CurtPalme.com Home Theater Forum

[mr_ro_co]

Hey guys,

Anyone here taking that single LFE channel from the audio processor and mixing it back in with the LCR channels so that LFE content, which I understand is unique from bass content in full range LCR channels with processor set to "large" speakers, gets heard through those LCR speakers?

Thanks guys,

Steve

[Nashou66]

Read the manual of your processor to see if it will send the LFE when menu is set to large.

Some will send all DD content to the mains this way, others do not. If it does you do not need to hook up
the LFE line level out.

Nashou

[ecrabb]

Nashou, I'm not aware of any processor that will send the LFE signal to the mains just because they're set to "large". Setting the mains to "large" in most DD/DTS processors usually just means the mains aren't crossed over and mixed with the LFE; the opposite doesn't usually automatically happen, though.

I don't think a lot of decoders will put the LFE mix back into the mains, but those that will would do so only when the mains were set to large AND Subwoofer was set to "NO", which would of course turn off the .1 line output. I think most receivers and processors would require you mix the LFE channel back in outboard of the processor, save for something crazy high-end with über control like a Datasat or something.

Here's the deal… Unless somebody has huge mains, they definitely wouldn't want to do this. Since the LFE channel often has sub-sonic energy in it, you'd need very large mains that are at least 20 or 25hz-capaple. Even with large mains, with that kind of signal getting mixed in, you'd better have some nice amplification with some serious headroom driving the mains too, as the LFE channel should go to 115dB reference vs. the mains 105dB played clean at reference.

Not being snarky, but why would somebody want to mix the LFE signal back into the mains?

Interesting.

SC

[Nashou66]

DD steve has the full range on all channel, at least it is suppose to. Some of the better Pre/Pros will send Full DD to all channels.

This way if you wanted you could add a Sub at each channel or use Full range speakers that have built in subs all the way around.

I read this on the Dolby site. Now this was a few years ago and not sure if if they changed their requirements for true DD.

And that is the reason you'd want the LFE at the mains or all channels to add subs at each channel.

I was thinking of doing this with the SVS PB1000's at 5 locations!

Nashou

[jeffslife]

Nash, you are a lunatic !

[ecrabb]

[Nashou66]

Steve read this, in some ways your correct but when it comes down to how DD was designed what I said is correct.


http://www.hometheaterhifi.com/volume_7_2/feature-article-misunderstood-lfe-channel-april-2000.html


The LFE info is copied from all channels or just the screen channels and also sent to the Sub or "boom" channel. But the LFE is still there on the screen channels if encoded that way. And some have it on all channels like Saving Private Ryan.

Some equipment will allow you to do this others will not have the full range. My Adcom send all info to all channels.


Here is an excerpt fom the article

So, on some soundtracks, sending only the LFE to your subwoofer could leave it with nothing to do while your mains struggle. While some people like to feed a full range signal to their main speakers, they should in addition send those channels’ bass to the sub so it can fill in the extreme bottom octave information that might be in those tracks. Mains which can reach as low as a dedicated subwoofer are few. Unfortunately this flexibility is not always available on consumer equipment; setting a main speaker to ‘large’ often excludes the subwoofer from getting a share of that signal.

On the flip side, you don’t need a subwoofer to hear the content of the LFE track. If your mains are of substantial mettle, and you don’t have a sub, bass management can usually re-route the LFE to your fronts.

Therefore, the subwoofer jack can contain only LFE (not recommended), a mixture of LFE and bass from the main 5 channels, or nothing at all.


Nashou

[mr_ro_co]

Nashou, Steve,

Thanks so much for the discussion and investigation on this!

Like Steve, I have always assumed that the content going to the LFE was unique (by design for consumer/residential surround sound decoding) so that it could be directed to a dedicated subwoofer to handle the sometimes very energetic, very low frequency information that channel contains. As he pointed out, this frees up the mains from doing that work and relaxes their amplifier requirement, not to mention size and expense implications for those speakers.

As Nashou explained, the original design intent of DD does not restrict LFE to just that dedicated channel, but this depends on how the surround sound for a particular film was encoded for home theater surround sound. Thus, for LFE content on the mains (or even surrounds as in Saving Private Ryan), this would vary by film and decoding standard/version being processed, and ensuring all LFE is produced by the mains only depends on the abilities and settings of the processor's bass management.

I did find interesting the recommendation that some users might be missing very low bass information on bandwidth restricted LCRs that if anything should be directed to the LFE subwoofer too.

I am using the processor in my OPPO BDP-93 player for surround decoding. It may be able to re-route LFE content to the mains by setting LCR to "large" and SUB to "no." I guess I should RTFM to answer this question, or reach out to OPPO's engineering support if the manual doesn't clear it up.

As to why I am interested in doing this: My LCRs will soon have high output infrasonic bass ability that exceeds most home theater subwoofers that are usually dedicated to LFE. My system will not have a dedicated subwoofer. Having the mains do all the bass including LFE will likely produce better (flatter) in-room power response as well, with LFE being produced in planewave, much like a real theater.

To absolutely ensure that I get the LFE in through the LCRs, I could set LCRs in the processor to large, leave the sub/LFE channel on and then send that LFE channel and the LCR channels to line level summing amps/buffers upstream of the LCR amplification. This could easily be done with a simple op-amp circuit or an off-the-shelf pro mixer. I'm curious if anyone has ever done this. This approach would ensure regardless of mix, the LFE would always be reproduced by the LCRs.

Steve

[ecrabb]

[mr_ro_co]