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Dialogue Low Pass Filter Effects Pedals, Units & Accessories
Old 11th June 2009
  #1
Dialogue Low Pass Filter

Hello all,

I'm new here and I'm very curious to the use of Low Pass filters in dialogue mixing for film. I usually use a LPF starting with a steep slope going down from 12K.
But I once read an article (can't recall who it was) where someone said that is is okay to lose everything above 8K.
What do you guys think?

All the best,

Herman
Old 11th June 2009
  #2
Quote:
Originally Posted by HermanP View Post
...But I once read an article (can't recall who it was) where someone said that is is okay to lose everything above 8K.
Really? That's news to me.... unless you're talking about transfers to mag stripe. I would only look at the top end if there are issues with noise or sibilance. I keep a much closer eye (or should it be ear) on the low end, rumble and sub-harmonic crud that can cause problems later.
-Bill
Old 11th June 2009
  #3
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Jfriah's Avatar
 

Wow, I'd sure like to read whatever you did that said it was ok to "lose everything above 8k" on DIA. Yeah, could be a delivery thing I suppose.

When I'm doing old cassette tape transfers/cleans, I will usually start ditching stuff above that, but not in any modern media!

(then again, if there was an 8k rolloff, some of those nice 16k squeals that make it into some mixes out there would be gone---something that always made me wonder: "I know the top end goes with age and exposure to levels, but was it that nobody in the chain heard it, or was it left in for technical reasons?")

-Jeff
Old 11th June 2009
  #4
Gear Guru
 
Brent Hahn's Avatar
 

In the olden days, when recording production audio, most folks used the Neopilotone 60hz sync system. But there was also this thing called the "Fairchild System" (yes, that Fairchild) which added a 14KHz tone to the full-track mono audio. While Neopilotone was self-cancelling when played back on a full-track machine (2 out-of-phase side-by-side 60Hz tones), the Fairchild 14K was not. Since optical tracks can't reproduce anything over 8K-ish, the assumption was that you'd LPF at 8k when you transferred to mag, which would get rid of the audible 14K.
Old 11th June 2009
  #5
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jahtao's Avatar
Quote:
Originally Posted by HermanP View Post
Hello all,
LPF starting with a hard knee going down from 12K
The correct terminology is slope not knee, that's for dynamics processors.
Old 11th June 2009
  #6
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jahtao's Avatar
Quote:
Originally Posted by Brent Hahn View Post
In the olden days, when recording production audio, most folks used the Neopilotone 60hz sync system. But there was also this thing called the "Fairchild System" (yes, that Fairchild) which added a 14KHz tone to the full-track mono audio. While Neopilotone was self-cancelling when played back on a full-track machine (2 out-of-phase side-by-side 60Hz tones), the Fairchild 14K was not. Since optical tracks can't reproduce anything over 8K-ish, the assumption was that you'd LPF at 8k when you transferred to mag, which would get rid of the audible 14K.

Cool!!
Old 11th June 2009
  #7
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dr.sound's Avatar
 

Yes, I used to know mixers in the analog 7.5 ips Nagra days that used to Hi Pass at 8-10 K. The signal chain has improved since then.
Have I ever done it in the past, yes, but it's been a while.
Old 12th June 2009
  #8
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BIGBANGBUZZ's Avatar
 

I still often Low Pass filter 10k , as quite often above this unfortunately is pure hiss on source material I deal with.
Old 12th June 2009
  #9
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Henchman's Avatar
I rarely do a LPF anymore, unless a specific piece of production REALLY needs it.
I'll use notch filters to get rid of the nastiness that can exist in the upper frequencies.

But simply lopping the bottom and the top off, to me, is not mixing.
It's being lazy.

There. I said it.
Old 12th June 2009
  #10
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BIGBANGBUZZ's Avatar
 

Quote:
Originally Posted by Henchman View Post
I rarely do a LPF anymore, unless a specific piece of production REALLY needs it.
I'll use notch filters to get rid of the nastiness that can exist in the upper frequencies.

