Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 519 - AVS Forum | Home Theater Discussions And Reviews
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post #15541 of 15551 Old Yesterday, 04:56 PM
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Originally Posted by AustinJerry View Post
The LFE track is encoded at 10dB lower than the other tracks. The AVR automatically adds the 10dB back, so there is no action required on your part, nor should you be concerned.
So the reason why REW ends up +10db for the sub LFE channel is because they aren't factoring in -10db to compensate for your AVRs +10db, which is assuming an input of -10db. Wow.

What started all this mess in the first place, I wonder?
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post #15542 of 15551 Old Yesterday, 05:18 PM
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Originally Posted by Soulburner View Post
So the reason why REW ends up +10db for the sub LFE channel is because they aren't factoring in -10db to compensate for your AVRs +10db, which is assuming an input of -10db. Wow.
No, the reason it ends up +10dB is because you don't understand how the LFE channel works and therefore don't adjust your system to get the same SPL as the others when measuring.

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What started all this mess in the first place, I wonder?
Someone decided the LFE channel should be capable of 115dB whereas other channels were capable of 105dB. That means the same digital signal will yield different playback levels depending on the channel.
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post #15543 of 15551 Old Yesterday, 06:29 PM
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Originally Posted by Stereodude View Post
No, the reason it ends up +10dB is because you don't understand how the LFE channel works and therefore don't adjust your system to get the same SPL as the others when measuring.
I don't think you understood the question. In REW, it is commonly reported in this thread that HDMI 4 gives +10db over the other channels. Jerry told us this is because the AVR makers add +10db to the LFE channel.

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Originally Posted by Stereodude View Post
Someone decided the LFE channel should be capable of 115dB whereas other channels were capable of 105dB. That means the same digital signal will yield different playback levels depending on the channel.
But if the AVR is adding 10db to LFE, and the LFE track really is, as Jerry tells us, encoded 10db lower by the movie studios, they'd cancel out. Hence the confusion.
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post #15544 of 15551 Old Yesterday, 08:35 PM
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Originally Posted by Soulburner View Post
In REW, it is commonly reported in this thread that HDMI 4 gives +10db over the other channels. Jerry told us this is because the AVR makers add +10db to the LFE channel.
Yes, that's correct.


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But if the AVR is adding 10db to LFE, and the LFE track really is, as Jerry tells us, encoded 10db lower by the movie studios, they'd cancel out. Hence the confusion.
If the studio wants something in the LFE channel to play at the same SPL as the other channels them they would reduce the signal by 10dB compared to the other channels. However, they're certainly not going to do that for all LFE content. Ultimately, they mix for what they want during playback and encode the signal accordingly. It seems like you're over thinking this 10dB offset that gives the LFE channel an additional 10dB of output capability.
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post #15545 of 15551 Old Today, 12:52 AM
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Originally Posted by Soulburner View Post
But if the AVR is adding 10db to LFE, and the LFE track really is, as Jerry tells us, encoded 10db lower by the movie studios, they'd cancel out. Hence the confusion.
The confusion seems to be that you think the REW signal is encoded differently according to which channel you use and respects some domain specific (film) encoding standards (hence is designed for use with AVRs only).

This isn't the case, it is just a signal generator that sends a certain scale signal and leaves any downstream processing to do whatever it wants. You therefore have to understand your signal chain if you want to understand the reported output.
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post #15546 of 15551 Old Today, 03:59 AM
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Quote:
Originally Posted by Stereodude View Post
If the studio wants something in the LFE channel to play at the same SPL as the other channels them they would reduce the signal by 10dB compared to the other channels. However, they're certainly not going to do that for all LFE content. Ultimately, they mix for what they want during playback and encode the signal accordingly.
That makes more sense.

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The confusion seems to be that you think the REW signal is encoded differently according to which channel you use
Not quite. From what I was reading it sounded like this: all signal levels from REW are the same, but AVR is boosting LFE 10db. However I saw what Jerry said and it got me caught up on the idea that ALL movies will have their LFE -10db, and since REW isn't a movie with that offset you end up with an extra 10db over the other channels. While the math works out in the end, the reasons for it I didn't understand correctly.
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post #15547 of 15551 Old Today, 04:13 AM
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Originally Posted by Soulburner View Post
all signal levels from REW are the same, but AVR is boosting LFE 10db
It doesn't boost LFE 10dB (if it was done on the DSP we would get heavy clipping on the subwoofer). It is better think about it this way:
1) AVR *calibrates* subwoofer output so it has 10dB more loudness headroom than satellites (the voltage at the pre-outs could still be the same or even lower than satellites - it depends on the gain set at the subwoofer, so it is not 'electrical' or 'digital' boost, it is setting the gain structure of the system so the maximum loudness of the channel is 10dB higher).
2) Pass LFE as is to the subwoofer output channel (that is calibrated to sound 10dB louder for the same input signal level).
3) Attenuates redirected bass by 10dB so it is the same loudness at both sides of the crossover.
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post #15548 of 15551 Old Today, 03:32 PM
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post #15549 of 15551 Old Today, 04:12 PM
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That is a nasty looking waterfall, Ray. Have you considered treatments?
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post #15550 of 15551 Old Today, 06:21 PM
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post #15551 of 15551 Old Today, 07:24 PM
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