Subwoofers and LFE

[AverageJoe]

A recent subwoofer/connection thread and a couple email conversations got me questioning some of my assumptions about LFE, and prompted a question or two for the subwoofer gurus out there.

The assumptions are (and any corrections are welcome) - LFE is a discrete channel for effects that is only available from Dolby Digital and DTS encoded sources (the .1 of 5.1). Depending on how I set up speakers and cross-overs, the LFE channel is combined with the low frequency program audio and routed to the subwoofer. Hope I'm right so far.

If that's correct, does that mean if I connect 5 of the 6-channel analog cables from the DVD player to the receiver, and the last one (subwoofer out) directly to the subwoofer, it will play only the LFE channel? Then, if I have two subwoofers, could I use one for only LFE and the other for low freq. program audio without LFE?

Any down-side or advantage to doing that?

 

[MACCA350]

The assumptions are (and any corrections are welcome) - LFE is a discrete channel for effects that is only available from Dolby Digital and DTS encoded sources (the .1 of 5.1). Depending on how I set up speakers and cross-overs, the LFE channel is combined with the low frequency program audio and routed to the subwoofer. Hope I'm right so far.

Correct, LFE channel always go to just the sub unless you tell your receiver or DVD player(if your using the analogue connections) you don't have a sub, in this case it will send the LFE channel to those speakers set to LARGE. Even if you use the 'LFE+MAIN' or 'Double Bass' feature in many receivers the LFE channel will still go to only the sub

If that's correct, does that mean if I connect 5 of the 6-channel analog cables from the DVD player to the receiver, and the last one (subwoofer out) directly to the subwoofer, it will play only the LFE channel?

This will depend on the bass management of the DVD player(where the same rules apply if the DVD player is capable), because now your using the analogue connection from the DVD player you are relying on it's bass management and not the receivers

Then, if I have two subwoofers, could I use one for only LFE and the other for low freq. program audio without LFE?

Any down-side or advantage to doing that?

No, you could have one with only LFE and the other with LFE + bass from other speakers(unless you use other equipment in the chain or use speaker level outputs to the second sub, but most subs with this ability can normally do this for just two channels)

I'll explain.
Say you set your DVD player to all speakers LARGE and subwoofer to ON ----> you'll get just the LFE channel coming out the analogue sub output

now you have the digital connection going to the receiver and you have its speakers set to SMALL and subwoofer to ON ----->you'll get the LFE channel(because you have told the receiver you have a sub it will always send the LFE channel to the sub(and to just the sub) unless you tell the receiver you don't have a sub)+ the bass(below the Xover point) from all the other channels because they are set to small

cheers

 

[shokhead]

Correct, LFE channel always go to just the sub unless you tell your receiver or DVD player(if your using the analogue connections) you don't have a sub, in this case it will send the LFE channel to those speakers set to LARGE. Even if you use the 'LFE+MAIN' or 'Double Bass' feature in many receivers the LFE channel will still go to only the sub

This will depend on the bass management of the DVD player(where the same rules apply if the DVD player is capable), because now your using the analogue connection from the DVD player you are relying on it's bass management and not the receivers


No, you could have one with only LFE and the other with LFE + bass from other speakers(unless you use other equipment in the chain or use speaker level outputs to the second sub, but most subs with this ability can normally do this for just two channels)

I'll explain.
Say you set your DVD player to all speakers LARGE and subwoofer to ON ----> you'll get just the LFE channel coming out the analogue sub output

now you have the digital connection going to the receiver and you have its speakers set to SMALL and subwoofer to ON ----->you'll get the LFE channel(because you have told the receiver you have a sub it will always send the LFE channel to the sub(and to just the sub) unless you tell the receiver you don't have a sub)+ the bass(below the Xover point) from all the other channels because they are set to small

cheers

So the difference in your DVD player when setting your main speakers to small or large is when running them through your analogs are?

 

[MACCA350]

So the difference in your DVD player when setting your main speakers to small or large is when running them through your analogs are?

