# First steps with REW and subwoofer measurement



## chrissi323 (Feb 7, 2011)

Hello,

first try, first post....

I got two SVS PB12nsd subs and thought that this is the ideal occasion to try out REW. I have a Onkyo SPL-meter and used that for measurements. It looks exactly as the old Radioshacks and the manual lists identical specs.

I went down the route the helpfile gave me.

After trying different locations and phase settings for the subs I ended up with a diagonal corners setup which gave me the following:









Before I took the measurement I did the "check levels" procedure and my SPL-meter showed 75 dB, I then calibrated my the input level to roughly 18 and as a last step calibrated REWs SPL-meter.

How does it look? I think it's ok for a rectangular room with no treatments, what do you think?

What I don't understand why are th readings so high. I plan to use a miniDSP (still waiting for the delivery ) to apply some filters. Now when I let calculate REW it warns that 83% of the measurement are above target level and asks, if the settings are right. Do I have problem with my settings I used the defaults for subwoofer with a 80Hz crossover which reflects my setup.

I would really appreciate a comment or hint.

Regards

Chrissi


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## savior sound (Nov 30, 2008)

chrissi323 said:


> Hello,
> 
> Now when I let calculate REW it warns that 83% of the measurement are above target level and asks, if the settings are right. Do I have problem with my settings


Manually raise your target level in Target Settings - try 80 db


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## chrissi323 (Feb 7, 2011)

Hi Steve,



savior sound said:


> Manually raise your target level in Target Settings - try 80 db


that takes care of the warning and applies less filters. I should have written that I already tried that. 

What I do not understand is why I'm getting so high readings at all and if that meaurement I took is usable.


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## jtalden (Mar 12, 2009)

Your measurement looks fine. Moving the target level up 3-5 dB is no problem. 

There is nothing magic about the measurement hitting 75 dB level exactly. The calibration is done on band limited noise signal and the measurement is on a sweep sine signal and there can easily appear to be a 3-4 dB discrepency. If you want the measurement level a little lower just drop the volume of your AVR accordingly.


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## chrissi323 (Feb 7, 2011)

Hey jtalden,

thanks for clarifying this for me, I played around a bit with the volume of my AVR and I can shift the whole curve and down a few dB without changing it's shape. So I guess I can use it to let REW calculate the filters for the miniDSP. Can't wait for it, but it's a long way from Hong Kong to Germany :bigsmile:


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## lsiberian (Mar 24, 2009)

chrissi323 said:


> Hey jtalden,
> 
> thanks for clarifying this for me, I played around a bit with the volume of my AVR and I can shift the whole curve and down a few dB without changing it's shape. So I guess I can use it to let REW calculate the filters for the miniDSP. Can't wait for it, but it's a long way from Hong Kong to Germany :bigsmile:


Just remember to apply filters only where it is really helpful and always verify the results. :T


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## chrissi323 (Feb 7, 2011)

lsiberian said:


> Just remember to apply filters only where it is really helpful and always verify the results. :T


Will do Sir  I'm surely coming back to ask for advice :R


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## savior sound (Nov 30, 2008)

chrissi323 said:


> Hello,
> 
> I have a Onkyo SPL-meter and used that for measurements. It looks exactly as the old Radioshacks and the manual lists identical specs.


What mic calibration file did you use?


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## chrissi323 (Feb 7, 2011)

savior sound said:


> What mic calibration file did you use?


I used RadioShack-33-2050-CS.cal. The SPL-meter I have looks like that:









I downloaded the manual for the RadioShack 33-2050 and it's word by word identical to the manual of my Onkyo, only substituting "Radio Shack" with "Onkyo", so I guessed the Onkyo is a clone. I hope I am right. 

If all goes well, a friend with a calibrated Behringer ECM 8000 mic will visit me in the next weeks to verfiy the measurements. Hey said his calibration file has the suffix .amt, I hope REW can read that.


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## JohnM (Apr 11, 2006)

chrissi323 said:


> If all goes well, a friend with a calibrated Behringer ECM 8000 mic will visit me in the next weeks to verfiy the measurements. Hey said his calibration file has the suffix .amt, I hope REW can read that.


Depends what's in the file  If it is a typical cal text file (lines of frequency and spl or spl+phase values) REW should be OK with it, but when you go to open the cal file set the file filter to "All files" as REW doesn't look for .amt extensions by default.


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