- Jan 1, 2010
- Washington, D.C.
Believe it or not, I am thinking of buying one. Thanks for the warning.Buy a telescope It suffers from the same flaw (worse, in fact) and for the same reason. They're complex instruments, each owner configures theirs a bit differently, and there isn't enough economy of scale to foot the bill for software that "just works."
@steelydave, you are the only one in this whole thread who's brought up that it's the playback system's job to send the appropriate low frequency material to the subwoofers.Like I said, if you have a full range setup with no bass management going on, maybe not. But if you're like me, and your speakers are all set to 'small,' so that the low frequency content from those speakers is being sent to the subwoofer, there's absolutely an audible effect on the quality and extension of bass frequencies as a result of (as @jimfisheye astutely pointed out) a comb filtering effect caused by the delay.
Nope, its why I don't have a LFE sub as its an effect channel, for it to work properly you should be feeling its effect! I'm not that much of a fan of the Centre either, as its really there to centre the speech in the middle of the screen in cinemas as people are sitting across a wide area. Atmos came about for the same reason but to help with surround effects placement. However, without 5.1 appearing we probably wouldn't have had music mixed into surround, and Atmos is allowing us to get new mixes, so its the rough with the smooth, but either way I'm just happy to get music in surround.@steelydave, you are the only one in this whole thread who's brought up that it's the playback system's job to send the appropriate low frequency material to the subwoofers.
It's called a "Low Frequency Effect" channel, not a "Subwoofer" channel. In their wisdom, the creators of 5.1 sound knew that it needs to be the responsibility of the playback receiver to crossover music material to the subwoofer. People who mix music and movies don't know what kind of subwoofer / satellite speakers you have, and what the crossover points are. Your receiver knows. To arbitrarily have some frequency range of music in the LFE channel is just complete folly, but somehow only a few 5.1 sound mixers seem to understand this.
With the possible exception of the canons in the "1812 Overture", no one should be mixing 5.1 music with any material in the LFE channel.
It kind of looks like most of these mixes are sending the musical low frequencies to the LFE channel, but not applying a similar hi-pass filter to the rest of the channels. This means it might be appropriate to mute the LFE material, let your receiver decide what to send to the subwoofer, and boost the subwoofer volume to compensate for the junky LFE data that we blocked.
Am I crazy?
OMG! Do we have a line on Mr. Wilson here? He's my god for his Yes mixes! I would love for him to comment on why he has music program material in the effects channel in the first place. I just looked at his Blu-ray of "The Yes Album", and there's material there in the LFE channel. It looks like it's crossed over at about 200 Hz (and yes, it's about 15-18 mS delayed).I'm still working on the B's, just got to Blackfield IV (5.1 mix by Steven Wilson).
Yup, 10ms LFE delay. Maybe someone could ask him?
Interestingly when I mentioned this delay issue to my kid who does sound design, their response was, are they sure it's not just the phase shift of the filter?[ now playing: Jethro Tull, "Wond'ring Aloud ]
OK - just what the hell is going on here, anyway?
This delay has now been demonstrated in so many titles, I've started wondering if there aren't just some natural phenomena at work here, as DuncanS humbly submitted waaay back up the road in this thread.
As we know, the LFE channel, among other treatments, is (ostensibly) a low-pass filtered extract from the main program. I understand for the most part the way filters work, and the phase shift they produce. But something with which I still struggle is the concept of group delay. I've read all the technical explanations of what it is, and they seem to make sense enough, but I'm just not able to grok the overall effect for some reason. But Duncan's reminder has stuck with me throughout my reading of this developing saga, and has made me curiouser and curiouser. So I decided to make an LFE channel of my own, from scratch, to see the exact changes that occur to the timing of the waveform.
I wanted something with a nice big convenient bassy transient right at the start, so of course I went straight to "Morph the Cat." Starting with the stereo CD mix of course, I loaded it into Cool Edit. First step was to do a mono mix, so I'd be starting with 2 identical, time-aligned waveforms to play around with. After a quick zoom-in to verify this, I then ran an 80 Hz, 4-pole Butterworth filter (a typical LFE treatment, I should think) on the left channel only, to do a direct comparison. Here's what came out:
View attachment 64154
The full-range version is on top, the filtered version of that same waveform below. I've used the selection tool to measure the delay; it starts at a waveform peak on the full-range, and ends with the corresponding peak on the low-pass filtered version. Way down in the lower-right corner I've circled the length of the selection (delay), which is 6 milliseconds.
To satisfy my own curiosity I did another round, this time moving the cutoff to 120 Hz just to observe any changes. Here's that output:
View attachment 64155
This delay came in at 4 mS.
The 2 conclusions I'm drawing from this experiment are:
1. Allowing for rounding errors caused by the 1 mS resolution of the Cool Edit timeline, these figures line up just fine with Duncan's formula above.
2. These delays are in the general area of those being discovered by so many here, and I believe they account in large part for what we're seeing. We all know that the processing of the LFE channel can vary widely from one title to the next, from the ridiculous full-range examples to any number of unspecified LP filter treatments. There's certainly no standard being adhered to with this stuff. In my estimation, this would account for a lot of the variation in delay times being measured.
So for me, the question now becomes: Why do some titles NOT show this delay?? Perhaps they were processed in the digital domain, using FIR filters (which can be configured for no phase shift or group delay) as opposed to the more conventional IIR types, which are basically digital versions of classic analog filters, with all the attendant phase behavior? That's my guess at this point.
Any other thoughts or ideas gratefully received.
Finally - Thanks DUNCAN!
I really find it interesting that so many people are going back and adjusting all these LFE channels. I'm not belittling the idea as I love making changes to surround mixes that don't sound right, but I just don't see the point in adjusting a wave diagram to "look correct" if the music/mix sounds fantastic already. For example, Beck "Sea Change" sounds amazing and has always been highly regarded by most surround enthusiasts (and myself), so what do I care if the LFE is off by a few milliseconds? For me, listening to the music is what's most important as opposed to looking at it. On the other hand, I'm sure many people here have better or more trained hearing than me, or their bass management is set up differently, so maybe making this small change yields audible rewards, and in those cases the extra work would be justified. It's very interesting the change in outlook that's occurred around QQ the last few years as more people have shifted to ripping music and looking at the wave forms. In the end, we audiophiles all seem to have a bit of OCD, so I can understand how knowing that something is off by a few milliseconds, audible or not, could decrease one's enjoyment of the music. Personally, though, a mix has to sound wrong in some way before I'll bother putting any work in.
Ugh. I dislike the use of that term in other contexts, and I'm surprised to see it used here. I guess I don't understand why this issue needs to be divisive. Those who don't care about it simply have to ignore this thread, and those who are interested in it can continue to look into it.+1,000 and coming from YOU means a lot to many of us here who have enjoyed your "renditions" of our favorite titles...one man's improvement is another man's OCD...I think you are spot on about the shift on the forum the last few years...more "experts" have surfaced...it used to bother me when new surround titles surfaced and the "honeymoon" of enjoying these treasures only lasted a day or so...but I've conditioned myself to ignore all the negativity...I just let the "experts" battle it out for attention of the masses...
Thanks for speaking up for the silent majority on here
Ugh. I dislike the use of that term in other contexts, and I'm surprised to see it used here. I guess I don't understand why this issue needs to be divisive. Those who don't care about it simply have to ignore this thread, and those who are interested in it can continue to look into it.