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The Low Frequency Content Thread (films, games, music, etc)

Bass Movies Bass Movie Measurements Deep Bass Movies Bass Waterfall Graphs Bass Graphs

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#2361 Aj72

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Posted 26 September 2014 - 01:39 PM

I run the bass a bit hotter for Dredd than some other films but it's very clean and dynamic for me. I have the 5.1 mix. I'm referring specifically to the bass.
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#2362 musichascolors

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Posted 26 September 2014 - 09:42 PM

I don't see any clipping in those godzilla screenshots. Could someone repost it without the red, and zoomed in at the top where it hits 0.0 db (if it does) if the top of the peak is flat, then it's clipping. If it isn't flat, it's not.



#2363 maxmercy

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Posted 27 September 2014 - 12:53 AM

It is clipped. This is not something I would mislead anyone about.  I zoomed in on many instances on many channels and there were flat tops a-plenty.  Is it the worst case I have ever seen?  No.  Just 1-2dB of attenuation across the board would have probably prevented all of it.  But someone should be at least glancing at the final product to see if it hits 0dBFS, and if it does so regularly, to do something about it before it is pressed onto a disc.  This is apparently not the case, given the frequency with which I see clipping in soundtracks.

 

JSS



#2364 musichascolors

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Posted 27 September 2014 - 02:35 AM

If true, that's pure incompetence. Lowering the volume a bit would be the best choice, but a simple limiter would have prevented clipping without reducing the volume. In theaters, the movie sounded incredible.



#2365 maxmercy

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Posted 27 September 2014 - 12:27 PM

Just a little more evidence that a lot of BluRays are mixed for the LCD (Lowest Common Denominator) sound systems out there, and poorly at that sometimes.  Too bad.

 

JSS



#2366 musichascolors

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Posted 27 September 2014 - 05:13 PM

Nothing to do with LCD. Clipping doesn't benefit anyone in any way. Likely they just bounced the seperate audio tracks without watching the master bus or applying a limiter.



#2367 Bossobass Dave

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Posted 28 September 2014 - 02:39 PM

My guess is that the problem arises when we sum the bass into a single SW channel, although it would help if those measuring clipped waveforms mention the method used. Soundtracks are mixed with no bass management (summing).

 

Measurements of the analog SW out using various discs yields surprising results. Summing signals from sats channels and the LFE channel can cause huge spikes in voltage and clipping in the signal chain so I imagine the same is likely in the digital realm. The SW output, after all, has finite headroom, so the summing aspect needs to be taken into consideration during production.

 

Just a thought.



#2368 maxmercy

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Posted 28 September 2014 - 07:58 PM

I know for a fact my Sherbourn clips a 'worst case scenario' track I created with tonebursts all encoded at 0dBFS from 1.5Hz to 200Hz.  Clips terribly unless the signal is attenuated prior to the AVR, I am using a minidsp nanoavr, but am having issues with 1080p24 passthrough.

 

I think this varies by brand, some probably have enough headroom in place.

 

The clipping in Godzilla is encoded in every channel.  By using the BassEQ process in the BassEQ thread, the shelving filters make the square waves into smoother sounding sawtooth-type waves, and the presentation is much improved, and it restores the bottom end that a giant monster film deserves.  Anyone with the DSP capability to do so should try it.

 

JSS 



#2369 MKtheater

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Posted 28 September 2014 - 08:45 PM

For your Nano to work make sure the 24hz option in your bluray player is turned off. Once I turn the 24hz off my nano works awesome.

#2370 Kvalsvoll

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Posted 28 September 2014 - 09:52 PM

My guess is that the problem arises when we sum the bass into a single SW channel, although it would help if those measuring clipped waveforms mention the method used. Soundtracks are mixed with no bass management (summing).

 

Measurements of the analog SW out using various discs yields surprising results. Summing signals from sats channels and the LFE channel can cause huge spikes in voltage and clipping in the signal chain so I imagine the same is likely in the digital realm. The SW output, after all, has finite headroom, so the summing aspect needs to be taken into consideration during production.

 

Just a thought.

 

Good point, some processors will be fine, though.

I checked this now on a Marantz and all channels at 0dB seems fine.


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#2371 maxmercy

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Posted 28 September 2014 - 10:52 PM

For your Nano to work make sure the 24hz option in your bluray player is turned off. Once I turn the 24hz off my nano works awesome.

 

Yes, but then you are dealing with interlacing artifacts and artifacts from turning a 24Hz presentation into a 60Hz one...they are not multiples, so judder will be introduced.  

 

JSS



#2372 MKtheater

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Posted 29 September 2014 - 02:56 AM

I can check my remote to see what output I am getting, the picture looks great.

#2373 SME

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Posted 30 September 2014 - 08:37 AM

An important point about clipping in playback equipment deserves mention.  While we often think of clipping as occurring in the power amplifier, clipping can occur just about anywhere in the signal chain.

