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[nwboater]

We have an Asus Essence St soundcard with it's analog outputs straight to the power amps in a 5.1 system.

My understanding is that in movies the LFE channel can contain content up to 120 Hz. My concern is how the LFE channel is directed. Does it only go to the sub? If so, and I have a Low Pass on the sub at say 60 Hz then I'm missing all LFE content between 60 & 120. Or with JRSS enabled does some of that LFE go to the mains?

Thanks,
Rod

[mojave]

If you don't know what you are missing . . . 

The LFE channel only goes to the sub. You are potentially missing the LFE or at least lowering its dB level by having a Low Pass on the sub. You can use Mix Channels to copy the LFE to a User channel, put a high pass on it, increase it by 10 dB, and add it to your mains.

The movie Red Cliff has info in the LFE channel up past 400 Hz.

[Matt]

I think it's best to disable any hardware cross-over on your subwoofer.  Or set it to something high like 200 Hz just as a safety valve.

[nwboater]

mojave & Matt,

Thanks for the info. My problem is that I have a Danley DTS-10 Tapped Horn sub. It will go up to about 120 HZ but from what I've read it's not that great above about 80.

How many subs that are good in the subsonic area are really good in those higher ranges?

You can use Mix Channels to copy the LFE to a User channel, put a high pass on it, increase it by 10 dB, and add it to your mains.

This sounds like a very good approach. I'll experiment with that.

The movie Red Cliff has info in the LFE channel up past 400 Hz.

That's darn near into the mid range!

I think it's best to disable any hardware cross-over on your subwoofer.  Or set it to something high like 200 Hz just as a safety valve.

Yes I will disable any low pass and try the approach Mojave suggested. I really think our Klipschorns will do a better job on anything above 80 or 100.

Thanks again to both of you for the suggestions.

Rod

[mojave]

I just read on the Genelec website that Dolby TrueHD and DTS-HD both have a spec for a full range LFE channel instead of the 120Hz cutoff. However, for DTS-HD it goes on to say, "In the DTS-HD codec only [DTS-HD Master Audio™ (lossless) and DTS-HD High Resolution Audio™ (lossy)] the DTS-HD decoder applies a low-pass filter at 100 Hz (-3 dB) with a 60 dB/octave roll-off onto the LFE channel. Red Cliff has a DTS-HD track so I wonder why I was showing so much up higher for the LFE channel. Maybe the software decoder from Arcsoft doesn't apply the low-pass filter.

There are a lot of low playing subs that will easily play up to 400 Hz. I've heard of a few playing up to 1000 Hz. Drivers with very low inductance (Le) will play higher.

[Matt]

Just to be clear, Media Center does not lowpass the LFE channel coming from a 5.1 / 7.1 source like a movie.  It also doesn't redirect high frequencies on the LFE to the other speakers (would that be called anti-bass management?).  I've never personally wanted or needed this, but if enough people think it's important, we could look into it.

Obviously when JRSS builds the subwoofer, the LFE channel is always low-passed based on the frequency you select in DSP Studio > Output Format.

[hulkss]

We have an Asus Essence St soundcard with it's analog outputs straight to the power amps in a 5.1 system.

The LFE channel power amp needs to have 10db more gain than the other channels.

http://yabb.jriver.com/interact/index.php?topic=70334.0

http://www.hometheaterhifi.com/technical-articles/163-the-misunderstood-01-lfe-channel-in-51-digital-surround-sound.html

[Matt]

The LFE channel power amp needs to have 10db more gain than the other channels.

I think nwboater has a properly calibrated system.

For anyone else, you should use the 'Level' checkboxes in DSP Studio > Room Correction and adjust the Volume Level sliders until all channels play at the same level as measured with a decibel meter.  After this, the subwoofer will be in the proper calibration (+10dB relative to other channels).

[hulkss]

The first article I referenced below points out that a wide band dB meter will typically read the LFE channel as +5.5 dB when a true measure with an RTA would show +10 dB in the lower frequency band. Also most inexpensive dB meters have C and A scale filters but do not offer "flat" frequency measurement.

[nwboater]

If you don't know what you are missing . . . 

I guess I didn't!  So I did this per your suggestion: "...use Mix Channels to copy the LFE to a User channel, put a high pass on it, increase it by 10 dB, and add it to your mains."

Played the first battle scene in Master and Commander at a very healthy volume and got some massive hits in the chest! Previously this kind of stuff would vibrate the concrete floor in our HT and I could really feel the super low stuff. But I've long wondered if I wasn't missing something in the upper bass. Well, I no longer wonder!

Have had very little time to do much more listening but I'm sure this will be a big improvement.

Thanks mojave!

Rod

[nwboater]

Just to be clear, Media Center does not lowpass the LFE channel coming from a 5.1 / 7.1 source like a movie.  It also doesn't redirect high frequencies on the LFE to the other speakers (would that be called anti-bass management?).  I've never personally wanted or needed this, but if enough people think it's important, we could look into it.

