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Old 01-05-2010, 02:29 PM
Dingo90 Dingo90 is offline
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Default Noob questions: Bass management and surround monitor calibration

Sorry for the newbie post, I've been looking into the subject of surround sound bass management and surround monitor calibration and I've seen multiple answers regarding the subject, can someone please give me some define answer to these questions: (yes, I've search the forum here and at gearsluts and it only added to the confusion...)


1) if I am mixing for material going to theatre/dub stage, should I mix with bass management on or off?

2) if I am mixing for material going direct to DVD, should I mix with bass management on or off?

3) My mixing room size is about 11'X11', and I've been told different answers as to what I should calibrate my surrounds monitors to, which of these answers is correct:
a) 85 db for all monitor
b) 79 db for all monitor (I've been told dolby recommends this for smaller room even if you are mixing for film)
c) 85 db for LCR and 83 db for Ls Rs
d) 85 db for LCR and 82 db for Ls Rs

4) Sub calibration, should they be calibrated at the same levels as the monitors?

Sorry for the long post

A very confused surround newbie...
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Old 01-05-2010, 05:22 PM
Postman Postman is offline
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Default Re: Noob questions: Bass management and surround monitor calibration

These questions get answered over and over. There is a long sticky near this forum's top in which the original poster has kept many links updated to cover this material. I'll give some quick answers but this is not a simple yes/no topic.

First I have to say that there are several versions of "bass management" in use, mostly in home systems, that have different gain structures. Then there is "bass redirection" which is a subset of "bass management". I'm going to assume you mean "bass redirection", where some small speakers (often surround) cannot handle low frequencies and so their low frequiencies are diverted to the LFE speaker to preserve low frequency balance that would otherwise be lost. Quickly, here goes...

Quote:
1) if I am mixing for material going to theatre/dub stage, should I mix with bass management on or off?
Assuming your speakers can go down to 30hz and below, ALWAYS OFF. Bass management is not used in film theaters (with the possible exception of DTS sound tracks, but let's not start down that path.)

Quote:
2) if I am mixing for material going direct to DVD, should I mix with bass management on or off?
You should probably check your mix both ways, particularly if you are directing sound already present in your main channels, into the LFE channel for extra bass. Bass management MAY increase those bass sounds more than without.

Quote:
3) My mixing room size is about 11'X11', and I've been told different answers as to what I should calibrate my surrounds monitors to.
For film theater the rear speakers are calibrated to play 3db lower than the fronts. For home and broadcast, the rears are calibrated to play at equal level to the fronts. The listening level your speakers are set for will be different depending on your room size and what you are mixing for. For film theater work in your room (a small square room is probably not the best film mix environment! You need distance from your speakers to make best judgements), I would try calibrating the fronts to 81 or 82 (rears therefore at 78 or 79) and see where your mixes end up. Whatever level, the rears will be 3db less.

Quote:
79 db for all monitor (I've been told dolby recommends this for smaller room even if you are mixing for film)
I'm not sure where this information came from and I'm not sure what you're talking about. At one time Dolby suggested that in very small mix rooms, like broadcast trucks, it might help to set the rears a couple of db lower than the fronts, because otherwise the rear speakers are next to your head and you may be fooled to think the rear sounds are too loud when they're not. If you are mixing for home/broadcast, then a monitor calibration level of 79 (as opposed to 85) is probably appropriate for many occassions. See the following link for more information. The two things I've just mentioned are unrelated.

Quote:
4) Sub calibration, should they be calibrated at the same levels as the monitors?
Do you mean LFE channel? The answer is yes and no. You need a realtime analyzer to set sub/LFE level correctly. If you've read the first post in the very long sticky near this forum's top you will find links to this information. This link tells you exactly how to do it: http://www.atsc.org/standards/a_85-2009.pdf That document even tells you how to approximate a useable setting without a realtime analyzer (but of course it is only an approximation).
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Old 01-06-2010, 01:10 PM
Dingo90 Dingo90 is offline
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Default Re: Noob questions: Bass management and surround monitor calibration

Hey, postman,

thanks for the answer, it's cleared up some confusion I had.

thanks again!
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Old 01-07-2010, 09:06 AM
nathand nathand is offline
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Default Re: Noob questions: Bass management and surround monitor calibration

I believe Postman has it backwards as far as terminology goes. At least as far as Genelec is concerned, with redirect engaged, "the subwoofer reproduces LFE frequencies up to 85Hz and reroutes all higher LFE content to the front center channel."

AFAIK, "Bass Management" is the term used to describe low frequencies from satellite speakers being rerouted to a subwoofer.
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Old 12-12-2010, 05:35 PM
SDDP SDDP is offline
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Default Re: Noob questions: Bass management and surround monitor calibration

Quote:
Originally Posted by Postman View Post
Do you mean LFE channel? The answer is yes and no. You need a realtime analyzer to set sub/LFE level correctly. If you've read the first post in the very long sticky near this forum's top you will find links to this information. This link tells you exactly how to do it: http://www.atsc.org/standards/a_85-2009.pdf That document even tells you how to approximate a useable setting without a realtime analyzer (but of course it is only an approximation).

The link doesn't work anymore, would you know the new one or how I can get to that pdf?

Thanks
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Old 12-12-2010, 10:24 PM
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dr sound dr sound is offline
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Default Re: Noob questions: Bass management and surround monitor calibration

Quote:
Originally Posted by SDDP View Post
The link doesn't work anymore, would you know the new one or how I can get to that pdf?

Thanks
Go to my "Room Calibration for Film and TV" sticky above.
Here is a copy from that link:
http://www.atsc.org/cms/standards/a_85-2009.pdf
It works, I just tried it.
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