My BFD subwoofer EQ thread

[Chris D]

Uh... not sure I understand all the reasonings for those things, Todd. Such as for the mains, why would they NOT be turned inwards, facing the primary listening location?

I've never heard of calibrating different speakers to different SPL levels either.

[ThomasW]

I think Todd missed the fact that first off we're just trying to get an accurate measurement setup operating.

After that's going, we'll deal with optimizing the system.

We're going to start with the sub by itself to see what the room is doing to the bass, since that's where we'll use EQ and bass traps if needed.

Later we'll add in the mains and make any other necessary adjustments to the levels of the other speakers.

Regarding your other points.

A) More readings that that are needed to optimize the EQ for just a sub let alone the other speakers. Getting someone to do multi-postion testing is frequently problematic

B) I don't know about Chris but I certainly have no interest in optimizing any high-end listening room per Dolby frequency response specs.

C) not interested..

D) I've never played 2 consecutive moves that were properly mixed for the channel levels. And frequently I need to change level settings during a picture since they've screwed up the mix such that the dialogue is too low, bass too high or something else is mucked up.

And finally I listen to DTS, Dolby and other multi-channel mixes, so having any specific dedicated setting isn't happening in my world.

[ToddAnisman]

Uh... not sure I understand all the reasonings for those things, Todd. Such as for the mains, why would they NOT be turned inwards, facing the primary listening location?

I've never heard of calibrating different speakers to different SPL levels either.

Chris-

Canting your mains in makes your sweet spot smaller and more focused. In a smaller room this is a matter of taste, but if you look behind every decent movie theater in Hollywood, you'll find that the speakers are straight.

However, I will also say this: is a dedicated music mixing room, the speakers are always canted in.

The speaker levels I gave are the Dolby standard in tuning a room. -

From the Dolby DP564 Manual-

"For film work, test noise at reference level should produce an SPL of 85 dBC for each of the main front channels (Left, Center, Right) and 82 dBC for each Surround channel . The lower Surround level is specific to film-style mixing rooms."

"If an RTA is not available, setting the subwoofer channel 4-6 dB higher, as measured by an SPL meter, provides an approximate level. For example, set the subwoofer channel to 89 dBC when the Center channel measures 85 dBC. "

http://www.dolby.com/assets/pdf/tech_library/1 (Chapter 5-1)


Hope this helps.

-Todd A.

[ToddAnisman]

I think Todd missed the fact that first off we're just trying to get an accurate measurement setup operating.

After that's going, we'll deal with optimizing the system.

We're going to start with the sub by itself to see what the room is doing to the bass, since that's where we'll use EQ and bass traps if needed.

Later we'll add in the mains and make any other necessary adjustments to the levels of the other speakers.

Regarding your other points.

A) More readings that that are needed to optimize the EQ for just a sub let alone the other speakers. Getting someone to do multi-postion testing is frequently problematic

B) I don't know about Chris but I certainly have no interest in optimizing any high-end listening room per Dolby frequency response specs.

C) not interested..

D) I've never played 2 consecutive moves that were properly mixed for the channel levels. And frequently I need to change level settings during a picture since they've screwed up the mix such that the dialogue is too low, bass too high or something else is mucked up.

And finally I listen to DTS, Dolby and other multi-channel mixes, so having any specific dedicated setting isn't happening in my world.

Thomas, if you're truly looking for accuracy, then you Must EQ the Mains channels as Mains channels. only looking at the Low Freq information is very deceptive and while I'd stop short of saying its a waste of time, you're going to have to change the freq response once you put the rest of the channel in play.

For reference, when you say "Sub", to me you're talking about Bass re-direction from the Mains channels, NOT the LFE. The LFE is a different beast in it's entirety.

The problem therein lies with the crossover point- even with a 24db/Oct Linkwitz Riley filter you're still going to have some overlap or dipping. That's why one must tune using Pink Noise an entire screen channel at a time. This is how George Augspurger, Coach form Dolby, Andy from Dolby, Mark Kenna from Dolby etc. et al tune rooms. This is just how it's done in the professional world. YMMV, and I understand why you would be interested in seeing the Sub response, I just don't think it's at all accurate in the bigger picture.


Regarding tuning what you refer as a "High End Listening Environment"-

Nothing is More high end than Todd-Ao, Sony Pictures, Wilshire Stages, Warner Bros, Lantana Etc et al.

All of them are tuned to the Dolby standard or a variation to suit taste of room/mixers etc.

Including those mixes that are done in DTS, SDDS, etc. the room tuning is a constant.

are there variations? absolutely. Dolby says that in smaller rooms, the freq response should be flat to 4K.

So the bottom line is that if you want to hear what was truly recorded/mixed, then you should tune your room to that freq response.