 

My guess is that the problem arises when we sum the bass into a single SW channel, although it would help if those measuring clipped waveforms mention the method used. Soundtracks are mixed with no bass management (summing).

 

Provided that the DSP arithmetic is handled properly, clipping should not occur during the bass management process in the processor/AVR.  However, depending on the playback level and the amount of gain on the equipment downstream, the summed signal may be enough to clip the output DAC and/or the pre-amp output.  This is absolutely the case on my Denon 3313CI AVR, which appears to implement the level trims in the digital domain.  In order to maximize my bass headroom, I adjust the gains on my subs until the correct level trim for calibrated playback is as low as possible.  I actually have my level trim at about -9.5, which is +2.5 above the minimum, so I can decrease it a tiny bit if need be.  I forget how much bass headroom that actually gets me, but IIRC it's near 120 dB rms.  Someone running with the sub trim near "0.0" would hit clipping at around 110 dB of output, which is quite low by sub standards!



#2374 Bossobass Dave

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Posted 30 September 2014 - 05:18 PM

An important point about clipping in playback equipment deserves mention.  While we often think of clipping as occurring in the power amplifier, clipping can occur just about anywhere in the signal chain.

 

 

Provided that the DSP arithmetic is handled properly, clipping should not occur during the bass management process in the processor/AVR.  However, depending on the playback level and the amount of gain on the equipment downstream, the summed signal may be enough to clip the output DAC and/or the pre-amp output.  This is absolutely the case on my Denon 3313CI AVR, which appears to implement the level trims in the digital domain.  In order to maximize my bass headroom, I adjust the gains on my subs until the correct level trim for calibrated playback is as low as possible.  I actually have my level trim at about -9.5, which is +2.5 above the minimum, so I can decrease it a tiny bit if need be.  I forget how much bass headroom that actually gets me, but IIRC it's near 120 dB rms.  Someone running with the sub trim near "0.0" would hit clipping at around 110 dB of output, which is quite low by sub standards!

 

 

Yes, well, the devil's always in the details.

 

Most would reason that a SW channel trim at '0' is optimum, so that's where we set it to take measurements. The term "running the sub hot" also implies setting the sub trim to a positive number, not a negative number. That goes for the channels as well and master volume level, which is an unknown on many AVRs.

 

The Oppo, for example, has a 0-100 scale on it's master volume level when using the analog outs (using the Oppo as a pre), and it's not a dB scale, so 0dBFS is arbitrary, and once you get above 95, the output goes unpredictably nuts regarding scale/voltage.

 

It's like roll off. There is no standard and most hardware roll off is unknown, certainly not a standard published spec.

 

In the case of the Sherbourn pre we measured at Adam's, it seemed as though the output was gated, making it impossible to do a loopback measurement because the 'gate' wouldn't open until the sweep hit 20 Hz or so. That made the result look as though there was a brick wall filter at 20 Hz. Still not sure what the hell went on there, but the point is that all hardware is different in many respects and those differences have to be gotten to the bottom of before measurements even begin.

 

 

Good point, some processors will be fine, though.

I checked this now on a Marantz and all channels at 0dB seems fine.

 

How exactly did you check the Marantz?



#2375 Kvalsvoll

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Posted 30 September 2014 - 08:57 PM

...

 

How exactly did you check the Marantz?

 

I only listened to it, if there is excessive clipping it will be audible.

 

However, according to the above post, mentioning that trim level can affect headroom, a more extensive analysis should be done to accurately determine what headroom is available, for different trim levels.

This is quite easy to do, only need to monitor the signal out from the processor before it enters the subwoofer dsp.

 

I find headroom issues to be the largest problem with ordinary avr/processors; they have too high noise floor and trim levels are not sufficient for speaker systems with large dynamics.


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#2376 Kvalsvoll

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Posted 30 September 2014 - 10:47 PM

This turns out to be quite simple on the Marantz:

 

- The subwoofer output clips at 4Vrms.

- MV+Trim must be <=-12dB to keep output below clip level at 4Vrms for a highly unlikely 7.1 signal with 0dB level in all channels.

- No combination of signal and trim causes digital clipping before the output clips at 4Vrms.

 

This means that if you watch at 0dB, the subwoofer trim must be set at -12dB to ensure no clipping is possible.

 

Here I have -6dB trim for flat, and that is sufficient for practical soundtrack signals.

However, some movies, such as WOTW, Kon-Tiki, will audibly clip if running 3dB hot with trim level at -3dB.

 

This shows that it definitely makes sense to calibrate subwoofer levels to the lowest possible trim level setting.

Calibrating for 0dB trim will actually loose 12dB headroom before the signal even enters the subwoofer dsp.

 

This is for my Marantz, other processors/avrs may be different.


