in setup but get the high output on the measured response.


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## mstailey (Jan 2, 2007)

Hi Wayne,
I was typing up my response to Ken when your post came in. 

I do just that (what you suggest)


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## brucek (Apr 11, 2006)

Are you saying you set the receiver level at the listening position to 75dB with the actual RS meter and then right after that clicked the *CALIBRATE* SPL button in REW to match REW to 75dB?

brucek


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## mstailey (Jan 2, 2007)

brucek said:


> Are you saying you set the receiver level at the listening position to 75dB with the actual RS meter and then right after that clicked the *CALIBRATE* SPL button in REW to match REW to 75dB?
> 
> brucek



That is exactally what I'm doing with one exception. I set levels before that step.

In otherwords (all done in the settings window):
I set levels with the RS Meter using the AV master volume to read 75db at the RS meter
Adjust my settings (Output, Wave and Input to around 12-14 db on output/ input VU meters)
Run REW calibrate SPL with the settings of the RS meter - again @ 75db


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## brucek (Apr 11, 2006)

> In otherwords (all done in the settings window):
> [1] I set levels with the RS Meter using the AV master volume to read 75db at the RS meter
> [2] Adjust my settings (Output, Wave and Input to around 12-14 db on output/ input VU meters)
> [3] Run REW calibrate SPL with the settings of the RS meter - again @ 75db


Excuse my numbering of your quote, but I want to direct you to number [2].

Changing the Output level will alter the 75dB reading on th RS meter.

You should 
[1] Set sweep to -12db
[2] Set Wave to 1.000 and Output to 0.500
[3] Adjust receiver volume to 75dB on RS meter.
[4] Set Input level to proper level ~-12dBRMS.
[5] Run CALIBRATE SPL routine and set REW level to 75dB
[6] You could run Set Target Level routine at this point and it should verify around 75dB....
[7] Measure

brucek


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## mstailey (Jan 2, 2007)

Hi Ken,




brucek said:


> You should
> [1] Set sweep to -12db
> [2] Set Wave to 1.000 and Output to 0.500
> [3] Adjust receiver volume to 75dB on RS meter.
> ...


I followed your steps without any improvement. I went back through your posts about the Spectrum function of REW and decided to try it with no nosie in the room. I'll save space and your time by not posting a bunch of graphs but I noticed a steep rise in the FR from 100hz on down to 10-11 hz with the analyzer just listining. I decided to try a different soundcard, went back to the Spectrum analyzer and sure enough - no rise in the FR I saw in the previous soundcard. Re-set it all back up and problem solved. Note all of this was performed with the soundcard left channel as reference in the Settings window.

Thanks for taking time to walk me through this.

BTW: soundcard I think is bad was a Soundblaster 24bit USB external. The soundcard I replaced with was the internal SigmaTel Audio that came with my Dell Vostro and much to my suprise it measured almost flat from 12hz --> 9.5khz.

Mike.


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## solid7 (Jan 31, 2008)

mstailey said:


> BTW: soundcard I think is bad was a Soundblaster 24bit USB external. The soundcard I replaced with was the internal SigmaTel Audio that came with my Dell Vostro and much to my suprise it measured almost flat from 12hz --> 9.5khz.
> 
> Mike.



It seems that I am having the same issues. I cannot get past the "measure" stage in the settings. Doesn't it seem a little unlikely that "bad soundcard" would be the culprit, here? Even more so when someone else appears with the same issue?

Thanks.

PS - I am not using the loopback from the left channel.


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## brucek (Apr 11, 2006)

> Doesn't it seem a little unlikely that "bad soundcard" would be the culprit, here?


Yes, I can't even imagine that the card is bad...

What problems are you having?

brucek


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## solid7 (Jan 31, 2008)

brucek said:


> What problems are you having?


I cannot get the card calibrated. (cannot achieve acceptable levels during the measurement portion of the calibration)

I am able to verfy that before taking any measures, my SPL meter does match REW.


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## mstailey (Jan 2, 2007)

brucek said:


> Yes, I can't even imagine that the card is bad...
> 
> 
> brucek


What evidence do you have to make that statement? I followed your instructions to the letter and no improvement so I change out my sound card and it improves. You know much more than I do however that being said, I go by end results. 

If you think I haven't solved my problem by changing the sound card why didn't you say so when I took the time to write back thanking you for your assistance?


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## brucek (Apr 11, 2006)

> What evidence do you have to make that statement?


