Surround sound queries

[gsh]

I have a capture of a concert (broadcast on NBC I believe) that has 5.1surround sound. Now I don't currently have a surround setup, and bearing in mind that 2 ch equipment discards the LFE channel on downmix, I was wondering if anyone had a suggestion for how much bass to add to the centre channel to accomodate for this. I quite liked the idea of keeping the 5.1 audio, but the LFE channel is very low anyway, and could probably do with a little boost. Suggestions/recommendations for how much to boost the LFE by (currently @ -30db) most welcome (bearing in mind I have no way of monitoring the muxed file properly - feel free to tell me it's a waste of time without the correct setup). Or would it just be easier to downmix to 2ch and keep the 5.1 version for the future?

[redwudz]

You left out the most important part, what are you saving it to to play? If it's DVD, I would just leave the 5.1 as is and let your amp downmix it to 2 channel while playing. Then if you do get a 5.1 setup, you would be set already.

If the LFE channel has the same type of audio that comes out of mine, your regular stereo speakers may have a hard time reproducing those very low frequencies anyway. If you boosted it too much, you might end up with distortion. If I wanted more bass with just the two channel, I would make the adjustment there with a equalizer and boost up the lower end instead. JMO.

[gsh]

Thanks - indeed this is a dvd compilation. I think I'll leave the 5.1 as is and do a 2 ch downmix for the time being.
Cheers.

[Cornucopia]

Here we go again...

One of the complexities of 5.1 that many are having recurring trouble with is the difference between the mixing/encoding strategy as regards Main Channels vs. LFE, and the decoding/playback/amplification strategy as regards Standard/Satellite speakers vs. Subwoofer.

Supposedly, according to Dolby Labs, the LFE channel is NOT supposed to be mixed in with the Main channels when doing a downmix. It's for "LowFreq. Effects" only.

If you have a multitrack audio editor, you could...
A. Demux and Decode the AC3 to multiple single-channel WAV's.
B. Load the WAV's into the Multitrack Audio editor--each in its own usual configuration, except the LFE, which would be added to ? the center? L+R? all channels? (pretending it's an additional voice on the other channels)
C. This could be encoded to 5.0AC3, or 2.0 AC3, or most other 2.0 formats

But Why?

The Main channels are FULL RANGE, meaning they support 20-20k (or more), so there shouldn't be ANY "thinness" in the bass on those channels, even when losing the LFE.

The Sat/Sub (aka Bass Redirection) assignment is something done with your receiver/amp and should allow for good bass playback, no matter what the channel.

For example, on my system, I have PrettyGood L & R speakers, Tiny C & Ls & Rs speakers, and a VeryGood Subwoofer.
My L, R encoded channels should go ONLY to the L & R speakers.
My C encoded channel goes to Center speaker, but also to L & R (at lower volume) for most all frequencies, until at ~120Hz it ALL goes to the Subwoofer.
My Ls, Rs encoded channels should go to their respective speakers for most all frequencies, until at ~120Hz they ALL go to the Subwoofer.
My LFE encoded channel should go to both the L & R speakers AND the Subwoofer.
This maintains matched levels, spectrum etc.

This all depends on the kind of playback system you have and is supposed to be irrespective of the encoding/mixing system and channel assigment.

Scott

[SingSing]

Cornucopia means just crank up the BASS, and enjoy yourself.

[Cornucopia]

I think? what I was trying to say was:

Leave the file alone.

Calibrate your playback system correctly (which MAY include "cranking up the bass").

Then you won't have to do anything else. Enjoy.

Scott

[gsh]

That's a lot of useful info - thanks.