Fixing Aqualung's Quad Mix: The Back Left Channel's Incorrect Polarity; Sometimes Laughably Out of Phase LFE; Swapped Back Channels of "Hymn 43"

[ssully]

Really easy.

you wrote:
"After Aqualung on Blu-ray, thought was given to releasing Aqualung Adapted in 4.0, but with pulling the tape again (and the cost), the decent Mew transfer was left at 4.1."

OK. It was too expensive to pull the 4.0 master again and re-do as a 4.0 digital version*.

you wrote:
"The approach on the Adapted Edition was to release the original master stereo with minimal adjustment. This is how all other quad was released. Give the fans the sound with minimal correction and in 4.0."

What does the refer to here? And why the mention of stereo?

Did you mean, "Adapted Editions were intended to include the original master quad (and stereo) recording with minimal adjustments. But the quad in the Aqualung Adapted Edition did not adhere to that approach."?



*Though come to think of it now, I'd assume there was a digital archive version of the transfer....i.e. a digital 'flat transfer' of the quad tape ...and that Mew copied it and made that copy into his 4.1 version. It would be very bad practice to not archive the flat digital transfer. With an digital flat master, there is no need to pull the tape again to make a revised version.

 

[ssully]

This is why I asked about removing/muting the LFE channel. I really appreciate DE's findings and recommendations, but they're a little complicated for this dummy, and if there is a simpler way to solve the LFE problem, I'd love to hear it.

Definitely easier if the LFE can simply be deleted without consequences, i.e., it simply 'doubles' what's in other channels.

But there's still the surround left channel needing to be inverted. It's out of phase with the surround right and the front channels.

 

[JohnN]

you wrote:
"After Aqualung on Blu-ray, thought was given to releasing Aqualung Adapted in 4.0, but with pulling the tape again (and the cost), the decent Mew transfer was left at 4.1."

OK. It was too expensive to pull the 4.0 master again and re-do as a 4.0 digital version*.

you wrote:
"The approach on the Adapted Edition was to release the original master stereo with minimal adjustment. This is how all other quad was released. Give the fans the sound with minimal correction and in 4.0."

What does the refer to here? And why the mention of stereo?

Did you mean, "Adapted Editions were intended to include the original master quad (and stereo) recording with minimal adjustments. But the quad in the Aqualung Adapted Edition did not adhere to that approach."?



*Though come to think of it now, I'd assume there was a digital archive version of the transfer....i.e. a digital 'flat transfer' of the quad tape ...and that Mew copied it and made that copy into his 4.1 version. It would be very bad practice to not archive the flat digital transfer.

Simply Adapted: I asked for the quad in 4.0. I mentioned the stereo because they were able to use the master to correct that with minimal EQ. Same with the future quad, minimal was done.

Usually confused ha ha.

 

[ssully]

You offset the original LFE, not the low-passed LFE, right?

Yes. The low passing was only used to determine the distance between corresponding waveforms. Then the filter was removed, and the LFE shifted. In the result a 'macro' OOP is quite visible between LFE and fronts (see where the boundaries of the 'selected' area fall in the attached image) . What LFE shift did you use for Cross Eyed Mary?

 

[paligap]

Thanks to Dynamic Editor for pointing this out and providing fixes. This is quite coincidental for me because I only recently got around to ripping all my JT discs, and I've been playing them while working (not listening critically or even actively).

 

[Dynamic Editor]

Yes. The low passing was only used to determine the distance between equivalent waveforms. Then the filter was removed, and the LFE shifted. In the result a 'macro' OOP is quite visible between LFE and fronts (see where the boundaries of the 'selected' area fall in the attached image) . What LFE shift did you use for Cross Eyed Mary?

It's at the bottom of the first post for all the tracks, but to actually answer your question, for the 96kHz blu ray, I moved the LFE 267,088 samples to the right and inverted its polarity (2 sec and 75,088 samples).

