Need help with Soundcard Cal

**strange_brew** · **06-04-07, 12:45 PM**

Hi there,

My first attempt at this so please be gentle with me. I followed the instructions to the letter (at least I think I did) to calibrate my soundcard. The first graph measuring the card looks pretty good, but the low frequency seems out of whack:

Then when I check the calibration I get this:

It doesn't look anything like the example in the Help section. The measurement itself "seems" ok except for the low frequency issue. Are they related problems? What I don't understand is why my calibration dashed line is in such a different place from the example shown. Can someone tell me where to start looking for problems?

Thanks!

**brucek** · **06-04-07, 01:06 PM**

Quote:

Can someone tell me where to start looking for problems?

I don't really see any problems. You created the soundcard.cal file that appears to create a flat line on the loopback cable when measured.

I wouldn't worry too much about anything below 10Hz - you won't be measuring there.

brucek

**strange_brew** · **06-04-07, 01:12 PM**

Quote:

brucek wrote:

I don't really see any problems. You created the soundcard.cal file that appears to create a flat line on the loopback cable when measured.

I wouldn't worry too much about anything below 10Hz - you won't be measuring there.

brucek

Thanks brucek. I was concerned about the first soundcard reading where there is nothing under 30Hz. Doesn't that mean that my soundcard isn't picking up anything below that level? In other words, how am I going to get accurate s/w measurements? Or is that what the .cal file does?

**brucek** · **06-04-07, 01:21 PM**

Look at the vertical graph scale on the soundcard response. It goes from -3dB to +3dB. It's an exaggerated scale to show high resolution. If you changed that scale to a realistic 50dB swing as opposed to the existing 6dB swing, the response would look quite good to you.

brucek

**strange_brew** · **06-04-07, 03:12 PM**

Quote:

brucek wrote:

Look at the vertical graph scale on the soundcard response. It goes from -3dB to +3dB. It's an exaggerated scale to show high resolution. If you changed that scale to a realistic 50dB swing as opposed to the existing 6dB swing, the response would look quite good to you.

brucek

Gotcha.

Ok, on to the next step. I have the Galaxy CM-140 and I can't for the life of me get the level over -30.4. The input is cranked. I've tried both channels, checked all the connections, changed the ranges, etc... no dice. When I run the measurement I get an error message saying the input level is too low. And this is the resulting graph:

Any ideas?

**brucek** · **06-04-07, 03:17 PM**

Are you using a mono to stereo adapter at the line-in of the soundcard. The Galaxy is mono and the soundcard is stereo, so you need an adapter to 'break out' the left and right channel, and only use the one channel and then select that channel in REW?

Did you run the Check Levels routine?

Did you run the Calibrate SPL routine?

BTW, it looks like you have your Target level set to 0dB. Set it to 75dB or run the Set Target Level routine.

Graphs should be posted with a vertical scale from 45dB to 105dB and a horizontal scale from 15Hz to 200Hz.........

brucek

**strange_brew** · **06-04-07, 03:26 PM**

Quote:

brucek wrote:

Are you using a mono to stereo adapter at the line-in of the soundcard. The Galaxy is mono and the soundcard is stereo, so you need an adapter to 'break out' the left and right channel, and only use the one channel and then select that channel in REW?

Did you run the Check Levels routine?

Did you run the Calibrate SPL routine?

BTW, it looks like you have your Target level set to 0dB. Set it to 75dB or run the Set Target Level routine.

Graphs should be posted with a vertical scale from 45dB to 105dB and a horizontal scale from 15Hz to 200Hz.........

brucek

I'm using the stereo mini-plug to RCA adapters on the soundmeter, line-in and line-out of the sound card. Then I'm running all the RCA cables on the left (white) channel. should the mono out from the soundmeter be mixed back into stereo into the soundcard? I thought I only needed to use one channel. Interesting thing was the soundmeter was only active on the left channel.

I ran both check levels and Calibrate SPL.

I edited the graph above to change the target level.

