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Discussion Starter #1
I spent a bunch of time troubleshooting a Dell laptop that I have because when I'd do the loopback cal, I'd get crazy measurements. Like +- 20 db from 20hz-20khz. Logically, assuming the that the mic input was not flat (as is common) , I tried an iMic that I had kicking around. It was better (but not good), around +- 12db. I even tried looping the output of the iMic to it's input (since it can output as well).

So then, I thought I'll disable whatever "enhancements" the laptop supports (boosting, eq, gain, etc). No change.

So then I bought a Tascam US122 MKII. Surprisingly, still terrible results.

All along it was the OUTPUT not the input that was the problem!

I've tested with 2 different HP laptops and I can now get +- .5 db. I'm sure it's written somewhere and I overlooked it, but I never would have guessed the output was the problem. I still suspect that there is some EQing going on buried somewhere in some settings for the laptop (you know, a "feature").

REW isn't the challenge, good hardware is!
 

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Discussion Starter #7
Did you try updating the driver?
The sound driver is current. I think that there are some additional EQ settings possibly buried in a sound card utility. There are some options to change the input via software between mic/line in. I would have thought that disabling the "enhancements" for the ports would have killed any driver features, but maybe not. The audio output ends up looking like a sine wave just about (from 20hz to 20khz), - something like +- 6db. Low end boosted, high end lowered.

I'm not really going to dig into it too much further - because when I have the USB port plugged into my MiniDSP and the charger plugged into the laptop - the charger injects so much noise into the loop it's insane. The HP power supply injects some noise, but it's not as bad.

It's not a complaint about Dells in general, the quirks just surprised me.

Even if it's not a fixable setting, the repeatability wasn't very good on my Dell laptop either. Even with REW trying to compensate for bad response, they fluctuated quite a bit, especially above 8-10k.
 

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I have a Dell Vostro 2510 . I too can get some pretty non-linear output ( but it's not systemic to my laptops card ) .

See these loop-backs of my built-in soundcard ( the first 3 are non-linear );






> #4 ( of 4 pics ) is what I run ( ie; SFX turned "off" ) .

:sn:
 

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Discussion Starter #11
Is the problem fixed by using an external (USB) sound card?
On the Dell laptop, no. It's improved, but the HF is still pretty wacky. It's not reliable.

So, I was doing laptop out to laptop mic in, and then I tried iMic (USB audio device) out to iMic input. I even tried iMic out to laptop in. I would think that whatever is going on with the output would be specific to the onboard - so I don't know how to explain what was going on.

I'll poke around next time I have a few mins. Part of what drives me bonkers is there is no standardization between models and manufacturers and what audio software is used. You can have a Realtek audio chipset on 2 machines and the software is entirely different.
 

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Crazy. I'll have to see how it does with my MacBook and with my Asus. I have an iMic as well and had planned to use it for REW.
 

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Discussion Starter #13
Crazy. I'll have to see how it does with my MacBook and with my Asus. I have an iMic as well and had planned to use it for REW.
I originally bought the iMic because it works really well with some scanner radio trunk tracking software that I was using. It doesn't mangle the audio data stream... I'll have to look at the FR of it, but I think it's pretty decent.

The problem that I was running into with the laptop wasn't so much the poor FR, it was that even when REW tried to correct it, it wasn't repeatable. It would correct by boosting the high frequencies, I'd do a sweep and it would still be off.

Pretty sure the iMic with my HP laptop was fine.
 

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Discussion Starter #14
I was wrong - laptop is a Dell 4300 (I believe it's just the smaller version of the 6400?)

The iMic actually looks OK now. Not flat, but about what I expected. It has the predictable slope. The other pictures are the multiple places where the sound card can potentially mangle the FR. I disabled everything.

The pink REW capture is the onboard card. The thick line represents the variance in the readings. That's actually a lot better than what I was getting before, but still resulted in some incorrect readings. REW said that the response from 20-20khz with the onboard card varied by +-7 db.

So, moral of the story is that you can make things work....... if you have to :coocoo:

Using my HP laptop and the Tascam USB interface that I bought, it's almost not even worth calibrating, since the response comes out nearly dead flat, +- .5 db.
 

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Discussion Starter #15
I used the iMic on a Dell desktop, and although I got +.5, - 6.6 db from 20hz to 20khz, once the sound card was calibrated, the results I got were correct (flat).

So, I think the iMic is very usable.
 
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