Calibration 20db off?

**bh48** · **04-24-09, 03:52 PM**

When I run REW on my Dell laptop I use the microphone in and headphone out jacks because that is all there is on this model. I get useful traces (and was able to make huge improvement in my system using them) but despite following the calibration instructions to set to 75db and turning my preamp volume waaay down during the sweeps, my results always show up at 95-100db. How can I get rid of this offset? I'm using a RS sound meter and the cal file from this site.

I just move the result up to match the sweep and proceed with BFD equalization, so its not much of an impediment, but its irritating. Any help you can give would be appreciated.

**dgilme** · **04-24-09, 04:02 PM**

Alot of microphone jacks on laptops have a boost setting. Is that turned off?

**bh48** · **04-24-09, 04:15 PM**

There is a volume "slider" for the mic input. But I leave it set midrange throughout the calibration and measurment process. So its at the same setting used for calibration when I measure. Would not think that it would cause an offset between the two.

Just had a thought -- The cal reading is taken from the RS meter visual meter. The measurement is from the electronic RCA output. Could the offset be the result of that big a mismatch between the two?

**dgilme** · **04-24-09, 04:23 PM**

From your volume slider go to options, properties and choose recording. Make sure microphone is checked and click ok. Then go Options, and make sure advanced Controls is checked. You should have an "Advanced" button under your mic slider now, click it and uncheck microphone boost and try again.

If you are calibrating your receiver volume setting to put out 75 db based on the need/display of the meter then feeding that signal to REW with the mic in on your laptop and boosting that signal I could see where that might cause a problem.

**Wayne A. Pflughaupt** · **04-24-09, 04:47 PM**

Quote:

Just had a thought -- The cal reading is taken from the RS meter visual meter. The measurement is from the electronic RCA output. Could the offset be the result of that big a mismatch between the two?

Make surer the meter's dial is set for 80 dB.

Regards,
Wayne

**brucek** · **04-25-09, 07:15 AM**

Quote:

I run REW on my Dell laptop I use the microphone in

Not allowed. The Radio Shack Meter is a line level device - not a microphone.

The mic preamps on a laptop have a very limited bandwidth that is designed to comply with a narrow voice frequency range that a cheap computer style microphone would supply, and they are quite noisy with high gain. Simply not suitable for a line device. You need to purchase an external USB soundcard to use with REW.

brucek

**bh48** · **04-25-09, 08:41 AM**

Thank you everyone. I will find an external card, get it set up sometime this weekend and see what differences result. More cables -- arrrgh!

**bh48** · **04-26-09, 09:46 PM**

Spent 3 full hours this weekend trying to interface an M-audio firewire solo to my Dell laptop with zero success. If a couple more tries doesn't result in a working unit, I'll have a Solo up for sale. It has now earned the disticntion of being the single most frustrating piece of electronics I've ever had the displeasure to own. The final word on this problem at the M-audio support site is:

" ... If two or more drivers have the same PCI number assigned you must work with the manufacturer to change the BIOS...."

If anyone reading this has any better ideas, I'd like to hear them.

**robertcharles123** · **04-30-09, 04:46 AM**

I spent the last 3 days fooling with a creative x-fi soundcard and no success. I feel what you are saying.

Good luck,

Robert

**bh48** · **04-30-09, 09:25 AM**

Was able to access Dell support on line and install their latest Bios and southbridge drivers. Haven't had time yet to test it with the external soundcard. Interesting that although the computer is only 18 months old Bios revision went from 00 to 08! The world of electronics moves quickly! Or they don't debug before they release. Or both. Keeps it interesting.

**bh48** · **05-04-09, 07:32 PM**

All the updated drivers and updated BIOS didn't fix a thing. Nor does following M-audio's advice to manage the PCI number conflict. Did and that was no help. Next time I'm in a city I'll pick up another firewire cable to check that it isn't the problem. Last resort, I might set up an old Mac and download the other version of REW onto it. Or just spend 30 bucks for a Behringer external soundcard in my next PE order. Since my Dell's firewire port works fine for video downloads, I'm fairly certain whatever is going on is on the M-Audio side. Again, if anyone has any other suggestions, I'm flat out.

**thewire** · **05-05-09, 11:00 PM**

This is just an idea but what is your subwoofer level? Does your gear use -15dB, -10dB, 0dB? Sometimes the LFE setting will be fixed for some inputs. This is the only idea I can think of... That usually is not a problem but if that is what is going on I'm afraid the only way to measure is with something else. You might try another input and see what happens. Sorry I'm not familiar with your equipment.

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