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Analyzing Waveforms of Heavy Hitting Movies


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#41 MemX

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Posted 14 October 2015 - 10:22 PM

Can't see the pics on the work computer, grrr, but looking forward to tests with the movie content!


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#42 Ricci

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Posted 22 October 2015 - 01:54 PM

Hey Shred.

Personally I'd like to see the amp manufacturers start using the CEA-2010 type waveforms for their "burst" or "peak" ratings and reporting the results at the following bandwidths.

 

 10Hz, 31.5Hz, 100Hz, 1kHz, 16kHz, 20kHz.

 

I think that would just about cover it when reported along with a long term output rating. I'd like to see that be something reasonable too like 3 seconds sustained power or something. No need for more than that in any realistic scenario. Yeah I know 5Hz is tougher than 10Hz for the burst testing but there are a ton of amplifiers that are high passed above 5Hz or will protect with that signal and manufacturers still treat 20Hz as the end game for the most part. I think 10Hz is a good compromise without testing every bandwidth.



#43 Shredhead

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Posted 25 October 2015 - 12:13 AM

This is continued from the pictures in post 40  http://data-bass.ipb...movies/?p=10248

 

Here is a scene from the movie Bourne Legacy where the cabin gets hit by a drone missile strike. 

There is an impressive transient when the missile hits the cabin that is an awesome effect especially coming from the peaceful quiet of the snowfall in the woods in the previous scene.  This effect can be missed if your amp doesn't have a sufficient cap reservoir.

e12c3b0967f7a5671f9d24d8ebcf4b09.png

 

Here is right after that where there is a sustained "boom" of the explosion.

e9ed4f72b8169a7ecef0baddcdecda9a.png

 

For this scene it looks like an amp would have to supply power for transient peaks of around 10ms. More scenes to come...



#44 maxmercy

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Posted 25 October 2015 - 12:36 AM

5.1 or 7.1 version of Legacy?  5.1 theatrical hits harder.  One of the only discs to offer the theatrical track.

 

JSS



#45 Shredhead

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Posted 25 October 2015 - 12:54 AM

That was from the 7.1 DTS-HD MA.  Had no idea about the 5.1.  I'll have to compare the 2 next. 



#46 SME

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Posted 25 October 2015 - 06:43 PM

I appreciate what you are trying to do here.  Please forgive me for pointing out a few things:

  1. The strongest frequency in the spec is at 38 Hz or so.  A full wave-length at 38 Hz is 1/38 or 0.026 seconds long, or 26 ms.  The distance between zero-crossings for the wave is half the wave length or 14 ms.  That's basically what you are seeing in the time-domain data you posted.  I expect almost all pro-amps should handle that transient just fine as they are designed to provide plenty of power down to at least 40 Hz or so.
  2. The data you posted is (I assume) is directly from the soundtrack.  What the amp actually sees is something different due to crossover filters and any downstream signal processing including Linkwitz-Transform (LT) type signal shaping.
  3. The crossover will remove a lot of higher frequencies (that appear as finer oscillations in the time-domain data).
  4. The signal-shaping used in a ULF-capable, multiple-sealed HT sub system will drastically increase the emphasis of the lowest frequencies (the coarser oscillations in the time-domain data).
  5. The consequence of these two things is that time-domain data for the signal presented to the amp will look totally different, and for "full-bandwidth" effects, the oscillations that dominate will be very low in frequency and will have half-wavelengths much longer than 10 ms.  The half wave-length for 10 Hz is 50 ms.  At 5 Hz, it's 100 ms.
  6. If your amp depends on capacitance to sustain peak output with longer wavelengths, you'll need closer to 100 ms worth of storage for output at 5 Hz.  (One of your earlier pictures shows 32 ms at 5 Hz where I think you meant 64 ms.)

If you are able to capture the output from the signal shaping device in your signal chain, I think that this data would be very interesting for us to see what your amp actually sees.  Of course, the signal seen by each person's amp will depend on what kind of signal processing is used in the chain, but I'm guessing that for "full-bandwidth" effects, ULF will dominate in the signal going to most amps that are being used for ULF reproduction.  Hopefully my explanation makes sense.



#47 Shredhead

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Posted 25 October 2015 - 07:46 PM

Hey max, here is that missile strike scene in Bourne Legacy with the 5.1 DTS track next to the 7.1 DTS-HD MA just for fun.

50c58bdf2e1d1e46dd83ddd1453315f3.png



#48 maxmercy

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Posted 25 October 2015 - 09:31 PM

Shred,

 

Pretty close.  I remember that the 5.1 was hotter overall, but not on this effect, apparently.

 

SME,

 

I used to use AVR processing/bass mgmt to study the tracks, but there are so many ways that AVRs handle the digital data with various xover and LFE cutoff points and slopes that I only look at the digital data now, no filters, only summation with proper channel levels.  While I know that isn't what a subwoofer amplifier sees, it is the most apples-apples way I could think of doing it.