Yes, those settings dont effect the digital connection.

cheers

 

[AverageJoe]

Thanks for the great explanations. But let me make sure I've got this right.

I'll explain.
Say you set your DVD player to all speakers LARGE and subwoofer to ON ----> you'll get just the LFE channel coming out the analogue sub output

... so I'll also have LFE on the other analog outputs (with speakers set to large) of the DVD player?

 

[shokhead]

Yes, those settings dont effect the digital connection.

cheers

So for the analogs,the xover in the player is what it is,rather the speakers are set to small or large?

 

[MACCA350]

Thanks for the great explanations. But let me make sure I've got this right.
... so I'll also have LFE on the other analog outputs (with speakers set to large) of the DVD player?

On what other analogue outputs?

So for the analogs,the xover in the player is what it is,rather the speakers are set to small or large?

Not sure I understand you're question. Some Players don't allow you to change the Xover point(they are usually at a fixed Fq, normally at 80Hz) The SMALL/LARGE setting tells the unit what gets sent to the sub and what stays with its original channel.

cheers

 

[AverageJoe]

On what other analogue outputs?

On the front left and right analog outputs of the DVD player, for example. I guess I was wondering about this comment regarding routing LFE and bass to two subwoofers:

"No, you could have one with only LFE and the other with LFE + bass from other speakers(unless you use other equipment in the chain or use speaker level outputs to the second sub, but most subs with this ability can normally do this for just two channels)"

If I remove the DVD's analog Sub Out from the receiver and connect it to the subwoofer, and set the speakers to Large (in the DVD bass management), will I still get LFE signals to the receiver via the L/R analog cables? Or, does the LFE ONLY go the the subwoofer? Let's assume no digital audio connection to the receiver.

 

[MACCA350]

If I remove the DVD's analog Sub Out from the receiver and connect it to the subwoofer, and set the speakers to Large (in the DVD bass management), will I still get LFE signals to the receiver via the L/R analog cables? Or, does the LFE ONLY go the the subwoofer? Let's assume no digital audio connection to the receiver.

OK, If your player has only the 6 analogue outputs(some players have an additional L/R analogue output that is only used for downconverted analogue stereo) and you connect it the way you said. Then your the receiver will not get the LFE channel through the analogue inputs, but unless your receiver has bass management on analogue inputs(only a handful of receivers do) the sub output from the receiver will have no signal to output and any sub connected to it will be silent(when in analogue input mode)

But the subwoofer connected directly to the player will get ONLY LFE channel signal. In this case this would be the same if you route it through the receiver

cheers

 

[AverageJoe]

Gotcha, Thanks!

While planning connections for new dedicated theater build, I was hoping for an easy way to separate just the LFE from my current setup, and route it to a 2nd subwoofer. Thanks for the info.

 

[Tomorrow]

Just to confuse me a little more....

What happens with the recommended setup (DVD LFE out to sub and not receiver), receiver set to Sub ("yes") Out and connected to a sub...but instead of a 5.1 DD or DTS source, you play a stereo cd (as one example)? Does the DVD l/r analog signal to the receiver carry the same signal it will be outputting to the sub connected to it...and therefore will the sub connected to the receiver now be playing identical material? (Assume that the DVD and receiver crossovers are also similarly set.) Or will the sub connected to the DVD remain silent?

(You guys didn't tell me this hobby required detailed knowledge of astrophysics. )

 

[MACCA350]

Just to confuse me a little more....

What happens with the recommended setup (DVD LFE out to sub and not receiver), receiver set to Sub ("yes") Out and connected to a sub...but instead of a 5.1 DD or DTS source, you play a stereo cd (as one example)? Does the DVD l/r analog signal to the receiver carry the same signal it will be outputting to the sub connected to it...and therefore will the sub connected to the receiver now be playing identical material? (Assume that the DVD and receiver crossovers are also similarly set.) Or will the sub connected to the DVD remain silent?

