LFE Channel Confusion

[FullFrequency]

Whatever enhances the mix! I don't put music there at all though, aside from the odd kick for impact in the right situation. A decent sfx edit will have specific sub sweeteners though!

[starcrash13]

First, don't use the built-in LFE send on the Pro Tools panner. Instead, use regular sends to a mono aux that has a subharmonic synthesizer-type plugin inserted. Something that simulates a dbx 120 (Lowender, LoAir, RectiFi). Route that aux feed to the Lf channel of your 5.1 bus.

Next, whatever sounds you want to make go "BOOM!", send them to your "boom".

Make sense?

[Smallbudgetguru]

I have been using the pro tools lfe from the track panner without any problems. I also send score to lfe.

I'm interested in the "boom" aux to feed the fx stem to sinulate dbx with plug however and wonder two thing:

1- what's wrong with doing it how I have been via panner?

2- is Rbass equally adequate for this purpose?

[starcrash13]

Nothing "wrong" with using the Pro Tools LFE fader. It does what it claims to do by sending audio from that channel to the Lf channel of a 5.1 bus. But that's not the way I work or how I've seen other professional mixers work.

The LFE is for "special effects" like explosions and earthquakes. I suppose you can editorially prep low end sweeteners and use the LFE fader to send those sounds to the Lf channel, but like I said, that's not the way most of us do it. Plus, keep in mind that the LFE channel is dropped completely in some formats like LtRt. Don't put anything in there that you'll really miss if it's gone.

In my experience, the fx editor should prep a full range fx track and then it's up to the mixer to decide which sounds get sent to the "boom". The plugin used should be able to generate a sound that's lower than the fundamental which, to answer Guru's question, I don't think R-Bass does. This way you can "boom" a gunshot if you wanted to, for example.

This should be no secret, it's pretty common practice. On a traditional film mix console, each channel for sound effects typically has a send that is bussed to a dbx 120 and comes up as a return on the console which is routed to the Lf channel of the fx stem. We simulate this in PT using the method I described. The PT LFE fader doesn't do this.

[insomaniac]

Originally Posted by Smallbudgetguru

2- is Rbass equally adequate for this purpose?

I believe that RBass (and MaxxBass) add harmonics to the sound while the 120 box and software equivalents (LowEnder, LoAir) actively synthesize sub-bass signals to add low end kick. Think of it as RBass adding slightly hire frequencies, while a 120 adds lower ones. Someone correct me if I'm wrong.

[D'Animation]

Originally Posted by insomaniac

I believe that RBass (and MaxxBass) add harmonics to the sound while the 120 box and software equivalents (LowEnder, LoAir) actively synthesize sub-bass signals to add low end kick. Think of it as RBass adding slightly hire frequencies, while a 120 adds lower ones. Someone correct me if I'm wrong.

Thats how I use Rbass - good for getting some deeper boom fx (or even adding weight to thin voiceover) to cut through TV speakers a little more without slamming the faders up or overpowering your meters with heavy bass frequencies (and yes, I still mix and review to the lowest common denominator, even if its 5.1/LtRt)

[Henchman]

I use Lowender on a send.
That's the one way to really control how much sub you are adding, as well as the ability to create what doesn't exist.

[Smallbudgetguru]

Thanks dudes ill play around and implement this method into my template cheers

[mikevarela]

you guys putting a low pass before the lowender (have lo air here) and cutting anything above say 200 or 300?

[postprosound]

What they are trying to say is simply why do you feel you need to send to the lfe track?
It's important to note that 5.1 configuration and bass management, while although sharing some details, are two different breeds of cats.

As a refresher:
5.1 consists of 5 full range channels, (20 hz to 20 khz), and one dedicate LFE channel going from 20 to aprox 120 hertz, thus the ' .1 '. A person mixes to the 5 full range channels as they see fit, and if they feel that the bass freq's will overload the main 5, or they want to add a punch, they send some of that 'extra' to the LFE or .1 .

Bass management is a way for the main 5 speakers to handle full freq if they are small, and can't handle full range. Over simplified, it takes all of the LFE channel, and any content below given frequency (often 120 hz) and sends it to the sub.
Obviously, this is very overly simplified, but it's a start.

So the question to the OP is, do you want to send to the LFE because your main '5' are overloading, or is it something else?

As a side note, at least for us, but i think it's pretty common, we send all of our stems as either LCR's for pointed fx and some foleys, and 5.0 for BG's and FX that need that need to go the the surrounds. we then let the mixer on the stage handle the sending to the '.1' part. We don't even deal with that. If you do a search here and at the DUC's post and surround forum, you'll note that you are encouraged never to send anything to the lfe exclusively, at least nothing that you don't mind loosing. Many formats often times either mix that content back into the 5 main channels, or delete it entirely.

[JesseG]

A lot of great info here guys. Thank you.

@postprosound

It's nothing in particular. I was just more or less curious as it's always been a point of confusion to me. This cleared up a lot though.

Hypothetically speaking - let's say I deemed that a particular effect needed some more boom, would I just place that effect again in the LFE track, or would I not want to duplicate it? Also, should the repeated effect be low-passed or is a low-pass something I put as say an insert on the entire LFE track (or is that not needed at all).

Again, I appreciate the help. As a student, hearing from working professionals like yourselves goes a really long way.

[maggot]

the main issue with the PT panner LFE slider is that it is a post-fade send.
so there's no way to send to the LFE without also going to the mains.
if you're using Spanner as the surround panner you have a pre-fade send for this purpose.
justin

[narcoman]

Originally Posted by starcrash13

LFE is for "special effects" like explosions and earthquakes. I suppose you can The PT LFE fader doesn't do this.

It does. I do this all the time with a master fader or an LFE within a buss and then use the mono component with an insert.

[nzl62]

Dolby implementation in the US is different to UK and other territories where bass management is not allowed. So sending a discrete element to the subs is key. If you say send using the lfe send from a a PT 5.1 pan it will go to the lfe track of course and a cinema processor will handle the rolloff but the fun and games start when you use that stem to make an LtRt or LoRo or other fold down as I understand that the lfe send is not filtered and is the same material as is going into the screen channels, which boosts the level and can introduce phase issues
The best way is to use some sort of harmonic synthesiser suchas low ender or rectify, low air etc to essentially derive new discrete material for the lfe track. Couple that with intelligent sfx track lay where specific elements are cut to go to lfe only which are different and complimentary to what is on the screen channels.
As I said at the start US theaters can use bass management but in the UK we could not.
As a side note, I mix assuming that the movie theater has its sub switched off or not runnign correctly(very common) and so I don't rely on it, the screen channels should tell the story, the sound be appropriately robust and the lfe adds the extra bit of "magic". Use it as a glorified low end eq and you are in for trouble