 

 

JSS 



#49 Shredhead

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Posted 26 October 2015 - 12:58 AM

There is a difference in the 2 waveforms so it's most likely a different mix of the film. I didn't feel up to comparing more scenes anyway but I don't have to cause I trust your ear.

#50 Ricci

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Posted 26 October 2015 - 02:59 PM

SME makes some of the points I was thinking to myself. It would be very useful to see a direct from disc waveform compared to the signal being sent to the amplifier after equalization, etc...He is right it will be much heavier emphasis on the sub 30Hz frequencies. As he states obviously that will be a bit different for each persons system but a comparison of just a couple of scenes from one or two of the heavy hitter movies would be great information.



#51 Bossobass Dave

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Posted 26 October 2015 - 05:25 PM

SME,

 

I used to use AVR processing/bass mgmt to study the tracks, but there are so many ways that AVRs handle the digital data with various xover and LFE cutoff points and slopes that I only look at the digital data now, no filters, only summation with proper channel levels.  While I know that isn't what a subwoofer amplifier sees, it is the most apples-apples way I could think of doing it.

 

 

JSS 

 

 

Agreed.

 

The exercise is to see what's encoded on the soundtrack.

 

Signal chain disparities are infinite and have nothing to do with what source an amplifier can reproduce. We already have a good idea how systems perform with internal signal manipulation using current test methods. For example:

 

9c6Htew.png

 

A mic'd version of this example, using soundtrack source, would reveal a huge distortion in presentation. That is more a matter of the amplifier/alignment/price/performance/driver(s) relationship than what the amplifier alone might be able to present in a waveform comparison.

 

The better comparison is what happens at the listening position, which includes the room, the system and the signal chain and the typically ham fisted post smoothing EQ.



#52 Shredhead

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Posted 26 October 2015 - 05:34 PM

I'm trying to keep this thread consistent with the sub out from 1 piece of equipment with no alterations to the signal for a baseline to compare film soundtracks.  Max has the best idea with digitally analyzing the soundtrack to purely see a comparison between soundtracks.  This is the next closest step to that as long as I keep it consistent with the output of this player.  Of course if you shape the signal it's going to change the waveform, that was never something that I overlooked SME, it's just not something that I'm getting into in this thread. 

 

I'll get into that when I start to publish the amp testing data that I've gathered over the past year but it will have to be in the bass gear side of things and I'll need enough time to spare to dedicate to the effort.  In my experience when analyzing the waveform of movie content most everything in the signal chain has an affect on it.  Even just the slew rate of the amp itself distorts what the waveform of the source should be.  It's an interesting topic for sure but not one for this side of the forum. 



#53 SME

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Posted 27 October 2015 - 01:55 AM

Shred,

 

I used to use AVR processing/bass mgmt to study the tracks, but there are so many ways that AVRs handle the digital data with various xover and LFE cutoff points and slopes that I only look at the digital data now, no filters, only summation with proper channel levels.  While I know that isn't what a subwoofer amplifier sees, it is the most apples-apples way I could think of doing it.

 

That makes perfect sense if the objective is to analyze the content directly rather than assess what kind of signal a sub  amp is being asked to reproduce.

 

I'm trying to keep this thread consistent with the sub out from 1 piece of equipment with no alterations to the signal for a baseline to compare film soundtracks.  Max has the best idea with digitally analyzing the soundtrack to purely see a comparison between soundtracks.  This is the next closest step to that as long as I keep it consistent with the output of this player.  Of course if you shape the signal it's going to change the waveform, that was never something that I overlooked SME, it's just not something that I'm getting into in this thread.

 

After re-reading this thread from the beginning, I totally get what you and JSS are saying here.  I think this is the right approach for comparing content between films.  However, in an earlier post, you wrote:

 

Stay tuned and I'll show some real world movie content shots of transient waveforms and their time duration zoomed in on to see if that helps pick a burst frequency that most closely matches the stresses that some of the coolest bass hits in movies inflict.  

 

And you followed this post with data for "Bourne Legacy" along with comments about how long an amp capacitor reservoir would need to be able to sustain output in order to reproduce the (mostly 40ish Hz) transient accurately.  That was the context for my comments.

 

If you want to know what various bass scenes demand from your amp, then you need to look at what signal is being fed to the amp or you need to calculate it based on knowledge and/or measurements of your signal chain response up to the amp.  If I had an easy way to get digital data off my discs (i.e., I ran Windows on a computer a Blu-ray drive), I'd consider doing some simulation examples.  If someone wants to send me some source data in a usable format along with a good "representative signal shaping" curve, I could do the required calculation.  It might be good to throw in a representative amp roll-off curve too, because presumably the roll-off will be in the input stage.  In other words, you don't expect heavy energy at 1 Hz to demand much from most amps just because most amps are heavily rolled-off at that point.