I have no evidence other than another person appears to have the same problems. 

We have hundreds of people pass through here with these problems and there has never been any evidence of a broken soundcard. 

It's almost exclusively something they are doing wrong. That's what I'm here for, giving up my free time.

Your problem cleared itself when you changed cards. Great, I have no idea what happened other than you're good to go.

Carry on................. 

brucek


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## solid7 (Jan 31, 2008)

mstailey said:


> If you think I haven't solved my problem by changing the sound card why didn't you say so when I took the time to write back thanking you for your assistance?


It sounds like you *did* solve your problem by changing out the sound card. However, your problem was simply that couldn't get the other one to work - not necessarily that it was a bad card. I don't believe that your card was bad, and I don't believe that mine is, either. So, newer friendlier card + desired result = problem solved. I'm still having your old problem.

For me, changing the card is not an option. I need to stick this out, and I'd like to figure out what is going on, if possible. I'm sure that this must be related to some lack of knowledge on my part, as there are too many people using this card to think otherwise, and perserverance will surely help someone else out later on.

For what I know, I'm probably not following some simple instruction somewhere. My hope was that somebody else did this, at some other point. I tried searching threads, but no real solid leads. I'll keep searching while I wait for an answer.

Thanks for your help!


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## JohnM (Apr 11, 2006)

solid7 said:


> I cannot get the card calibrated. (cannot achieve acceptable levels during the measurement portion of the calibration).


What level do you get? 
What OS are you running, XP?
Have you been through the steps of the help file for the SB Live?
Output volume needs to be 1.0 rather than 0.5.


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## solid7 (Jan 31, 2008)

JohnM said:


> What level do you get?
> What OS are you running, XP?
> Have you been through the steps of the help file for the SB Live?
> Output volume needs to be 1.0 rather than 0.5.


1] See post #12 - that's as far as I went (since I couldn't attain good numbers here, I didn't go further)
2] XP, SP02
3] Yes. Repeatedly, and with much scrutiny.
4] I have tried both 1.0 and .5 (per the instructions, and as posted here)


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## JohnM (Apr 11, 2006)

The levels shown in post #12 would work fine. Set the output volume to 1.0, which will get them closer, and carry on from there.


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## solid7 (Jan 31, 2008)

JohnM said:


> The levels shown in post #12 would work fine. Set the output volume to 1.0, which will get them closer, and carry on from there.


Hello, John, and many thanks for your reply.

I think that I may have misunderstood the graphical representation on the right hand side of the screen shot that I posted. (looking at that, where I should have been checking my SPL meter reading) So what exactly do the numbers in that graph represent, and at what point of discrepancy do I need to be worried?

FWIW - my SPL meter matches REW. (or vice versa)


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## brucek (Apr 11, 2006)

solid7,

I see that you have the Radio Shack SPL meter calibration file loaded into the spot where the soundcard calibration file is to be loaded. I didn't notice this before, so clear that out and load it into its proper spot in the Settings page Mic/Meter tab......

Next you are to do a soundcard calibration using the cable shorted from left channel line-out to left channel line-in (because that's what you show in your pic above - may as well stick with that).

The VU meter labelled OUT is simply that. The output level from the soundcard. You show -12dB RMS with a -9dB peak - perfect.

That signal travels from the line-out to line-in and it appears on the LEFT input VU meters left channel in your pic at about -22dB. That's a little low, so turn up the output level from its present 0.5000 until it reaches ~ -12dB on the LEFT VU meter. Complete the soundcard calibration and store the file on that settings page. Now remove the short and do your measurements.

brucek


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## JohnM (Apr 11, 2006)

The numbers show the levels relative to digital full scale, if the input is within 10dB it should be OK.


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## solid7 (Jan 31, 2008)

I do not have the proper cables for the left channel loopback. From what I have read so far, this is optional. Did I misunderstand that part? No big deal if I need it, I'll just make a trip to RS tonight!

Thank you for taking your time. It's nice to have a forum where people directly support their own products. I have to admire you for doing so, because I know from running my own business that it must be incredibly hard to dedicate time to such things, in addition to your regular life.


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## brucek (Apr 11, 2006)

> I do not have the proper cables for the left channel loopback. From what I have read so far, this is optional. Did I misunderstand that part?


I think you're a bit confused here.

There are two ways to do use REW.

