Another Take On Reference

Dr. SpecDr. Spec Posts: 3,780
edited July 2002 in Music & Movies
Guys:

This was a post I found on another HT forum regarding the term "reference levels". Pretty interesting stuff - sort of meshes Mantis' and my posts in the sub section. Hope it helps............I quoted it because I did not write it.

Doc


"But reference level IS the same for everyone. When people talk about "reference level", they are talking about how loud a particular recorded sound is at a person's usual listening position.

That is to say, if YOU are listening to the pod race scene from the Phantom Menace at reference level sitting in your favorite chair in YOUR living room, and I'm also listening to the pod race at reference level sitting in MY favorite chair in MY living room, it will be EXACTLY AS LOUD for both of us.

(More importanly, it will be EXACTLY AS LOUD as it was for the audio engineer when he was mixing the sound track.)

Notice that "reference level" refers to how loud things are. It does not say anything about the volume control or the sub trim level on your receiver. And for good reason. Even if you and I had the exact same equipment, you would need to crank your receiver up a lot farther in your large living room than I would in my much smaller living room. And since you and I have different equipment, we can't even compare the volume settings on our receivers. But we can compare what our ears (or SPL meters) hear.

According to the standards for the way sound is recorded on DVDs, the loudest sound that can be recorded for any one channel (except the LFE channel) is intended to be played back at 105dB. That is, if you only had your left front speaker hooked up, you shouldn't hear anything louder than 105dB while sitting in your favorite chair. (That's not really true, because of certain exceptions, but....)

The LFE channel can have sounds recorded as loud as 115dB. Note that if you use the Bass Management on your receiver to reroute bass from other speakers to your sub, the sub may get loud bass from the five other channels that is ADDED to the 115dB. I guess in the most extreme case (with all speakers set to small), the sub may need to generate 121dBs. (No single sub is going to be able to achieve that in your big room. At least no commercially available sub that you could afford.)

Even though 105dB/115dB is the MAXIMUM that you can put on a DVD, most of the time things are a lot quieter than that. I believe that the rule of thumb is that when people in the movie are speaking at normal levels, their dialog is supposed to be recorded at around 75dB. (I may be wrong about the exact number here.) That leaves the recording engineer with another 30dBs of headroom (40 dBs of bass) above that for all the loud stuff, like explosions, crashes and people shouting."
"What we do in life echoes in eternity"

Ed Mullen ([email protected])
Director - Technology and Customer Service
SVS
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