(You guys didn't tell me this hobby required detailed knowledge of astrophysics. )

Firstly I'm not recommending this setup, but in the above scenario,

Does the DVD l/r analog signal to the receiver carry the same signal it will be outputting to the sub connected to it

The sub connected to the receiver will be silent because there is no analogue sub input signal to play, all the bass in this situation is in the L/R channels from the player. If you use the Digital connection then the receiver can do the bass management and depending on those settings only then will the sub connected to the receiver play the bass

Or will the sub connected to the DVD remain silent?

Yes the sub connected to the DVD player will remain silent because the player has speakers set to 'LARGE'

cheers

 

[Tomorrow]

The sub connected to the receiver will be silent because there is no analogue sub input signal to play, all the bass in this situation is in the L/R channels from the player.
cheers

I thought the sub connected to the receiver would get the redirected bass that was below the receiver xover setting. No?? When set to "both" does the receiver sub not get both LFE (not present in this case) AND all the bass signal below the xover...therefore not being silent?

 

[MACCA350]

I thought the sub connected to the receiver would get the redirected bass that was below the receiver xover setting. No?? When set to "both" does the receiver sub not get both LFE (not present in this case) AND all the bass signal below the xover...therefore not being silent?

Yes, but only when you use the digital input signal not the analogue input connections(unless your receiver does bass management on the analogue inputs, very few receivers can) The above scenario does not use the digital connection.

cheers

 

[shokhead]

I thought the sub connected to the receiver would get the redirected bass that was below the receiver xover setting. No?? When set to "both" does the receiver sub not get both LFE (not present in this case) AND all the bass signal below the xover...therefore not being silent?

When running the analogs,the receiver does nothing but volume. The player setup,small,large,distance,bm and all that is used. BTW,it might have 2 setups,multi-channal and dvd.

 

[Nick250]

When running the analogs,the receiver does nothing but volume.

The big picture reduced to a single, simple sentence. That fills in all the holes for me. Thanks.

Nick

 

[rynberg]

I honestly don't understand why people go out of their way to make things harder and more complex!

If you want to feed LFE to two subs, you run a y-connector and two cables out of the sub-out jack. This is NOT rocket science.

I run a universal player (SACD/DVD-A). I run both a digital audio connection and 6-channel analog to the receiver. The digital connection is used for DVD playback, the 6-channel analog for everything else. Do not bypass the receiver with the sub-out!

Furthermore, if you only have a CD/DVD player, there is no reason to run analog connections. Just run a single digital audio cable and let the receiver do the work!

 

[MACCA350]

I honestly don't understand why people go out of their way to make things harder and more complex!

If you want to feed LFE to two subs, you run a y-connector and two cables out of the sub-out jack. This is NOT rocket science.

I run a universal player (SACD/DVD-A). I run both a digital audio connection and 6-channel analog to the receiver. The digital connection is used for DVD playback, the 6-channel analog for everything else. Do not bypass the receiver with the sub-out!

Furthermore, if you only have a CD/DVD player, there is no reason to run analog connections. Just run a single digital audio cable and let the receiver do the work!

The reason this thread became complex is the OP(Averagejoe) wanted to know if by doing things differently he could have:

1 sub to play only the specific LFE channel and the,

2nd sub play the redirected bass from other channels and NONE of the specific LFE channel

This is why we went into detail about the different ways bass management works with receivers and dvd players

cheers

 

[rynberg]

The reason this thread became complex is the OP(Averagejoe) wanted to know if by doing things differently he could have:

1 sub to play only the specific LFE channel and the,

2nd sub play the redirected bass from other channels and NONE of the specific LFE channel

This is why we went into detail about the different ways bass management works with receivers and dvd players

cheers

Right, I just don't understand how people come up with these ideas. I can think of no benefit in doing this, that's all.

 

[AverageJoe]

I honestly don't understand why people go out of their way to make things harder and more complex!

If you want to feed LFE to two subs, you run a y-connector and two cables out of the sub-out jack. This is NOT rocket science.

I don't have too many problems with the incredibly obvious, only the obvious.

While not rocket science, I got very helpfull information from MACCA350 (thanks very much) about a specific question.

...and I also thank you for the review of the incredibly obvious