**brucek** · **06-04-07, 03:30 PM**

Quote:

RCA adapters on the soundmeter

The Galaxy isn't an RCA connector. It's a 1/8" (3.5mm) phono......

Quote:

should the mono out from the soundmeter be mixed back into stereo into the soundcard? I thought I only needed to use one channel.

Don't understand? Galaxy mono to one channel into the line-in.

brucek

**strange_brew** · **06-04-07, 03:38 PM**

Quote:

brucek wrote:

The Galaxy isn't an RCA connector. It's a 1/8" (3.5mm) phono......

I'm using 3 Radio shack stereo mini-plug to RCA adapters (the ones pictured in the help files)

1 plugged into the soundmeter
1 plugged into the line-in of the computer
1 plugged into the line-out of the computer

Then I ran RCA cables from the Left (white) RCA jack:

From the soundmeter to the line-in on the computer
From the line-out of the computer to an analog input on my pre-amp

Is that not correct?

**brucek** · **06-04-07, 03:42 PM**

Quote:

1 plugged into the soundmeter

There's the mistake....The Galaxy is a mono 1/8" (3.5mm) phono. You can't use a stereo plug. It won't mate inside the meter properly.....

The line-in and line-out are stereo, so they're correct......

GALAXY OUTPUT CONNECTOR

Name: galaxy.jpg
Views: 127
Size: 41.4 KB

brucek

**strange_brew** · **06-04-07, 03:46 PM**

Aha. So I should be just using a 1/8 mono mini-plug to RCA adapter and then straight into the applicable channel on the line-in.

Thanks brucek. I'll be back shortly

**strange_brew** · **06-04-07, 05:16 PM**

Ok, so I fixed the connections, but I now have the opposite problem.

When I first re-connected everything there was no change - I still could not get past -30.4. So I looked again in my soundcard settings (onboard Nforce2) and found the problem. There are settings for changing the input to "line in", "stereo mix", and "mono mix". "Line in" will not go past -30.4. "Mono Mix" I can't get under -4.0 and "Stereo Mix" I can get to -10.8 but that's about it.

I ran the measurement under "Stereo Mix" and I didn't get any errors. But this is the graph I got. There is obviously something wrong here - I'm pretty sure my Subs don't pick up steam below 20Hz and the frequency response can't possibly be that flat. Is this caused by the input level? If so I guess I need to get a new soundcard. Or is it something else?

**brucek** · **06-04-07, 05:48 PM**

Note how the graph is the exact mirror image of the calibration file? That's because the output is internally being looped back to the input. You have an internal soundcard monitor turned on. You can't use stereo mix. You must use line-in.

Quote:

If so I guess I need to get a new soundcard

No, you're simply doing something wrong.

Post a picture of your mixer settings and a picture of REW settings page, so I can get a look at what you're doing.

Also test your SPL meter by plugging it into the AUX or CD input of your receiver and sing (it's a microphone) and be sure it works.

brucek

**strange_brew** · **06-04-07, 07:37 PM**

Quote:

Also test your SPL meter by plugging it into the AUX or CD input of your receiver and sing (it's a microphone) and be sure it works.

Bingo! It was a faulty RCA cable from the SPL meter to the AV processor. Not sure when that cable was damaged but there you go. Thanks - it would have taken me forever to troubleshoot that.

So that fixed the input level. Now onto the next problem. I'm getting MASSIVE amounts of feedback. To the point that I can't go anywhere near 75db. I've tried lowering the input levels but that doesn't really help. Now what?

EDIT: Duh! forgot to mute the Line in

**brucek** · **06-04-07, 07:46 PM**

I would say that you've still got a monitor turned on in the soundcard software. Most soundcards offer this feature (and call it various goofy names), but its purpose is to allow you to hear what you're recording (when using the soundcard for that purpose). In REW we want that feature shut off, including all other effects features and multichannel features - stereo only, no effects....