 

[ssully]

My LFE shift equates to +267,264 samples (if I use +2.784 sec) or, if I use +2.763 sec, which looks a tiny bit more accurate, that's +267,168 samples, about ~100 samples more than yours . I don't use a correlation meter so there's bound to be difference. But that difference isn't enough to change the 'macro' OOP. It's still there if I use your LFE offset value instead of mine. (~100 samples is a miniscule amount)

 

[AYanguas]

LFE is unnecessary in virtually all music releases. It was created for movie special effects like explosions and earthquakes. Yet they keep adding it.

Some say that LFE for mch music is added for those people that doesn't know how to properly setup bass management, and/or have very simple speakers and the SUB in their home theater.
So that they dont listen to multichannel with a very weak sound.

I wonder if those people don't know how to appreciate good sound quality in music either, and therefore it doesn't matter either.

 

[Malhomme]

Well, we have to account for the fact some systems are built with a 'necessary' LF speaker. My KEF system has a great sounding satellites, but their bass extension isn't adaptated to work without a LF speaker.

 

[ssully]

Well, we have to account for the fact some systems are built with a 'necessary' LF speaker. My KEF system has a great sounding satellites, but their bass extension isn't adaptated to work without a LF speaker.

An 'LF speaker' is indeed necessary for any system that doesn't feature full range speakers. But that doesn't mean that music releases need an LFE channel in their mix.

Your KEF system expects you to use bass management (I would guess it uses it by default). Your LF speaker is for the bass-managed, low frequency content extracted from the main channels. In a rational world, that's all music releases would need. But instead we get music releases that also have an LFE track. Its content goes to your LF speaker too.

 

[Wagonmaster_91]

I think it also has to do with the (deliberate) blurring by electronics manufactures of the definition of a "subwoofer" vs. a "woofer". When the concept of a system having a subwoofer became popular, that speaker was designed to only carry very low frequency information - 10 - 60hz. (Frequencies you 'feel' more than 'hear'.) The woofer was for information in the 50hz up to where the mid-range driver takes over.

When speaker manufactures started pushing satellite systems they began referring to the woofer incorrectly as a "subwoofer". (Sounds more 'hi-tech'.) Next were speaker systems for computers. (Really? A three inch speaker can be a subwoofer? ummm..no.) Then center channels and soundbars started calling their woofers "subs". Putting a woofer in a separate box that sits on the floor doesn't make it a sub. The frequencies that speaker produces determines whether it is a woofer or a subwoofer. This is the same difference between a "tweeter" and a "super-tweeter".

In multi-channel music, the LFE channel should be used for "effect" (hence Low Frequency Effect). The "punch" of a bass drum, not the tuning of the head. The attack of a bass guitar pluck, not the full tone of the note. The other elements of those sounds are the job of the system's woofers.
When properly setup, unless you know a song very well, you should not really be able to tell what the song playing is if you only listen to the subwoofer.

 

[ssully]

In multi-channel music, the LFE channel should be used for "effect" (hence Low Frequency Effect). The "punch" of a bass drum, not the tuning of the head. The attack of a bass guitar pluck, not the full tone of the note. The other elements of those sounds are the job of the system's woofers.
When properly setup, unless you know a song very well, you should not really be able to tell what the song playing is if you only listen to the subwoofer.

Largely agreed but the attack of a kick drum and certainly the pluck of a plectrum don't require an LFE, or even necessarily a subwoofer.

The LFE was invented because magnetic film soundtrack content < 40Hz wasn't well handled by existing speaker setups So a pair of subwoofers were addeed that for the contents of an added LFE channel . More headroom for very low , loud bass. the 'effects' aren't kick drums. They are explosions, crashes, cannon fire.

A kick drum goes down to maybe 50Hz. 'Tower' speakers exist that can go down there, and room boundary reinforcement can help. But loud low bass does require lots of power, and for that a subwoofer (though again, not necessarily an LFE) offloads the work.

 

[Wagonmaster_91]

I agree with what you are saying about the purpose of the LFE in regard to movies - explosions, thunder, etc. I was speaking only in terms of music reproduction. The LFE is most effective to enhance or compliment bass reproduction rather than handle to whole low frequency spectrum.
You can achieve the similar results with an outboard electric crossover that routes the sub frequencies to the sub amp/speaker without having a dedicated LFE channel.

