maxmercy

I did throw out tons of numbers....but lemme make it more manageable.

Do you and your spouse like how loud a good cinema is?  You can consider that 'reference'.

You can think of 10dB steps below that as each one being '1/2 as loud'.

When I used to demo my old system, I would tell people that it played at '1/2 the volume' of a good cinema, at 10dB below reference.

On my first ever HT, I rarely ever played louder than '1/4 as loud' as a cinema, or 20dB below reference.

As for frequency, I tell people that 40-50Hz is most 80s-90s hip-hop.  30Hz is around where some EDM music has their lowest bass, and as low as most good cinemas go; e.g. the low end of the sweep during Ironhide's somersault in the 2007 Transformers movie.  20Hz is something that is rarely achieved in a typical commercial setting, IME.  Hopefully this will change with products such as the Meyer VLFC, and it's role in the remix of Apocalypse Now.

From the Meyer Sound website:

"The system for the VR installation utilizes two different Meyer Sound systems. One is the 1100-LFC low-frequency control element, a staple in touring systems for artists as diverse as Celine Dion, Ed Sheeran and Metallica. The other is the new VLFC very low frequency control element, recently in production but with limited availability, that is bolstering the extreme low end on the current Metallica tour. The VLFC powerfully reproduces sound only in the single octave that bridges the threshold of hearing, between 13 Hz and 30 Hz.

“We developed the first versions of the VLFC for NASA to use in vibration testing,” says Meyer. “But we decided to continue development for uses in both cinema and concert applications. We have done extensive double-blind testing here in our own Pearson Theatre. There’s no doubt that people have a different psychological response when we add in or remove that extra octave from 13 to 30 Hz.”"

JSS

Return of the King Extended Edition DVD vs BD:

Very similar again, with the BD having slightly better dynamics and more clipping noted on the DVD version.

DVD Stats:

DC offset  -0.000001
Min level  -0.541110
Max level   0.589154
Pk lev dB      -4.60
RMS lev dB    -35.16
RMS Pk dB     -10.58
RMS Tr dB    -190.65
Crest factor   33.76
Flat factor     0.00
Pk count           2
Bit-depth      24/24
Num samples     758M
Length s   15794.069
Scale max   1.000000
Window s       0.125

BD Stats:

DC offset  -0.000000
Min level  -0.630937
Max level   0.592822
Pk lev dB      -4.00
RMS lev dB    -34.94
RMS Pk dB     -10.14
RMS Tr dB    -468.38
Crest factor   35.23
Flat factor     0.00
Pk count           2
Bit-depth      24/24
Num samples     758M
Length s   15797.877
Scale max   1.000000
Window s       0.125

Crest Factors listed on all the stats are simple ratios of RMS vs peak amplitude, they are not in dB.

This film has even more full bandwidth LCRS than the previous two films, with significant infrasonics in the back center channel (DVD and BD), and little roll-off in the LCRS save for under 10Hz.

Basically, the DVD and BD presentations of these films are essentially the same.  No tampering or shelving like we saw in 'Master and Commander'.

JSS

The Two Towers Extended Edition DVD vs BD:

Again, virtually identical graphs.

Clipping in this film is more prominent, especially in the LCR channels, both on DVD and BD, with more clipping in the DVD version.

Stats for DVD:

DC offset  -0.000001
Min level  -0.461359
Max level   0.464815
Pk lev dB      -6.65
RMS lev dB    -37.72
RMS Pk dB     -14.70
RMS Tr dB      -1.#J
Crest factor   35.74
Flat factor     0.00
Pk count           2
Bit-depth      23/24
Num samples     678M
Length s   14125.920
Scale max   1.000000
Window s       0.125

Stats for BD:

DC offset  -0.000000
Min level  -0.521735
Max level   0.440078
Pk lev dB      -5.65
RMS lev dB    -37.58
RMS Pk dB     -14.72
RMS Tr dB    -143.65
Crest factor   39.49
Flat factor     0.00
Pk count           2
Bit-depth      24/24
Num samples     678M
Length s   14131.499
Scale max   1.000000
Window s       0.125

Similar stats with slightly more dynamics on BD, but essentially the same track.  This film had some strange filters applied to the LFE channel, and full bandwidth LCR channels, extending even deeper than FOTR.  It is BEQ-able, with a possible pre-post:

JSS

Boomer,

Something you need to ask yourself is how loud will you be listening?  Reference Level is what most folks compare their listening SPL to for movies/films.  In fact, most receivers have their volume knob in gradations in dBs below a 'zero' level, like -20dB. 