I believe I'm doing just that using mojave's technique in my post above. It would certainly be cleaner for setup if you had this as an option. I'm wondering how others deal with this issue. Do most send full range to their sub(s)?

Rod

[nwboater]

Obviously when JRSS builds the subwoofer, the LFE channel is always low-passed based on the frequency you select in DSP Studio > Output Format.

So for my application with movave's 'Mixing' I don't think I should use the Low Pass you mention. I believe I should use 'Silent ( use Room Correction to redirect bass)', or 'Send all frequencies to subwoofer'.  And I think the former is the correct choice. I do use MC for both movies and music listening in our 5.1 system.

Rod

[Matt]

So for my application with movave's 'Mixing' I don't think I should use the Low Pass you mention. I believe I should use 'Silent ( use Room Correction to redirect bass)', or 'Send all frequencies to subwoofer'.  And I think the former is the correct choice. I do use MC for both movies and music listening in our 5.1 system.

It's best to build the LFE channel using JRSS from 2.0 music (the default cross-over is around 60 Hz, which is a good choice if you have full range mains).

This gives you the cleanest subwoofer.  Bass redirection from Room Correction will get automatically disabled in this case so 'Move bass' will become 'Remove bass'.

In other words, the default settings will give you the best sound in my opinion.

[nwboater]

The LFE channel power amp needs to have 10db more gain than the other channels.

http://yabb.jriver.com/interact/index.php?topic=70334.0

http://www.hometheaterhifi.com/technical-articles/163-the-misunderstood-01-lfe-channel-in-51-digital-surround-sound.html

I think nwboater has a properly calibrated system.

For anyone else, you should use the 'Level' checkboxes in DSP Studio > Room Correction and adjust the Volume Level sliders until all channels play at the same level as measured with a decibel meter.  After this, the subwoofer will be in the proper calibration (+10dB relative to other channels).

I believe I have had a well calibrated system for music listening. I've used a calibrated mic with REW and have it fairly well dialed in for 2.1. But I haven't done much for video, especially 5.1.

Hulks thanks for pointing out the need for 10 db boost and the differences between a sound level meter and calibrated mic.

I have been following the difficulties with the 10 db boost for you folks using Audiolense. I'm not using it yet, so don't have that issue to deal with.

What I don't recall is if MC is now boosting the LFE (sub?) channel for the audio in video only, or for all audio? If it's the latter then there is a 10 db boost for music listening that shouldn't be there. In that case I guess our only option is to use Zones with a separate zone for Audio and Video.

Rod

[Matt]

What I don't recall is if MC is now boosting the LFE (sub?) channel for the audio in video only, or for all audio? If it's the latter then there is a 10 db boost for music listening that shouldn't be there. In that case I guess our only option is to use Zones with a separate zone for Audio and Video.

Configure the levels with Room Correction like I described above and levels will be correct for all media.  There's no difference between audio and video.

[nwboater]

Configure the levels with Room Correction like I described above and levels will be correct for all media.  There's no difference between audio and video.

? Now I'm really confused! As Hulkss pointed out there is a 10 db boost required on the LFE channel for movies. Are you doing that in MC? He suggested doing it on the subwoofer power amp.

But for music listening I don't believe that boost should be there. A house curve perhaps, but not just an intentional 10 db boost on the sub channel.

Rod

[Matt]

When a movie has an LFE channel, it knows the LFE will be +10 dB.

When Media Center builds an LFE channel, it knows the LFE will be +10 dB.

See how they're the same?

So to make sure your LFE really is +10 dB (not +8 dB, or 0 dB, or -20 dB, or whatever), you use the volume calibration method I described above.  

Everything in Media Center understands that the LFE channel is at a different level, so it's not something you as a user ever need to worry about (other than setting levels one time).  You can set levels using DSP Studio > Room Correction, or by adjusting a physical volume on your subwoofer, or any combination of the two.

Does that make sense?

[mojave]

Played the first battle scene in Master and Commander at a very healthy volume and got some massive hits in the chest! Previously this kind of stuff would vibrate the concrete floor in our HT and I could really feel the super low stuff. But I've long wondered if I wasn't missing something in the upper bass. Well, I no longer wonder!

Have had very little time to do much more listening but I'm sure this will be a big improvement.

I'm glad you got it working and noticed an improvement. I did some checking yesterday and as far as I know no receiver will ever route the LFE back to the mains using a crossover. You can copy the entire LFE to mains, but not certain frequencies.

Bass redirection from Room Correction will get automatically disabled in this case so 'Move bass' will become 'Remove bass'.

I must have missed the memo on this or forgot about it. I'll have to try setting the crossover in JRSS again.

