Reference Level and more speakers

[Epetti]

I had a basic question that I can never find spelled out in descriptions of THX reference level and various surround mixes. Are the assumptions of decibels at reference level based per speaker or for the entire mix? So if you are playing at reference, is each speaker playing at average 85dB or the whole mix?

And following on that question, are the mixes rebalanced based on number of speakers? Is Atmos louder than 7.1 louder than 5.1? Is 7.1.4 Atmos louder than 5.1.2 Atmos?

Any clarity very much appreciated. Seems like it could make reference just a little less reference in terms of how loud you can expect a soundtrack to be based on what the mix is.

 

[lovinthehd]

The spl measurements are in terms of average and peak levels (85 dB average with allowance for 20dB peaks for speakers, add 10dB to both for LFE) generated by each speaker individually measured at your seat. So each speaker's demands will vary with distance from your seat. If you take all speakers together the average spl at your seat will be greater due to all the speakers' combined output. Generally the surrounds and rear surrounds receive a lesser signal than mains to create the ambient effects of surround, but will also depend on mix (and type of movie to an extent).

The mixes still refer to spl at the seat.

Mixes vary as to how they adhere to such standards, tho. Some will be less, some will be more. Some will concentrate on fronts some will spread it around more...

 

[TLS Guy]

I had a basic question that I can never find spelled out in descriptions of THX reference level and various surround mixes. Are the assumptions of decibels at reference level based per speaker or for the entire mix? So if you are playing at reference, is each speaker playing at average 85dB or the whole mix?

And following on that question, are the mixes rebalanced based on number of speakers? Is Atmos louder than 7.1 louder than 5.1? Is 7.1.4 Atmos louder than 5.1.2 Atmos?

Any clarity very much appreciated. Seems like it could make reference just a little less reference in terms of how loud you can expect a soundtrack to be based on what the mix is.

I would not worry about reference levels. The calibrations do it to make things like Audyssey's Dynamic Eq and Volume Eq work properly. However these programs are based on false assumptions and are best avoided. The worst part of the level setting is that if you have reasonably sensitive speakers, then Audyssey will reduce speaker volumes to the point where the gain structure of your receiver or pre/pro is absurd. This seriously degrades signal to noise ratio and performance.

Just make sure your speakers are not reduced crazy amounts like -8 db, avoid Dynamic Eq and that sort of nonsense and set your volume to a comfortable level.

All this reference level BS is just calculated to handicap your system out of the starting gates. Just forget it and enjoy.

 

[Epetti]

I guess my question is more about how movies are mastered with respect to it. It's not really an Audyssey thing so much as an industry standard. But I'm wondering if mixes are normalized based on number of speakers so that MLP hears the same loudness whether it's a 5.1, 7.1, or Atmos mix. Or if it's per speaker do that discs that have a higher order mix will be expected to be louder.

In either case I'm going to set the volume where I'm comfortable regardless. I'm more wondering from a technical/philosophical perspective.

 

[lovinthehd]

It's mastered for reproduction at the MLP, with properly setup gear/speakers. The speakers should be capable of such levels as well as your amplification (and the ability of the particular speakers will vary with distance from MLP).

 

[j_garcia]

Your understanding is not quite right. Regardless of how many speakers, tracks are mastered to a given level. That level depends on the audio engineer in reality, which is why some films are soft and others are hot. Number of speakers in the mix has no bearing on the level of that mix. Simply because the engineer mixes for Atmos does not mean it will be louder, but it may be louder than another Atmos movie.

 

[DigitalDawn]

Just to give you a good idea of how this works, Triad has a room size guide that shows how many of their speakers you would need to reach reference level in a room. It's based on cubic room volume as well.

 

[mtrycrafts]

What you need to be sure is that all your speakers are set to the same spl with a known equal signal input to each channel. That is how the mastering stage is set. then the engineer decides how much goes into the surrounds by taste.
If yours are not matched, you might get drastically different response.