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#2377 maxmercy

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Posted 01 October 2014 - 01:14 AM

Transformers: Age of Extinction (Dolby TrueHD 7.1, no ATMOS content included)

Level - 5 Stars (114.59dB composite)
Extension - 3 Stars (just over 15Hz)
Dynamics - 3 Stars (23.15dB)

Execution - Hotly contested, 5 Stars (by poll)

 

Overall - 4 Stars

 

Recommendation - Buy (by poll)

Notes - It not only appears to be the loudest film of all time, given its nearly 3 hour run time with those numbers, but it definitely sounds and feels that way, see my post on page 2.  It is brick-wall limited at around -0.5dBFS.  In other words, it clips terribly, and often.  As usual, the center channel is the worst offender, followed closely by L, R and LFE.  Surrounds much less so.

JSS

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#2378 raynist

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Posted 01 October 2014 - 01:50 AM

Anyone see Godzilla in a theater with decent capabilities?  Clipping that bad would almost certainly be audible in a movie theater, provided that it isn't running out of headroom for those passages.   I know audio memory isn't very reliable, but I'd really like to figure out where most of this clipping is getting introduced.
 
As for using clipping intentionally to imitate a very loud real life effect, I don't think it works well unless it's done very skillfully.  The thing is, digital clipping sounds nothing like ear clipping, which involves both mechanical and psychoacoustic mechanisms.  In any case, most of the really loud sounds in real life like jets and rockets are dominated by lower frequency energy, enough that you'll be feeling intense pounding in your body before your ears start distorting significantly.  I'm rather glad movie sound effects aren't as loud as their real life counter parts, but in the interest of realism, I believe getting the bass right goes a long way.  I think the Hell Carrier engines were done well in this respect.  The real life event would likely be loud enough to damage internal organs, but we can suspend our disbelief very well when we hear the same sound as we would from a safe distance.  In the Space Shuttle launch recording I posted, I believe SPL peaked well above 120 dB with the highest energy in the low 20s Hz and the bulk of the energy lying below that.  There is no ear clipping at all, just a lot of pounding bass.


Hey,
Where can I find the space shuttle launch posting?

Thanks
Ray

#2379 SME

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Posted 01 October 2014 - 07:30 AM

This turns out to be quite simple on the Marantz:

 

- The subwoofer output clips at 4Vrms.

- MV+Trim must be <=-12dB to keep output below clip level at 4Vrms for a highly unlikely 7.1 signal with 0dB level in all channels.

- No combination of signal and trim causes digital clipping before the output clips at 4Vrms.

These figures are very close to my own observations.  I used the relative input level indicator on my MiniDSP 2x4 along with its published specs to deduce a max output voltage for my Denon of 4.0V rms.  I also installed a few extra attenuators on the line and turned on a sub to hear the clipping.  Right at -3.0 dB from the point at which the output saturated, clipping became audible, and it became much more severe with each 0.5 dB increment.  Having done a lot of computer music in the old days, it sounded exactly like hard digital clipping.

 

What surprises me is that you have to use the minimum trim of -12 to not clip a 7.1 channel digital full-scale signal at master volume "0".  Even then, Audyssey may boost the signal at certain frequencies and still cause clipping.  By your numbers, someone running with the sub trim at "0" and master volume at "0" will clip above 113 dB, which is less than digital full-scale on the LFE channel alone.

 

In my current system configuration, I have meticulously EQed my subs to be as flat as possible across the listening area using my MiniDSP so that Audyssey is not tempted to boost anything too much.  It mostly works, and thankfully soundtracks aren't pushing digital full-scale in all 7.1 channels just yet.  The sad thing about all of this is that all they had to do was give up 2 bits of fidelity (probably at a level way below the noise floor of any realistic listening room) to get back 12 dB more headroom.  If they let you set the trim well below -12 dB, then there'd at least be a work-around.

 

Judging by what I read in other places, I bet some other AVRs are even more headroom limited than the Denon/Marantz.  It'd be nice if review sites could report on stuff like this instead of talking about how much warmer AVR "A" is compared to AVR "B".  Ugh.



#2380 SME

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Posted 01 October 2014 - 07:53 AM

Notes - Have not seen it yet.   It appears to be the loudest film of all time, given its nearly 3 hour run time with those numbers.  It AVERAGES 101.14dB!!!  And it is brick-wall limited at around -0.5dBFS.  In other words, it clips terribly.  As usual, the center channel is the worst offender, followed closely by L, R and LFE.  Surrounds much less so.

 

Shame!  Even at -10, this thing will likely sound very loud and fatiguing.  I gather the theatrical version was quite loud and probably took advantage of the headroom Atmos provides, and then they boosted it further for the home mix.  It's so sad that many of today's headline releases have worse sound than some stuff done in the 1980s.

 

By the way, I recently learned a couple reasons hard limiters at levels just below digital full scale get used:

  • Some DACs behave very badly when presented with digital full-scale signals.  Some may even repeatedly invert the output signal.
  • Lossy compression can sometimes introduce just enough boost to cause a nearly-full-scale signal to become full-scale.  See above.

As such, it seems to be a very good to add a hard limiter somewhere slightly under digital full-scale.






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