I don't know what films you are referring to that are so messed up, but there are a couple of things that happen in between the Dubb stage and your DVD player-

A) the AC3/DTS encoding. this is by far the most misunderstood process. If you look closely, the Dolby Meta-Data has a parameter for something called "Dialog Normalization". I'll bet you dollars to dimes that almost all of your DVD's have one off two settings:

-31dBfs or -27dBfs.

Guess what?

That's totally wrong. The Dialnorm setting is specific for the film being mixed- For example if Armageddon has a Dialnorm setting of -20dBfs, then Cider house Rules would be around -30dBfs. Each would then get encoded at the appropriate level. That embedded Metat-Data then turns your AC3 Decoder into a leveling device, and turns the volume up or down according to the embedded value. If arbitrary levels are used, then it's random- Armageddon would be crankin and Cider would be too quiet. Properly encoded the AC3 File would be at the same relative listening value for any program.

B) The quality of the transfer itself. the headroom of a Dolbyh or DTS printmaster is +26dBu. Guess what the headroom of Digital is +20dB over.(where 0= -20dBfs). so, as you can see, it can be very tricky to get all that properly on the final DVD. this often results in changes being made to a particular stem in order to make the headroom work.

final rub is this- you really can't be critical and say that most mixes are lousy if your room isn't setup in the same manner as the Films are mixed. That's like saying a music mix sounds terrible when you're listening to it on an AM radio. It' just not a fair comparison.


Ultimately, if you're happy, then cool. I present this for those that really want to be accurate and have the most realistic film reproduction possible. Take it for what it's worth, enjoy!!!!!

-Todd A.

[ThomasW]

Todd,

final rub is this- you really can't be critical and say that most mixes are lousy if your room isn't setup in the same manner as the Films are mixed.

That's not what I said. I said that setting fixed speaker output levels wasn't practical, given the different output levels at which the soundtracks were mixed.

I've never been critical of the sound quality. Quite frankly I'm amazed at the level of detail contained on most soundtracks since the introduction of DD/DTS.

Nothing is More high end than Todd-Ao, Sony Pictures, Wilshire Stages, Warner Bros, Lantana Etc et al.

My modest home system isn't on par with commercial installations where you work.

This is a picture of one of my 93" tall mains. I'm reasonably certain none of the commercial installations mentioned above are running quad-amped electrostatic, planar magnetic, leaf, hybrid speakers like these.....



Now the commercial installations certainly have more subwoofers with bigger drivers, etc, etc. But I doubt that any are running true infinite baffle alignment subwoofers. This one consists of a dozen 12" drivers with the outlet centered between the main speakers. And no, no bass mgt. Everything is fully balanced with 24dB/octave, L/R active filters.

Image not available

Just my humble home system. BTW it is pretty 'accurate'.

Regards
ThomasW

[ToddAnisman]

Todd,

That's not what I said. I said that setting fixed speaker output levels wasn't practical, given the different output levels at which the soundtracks were mixed.

I've never been critical of the sound quality. Quite frankly I'm amazed at the level of detail contained on most soundtracks since the introduction of DD/DTS.

My modest home system isn't on par with commercial installations where you work.

This is a picture of one of my 93" tall mains. I'm reasonably certain none of the commercial installations mentioned above are running quad-amped electrostatic, planar magnetic, leaf, hybrid speakers like these.....



Now the commercial installations certainly have more subwoofers with bigger drivers, etc, etc. But I doubt that any are running true infinite baffle alignment subwoofers. This one consists of a dozen 12" drivers with the outlet centered between the main speakers. And no, no bass mgt. Everything is fully balanced with 24dB/octave, L/R active filters.

Image not available

Just my humble home system. BTW it is pretty 'accurate'.

Regards
ThomasW

Thomas- your stuff is georgeous!!!!!

On par is a relative term. And yes, you would be correct to assume that Commercial stages really don't have anything like what you have there. I am not aware of any infinite baffle systems used, and certainly nothing like your mains....


You would be extremeemly surprised and how UNsophisticated a dubbing stage is in some respects.

I'll post more in a few days to explain, I'm heading up the Mountain to get some Skiing in w/ My Dad (He's 75!!!!!).

when i return, I'll post a schematic of SPG's Amp rack.

-Todd A.

[Chris D]

A bump on this old thread, as this may help someone.

[Gene Simmons]

Thanks Chris for bumping this thread. I have a question I hope someone can help me with. I have a BFD on order, and I read the manual online...

I'd prefer to use RCA to XLR jacks, and from what I can see from the manual I'm going to need a RCA to male XLR cable, and a RCA to female XLR cable... is that correct?

Thanks guys.

[Chris D]

I suppose, if you're going to use the XLR jacks. Me, I use the 1/4" TRS jacks. Doug at CAT Cables made me some nice custom cables for it.