But simply lopping the bottom and the top off, to me, is not mixing.
It's being lazy.

There. I said it.
I use HPF, LPF, and Notch, bot mostly notch . most of the dia I'm working with there isn't anything below 130hz that is usable and mostly above 12k is hiss, unless its a VO or ADR.
Old 12th June 2009
  #11
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Henchman's Avatar
Quote:
Originally Posted by BIGBANGBUZZ View Post
I use HPF, LPF, and Notch, bot mostly notch . most of the dia I'm working with there isn't anything below 130hz that is usable and mostly above 12k is hiss, unless its a VO or ADR.
I find that even when mixing reality TV stuff, there's stuff in the dialog below 130 and above 12khz that I don't simply want to lop off.
Old 12th June 2009
  #12
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danijel's Avatar
Quote:
Originally Posted by Henchman View Post
I rarely do a LPF anymore, unless a specific piece of production REALLY needs it.
I think we should LPF at least somewhere (however high that is), to cut the content we don't hear but kids perhaps do.
Old 12th June 2009
  #13
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Henchman's Avatar
Quote:
Originally Posted by danijel View Post
I think we should LPF at least somewhere (however high that is), to cut the content we don't hear but kids perhaps do.
Like I said, If it needs it. But I don't do it as a starting point. As I find there are is certainly stuff below 130 in the dialog that I want to keep, and stuff above 12k that I don't necesssarily want to lose either
.
Old 12th June 2009
  #14
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jahtao's Avatar
Doing 13x 1hrs reality atm. Rolling off the low end using a HPF set to 100Hz & 12dB/octave - that's my starting point for all dialog on this show. Usually I'll start with 70Hz but this show is non-stop music and children's tv (kids aint got much bass) plus budget is low so I'm being a bit more rough and ready. Not that I think it's a massive issue or anything. 130Hz HPF, if it was a 12dB/octave filter, sounds a bit severe to me.
Old 12th June 2009
  #15
I think cutting above 12k adds a nice feeling of continuity to the overall dialogue mix and it also helps a little bit in matching the ADR.
Old 12th June 2009
  #16
Quote:
Originally Posted by jahtao View Post
The correct terminology is slope not knee, that's for dynamics processors.
You're right, steep slope I mean....
Old 12th June 2009
  #17
I'd say that for me the most important things in dialog happen between 200Hz and 5KHz. If getting it right in this range calls for filtering low and hi end, I'll do it.
Other important thing is that loud dialogue is easier to listen to if some of the top end is rolled off. Other rule says that if you roll off at one end, you should roll it off at the other end too, to keep the balance. Combining these, one can find his way. There's no golden rule - if it sounds right, it's right. I don't look at the frequency display when I'm tuning my filters, but I'll do it on my next session, just for curiosity.
Old 16th June 2009
  #18
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I read about this technique in Bob Katz's book on mastering. I will use a parametric EQ and set the center frequency either as high or low as possible (usually 16Hz, 20kHz) and lower the gain to between -10 and -18. The 'Q' of the filter, then becomes the slope of the rolloff. I find that this allows for finer control than simply using a HPF/LPF.
But like Henchman said, only if it needs it...

Randall


Quote:
Originally Posted by HermanP View Post
Hello all,

I'm new here and I'm very curious to the use of Low Pass filters in dialogue mixing for film. I usually use a LPF starting with a steep slope going down from 12K.
But I once read an article (can't recall who it was) where someone said that is is okay to lose everything above 8K.
What do you guys think?

All the best,

Herman
Old 16th June 2009
  #19
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Matti's Avatar
Lpf were used for optical transfers to not keep the noice reduction valve / mask open with unaudible ( for optical ) frequencies.

Matti
Old 16th June 2009
  #20
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soundshaper's Avatar
 

If anything, I find that I need to add a little gain in the higher frequencies to enhance the articulation. Of course, this is usually not quite as high as 8kHz.

As many others have stated, I use a steep sloped HPF around 100Hz, but then slightly boost the speaker's (person speaking) low fundamental frequency just above that to control presence.
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