'Reference' in cinema size venues means peaks from the LCRS can hit 105dB, and from the LFE channel 115dB.  It is impactful and loud (no 'rewind' button in a cinema, you gotta hear it the first time).  It is hard to find a good enough cinema that can play at reference without significant strain to both equipment and audience.  Most play lower due to patron complaints.  My usual listening level is -15dB to -7dB below reference, my max is usually -3 to -4dB below.  Getting clean bass down to 20Hz and below at -10dB and louder does take some doing.  Getting clean bass at -20dB below reference is MUCH easier.  Getting clean (less than 5% THD, preferably lower) <20Hz bass at full reference level is not an easy undertaking in most cases; no matter what people on forums would lead you to believe.  Due to most home systems using a .1 channel for bass, most, if not ALL, of the lowest frequencies from the LCRS get sent to the sub as well as the LFE signal.  At full reference level, that can mean peaks in the range of 125dB, and as high as 128dB.  That takes some serious horsepower.  Listen at -10dB, and those numbers get more manageable.  At -20dB, and a lot of decent home systems can do it reasonably well, and I really enjoyed films through a -20dB system for a long time, until this one THX trailer distorted my subwoofer over and over again....and then I went down this rabbit-hole you found me in.

How low do the subs need to dig to?  Do you want to feel things shake in your house and fall off of shelves?  Put it this way: Most cinemas do OK to 40Hz.  Some good ones do well down to 30Hz.  I have yet to be in a cinema that can do 20Hz without significant distortion.  To get 'good cinema' sound, you only need 25-30Hz and up.  Films contain content much lower at times.  But if your goal is a 'cinema at home', you don't need support down to 10Hz (it is fun, though).  This is the data-BASS forum, after all...

Do your LCRS provide enough SPL that you are only looking for low end support to help them out?  This goes back to the 'how loud' question above.  At levels above -15dB to -10dB below reference, LCRS will start to sound strained, and listener fatigue can be the end result.  A lot of 'slam' and 'impact' come from good fidelity and SPL in the higher frequencies that the LCRS handle, and they need to combine with the sub system to provide a coherent wavefront to get that 'slam'.  It is hard to get in a small (home-sized) space.

How much space do you have to spare for subs?  No one is exempt from Hoffman's Iron Law, especially on a budget.  One of the systems I miss went down to 16Hz at -10dB below reference, but it required 36 cubic feet worth of subs.  However, it was in a basement, and that made those subs dig deeper than they would have in an open floor plan due to room gain.

What is a reasonable budget for you?

Answers to these questions will make things easier for the members here to make recommendations for you. 

I have been able to get 'budget' systems to sound 'decent' and dig pretty low and loud for the cash outlay, if you are willing to sacrifice some cubic footage and make some sawdust.

JSS

Prelim BEQ for Fellowship:

Lots of under 3Hz noise, hence the extra highpass down low, now I just need the time to screen it properly.  These are long films.

JSS

Even on a modest home system, I remember wondering what was 'wrong' with the sound of Batman Begins on Bluray.  It turns out the BD would default to the lossy soundtrack.  I couldn't put my finger on it, just that the lossless track sounded 'airier' and more 'crisp'.  Looking at HF content in DVD vs BD I see the following: RED trace is the BD.

There is a transition in the 14-15kHz region.  Not sure I can hear that, and I'm not sure if this is not just an artifact of lossy compression.  Has anyone done any experiments on what AC3/DTS compression does to a spectrogram/FFT?

JSS

So by request, the comparison of DVD vs BD LOTR Extended Edition.

I remember graphing them a few years ago, but with the LF content thread request, I dug a little deeper.

Here is the comparo between DVD and BD Fellowship of the Ring:

The DVD has the green Peak and red Avg graph, the BluRay the cyan Peak and the green Avg graph.

Stats for the DVD mix:

DC offset  -0.000046
Min level  -0.663155
Max level   0.593566
Pk lev dB      -3.57
RMS lev dB    -32.86
RMS Pk dB     -10.99
RMS Tr dB    -119.97
Crest factor   29.15
Flat factor     0.00
Pk count           2
Bit-depth      24/24
Num samples     657M
Length s   13686.741
Scale max   1.000000
Window s       0.125

The DVD clips in 12 locations across all 7 channels, mainly in the Right Surround channel.