 

We can also take this discussion to another thread.



#54 maxmercy

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Posted 27 October 2015 - 02:35 AM

Another thread would be ideal.

 

The signals fed to the SW out can be higher than what is encoded on the disc, as I used to measure through the sub out of an AVR with all speakers set to small and crossed at 250Hz.  There were several films that had >128dB content, clipping the soundcard input setup to to record a max 128dB (Immortals, TF3, and TDKR come to mind).  Replicating that processing in the digital world had very similar results, but still leaves out the DAC step.  Those lowpasses, esp if applied to clipped content in the LFE channel, can make for some signals hotter than expected.  Usually just by a dB or two, but once summed, they make a difference.  

 

That's why I like WCS scenarios to test with, more for the signal chain than anything else, as I have found some AVRs and processors quite lacking in the headroom department when it comes to channel summation.

 

JSS 



#55 Shredhead

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Posted 27 October 2015 - 03:53 AM

Hey SME, fuck off.  I said I want to keep the waveforms in this thread consistent with the output of the player as a database of content to refer to.  I'm allowed to do that fuckface. 



#56 Ricci

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Posted 27 October 2015 - 02:46 PM

Hey SME, fuck off.  I said I want to keep the waveforms in this thread consistent with the output of the player as a database of content to refer to.  I'm allowed to do that fuckface. 

 

So what you're saying is you don't like him or his face...?

 

This is blown out of proportion... I wasn't suggesting change your thread or that it be a long term thing and I don't believe SME was either. To the best of my knowledge I've never seen anyone post an SL or waveform capture comparison of what is on the disc vs the modified signal going into the amp with a capable boosted sealed system. I think that would be really cool information to see posted by someone. Just a couple of screen caps from a heavy hitter movie posted in a different thread, one time, to show what the amps are really being asked to do. I like the format you have been using in this thread and you have access to good equipment and the right sort of system to do it that's why it was suggested.  



#57 3ll3d00d

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Posted 27 October 2015 - 03:04 PM

This is blown out of proportion... I wasn't suggesting change your thread or that it be a long term thing and I don't believe SME was either. To the best of my knowledge I've never seen anyone post an SL or waveform capture comparison of what is on the disc vs the modified signal going into the amp with a capable boosted sealed system. I think that would be really cool information to see posted by someone. Just a couple of screen caps from a heavy hitter movie posted in a different thread, one time, to show what the amps are really being asked to do. I like the format you have been using in this thread and you have access to good equipment and the right sort of system to do it that's why it was suggested.  

I posted some examples in http://data-bass.ipb...-closed/?p=9425



#58 Shredhead

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Posted 27 October 2015 - 03:10 PM

Yeah Josh, like I said I can show that stuff when I post amp data on the other side of the thread.  And no, I don't like SME.  He can go find someone else to fuck with.  If you think that's not what he's doing then please go find me some of his posts to me that don't end up scrutinizing something I've said/done and derailing the thread while he contributes his usual nothing in return.



#59 Shredhead

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Posted 12 November 2015 - 04:54 PM

220px-Terminator_Genisys.JPG

Terminator Genisys -Atmos track defaulted to 7.1 Dolby TrueHD

Biggest hits seem soft limited to 1.3Vpk which is -6.91dBV from a WCS

Zooming in on waveform for the largest peaks doesn't indicate the use of square waves for the soundtrack.

 

00:02:05

eb811c4879c5bfadbff1143cbe8ba206.png

bf8bbb71d26c5790c9bdcd6a5d9a4fcd.png

 

 

01:28:32

748def2b49d9e16ddfcab332e3227e2c.png

65676aea950620970ffc54aa12319c48.png

 

 

01:45:17

f82c8ffff6272f835b9016f1a18b72c8.png

235f0c4a63b36817fff752f52591e91f.png

 

 

01:47:40

486fa93df76de12212820546b2043071.png

a5c926a6c5e0f22c49ae7feef71d7f8f.png

 

See rest of SL shots here: http://data-bass.ipb...ic-etc/?p=10658


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#60 Shredhead

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Posted 02 December 2015 - 11:51 PM

The Man From U.N.C.L.E.

220px-The_Man_from_U.N.C.L.E._poster.jpg

 

Biggest hit -1.08Vpk which is -8.52dBV from a WCS

Zooming in on waveform looks like no square waves were used in production.

This is a fairly low level for the sub out.

 

1:42:45

5ca8a4590f4e8ac02073b5a01ef719b3.png

 

1:45:30

8e81e4607103f90c542ce54d1c2ef2a6.png

c92bd4b0c28dc5050cfc6fc96740e918.png

See rest of SL shots here: http://data-bass.ipb...ic-etc/?p=11046






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