Noob question on RS SPL

**sammythebu11** · **07-10-06, 12:08 PM**

Hi,

thanks a lot for your excellent software, it would take hours to calibrate a room without it.

I just plugged in a Radio Shack Digital SPL meter to my Mac and PC and as soon as I turn it on to 80db, REW shows 46db (or so), is this normal behavior? do I have a bad SPL meter? do I have a bad cable? when the SPL is not connected REW shows 3-4db. I have tried left channel and right channel with the same result.
I am hooking it up to the Line in of the computers using an RCA cable and a Stereo RCA to mini plug.

Thanks,

The Bu11

**brucek** · **07-10-06, 12:57 PM**

Quote:

as soon as I turn it on to 80db, REW shows 46db (or so), is this normal behavior? do I have a bad SPL meter? do I have a bad cable? when the SPL is not connected REW shows 3-4db

Yes, it's normal. The 46dB is the noise level in the room. Go ahead and speak into the meter (it is a microphone) and watch the SPL respond.

Certainly when no cable or meter is hooked up you'll get a few dB from the card itself, I get about 10.

Go through the entire setup though to ensure your REW Program is calibrated to the meter....

brucek

**sammythebu11** · **07-10-06, 02:39 PM**

Thanks,

I'll give it a try tonight.

The Bu11.

**sammythebu11** · **07-10-06, 05:30 PM**

Ok,

I must be doing something wrong now, the SPL shows 75 on the digital meter but REW shows 67.5, am I doing something wrong? should I use the value on the meter to calibrate or should I use the value on REW?

Thanks for your help and patience with this rookie.

The Bu11

**brucek** · **07-10-06, 05:40 PM**

Once you've completed "SET MEASUREMENT LEVEL" and "SET INPUT VOLUME" and are in the "CALIBRATE" setup, REW asks for the reading from your actual SPL meter to be entered into the REW meter so that they match. After that's entered you will "SET TARGET LEVEL".... then you're ready to do an "AUTOMATIC MEASURE".

brucek

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