Stats for the BD mix:

DC offset  -0.000048
Min level  -0.629489
Max level   0.594391
Pk lev dB      -4.02
RMS lev dB    -33.07
RMS Pk dB     -11.22
RMS Tr dB    -234.33
Crest factor   28.36
Flat factor     0.00
Pk count           2
Bit-depth      24/24
Num samples     657M
Length s   13697.685
Scale max   1.000000
Window s       0.125

The BD clips in only 2 locations across all 7 channels.

The tracks differ only about 1/2dB all around, including only 1/4dB difference in dynamics.  They appear to be very similar, likely the same track save for some minor differences when putting the whole thing together.  Given SME's prior remarks, and the BD's lack of clipping, I think the BD is the track to get since it is lossless and may contain more HF content compression may take away. 

Looking at every channel's PvA, it is quite obvious why this track is held in high regard for LF content.  ALL the LCRS channels extend to nearly 5Hz.  This track may be amenable to BEQ.

The Two Towers and Return of the King as I have time.

JSS

Godzilla: KOTM has an improvement:

It gains some needed heft and slam, but the film overall is lacking.  Will post BEQ correction later.

JSS

On 9/17/2019 at 6:18 PM, Smk86 said:

Hey guys, are the LCR clipped in godzilla king of monsters uhd/blu ray? Was watching at a fairly low volume level and could hear some distortion especially from center channel in the scene when Godzilla swims past the submarine type vessel

GKM clips only a few times in the LCR.  Center is the worst, but only a few samples worth of flat-tops.  From the waveforms, great use of the SPL available without obvious flat-tops.  But a horrible dynamic range, Only 24dB in dynamics for a 3-Star score.  This film must have loud scenes throughout.  Will try to check it out this weekend, it got the 'Pacific Rim' filter.  Not unforeseen, as Legendary did both PacRim and Godzilla.

Nice that they included ATMOS on the BD release, though.

JSS  

4 hours ago, Ricci said:

I cheat and use one of my DCX2496's in the chain usually. They will take an input of >10 volts before clipping and can easily reduce the signal to something that your SC input can handle when looped back.

That is an awesome tip.  I'll  have to use that in the future.

JSS

The process would be to use the HDMI out from REW for your signal.  You can use EqualizerAPO to 'copy' the signal to other channels in the 7.1 channel bed.  Measure at the subwoofer out, at low AVR volume, with a low signal drive level.  Add AVR volume until you are at your 'max' listening AVR volume setting, keeping track of both the soundcard input signal level (so as not to clip it and overload/fry the card) as well as the waveform on REW.  One or the other will clip as you increase drive level.  You want to protect the soundcard while you find the limit for the subwoofer out.  You may need a voltage divider circuit to do this, some AVRs can generate significant voltage from the SW out.  

MOST AVRs will clip the SW out with a WCS (Worst Case Scenario) signal, especially if the AVR output levels for each channel (esp subwoofer) are at "-0" or at "+anything". 

To make a WCS signal, use channel 4 on the REW HDMI out, and use EqualizerAPO to copy that signal to all other channels.  Be careful, that is a lot of signal to be bass-managed, you have to start low on both drive level (-30dB or below), and AVR volume.  I would disconnect all speakers powered by the AVR to do this.

Once you find what bass-managed signal strength clips the AVR output, you have to make sure it doesn't clip the MiniDSP input.  You can either measure a 60Hz signal with a voltmeter at the SW out to make sure it isn't above 4V, or hook up the MiniDSP and look at it's input levels as you play the 60Hz WCS tone with REW and EqAPO as you increase volume to the point where you clipped above.

Once you have done that, You have to make sure your EQ is not going to clip the MiniDSP output, and that your MiniDSP output is not clipping your Amp input.  Easiest way to do that is look at the MiniDSP out with your craziest EQ scheme and sweep, making sure to protect the soundcard. 

To see if you clip the subwoofer amp input,  you can apply the craziest boost you can to a 60Hz tone again, and use a voltmeter to make sure the V out of the MiniDSP is not clipping, and below your amp's voltage sensitivity rating.  You can also measure directly out of the amp with the amp turned down and a voltage divider to protect the soundcard.

Lots of things can clip in an audio chain, and if anything in the chain does, it will increase distortion VERY quickly.

