# Calibration Of Mic with Rew Spl reading



## varun432 (Aug 14, 2015)

Hello Guyz!!! 
I am new to room measurement and have very little knowledge..

When I try to calibrate my spl readings... I keep my phone (using it as spl meter) close to Audyssey Mic using it as my measurement mic..
Now I enter those values in Rew...and I start getting almost similar readings..

But as soon as I finish and the test tone goes off..
My phone shows spl of 35-40db which it should be in an ideal completely silent room vs the reading on spl meters on the ReW app shows 50-55 Db.....

Also when I generate the waterfall graph the frequencies below 60-70hz till 10-20hz fail.to decay and remain stagnant at 40-60dbs...

What could be effecting ? 
Where am I going wrong


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## varun432 (Aug 14, 2015)

Like when I send test tone to calibrate the Rew spl meter..
My iPhone spl reads 80db.. I then feed that 80db to Rew and both the spl of iPhone and Rew match... +- 1-2db difference..

But as soon as the test tone finishes..

The Rew shows 50-55db on its spl while it should be 30-40db...
Mobile showing 35-37 range..

What's happening


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

It’s probably a difference in weighting between the two. But don’t worry about it. Go ahead and take a measurement. :T

By the way, welcome to the Forum!

Regards, 
Wayne


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## JohnM (Apr 11, 2006)

Weighting curve selection is certainly one candidate, if the iPhone is using C weighting make sure the REW meter is set the same. Might also be a high noise floor due to an odd input volume setting, so could try changing the input volume to see what effect that has.


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## varun432 (Aug 14, 2015)

Here are a few graphs I took..,
Please feel free to comment!!

Also again that very high output as well no volume decay on waterfall in low frequencies seem to me as some kind of noise other than my speakers..

Besides that what all can I improve...


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## varun432 (Aug 14, 2015)

Hi Johnm,

Mobile was on A weighting and the option on ReW was also unchecked ! 

Any other guess to troubleshoot..
It definitely is effecting the lower frequency..,
Hopefully I can check it by measuring output without providing any sound through my speakers..
In that case only noise will be measured
Am I correct ?


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## varun432 (Aug 14, 2015)

More graphs if it helps!!


Sent from my iPhone


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## varun432 (Aug 14, 2015)

here you go...

Also my sub plays till 80hz...
I see a dip at 80hz...


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## varun432 (Aug 14, 2015)

Hey Guyz!!!

No reply...


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

The long-window waterfall is enlightening. It indicates that your low freq issues are coming from the speaker or subwoofer, and/or the room acoustics. If it were some kind of background noise, it would be constant and never decay, as you see at 50 Hz.

Regards, 
Wayne


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## varun432 (Aug 14, 2015)

Oh! Okay... Let me see the response I get on my other listening positions...

My sub is at the back of my seat.. And my seat is very close to the back wall... About 3 feet...
I'll also try to move my seat 6 inch to 1 feet foward...

Besides this any other place I should concentrate on improving


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

Fixing the hole at 200 Hz would make an audible improvement. :T

Regards,
Wayne


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## varun432 (Aug 14, 2015)

Hi Wayne...
Good Morning from India..

so without making any changes in the room i did some measurements...
mlp- at my listening position...
mlp+12 inch at my listening position +12 inch..
my front row sitting of hometheatre...

room treatments: although my side walls are heavily treated with 4" of fiber glass + 4" gap.. + bass absorbers on all 4 corners...

my front screen wall and my back wall and sheetrock roof is untreated...
i have 2 subs running 1) Klipsch rw12d sub + pb12plus.. 
both subs are placed behind my first row between seats and wall facing the screen...

these are my various readings at various locations in the room?


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