# Help with first rew graph



## ps3bluray (Sep 26, 2009)

This is my firrst rew graph, I'm not sure how to read it, if anyone can give me feedback on it that be great, tks kenny


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to the Forum Kenny!

It’ll be much easier to evaluate your graph if you’ll change your horizontal and vertical axis to our standard – see this post: Getting Graphs Ready to Post

Regards,
Wayne


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## ps3bluray (Sep 26, 2009)

Thanks Wayne, sorry about the graph!


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## ps3bluray (Sep 26, 2009)

Is this graph set properly?


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## ps3bluray (Sep 26, 2009)

Is there a reason why its not coming anywhere close to my target. From looking at other ppl's graphs, there coming alot closer to the 75 db target


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## brucek (Apr 11, 2006)

> Is there a reason why its not coming anywhere close to my target. From looking at other ppl's graphs, there coming alot closer to the 75 db target


Yes, you forgot to run the Calibrate SPL routine after you ran the Check Levels routine.

brucek


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## ps3bluray (Sep 26, 2009)

No I believe I did that. Clicked calibrate spl. It ran the tone. Checked the level on the meter. It said 75db and the calibrate box also said 75db. This stuff can be really confusing at first. Wow
_Posted via Mobile Device_


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## glaufman (Nov 25, 2007)

Yes, it can be a little confusing your first few times. We're here to help.

It certainly sounds like you ran the routine. Once you confirmed the reading, to close the dialog box did you click "Finished" or "Cancel"?
Also, for this frequency range, make sure you chose "Use REW subwoofer cal signal" when starting the SPL calibration.

Which meter were you using to calibrate the level? Was it set to "C weighting?" Where was the range dial set?


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## ps3bluray (Sep 26, 2009)

When I was done I hit finished. I'm using the subwoofer cal signal. I'm using a Radioshack spl meter. Was gonna purchase an ecm8000 and probably still will, but for sub testing the rs spl should be fine? My spl was set on 70db. 

I wanna get into full range Testing. I've build 8-4 inch acoustic absorbing panels for first reflections, and plan on doing corner superchunks. So learning rew is important cause I wanna do some before and afer tests.

Kenny
_Posted via Mobile Device_


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## brucek (Apr 11, 2006)

> My spl was set on 70db


On that scale, the highest level that the meter can register would be 76dB before it clips.

Use the 80dB setting with Radio Shack Meters.



> I've build 8-4 inch acoustic absorbing panels for first reflections


You'll want to familiarize yourself with ETC graphs then and concern yourself with a range above 100Hz. Take a peak at this post.

brucek


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## ps3bluray (Sep 26, 2009)

Tks Bruce. So I'll use 80 db range but calibrate it to 75db?
_Posted via Mobile Device_


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## brucek (Apr 11, 2006)

> So I'll use 80 db range but calibrate it to 75db?


Yes. The 80dB range allows more room for peaks in the response above the 75dB that you have calibrated at. When you are calibrating (Check Levels + Calibrate SPL), the needle is indeed a bit hard to read at 75dB on the 80dB range, but it isn't critical to be exact on the 75dB.

But, if you use the 70dB range, the needle is almost pegged already at 75dB, so you know the needle will be pegging during measurement.

This where a Galaxy is a bit better as it has a wider range setting, or a microphone of course where there is no range setting. The Radio Shack meters have their limitations.

brucek


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## ps3bluray (Sep 26, 2009)

Just run another rew session with a 80db meter setting, calibrated to 75db, not sure it made anything different but here it is.

kenny


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## Moonfly (Aug 1, 2008)

That graph looks a bit more like it. Just to clarify your setup procedure: you hit calibrate, while the tone plays adjust your system volume till the spl reads 75db then make sure the REW also shows 75db and finish. 

As long as your levels are ok when you press check levels before you take a measurement sweep, the graph will be correct.

Reading the graph is fairly straight forward, you simply want your subs response to follow the blue reference line as closely as possible. The flatter your subs response, the more even the sound it produces is. Peaks will tend to drown out dips, so when listening these frequencies become more prominent while the frequencies that show dips will be much quieter and possibly not audible at all. Obviously this means your missing some of the content in the material when listening to soundtracks. Large peaks will also make the system sound boomy which can become very distracting.

BTW, it looks like your running the sweeps with your speakers on as well. You need to turn your speakers off to see the subs response to follow the blue line.


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## Wayne A. Pflughaupt (Apr 13, 2006)

ps3bluray said:


> This is my first rew graph, I'm not sure how to read it, if anyone can give me feedback on it that be great


Well, it certainly looks like you could benefit from some equalization. EQ would help bring down the 40 Hz and 70 Hz peaks. Also, your extension (after EQ) only gets down to ~30 Hz, which is pretty poor for home theater (but not so bad for music). Maybe you could benefit from either a better sub, or a better location of the one you have.

Regards,
Wayne


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