JSS

What you really need is an oscilloscope.  You can do it with a soundcard and a voltage divider and some apps are out there for it.

To view a signal realtime:

https://makezine.com/projects/sound-card-oscilloscope/

Or, you can use REW itself and use the Oscilloscope window and look at the captured trace and look for flat tops.  Measure from each input/output to ensure no clipping with a -0dBFS sweep level.  Just be sure not to fry the soundcard input by checking levels carefully or using a voltage divider.

I was thinking of making a true WCS test disc, but REW is pretty good at doing almost everything the disc would do.  With REW and EqualizerAPO  (https://sourceforge.net/projects/equalizerapo/) you can simulate a WCS, and see where it clips in the signal chain (watching to make sure you do not clip any inputs), and then KNOW you will be free from clipping no matter what signal content is fed into the system. 

EDIT:  Apparently REW beta now has a LIVE oscilloscope feature tracking the measurement and reference channels in real time.  THAT is a very handy tool.  If you guys have PayPal, donate a few bucks to REW.  It is truly a terrific tool that many have gotten better audio experiences from.

JSS

I'll check it out.

JSS

On 9/12/2019 at 1:57 PM, SME said:

It's also entirely possible that the two rooms use very different technologies including "room EQ" or whatever, so the greater bass in the Atmos mix certainly could be compensation under the mistaken assumption of being "calibrated".

On 9/12/2019 at 11:12 PM, Infrasonic said:

The amount of over-generalizations that continue in these discussions never fails to make me chuckle but I gotta tell ya there are so many variables that account to what we end up getting on disc and play back at home. Nobody (who creates/produces what we hear) has time to go through each and every release made with a fine tooth enthusiast-audiophile "is-this-gonna-sound-awesome-on-my-home-stereo" kind of mentality.

Agree on both points.  Queue the "Circle of Confusion" lecture by Dr Toole....and add that everyone is under time pressure, and director's intent, as well as adding their 'style' to the mix.  

On the plus side, while it sounded a little heavy handed at times, Spider-Man: into the Spider-Verse was a pretty good ride.  No TIH bass, but pretty good.  I'll graph it, and see if I have time to dig into the LOTR trilogy.  IIRC, The DVD:EE and BD:EE were very similar.

JSS

Speakons have nothing on these:

http://www.machinadynamica.com/machina31.htm

I cannot read that without laughing, but I bet they sell thousands of them.

JSS

MK/SME,

I remember doing some comparisons:

I can revisit this if there is enough interest.  Apparently we will get a 4k version in 2021.

JSS

How is this done?  In AVRs, the subwoofer crossover is not adjustable for slope in most cases.

JSS

Not only improperly calibrated subwoofers, but crossovers can also degrade the phase/GD:

It is a generic drum sound (top) with 80Hz 1st order BW, LR2, and LR4 crossovers applied.  For best fidelity/coherence, FIR can be used to fix the phase/GD problems that a subwoofer crossover imparts to the signal.  

To tell the truth, if you get this far and have solved all of the other problems with bass and sub integration in small rooms that you are correcting the sub crossover, you probably already have a well optimized, terrific system.

JSS

Avengers: Endgame (Dolby ATMOS 7.1 channel bed)

Level: 4 Stars (110.9dB composite)

Extension: 3 Stars (16Hz)

Dynamics: 5 Stars (29.44dB)

Execution: TBD

Overall: TBD

Notes: the DTS 7.1 track is not as dynamic as the ATMOS track.

JSS

Is this question for real?  In this thread?

JSS

Sometimes XT32 tries to do things it shouldn't, but overall, it is a pretty decent product.

JSS

The blue response looks good.  Getting 30-200Hz right (especially integration with mains and center) is much more important than getting extra output below 30Hz.  Slam and impact can be very elusive in a small space.  Displacement will net you infrasonics.  If not, there's always Crowsons.

JSS

Very nice response, no suckouts is a good thing.  Is this with the sonotubes in place?

JSS

On 5/12/2019 at 5:38 PM, AmerCa said:

In other news, the new Hellboy II 4k DTS:X mix has been butchered. I first heard about the H2 mix here, and I know it was considered among the greatest. But the new mixers considered it was appropriate to filter it and reduce the levels. 

That is awful.  

JSS

The blu-ray I hope has the infrasonic content.  I will buy this title if it does.

JSS