 

[ssully]

I agree with what you are saying about the purpose of the LFE in regard to movies - explosions, thunder, etc. I was speaking only in terms of music reproduction. The LFE is most effective to enhance or compliment bass reproduction rather than handle to whole low frequency spectrum.
You can achieve the similar results with an outboard electric crossover that routes the sub frequencies to the sub amp/speaker without having a dedicated LFE channel.

well, yes, that's called bass management, which has been the norm in AVRs for about two decades, and is all music really needs.

Not for nothing, cinema DTS was 5.0, employing bass management only, no LFE. All the cinema subwoofer content was derived from lowpassed signal of the main channels (which themselves output highpassed signal).

(And cinema Dolby actually used an LFE plus bass management, but did not high pass the main speakers. Not recommended at home.)

 

[TVB]

It seems to me that any woofer that can reproduce 10-60 frequencies properly should work just fine because the LFE signal should only be sending out low 10-60 tones. The content of the LFE channel disappoints me on a regular basis.

 

[ssully]

The existence of LFE on music releases that don't contain gunshots, cannon fire, or volcanic eruptions, disappoints me on a regular basis.

Those high level low bass cinematic events are what LFE is for...not bass guitars or kick drums.

LFE bandwidth is 120 Hz, as per Dolby spec, though not all mixes use that much. (Some mixes actually have a full frequency range signal in LFE...uselessly)

 

[AYanguas]

The argument that I have found in this post:
https://gearspace.com/board/mastering-forum/372693-surround-mixing-lfe-channel-signal.html

seems to explain well the reason why some (or the majority of) music producers use the LFE channel:

"""""""""""
Use only for special extra effects, like in the movies.

If you don't use it for that, then you may need to come up with a little something just so the client sees the channel in use. I know this seems silly, but in trying to leave it blank, even on jazz projects with the artist in agreement, the label has come back and said, "we're selling 6 channels of audio, there has to be something there." To avoid this, but also avoid the problems above, the best compromise is to filter it very, very low, and not put too much in, nor from too many sources. That way, the meters move on the channel, the client can't accuse you of jipping them of one of the channels, and the interaction with the bass management should be minimal.
"""""""""""

 

[TVB]

How great would it be if surround disc's producer's would start putting 30-60 hz frequencies into the lfe output of a disc that would the augment the bass tones of a music album. We would be feeling the bass instead of just hearing it. My lfe goes straight from my oppo to the amp and sub so there is no electronics interference (like bass management) getting in the way.

 

[ssully]

The argument that I have found in this post:
https://gearspace.com/board/mastering-forum/372693-surround-mixing-lfe-channel-signal.html

seems to explain well the reason why some (or the majority of) music producers use the LFE channel:

"""""""""""
Use only for special extra effects, like in the movies.

If you don't use it for that, then you may need to come up with a little something just so the client sees the channel in use. I know this seems silly, but in trying to leave it blank, even on jazz projects with the artist in agreement, the label has come back and said, "we're selling 6 channels of audio, there has to be something there." To avoid this, but also avoid the problems above, the best compromise is to filter it very, very low, and not put too much in, nor from too many sources. That way, the meters move on the channel, the client can't accuse you of jipping them of one of the channels, and the interaction with the bass management should be minimal.
"""""""""""

well, yes, s mentioned previously on this thread, it's basically 'fan service' for subwoofer owners. The thing is, the only people who would notice the absence of "channel use" are the ones who have full range speakers all around and use their sub ONLY for LFE. A rare breed,

 

[ssully]

How great would it be if surround disc's producer's would start putting 30-60 hz frequencies into the lfe output of a disc that would the augment the bass tones of a music album. We would be feeling the bass instead of just hearing it. My lfe goes straight from my oppo to the amp and sub so there is no electronics interference (like bass management) getting in the way.

The 'electronic interference' you abhor actually helps your amp and speakers deliver power with less effort.

There is no reason whatsoever to create LFE channel content, which again was intended for LOUD, LOW bass events, for most music releases. Most music simply doesn't contain such content.