# Please be gentle with me



## flamemax (Jan 15, 2010)

Greetings, 


I have been on AVS forums for several years and was directed to HTS when I asked a question concerning a software spectrum analyzer (REW).

This has opened a can of worms for me as I am yet again experiencing steep learning curve with calibtating my system

For those that whish to know, system consists of:
Denon 1910 AVR
JBL Stage RF + LF
JBL Voice for the center
JBL Balcony for surrounds 
SVS 20-30PCI for a sub (considering adding another) 


This is my setup for running REW

RS SPL meter (the digital one ?55xx?)

Dell E6500 - Laptop with built in Sound card that detects the difference between line-in and mic-in through the same jack. Is this feasible - I ran the calibration for the Sound Card (loop back) and I managed to get the levels balanced out. Should I be ok whith this?

What are the pit falls of having a incompatible sound card?

Thanks for any and all feedback!


Robb AKA Flamemax


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## glaufman (Nov 25, 2007)

Hi Max, and welcome to the Shack! I'm used to hearing about soundcards that have a dual mic/line in jack that can be manually switched, an automatic one is new to me...
My suggestion is to go to our post padding thread, get yourself up to 5 posts, wait for an hour for the system to upgrade your status, and then post a screenshot of you soundcard calibration, and we'll have a look and see whether it looks reasonable.
The biggest pitfall I can see if this automatic detection doesn't work are
1) not being able to get levels set properly so the additional gain ends up overloading/clipping the mic-amp or ADC...
2) mic inputs are often very BW limited to the range that's important for speech intelligibility... not what you're looking for I bet...


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## flamemax (Jan 15, 2010)

Greg, 

Thanks a bunch. To add some clarity to the built in laptop sound card - 
If I plug a loopback cable into the line-in/mic-in a window pops up stating that I plugged a line-in into the jack. If I plug a mic (say the mic that came with my AVR) it auto detects it as being a mic.
I also have the optiono to hard-overide any of these settings.

As for posting the results of my Soundcard calibration - what is it that I should post?
I followed the wizard in the soundcard calibratin of REW - but did not see any graphs short of the level graph bars.

PS I have added the RS SLP meter calibrationo file to REW.

Thanks for the insight.

Robb AKA Flamemax


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## glaufman (Nov 25, 2007)

Ok. So I don't see any reason this shouldn't work, but if you want to be sure:
Start by removing the mic (SPL meter) cal data from REW. Connect your loopback from out to in. Make sure your soundcard cal is loaded, go to measurements, and run a scan. 
The results should show up on a plot with both a trace for the measurement, and a trace for the soundcard cal file. The trace for the measurement should be a flat line.


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## flamemax (Jan 15, 2010)

Greg, 

May I ask why I should unload the SPL cal. file? Is it because I am performing a loopback calibration and the SPL is not being used for that test?

I feel like I'm stating the obvious... lol


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## flamemax (Jan 15, 2010)

And another question - 

You say that the sound card cal. should be loaded, is that not the purpose of running the loop back test - to calibrate the sound card?

Thanks!


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## JohnM (Apr 11, 2006)

Greag was meaning to load the soundcard cal after running the calibration, then making a measurement with the loopback still in place to check the result is flat. You are correct re the SPL meter cal, if you have it loaded for a loopback you will see the shape of the cal file inverted.


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## flamemax (Jan 15, 2010)

Greg, 

I think I got it - you meant to make sure that once the loopback test is performed - to make sure the result is loaded and then run the measurement - 

Done and done - I also unloaded the SPL calibration.

I have the measurement file - saved as a .mdat.
I'm guessing I just now have to wait an hour to upload it?

Thanks again for the help!

PS. The results peak at 105 db at 10hz then roll off to 80db all the way to 10k then sweep up to 95db to 20 k.

I can copy the .txt export if that will help you.


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## glaufman (Nov 25, 2007)

Well, the easiest way is to load it in REW, then click on the "disk" icon in the lower left of the plot, this will allow you to save a jpg that you can upload. In this version of REW, it's the only way to make sure I see the plot after the adjustment for the calibration file without posting the calibration file as well...


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## flamemax (Jan 15, 2010)

Hello and good morning, 

Below please find the results of my soundcard loopback test; 

 


Is this OK?

Thanks!!!

Robb AKA Flamemax


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## glaufman (Nov 25, 2007)

Almost... If you uncheck the "C-weighted" box in the microphone settings, you should be able to achieve a flat line with that scan... but you'll then want to re-check the "C-weighted" box before running a real scan when using the RS meter as the mic...
I'd be more confident if before you saved the jpg you clicked the button to show the soundcard calibration trace on the plot...







(It's grayed out in my image, but should be selectable in yours...)


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## Jumpa (Jan 22, 2010)

*I need to get my five posts out of the way sorry I jumped in cant find a welcome board 

4 to go
Respectfully 
Rich:wave:*


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## flamemax (Jan 15, 2010)

It's looking up!!!


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## flamemax (Jan 15, 2010)

I could only check the Use Soundcard Cal checkbox if I applied the soundcard cal after taking the measurement ... you prolly know this already, and once again I feel that I am stating the obvious lol.


Thanks again for all input.

Robb AKA Flamemax


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## glaufman (Nov 25, 2007)

Jumpa said:


> *I need to get my five posts out of the way sorry I jumped in cant find a welcome board
> 
> 4 to go
> Respectfully
> Rich:wave:*


Welcome to the Shack Rich! Assuming you're not a spammer, you can use our post-padding thread here:
http://www.hometheatershack.com/forums/testing/21659-post-padding-thread.html


flamemax said:


> It's looking up!!!


That looks just fine. I'd say you're good to go!


flamemax said:


> I could only check the Use Soundcard Cal checkbox if I applied the soundcard cal after taking the measurement ... you prolly know this already, and once again I feel that I am stating the obvious lol.
> 
> 
> Thanks again for all input.
> ...


No problem there. Helps just to confirm. Yes, the purpose of this was to make sure you get a flat response to the corrected soundcard. Now just don't forget to check the "c-weighted" box before using a c-weighted meter as the microphone.


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## flamemax (Jan 15, 2010)

Thank you for all the assistance!!!


MUCH appreciated!


Now just as a matter of fact - there are built in laptop soundcards that have an auto detect on the line-in/mic-in jack. 

The jack server a dual purpose, amplified mic-in and non boosted line-in in the same Jack.

The card is an onbobard card that came with my recent Dell laptop E6500 - It is an IDT High definition card for those who want to know.


Robb AKA Flamemax


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## glaufman (Nov 25, 2007)

Sounds good, and I've learned something here... thanks!
As a side note, I still wouldn't use the mic-in as a mic-in without testing it's range, both amplitude and freq. Still a good chance the mic-in, or its preamp etc, is optimized for the speech intelligibility range, in the absence of any MFRs claims to the contrary...


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## flamemax (Jan 15, 2010)

So have I Greg, so have I


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