Surround Sound

[Dumb-Ask]

OK, here are a few questions about surround sound that i would loved know the answer for.

 

1)Do you put a low pass filter on the LFE channel (will it effect the encoding somehow)?

2)How do you get the surround panner to position in the exact center ?

3)To get a smooth transition between L ,center and R speakers does the center channel pan slider need to be pushed all the way up?

4)should I keep the LFE pan slider in the center for most sounds or should I drop it down completely unless I'm after a low frequency effect like an explosion ?

[fader8]

1)Do you put a low pass filter on the LFE channel (will it effect the encoding somehow)?

 

Yes. (No) What are you encoding with?

 

2)How do you get the surround panner to position in the exact center ?

 

Option-click it.

 

3)To get a smooth transition between L ,center and R speakers does the center channel pan slider need to be pushed all the way up?

 

Not presently possible in Logic using the surround panner. If you want a transition from L-C-R, create 3 mono tracks and automate their respective levels. This is a long-standing bug in Logics surround panner.

 

4)should I keep the LFE pan slider in the center for most sounds or should I drop it down completely unless I'm after a low frequency effect like an explosion ?

 

You can't rely on the various forms of bass management systems out there. It's best (safest) if you reserve the LFE for it's intended purpose, LFE.

[Dumb-Ask]

Hi fader8

 

Thank you for answering all my questions

 

I will be using Sony Vegas Dolby-licensed 5.1 surround sound AC-3 encoding plug-in. do I need a filter for that and if so what sort of filter should I be using at at which frequency and octave

[fader8]

Thank you for answering all my questions

 

With a name like Dumb-Ask, how could I resist.

 

I will be using Sony Vegas Dolby-licensed 5.1 surround sound AC-3 encoding plug-in. do I need a filter for that and if so what sort of filter should I be using at at which frequency and octave

 

Yes, you should filter it. The intent of the LFE is for special effects below 120Hz. What rolloff you use is really up to you, but it should be pretty steep. Here's why. AC3 encoding, to save space and bandwidth, uses a low bit rate for the LFE channel. That's OK, as it doesn't need a high bitrate to reasonably reproduce those frequencies. If the AC3 encoder you're using doesn't do the filtering for you, then you're going to have some bad sounding highs on that channel. If the user's playback system has no subwoofer for the LFE channel, then some users switch the bass management to mix the LFE stuff into the mains. If this little embedded mixer doesn't filter at 120 then they're listening to those crap highs mixed in with the mains L and R signal. This can sound disastrous.

 

This is also the reason it's unwise to use the LFE for the low end of your mix in general. Here again, the end users bass management must be considered. If they have a small satellite system with sub, then their receiver will take care of mixing the bass from the mains and sending it to the sub to enhance the systems perceived bandwidth. If you've already got mains stuff mixed to the sub to begin with, this can sound really disastrous.

 

This is a good reason never to use "small" monitors to produce for surround. It's really easier to produce for cinema than for DVD. You know fairly closely how it wil be played back. To produce for compatibility with all the wacko home systems out there is a royal pain in the butt.

[Dumb-Ask]

Thank you you're a star

 

BTW,Which filter do you use to filter the LFE ?

[fader8]

BTW,Which filter do you use to filter the LFE ?

 

UAD Cambridge Lo-pass Butterworth 6 at 130Hz.

[David Nahmani]

]Not presently possible in Logic using the surround panner. If you want a transition from L-C-R, create 3 mono tracks and automate their respective levels. This is a long-standing bug in Logics surround panner.

 

You can have a pretty smooth transition from L to R. You shouldn't usually use the center speaker for those, since the center speaker is supposed to be for dialog only. But you can still transition from L to R. You can either use a regular pan, or the surround pan. If you use the surround pan, just open your angle automation and make sure the center jump is vertical.