*1. Soundcard calibration file method.*
A file must be created that matches the response inaccuracies of your soundcard. This only needs to be done once and then the file is loaded in REW.
To create this file you must install a cable between _either_ the left or right channel line-out to line-in. Then REW must be told which channel that the short cable is connected to by selecting the Left or Right choice button on the settings page. The LEFT CHANNEL CALIBRATE check-box is unchecked and *never* used for this method.
Once the short cable is connected and the Left or Right channel selected, the Measure button on the Settings page is pressed to create the file..... follow through it instructions. Save the file.
Now the short is removed forever.
Normal measurements (after Check levels routine) can now be taken using either the left or right channel as long as REW is told which one by selecting the Left or Right choice button on the settings page.

*2. Left Channel Calibrate method*
This method doesn't use a soundcard file and one is never loaded. A short cable is connected from the Left channel line-out to line-in and it remains forever. The Left Channel Calibrate checkbox is checked and always remains checked.
Normal measurements (after Check levels routine) can now be taken using the Right channel only (since the Left Channel is already used).

brucek


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## salvasol (Oct 31, 2006)

solid7 said:


> I do not have the proper cables for the left channel loopback. From what I have read so far, this is optional. Did I misunderstand that part? No big deal if I need it, I'll just make a trip to RS tonight!...


You don't need extra cables ... what you need to do is use the right channel (that's what the instructions suggest; yes the left channel is optional ... but in your case it appears that you're using the left instead of right.

I had problems to calibrate my card too, the problem was that I didn't connect the cables right; to avoid problems use a 3.5mm to RCA cable, then use the right channel (red) and don't connect anything to the left (white) ... this will work. 

Don't forget to mark in the setting that you'll be using the right channel instead of what you have marked "left" ... hope this helps and I didn't confuse you more :hide:


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## solid7 (Jan 31, 2008)

I do not have a "left" and "right" channel. The Soundblaster Live! 24-bit uses Front, Rear, and Subwoofer channels by way of stereo mini plugs.

So maybe I am confused. The loopback is absolutely required? (because I thought that I had read otherwise) If so, I need to get a mini jack splitter....

I keep getting this error message when attempting measurements, and I'm wondering if it's related to this loopback issue:


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## brucek (Apr 11, 2006)

> I do not have a "left" and "right" channel. The Soundblaster Live! 24-bit uses Front, Rear, and Subwoofer channels by way of stereo mini plugs.
> 
> So maybe I am confused.


Of course you have a left and right channel. 

The soundcard should be set in stereo two channel mode only, which engages the *FRONT* jack, which has a left and right channel. That jack is a stereo jack which requires a stereo plug, which has a left and right channel.



> 8426
> So maybe I am confused. The loopback is absolutely required?


Reread this post

brucek


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## JohnM (Apr 11, 2006)

For the output use Front, which is a stereo output (front left and front right). The input should be on the line in, which is also stereo. The error message suggests you have no connection to whichever of the line in channels you have told REW to listen to.


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## solid7 (Jan 31, 2008)

brucek said:


> Of course you have a left and right channel.


There is no *dedicated* Left and Right channel, which is what I thought the other person was saying. Please forgive my ignorance, as I have always regarded what you call stereo left and right as a split signal. (like mono X2) I was just implying that I did not have a soundcard with a designated left and right channel. The rest I understand.




brucek said:


> Reread this post
> 
> brucek


brucek - what I am apparently misunderstanding - but now seem to realize - is that this loopback is required only once. I read some other posts that (I thought) insinuated that the loopback was not required at all, but I think I realize that this requirement that was being spoken of, was for subsequent use of REW after initial calibration.

Will give it another go with loopback in place.


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## solid7 (Jan 31, 2008)

I have soundcard line out going into BOTH AUX L and R on my receiver. I just caught this. Is this a problem?

I still can't get a measurement, but it's getting better...


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## Wayne A. Pflughaupt (Apr 13, 2006)

Not a problem - I feed split the mono feed from REW to both channels on my amplifier. All I can say, I 'm sure glad I went with a plain old stereo sound card!

P.S. How was the cruise? 

Regards,
Wayne


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## salvasol (Oct 31, 2006)

solid7 said:


> I have soundcard line out going into BOTH AUX L and R on my receiver. I just caught this. Is this a problem?
> 
> I still can't get a measurement, but it's getting better...


I used the same connections ... just a couple of reminders: 1) Connect to right side and test that speaker, then to the left to test the other speaker ... and finally you can leave it in L and R to test them together.

