Difference between LFE and Bass Management

[mga2009]

Hi,

From THIS VIDEO

Charles Sprinkle mentions they are using 2 subwoofers NOT for bass management but for LFE.

I kind of know that LFE is a special channel for "Low Frequency Effects" meaning a 5.1/7.1 soundtrack will have an LFE mono channel for effects below 120Hz (per Dolby standard?)

OTOH, Bass management I guess is the process when there is NO LFE channel and you high pass your speakers and you mix the lower end and send it to one or more subwoofers.

But isn't that practically the same? What´s the real difference then?

I understand that If I have a -say- Bluray with LFE channel, can I still do some bass management (If I have the proper DSP equipment)? I know I will be limited to a mono signal which I can distribute in different SW and adjust delay/phase/eq to integrate them with the mains and the room.

 

[DVDdoug]

The bass management always works. If you are configured to send the "regular bass" to the subwoofer it always re-directs the regular bass with stereo or surround sources. If there is an LFE, it get's mixed with the other bass and it's all sent to the subwoofer.

As you may already know, the LFE is lost in regular stereo mixdown. So if you are playing a Blu-Ray or DVD but you don't have a sub you'll still get the all of the regular bass through your existing speakers, but no LFE.

Or you could simply say... The point-one LFE channel always goes to the subwoofer and only to the subwoofer. The other bass can be optionally diverted to the subwoofer.

P.S.
There is a rumor that on the original Jurassic Park release they forgot to include sound from the dinosaur-steps in the main channels. So people watching with regular stereo sound weren't hearing anything while the video is shaking to show the ground vibrating! Kinda' like the TV version of Blazing Saddles with the silent farting. But luckily, THAT'S not LFE!

 

[sam_adams]

Dolby direct to you: What is the LFE Channel?

 

[mga2009]

The bass management always works. If you are configured to send the "regular bass" to the subwoofer it always re-directs the regular bass with stereo or surround sources. If there is an LFE, it get's mixed with the other bass and it's all sent to the subwoofer.

As you may already know, the LFE is lost in regular stereo mixdown. So if you are playing a Blu-Ray or DVD but you don't have a sub you'll still get the all of the regular bass through your existing speakers, but no LFE.

Or you could simply say... The point-one LFE channel always goes to the subwoofer and only to the subwoofer. The other bass can be optionally diverted to the subwoofer.

OK, I get it about "bass management"

So... If I understand correctly what Charlie Sprinkle meant is that in his case, the 2 SW will only reproduce the LFE channel and not ALL the bass (ie. under 80hz), whereas the case if they were used to bass management they will be high passing the speakers and distributing that bass in the 2 SW.

 

[audio2920]

There is a rumor that on the original Jurassic Park release they forgot to include sound from the dinosaur-steps in the main channels

I suspect that could be true, but it probably wasn't a mistake. Back in 1992/1993 (?) they likely just had no concept that someone would play their mix with a channel missing entirely

 

[Vladimir Filevski]

So if you are playing a Blu-Ray or DVD but you don't have a sub you'll still get the all of the regular bass through your existing speakers, but no LFE.

Or you could simply say... The point-one LFE channel always goes to the subwoofer and only to the subwoofer. The other bass can be optionally diverted to the subwoofer.

Dolby is not agreeing with you:
"all of the bass information in the program, including the LFE channel, can be reproduced by the main speakers." (from the link in post #3)

 

[abdo123]

Dolby is not agreeing with you:
"all of the bass information in the program, including the LFE channel, can be reproduced by the main speakers." (from the link in post #3)

Some processors are capable of doing this yes.

 

[Vladimir Filevski]

Some processors are capable of doing this yes.

You got me interested - which modern AVR (since 2010) doesn't have processor capable of redirecting LFE channel to main speakers?

 

[sarumbear]

I have a separate subwoofer for the LFE channel separate from the two stereo subwoofers fed by bass-management. I find out that on some films LFE is so vicious that if I mix it with the bass managed subwoofers their output is distorted. Hence, I keep LFE separate as it is originally intended. After all bass management is only there because we can’t practically fit full range speakers for all channels in our houses.

 

[alex-z]

The LFE channel is 10dB higher than the others. So when you use LFE + bass management, you need a lot of output headroom on your subwoofer setup.

You don't need external DSP in 100% of cases. Any AV receiver can do basic bass redirection + LFE. Only when you want to start applying different EQ settings to each sub do you actually need something like a miniDSP 2x4HD. If you need FIR filtering for phase correction, then more powerful hardware is required.