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Author Topic: LFE channel question  (Read 1915 times)

ppataki

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LFE channel question
« on: July 27, 2017, 02:40:59 am »

Hello,
I would have a generic question re. LFE
If digital crossover is applied to move/add sound below e.g. 50Hz from the main channels to the LFE channel then what happens to the material that is already there above 50Hz?
I mean if there is content in the main channels above 50Hz ( surely there is) and if there is content above 50Hz already there in the LFE channel then there will be an overlap - would't that cause a bump there?
Or maybe I am missing something
Thank you
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flac.rules

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Re: LFE channel question
« Reply #1 on: July 27, 2017, 04:11:29 am »

Hello,
I would have a generic question re. LFE
If digital crossover is applied to move/add sound below e.g. 50Hz from the main channels to the LFE channel then what happens to the material that is already there above 50Hz?
I mean if there is content in the main channels above 50Hz ( surely there is) and if there is content above 50Hz already there in the LFE channel then there will be an overlap - would't that cause a bump there?
Or maybe I am missing something
Thank you

If i understand you right, it causes no bump. The LFE and main channels together have the "right amount" off bass. Not rerouting the mains to the LFE in the 50-120 Hz range wouldn't change the total amount. (of properly implemented)

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Fitzcaraldo215

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Re: LFE channel question
« Reply #2 on: July 27, 2017, 01:08:11 pm »

Hello,
I would have a generic question re. LFE
If digital crossover is applied to move/add sound below e.g. 50Hz from the main channels to the LFE channel then what happens to the material that is already there above 50Hz?
I mean if there is content in the main channels above 50Hz ( surely there is) and if there is content above 50Hz already there in the LFE channel then there will be an overlap - would't that cause a bump there?
Or maybe I am missing something
Thank you

Bass management in JR or elsewhere applies an xover to all input channels except the LFE channel.  It redirects the bass below the xover from each of those channels to the output .1 channel and removes it below the xover from the other output channels, all as you described.

But, it also sums the resulting .1 channel plus the input LFE channel with no xover applied.  So, all the signal in the LFE goes out to the .1 channel.  Normally, that is limited to 120-130Hz on the input file in the mastering of the file.  Some AVRs, prepros, etc.  have an LPF of LFE setting, a low pass filter, to limit frequencies above a certain point in the LFE and prevent them from going out to the sub via the .1 channel.  Often, that LPF of LFE defaults to 120-130 Hz.

It works fine for me using JR bass management in a 7.1 system.
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ppataki

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Re: LFE channel question
« Reply #3 on: July 27, 2017, 04:27:05 pm »

Thank you for the clarification!
So you suggest a low-pass filter on the LFE channel at around 130Hz? Or shall I just omit the LPF?
Many thanks
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Fitzcaraldo215

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Re: LFE channel question
« Reply #4 on: July 27, 2017, 04:34:12 pm »

I don't think it makes much difference, but yes 130 Hz LPF of LFE would make sense.
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