2) Even if you connect the line out from soundcard to AUX L and R ... remember to use just the right side from line out (red side) ... you can't use L and R in the line out, but you can combine that signal to the receiver input (AUX) :yes:


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## solid7 (Jan 31, 2008)

Wayne and Salvasol - thank you both for the feedback. Unfortunately, I've got little ones about, and I don't get much of a chance to test. (due to "ambient" noise) However, when I get a good chance, I'll run again, and see what I get.




Wayne A. Pflughaupt said:


> P.S. How was the cruise?


It really wasn't my thing - but my wife enjoyed it, and you have to know that makes me happy. :T


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## moreira85 (Jul 10, 2008)

mstailey said:


> Why is the measured response so high (spl) after carefully setting levels? The SPL calibration is 75.x spl, the check levels is way within limits and after running set target level (which is 75.x spl) the measured response is way high. Running find peaks, the program goes nuts.
> 
> What am I doing wrong?


question regarding checking levels.
When adjusting the input channel should you be looking at the colored green bar graph or the red line?
What is the difference between the green bar graph and the red line on top of it?
When you are checking levels and trying to get the input between 12 to 24db should you do this for both the right and left channel?


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## moreira85 (Jul 10, 2008)

brucek said:


> Excuse my numbering of your quote, but I want to direct you to number [2].
> 
> Changing the Output level will alter the 75dB reading on th RS meter.
> 
> ...


I am not questioning you here but simply trying to understand. 
The goal is to get the input levels between 12-24dbs. 
If you follow these steps 1-7
Set the sweep -12
Set wave and ouput
adjust receiver volume to 75 db RS meter
NOW HOW DO YOU ADJUST THE BARS ON THE INPUT CHANNELS TO GET BETWEEN 12-24 DURING CHECK LEVELS? Wont adjusting the input volume change the spl 75 db reading on the RS meter that you did in step 3?


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## JohnM (Apr 11, 2006)

The red line is the peak level of the input, the green is the rms level. It is the rms level that should be between -12 and -24 dB FS. The input volume referred to is the soundcard input volume, it has no effect on the replay volume so will not affect what the RS SPL meter reads. After the levels have all been set up there is a separate step to calibrate REW's SPL meter so that it reads the same levels as the external meter.


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## moreira85 (Jul 10, 2008)

should you be setting both L and R input channels to between 12 and 24 or just the right? 
I find that my right channel input plays 5 or 6 db higher than the L input meter.


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## moreira85 (Jul 10, 2008)

JohnM said:


> The red line is the peak level of the input, the green is the rms level. It is the rms level that should be between -12 and -24 dB FS. The input volume referred to is the soundcard input volume, it has no effect on the replay volume so will not affect what the RS SPL meter reads. After the levels have all been set up there is a separate step to calibrate REW's SPL meter so that it reads the same levels as the external meter.


So should you be looking at the number at the top of the bar graph or the just the top of the green line?


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## laser188139 (Sep 19, 2009)

moreira85 said:


> So should you be looking at the number at the top of the bar graph or the just the top of the green line?


Are you using REW v4 or v5? With v5, the numbers are now at the bottom. The number appears to be giving an RMS level, equivalent to the green line. As John wrote, the target is for this to be between -12 and -24dB. You want to be sure the red peak line does not exceed 0dB. 



moreira85 said:


> should you be setting both L and R input channels to between 12 and 24 or just the right?
> I find that my right channel input plays 5 or 6 db higher than the L input meter.


If you have cabled the left channel as a loopback, its level is determined by the combination of the output and the input levels. If it is too low or too high, you would need to adjust the output level up or down, then adjust the volume on the AVR in the opposite direction to keep the same absolute level in the room. If it is only a little different, and does not exceed the peak limit of 0dB, don't worry about it. Its level is not critical; with v5 it is used as an absolute timing reference, with v4 it could be used as a substitute for a soundcard calibration. 

Bill


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## TreyS (Dec 22, 2010)

moreira85 said:


> HOW DO YOU ADJUST THE BARS ON THE INPUT CHANNELS TO GET BETWEEN 12-24 DURING CHECK LEVELS? Wont adjusting the input volume change the spl 75 db reading on the RS meter that you did in step 3?


Just change the volume on the soundcard. In my case, it was the PC volume. Don't mess with the receiver volume once it's set to 75db. I think you are confusing the two.


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