Problems with measured levels

**mstailey** · **04-21-08, 11:14 AM**

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?

**brucek** · **04-21-08, 12:19 PM**

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

**Wayne A. Pflughaupt** · **04-21-08, 12:25 PM**

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

**mstailey** · **04-21-08, 12:29 PM**

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.

**mstailey** · **04-21-08, 12:31 PM**

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

I do just that (what you suggest)

**brucek** · **04-21-08, 12:43 PM**

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

**mstailey** · **04-21-08, 12:56 PM**

Quote:

brucek wrote:

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

**brucek** · **04-21-08, 01:33 PM**

Quote:

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

**mstailey** · **04-22-08, 06:58 PM**

Hi Ken,

Quote:

brucek wrote:

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

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.

**solid7** · **04-27-08, 03:57 PM**

Quote:

mstailey wrote:

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.

**brucek** · **04-27-08, 04:16 PM**

Quote:

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

**solid7** · **04-27-08, 06:38 PM**

Quote:

brucek wrote:

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.

**mstailey** · **04-27-08, 07:01 PM**

Quote:

brucek wrote:

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?

**brucek** · **04-27-08, 07:18 PM**

Quote:

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

**solid7** · **04-27-08, 07:35 PM**

Quote:

mstailey wrote:

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!

**JohnM** · **04-28-08, 04:17 AM**

Quote:

solid7 wrote:

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.

**solid7** · **04-28-08, 06:17 AM**

Quote:

JohnM wrote:

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)

**JohnM** · **04-28-08, 08:29 AM**

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.

**solid7** · **04-28-08, 10:07 AM**

Quote:

JohnM wrote:

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)

**brucek** · **04-28-08, 12:19 PM**

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

**JohnM** · **04-28-08, 12:21 PM**

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

**solid7** · **04-28-08, 12:39 PM**

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.

**brucek** · **04-28-08, 01:06 PM**

Quote:

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

**salvasol** · **04-28-08, 01:15 PM**

Quote:

solid7 wrote:

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

**solid7** · **05-10-08, 05:07 PM**

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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