# Radio Shack 33-4050



## v1rtu0s1ty (Dec 10, 2007)

Hi folks. I have an analog spl meter. I need help finding the correct .cal file for this. I'm trying to learn REW. Can someone please provide me the link to download the correct .cal file?

Thanks,

Neil


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## brucek (Apr 11, 2006)

Did you try here? 

We have cal files for all the types of Radio Shack meters........

Hopefully you've read the REW HELP FILES....................










brucek


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## v1rtu0s1ty (Dec 10, 2007)

Yep, I saw it earlier. Just wondering what wrong I am doing. Here is what I got. Honestly, it's my first time to do this. I don't know what's going on.  I don't even know if the graph is bad or good.


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## brucek (Apr 11, 2006)

You need to meaure with a target level of 75dB...............

You also need to shut off the mains and measure the sub only to start. Use the normal crossover that you like and have the receiver in stereo mode.

brucek


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## v1rtu0s1ty (Dec 10, 2007)

I set my calibrate spl to 80 because that is what I was seeing on my meter. Is it correct? Please see screencapture.


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## v1rtu0s1ty (Dec 10, 2007)

brucek said:


> You need to meaure with a target level of 75dB...............
> 
> You also need to shut off the mains and measure the sub only to start. Use the normal crossover that you like and have the receiver in stereo mode.
> 
> brucek


When you say shut off the mains, did you mean remove the wire for the left and right?


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## v1rtu0s1ty (Dec 10, 2007)

I redid it again by removing one wire on the mains. Now it's just the sub. I recalibrated then I set the volume on my yamaha receiver so that spl meter says 75db. That means, it's set to 75db and I've also clicked FINISHED button.


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## v1rtu0s1ty (Dec 10, 2007)

Here is an update.

Here is the pic while check level was running.









Here is the pic when check level completed.









And here is the graph. Can you please explain to me in layman's term what the graph means? Is the reading good or bad?


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## brucek (Apr 11, 2006)

> Can you please explain


Well, you certainly did everything correctly, so that's good.

You have a couple of peaks. One around 28Hz of about +12dB and another around 60Hz of about +25dB. If you had a parametric equalizer (BFD) you could remove those very easily. The problem with them is that you'll hear those peaks at the exclusion of the other frequencies. Often, moving the sub around to different spots can result in a much smoother response. I would advise trying that first (if it's possible).

BTW, be sure to have the power off when you remove and attach the mains wires and keep them apart when the power is on.

After you get a smooth response, you add the mains and do another measure to see that the two levels are appropriate and that the transition area around the crossover is as smooth as possible. If not, adjust the phase control on the sub...

brucek


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## v1rtu0s1ty (Dec 10, 2007)

Thank you sir!!!  I'm good for now. At least I've learned the basics of REW.  I'll have to finish my theater first because I don't have any carpet, just bare concrete floor and not walls either.

Oh, I placed the spl meter about 1' to 2' from the sub. Is this the correct way of measuring? If so, is the position of the spl correct(please see pic below)? Or should I redo everything and put the spl meter in the listening position?

And also, I don't have an equalizer yet. How does it really sound when the sub has been calibrated properly and equalizer adjusted? Is our objective to make the sub as flat as possible just like the reference line on the graph?


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## brucek (Apr 11, 2006)

> Oh, I placed the spl meter about 1' to 2' from the sub


Nope, it's suppose to be at the listening position when all your speakers are in place. 

If you're just doing a near-field of the sub though before you get everything done and in position, you did the correct thing. Generally to do a near-field (to determine the subs response with as minimal effect from the room as possible), it's best to do it in the middle of the room.

When you do a proper listening position measure, the radio shack meter is usually placed with the element pointed up at an angle toward the front of the room 



> How does it really sound when the sub has been calibrated properly and equalizer adjusted?


Much smoother than with peaks.....



> Is our objective to make the sub as flat as possible just like the reference line on the graph?


Yeah, you're trying to get close to the target line - but you don't have to get crazy.


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## v1rtu0s1ty (Dec 10, 2007)

Thank you very much! I have learned a lot from you today!!!  It will be few months before I can start putting up the walls.  But I'll get there. 

Have a great evening! Thanks again.


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