Take a look in your soundcard software.

brucek

**strange_brew** · **06-04-07, 07:47 PM**

I "think" I finally got a valid measurement. Not too great I must say considering all the sound treatments in the room!

Thoughts? (thanks for all the help so far btw!)

**strange_brew** · **06-04-07, 07:49 PM**

Quote:

brucek wrote:

I would say that you've still got a monitor turned on in the soundcard software. Most soundcards offer this feature (and call it various goofy names), but its purpose is to allow you to hear what you're recording (when using the soundcard for that purpose). In REW we want that feature shut off, including all other effects features and multichannel features - stereo only, no effects....

Take a look in your soundcard software.

brucek

Thanks - looks like my edit was after you wrote this - I forgot to mute line-in. First real measurement result is above

**brucek** · **06-04-07, 08:45 PM**

Quote:

Thoughts?

You're measuring a sub. Change the graph scale (use the Graph Limits icon) to a vertical scale of 45dB to 105dB and the horizontal scale from 15Hz to 200Hz. Lets see what it looks like..

Did you press the Set Target Level button before measuring?

brucek

**strange_brew** · **06-04-07, 09:41 PM**

Quote:

brucek wrote:

You're measuring a sub. Change the graph scale (use the Graph Limits icon) to a vertical scale of 45dB to 105dB and the horizontal scale from 15Hz to 200Hz. Lets see what it looks like..

Did you press the Set Target Level button before measuring?

brucek

Ok, I ran through the entire procedure again right from the beginning. I'm not sure what step I missed before but obviously I screwed something up. Here is the result using the scale per your suggestion. This is about what I expected - I told a buddy of mine I thought I had a massive valley at 60Hz and I wasn't far off! I also knew I was missing a bunch of bottom end punch and this bears out that assumption. Now how to fix it?

I don't have my BFD yet, but I'll start with moving the subs around and see what happens. I currently have 2 subs on my front screenwall and I can only move them laterally across the front. Any suggestions for placement? Right now they are each about 1/3 of the way in from the sidewalls. I could also employ the notch filters in my B&K Ref 50 pre-amp....

**brucek** · **06-04-07, 09:49 PM**

Quote:

Right now they are each about 1/3 of the way in from the sidewalls

You should always measure the subs without the mains to see what's really going on. We only add the mains after the subs are equalized, so as to check the integration at the crossover area.

Place both subs together (either stacked or side by side) in a front corner.

brucek

**strange_brew** · **06-04-07, 10:44 PM**

Quote:

brucek wrote:

You should always measure the subs without the mains to see what's really going on. We only add the mains after the subs are equalized, so as to check the integration at the crossover area.

Place both subs together (either stacked or side by side) in a front corner.

brucek

Ok, here is the measurement with the Subs only but in the same position:

**strange_brew** · **06-04-07, 11:04 PM**

Here's what the front wall of my theater looks like just to give you an idea.

The subs are currently directly on either side of the center channel.

**brucek** · **06-04-07, 11:05 PM**

OK, now it's easier to see what going on.... good.

BTW, you do have the Galaxy.cal meter calibration file loaded. I trust?

Did you tell us what type of subs you are using?

Quote:

The subs are currently directly on either side of the center channel.

Not the best spot. Co-locate them both in the same corner and test....

brucek

**strange_brew** · **06-04-07, 11:24 PM**

Quote:

brucek wrote:

BTW, you do have the Galaxy.cal meter calibration file loaded. I trust?

I do now

Quote:

Did you tell us what type of subs you are using?

B&W ASW1000's

Here is the measurement with the .cal file loaded. I'll move them and post the next result.

**strange_brew** · **06-04-07, 11:56 PM**

Ok, stacked the subs on top of each other and moved close to the left corner. Looks like it improved things a bit. But I still have those nasty dips at 26db and 74db and the entire bottom end is pretty weak. I suppose the peaks can be dealt with by the BFD but what does one do about the dips? Keep moving the subs? Unfortunately I don't have a lot of wiggle room to move them around...

Advertisement