I found the change:

16.0.83 (5/6/2011)
2. Changed: In cases where the subwoofer channel is created using JRSS Subwoofer, bass redirection 'Move bass to subwoofer' will be treated like 'Remove bass'.

[nwboater]

When a movie has an LFE channel, it knows the LFE will be +10 dB.

When Media Center builds an LFE channel, it knows the LFE will be +10 dB.

See how they're the same?

So to make sure your LFE really is +10 dB (not +8 dB, or 0 dB, or -20 dB, or whatever), you use the volume calibration method I described above. 

Everything in Media Center understands that the LFE channel is at a different level, so it's not something you as a user ever need to worry about (other than setting levels one time).  You can set levels using DSP Studio > Room Correction, or by adjusting a physical volume on your subwoofer, or any combination of the two.

Does that make sense?

I think some of the confusion, at least for me is the often used interchangeability of LFE and subwoofer.

If I understand things correctly from Matt:

1. A movie that is 5.1 encoded has an LFE channel that is 10 db down in volume.
2. MC does the following if the system has been calibrated per Matt's procedure in post #7 above:
     A. For a 5.1 encoded movie MC will add 10 db to the Subwoofer channel.
     B. For a 2.0 movie MC will have JRSS build an LFE channel that will be routed to the subwoofer. It will have
        10 DB boost applied by MC.
     C. For 2.0 Music JRSS will convert it to 5.1 and the Subwoofer channel will have no boost.
     D. For 5.1 encoded music there will be no boost applied to the subwoofer channel.


So Matt what you say makes sense. My difficulty is I have read in several places that a 10 db boost needs to be applied to the LFE channel besides anything MC does. mojave mentioned it in his suggestion to add 10 db in the 'mixing procedure' and hulkss mentioned that the subwoofer power amp needs a 10 db boost. I'm sure not trying to start a war here, just need to fully understand this.

I would really appreciate it if anybody disagrees with anything I have in my outline above that they would clarify it.

Thanks everybody for your input.

Rod

[mojave]

Rod, you are wrong on a few points. Here is a revision.

1. Any music or movie that is 5.1/7.1 encoded has an LFE channel that is -10 db relative to the other channels. This applies to DVD, Blu-ray, DTS-Audio, SACD, iTrax, etc.

2. MC does the following if the system has been calibrated per Matt's procedure in post #7 above:
     A. For a 5.1 encoded movie MC does nothing to the LFE channel. The user adds 10 dB at the subwoofer amp. The calibration tones will all be the same regardless of when you use JRiver's calibration, a calibration DVD, or a calibration Blu-ray. The user usually doesn't even know the LFE was originally down 10 dB. If the user doesn't have enough subwoofer amp gain, he may need to add some in JRiver.
     B. For a 2.0 movie MC will have JRSS build an LFE channel that will be routed to the subwoofer. It will also be -10 dB.
     C. For 2.0 Music JRSS will convert it to 5.1 and the Subwoofer channel will be at -10 dB relative to the other channels.
     D. For 5.1 encoded music the subwoofer channel is also encoded at -10 dB and will work fine. The only exceptions have been found on a few SACD's or DVD-Audio's which probably aren't being played back in JRiver anyway. If they are, the user can just add the 10 dB by using a separate zone and call the zone "LFE Channel Isn't Mastered Correctly". 

[nwboater]

Rod, you are wrong on a few points. Here is a revision.

1. Any music or movie that is 5.1/7.1 encoded has an LFE channel that is -10 db relative to the other channels. This applies to DVD, Blu-ray, DTS-Audio, SACD, iTrax, etc.

2. MC does the following if the system has been calibrated per Matt's procedure in post #7 above:
     A. For a 5.1 encoded movie MC does nothing to the LFE channel. The user adds 10 dB at the subwoofer amp. The calibration tones will all be the same regardless of when you use JRiver's calibration, a calibration DVD, or a calibration Blu-ray. The user usually doesn't even know the LFE was originally down 10 dB. If the user doesn't have enough subwoofer amp gain, he may need to add some in JRiver.
     B. For a 2.0 movie MC will have JRSS build an LFE channel that will be routed to the subwoofer. It will also be -10 dB.
     C. For 2.0 Music JRSS will convert it to 5.1 and the Subwoofer channel will be at -10 dB relative to the other channels.
     D. For 5.1 encoded music the subwoofer channel is also encoded at -10 dB and will work fine. The only exceptions have been found on a few SACD's or DVD-Audio's which probably aren't being played back in JRiver anyway. If they are, the user can just add the 10 dB by using a separate zone and call the zone "LFE Channel Isn't Mastered Correctly". 

Thanks a lot for taking the time to make a corrected version.

I had based my chart on what I understood of Matt's calibration procedure in post # 7. I read it to say that I don't need to add any gain externally to the sub amp; that it would all be handled by MC. Matt, did I misunderstand you?

