Understanding the .1 in 5.1

[pvsurfer]

I'm kind of new to HT so I need to understand this better than I now do. While I've read some feature articles on the subject, I still have some basic confusion...

Does Dolby Digital's bass management send ALL of the base (below the selected cross over) that would otherwise exist in the front, center and surround channels to the LFE? Or does DD's bass management send the bass from only the L & R fronts to the LFE?

I'd appreciate any clarification...

 

[MDS]

Does Dolby Digital's bass management send ALL of the base (below the selected cross over) that would otherwise exist in the front, center and surround channels to the LFE? Or does DD's bass management send the bass from only the L & R fronts to the LFE?

Your're mixing two different concepts. 'Bass' and 'LFE' are both low frequencies but are diistinct concepts and how and where each gets routed depends on a number of settings in the receiver.

'LFE' is a discrete channel on the disc that is limited to 120 HZ and below. Because it contains only very low bass it is called the Low Frequency Effects channel. In a system with a subwoofer, LFE always goes to the sub. If there is no sub, LFE is routed to the front speakers (and most receivers will automatically set the fronts to Large if sub=no because Large means the speaker gets all frequencies).

'Bass' is low frequency information that did NOT come from the special .1 channel on the disc. Any channel set to Small will have the bass below the xover setting sent to the sub and similar to routing of LFE, if there is no sub, it gets routed to the front speakers.

Nothing is ever routed to LFE. The LFE channel either exists or it doesn't.

 

[pvsurfer]

MDS, I really appreciate the education! So when you said

'LFE' is a discrete channel on the disc that is limited to 120 HZ and below...

I then take it that the LFE (.1) channel is not influenced by the receivers bass crossover setting - correct?

Also,

'Bass' is low frequency information that did NOT come from the special .1 channel on the disc. Any channel set to Small will have the bass below the xover setting sent to the sub...

Ok, so since the speakers I use for each of my 5 channels (Infinity TSS series) roll-off at 120 Hz, I should set ALL of those channels to Small and set the bass crossover frequency to around 120 Hz so that my sub (an Infinity PS210) handles the contents below that frequency from each of the 5 channels - is that correct? (and is it preferable to use the receiver's crossover rather than the sub's)?

However, I am now confused about the sub's cabling. Will the coax cable going to its LFE input carry ALL of the above or does that cable handle only the .1 channel? ...and if the latter, do I then need two additional speaker wires going to my sub to handle the bass content from the other 5 channels?

 

[MDS]

I then take it that the LFE (.1) channel is not influenced by the receivers bass crossover setting - correct?

Correct...but with a catch (there's always a catch). Some receivers have a setting to set the highest frequency for the LFE channel and naturally it goes by different names on each receiver (like 'LFE low-pass'). The setting is in effect a xover for the LFE channel. The LFE channel can go as high as 120 Hz but if the receiver has that setting you can set it to say 80 Hz and nothing higher than 80 Hz from the LFE channel goes to the sub. THX certified receivers set that at 80 Hz.

so since the speakers I use for each of my 5 channels (Infinity TSS series) roll-off at 120 Hz, I should set ALL of those channels to Small and set the bass crossover frequency to around 120 Hz so that my sub (an Infinity PS210) handles the contents below that frequency from each of the 5 channels - is that correct? (and is it preferable to use the receiver's crossover rather than the sub's)?

Correct and I think it's preferable to use the receiver for all bass management. Cabling is simpler and you can make adjustments on the fly with your remote.

However, I am now confused about the sub's cabling. Will the coax cable going to its LFE input carry ALL of the above or does that cable handle only the .1 channel?

All of the bass - LFE from the .1 channel AND bass redirected from channels set to Small. A sub with an input labeled 'LFE' just means that that input is unfiltered (the sub's internal xover is disabled). Some subs have only one input labeled 'line-in' and an additional switch you can set to enable or disable the sub's internal xover instead of a dedicated input labeled 'LFE'. It's just a naming convention that HT enthusiasts recognize to mean that that input does not apply the xover and you will use the receiver to do the filtering.

 

[Audioholics]

We'll generalize for simplicity. The receiver is the "brains".

It takes the low frequency information destined for any speakers set to SMALL and re-routes it to the Subwoofer output (that analogue "coax" as you indicated).

The receiver also sends the LFE (.1) signal (present in dts and Dolby Digital soundtracks) to the same Subwoofer "coax" output as well.

The Subwoofer receives both these signals (since they are both included in the single "coax" subwoofer output from the receiver) and plays back the information.

 

[pvsurfer]

Thanks so much guys. I think that I finally understand this (and I'm also glad to hear that the subwoofer coax cable takes care of it all)!

 

[corey]

Any chance that the pv in your name is Palos Verdes? I used to surf the Cove back in the 60's.