Noob question about LFE and bass management

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Hi guys.

So we are working on an indie show. First time to try mix 5.1 for AC3 encoding. No budget so its time to learn some surround, no producers to kill one afterward.
Now my confusion

We are using JBL 5,1 setup which has own bass management facility built in (SLR4328p) . We mostly, until now where mixing Stereo PCM for music and DVD, so I hope it was right to leave BM on.
Now when I mix to AC3 should I control the LFE from Nuendo and bypass BM on the speakers chip?
I assume it this the way to go, since the encoding will take place in Nuendo or other AC3 software.


Hope it make sense my question.

Thanks in advance.

regards

[Tumppi Järnefelt]

Hi!
Are your JBLs full range monitors (go down to about 30 Hz, even to 20 Hz)?
If they are don't use BM.
If on the other hand they are not full range monitors you must use BM.

Subwoofer speaker with BM and LFE are two different things. LFE uses (is routed to) subwoofer to playback those low rumbles etc. But always remember that LFE is its own channel/track (.1).
Subwoofer with BM is just an extension for the main monitors for lower frequencies...

Bye / Tumppi

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Hi Tumppi
Thank you for your reply.
I'm still a little confused.
Let me explain more
The JBLs I think only go down to 40Hz. So I should leave it on. I'll check it
But how does the playback know what to play in the sub, does it have an BM build in? So on the client Yamaha encoder if he plays 5.1 I mixed with BM on it still will play/extend to the sub?.
So if I understand properly, I live the BM on and If I need the explosion to shake my butt I route some Low Frequency stuff thru LFE which then play on the SUB.
I hope I dont sound stupid. Can you point me to some reading maybe.
Thank you very much

regards

[Tumppi Järnefelt]

Hi Tumppi
Thank you for your reply.
I'm still a little confused.
Let me explain more
The JBLs I think only go down to 40Hz. So I should leave it on. I'll check it
But how does the playback know what to play in the sub, does it have an BM build in? So on the client Yamaha encoder if he plays 5.1 I mixed with BM on it still will play/extend to the sub?.

You said that your system has BM. So you use it.
The other guy at home or anywhere else uses his systems BM to have full frequency playback if his/hers system don't have full range monitors.
BM is not coded anywhere. It is just basically a filter that divides lower frequencies from the mids and highs and routes lowest stuff to subwoofer.



So if I understand properly, I live the BM on and If I need the explosion to shake my butt I route some Low Frequency stuff thru LFE which then play on the SUB.
I hope I dont sound stupid. Can you point me to some reading maybe.
Thank you very much

regards

You have understood correct.

More info for example here: http://www.genelec.com/faq/multichannel/lfe-channel/
And here: http://www.genelec.com/faq/multichannel/bass-management/
And here: http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/38_LFE.pdf
and especially here: http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/L.mn.0002.5.1guide.pdf

Bye / Tumppi

[Michael Tibes]

I'd simply think of it as 2 independent issues: bass management extends the frequency range of your main speakers - set and forget (just set it right though). LFE is the special lo freq fx channel, which in your case accidentally uses the same speakers (the subwoofer) - but that doesn't bother you. Just get the levels right, the digital lfe channel has 10 db more headroom, so it needs to have 10 db more gain - if I got things right in my little brain.

Michael

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Thx guys
It helped me a lot. I'm good to go now.
regards