SurroundByUs.com

Hi everyone

I'm completely new to surround sound. However, I've been practicing on making my own 5.1 mixes by trying to convert my own band's material into surround sound. I've gotten the 5 main channels all set, but how do I set up the LFE channel? I am using the isolated tracks to make this mix (as in, I have separate wav files for each instrument... bass, guitar, acoustic guitar, strings, drums etc). I've also been using Audacity and for the actual audio editing so that makes using the tutorials on the website difficult. What is the best way to go about making an LFE channel when you have isolated instrument tracks? And is there anyways I can damage my sub by making a mistake?

Thanks!

Well first there is the often held argument about should or shouldn't you use a .1 channel in surround Music.

Without going into a ton of detail the technical answer is usually no (.1 is for sound effects not music) but in practice the end listener expects that .1 indicator on their HT to light up so you sometimes have an empty (or really low volume) LFE channel and the listeners Bass Management system will take care of sending low frequencies to their sub woofer.

But your question was how to do it so here goes.

On this site we are mainly concerned with conversion or upmixing from stereo to 5.1. In that case we sum the stereo signal and send it to an "LFE" group of three filters:

Lowpass (typically 80 Hz very steep)
Peaking (typically 40 Hz)
Highpass (sub sonic filter, typically 20 Hz very steep)

Then a gain stage and the output feeds the LFE channel.

This is similar to what you would see on a subwoofer electronic crossover/amp.

In your case you could sum all of your channels or instruments (maybe an effects send) and feed the sum to the filter.

This is almost a bass management system, except that we DON'T want to cut the bass out of the 5.0 channels, so another way you could do this would be to use a bass management VST, but don't use the 5.0 outputs, only the sub out to feed the LFE channel.

A serviceable free bass management VST can be found here:

There are also other VSTs but if you are working in Plogue I would just use the LFE filter that we have in our most recent SPEC layouts.

Let me know if you want to do that an I can provide additional guidance. We think this new three stage filter outperforms previous hnm filter based LFE designs.

Cheers,
Z

I forgot to mention one very important aspect.

Just as with the other 5 channels, if you're going to add an LFE channel it needs to be time aligned with the other 5. If you are doing any processing that has latency in the 5.0 channels, you need to either use the same processing VSTs on LFE, or use a delay line with the same latency.

Silmlarly, if you are using fliters with phase shift on the LFE, you should consider using a delay line on the other 5 channels so that the bass frequencies you are trying to highlight with LFE are time alinged with those in the other 5 channels.

This is something that is built into our stereo to surround conversion layouts.

Excellent, thank you very much!