In any event it's really good to know that things will be consistent for all types of media, with the tiny exception of the few that mojave mentioned.

Thanks,
Rod

[Matt]

So Matt what you say makes sense. My difficulty is I have read in several places that a 10 db boost needs to be applied to the LFE channel besides anything MC does. mojave mentioned it in his suggestion to add 10 db in the 'mixing procedure' and hulkss mentioned that the subwoofer power amp needs a 10 db boost. I'm sure not trying to start a war here, just need to fully understand this.

This topic is tricky (for me too) for several reasons: subwoofer vs LFE, is it -10dB or +10dB (it depends how you look at it), the wide variety of configurations, etc.

However, for a normal configuration with no convolution, you can get great results easily.  You don't need to think about the +10dB shift for the LFE at all.  You do need some sort of dB meter, but even a phone will get you pretty close.

Here are the instructions:
http://wiki.jriver.com/index.php/Audio_Setup#Room_Correction

If you have a volume control on your subwoofer, you can use it interchangeably with the volume level slider for the subwoofer in Room Correction.  It's probably better to turn the hardware volume up before you turn the software volume up, but it's not a big deal either way.

[mojave]

So Matt what you say makes sense. My difficulty is I have read in several places that a 10 db boost needs to be applied to the LFE channel besides anything MC does. mojave mentioned it in his suggestion to add 10 db in the 'mixing procedure' and hulkss mentioned that the subwoofer power amp needs a 10 db boost. I'm sure not trying to start a war here, just need to fully understand this.

I forgot to address this in my last post. Because the LFE channel is -10 dB relative to the other channels, anytime you mix to or from the LFE channel you need to change levels. When you move info from the LFE to the mains, it needs to be increased by 10 dB since you are combining it into one signal. When bass management moves info from other speakers to the LFE channel, it is attenuated and then added to the LFE content. The remixed LFE channel is still -10 dB and then needs an external boost with the subwoofer amp. This preserves maximum headroom.

[mojave]

You do need some sort of dB meter, but even a phone will get you pretty close.

I just bought some smoke detectors and noticed that the warning beep is 3200 Hz and is 85 dB at 10 ft. I've thought about doing an April Fool's post at AVS about how to calibrate your microphone and Room Equalization Wizard to the correct SPL by using a smoke detector. 

[JimH]

Didn't some guys at the Omaha fire department discover that?

[nwboater]

This topic is tricky (for me too) for several reasons: subwoofer vs LFE, is it -10dB or +10dB (it depends how you look at it), the wide variety of configurations, etc.

However, for a normal configuration with no convolution, you can get great results easily.  You don't need to think about the +10dB shift for the LFE at all.  You do need some sort of dB meter, but even a phone will get you pretty close.

Here are the instructions:
http://wiki.jriver.com/index.php/Audio_Setup#Room_Correction

If you have a volume control on your subwoofer, you can use it interchangeably with the volume level slider for the subwoofer in Room Correction.  It's probably better to turn the hardware volume up before you turn the software volume up, but it's not a big deal either way.

Okay maybe there really is no conflict in what everybody is saying - just my interpretations.

I am now thinking that what Matt is saying with his calibration procedure is that when it is done that it actually forces the subwoofer amp to add the required 10db.

Is that correct? If so guess I really have been "Thinking" about this too much!

Rod

[Matt]

I am now thinking that what Matt is saying with his calibration procedure is that when it is done that it actually forces the subwoofer amp to add the required 10db.

It forces things to be in calibration.

It doesn't matter if the software is adding gain or the hardware is adding gain.  If you turn up the hardware, you'll turn down the software.  And vice versa.

For example, I don't have a subwoofer amp -- my subwoofer is connected just like all my other speakers to the same amp.  So I use Room Correction to add a huge gain to my subwoofer until it's in calibration.  Internally the program does a lot of smart things to maintain the best output levels possible in this case, but that's not really something you need to understand to enjoy the results.

[nwboater]

It forces things to be in calibration.

Thanks Matt.

Guess everybody is basically saying the same thing and the differences are pobably in the calibration procedures they use to end up at the same point.

Bottom line to me is that the subwoofer channel is down 10 db and that needs to be made up for somehow. Can be done by using Matt's procedure, or some other method to add the 10 db.

Thanks everybody for your patience in getting this clarified.

Rod

[hulkss]

I forgot to address this in my last post. Because the LFE channel is -10 dB relative to the other channels, anytime you mix to or from the LFE channel you need to change levels. When you move info from the LFE to the mains, it needs to be increased by 10 dB since you are combining it into one signal. When bass management moves info from other speakers to the LFE channel, it is attenuated and then added to the LFE content. The remixed LFE channel is still -10 dB and then needs an external boost with the subwoofer amp. This preserves maximum headroom.

Perfectly said.