# REW levels compared to Dolby reference



## maxmercy (Apr 19, 2008)

Hello everyone, 

Long time lurker, first time poster. My question concerns the levels used for freq. sweeps measurements. The default on REW is -12.0dBFS, and the default target is 75dB. For appropriate reference levels (105dB for mains, 115dB for LFE), wouldn't a -30.0dBFS level sweep with a 75dB target be more appropriate? Or a -12.0dbFS level sweep with a 93dB level target? 

My other question concerns LFE levels. I understand that the LFE track on DD5.1 and up encoding has an extra 10dB to play with (hence the 115 number above). If this is so, how can REW account for this (or does it already)? In other words, should I set my sub to run 10dB hot using a REW sweep? Or just make sure the sub can handle an extra 10dB thrown at it? I hope I am making sense.

Thanks for everyone's help, and REW has been such a great tool to use...


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## brucek (Apr 11, 2006)

> wouldn't a -30.0dBFS level sweep with a 75dB target be more appropriate?


No, the closer to full scale, the better the signal to noise of the signal. We're not setting absolute levels with REW, we're using it to measure response and set up equalizers. 75dBSPL is quite appropriate for that.



> If this is so, how can REW account for this (or does it already)?


It doesn't, it's up to you to set your levels. REW measures response. Set any levels you like after you've found the proper spot for your subs and mains and room treatments.

brucek


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## maxmercy (Apr 19, 2008)

I see. So after equalization and any house curves, just pink noise and SPL meter? But sub set 10dB above mains, or equal to mains, in order to experience the sound designer/editor's intent (and where does the extra 10dB allocated to the LFE channel fit into this)? I do realize amount of low end is a matter of taste, but sometimes I want to experience what the sound designer had in mind before I think of modifying it, and I just want to know what level settings I need to accomplish that...

Thanks so much for your help, this is a great website.

JSS


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## brucek (Apr 11, 2006)

> So after equalization and any house curves, just pink noise and SPL meter?


Well, most people simply use their receivers internal test tones to set the relative level of all the speakers and sub before they begin with REW and any equalization. Then after they're finished with REW and EQ, treatments, etc, they touch up the levels again to taste or with the receiver test tones.

You must realize that REW is a mono signal and that all measurements with it are with the receiver in stereo only mode using just the sub, or the sub plus mains. DD, DTS, PLII, multichannel are not a possibility with REW. 

brucek


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