Adventures in Waterfalling: Understanding Signal Levels in Time-Domain Graphs

Wayne A. Pflughaupt

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Adventures in Waterfalling
Understanding Signal Levels in Time-Domain Graphs


Once upon a time in a land far, far away, the capability to generate waterfall graphs was limited to expensive software programs available primarily to professional speaker designers and acoustics engineers.

However, the advent of affordable measurement platforms like TrueRTA, Room EQ Wizard and others has made these powerful analytical tools available to the general public, most of whom have no formal training or experience in the relevant sciences. As a result we now have a curious mix of enlightenment and chaos: Someone downloads a sophisticated measurement platform, and in a few days he's an expert dispensing wisdom to the even less-informed on the audio forums. Do a search on “rew waterfall graph images” and you’ll find all kinds of crazy-looking stuff.

Over at Home Theater Shack you’ll find an old thread on waterfall graphs, dating back to the early days of the REW program, that runs for 17 pages. A thread doesn’t go on for 17 pages unless there is a lot of debate over conflicting ideas and interpretations, not to mention people just trying to get a handle on this new (to them) topic. And I’d have to include myself in that category as well, at the time. The ever-patient and affable John M. endured our pathetic musings without throwing up his hands and calling us all a bunch of idiots. At least not publically.

It’s surprising the amount of confusion and misinformation that still surrounds the subject of low frequency ringing and waterfall graphs after all these years. Equally problematic is the question of how to address ringing, and even more so, how to determine if it has been improved. It's common to see people confuse say, mere gain changes (as we often get with equalization) with an improvement (or not) in ringing.

For instance, I’ve seen threads where people were happy with the audible results of equalizing their subwoofer, but were disappointed that it didn’t get them an improvement in ringing. And others who, after boosting at 20 Hz to compensate for their sub’s lack of extension, were annoyed that equalization actually introduced ringing – completely unmindful of the fact that such an adjustment will make a time-domain graph appear worse than before. On the flip side, I’ve seen others who claimed to have achieved a 300-400 ms improvement in ringing after subwoofer equalization, which is patently impossible.

Sadly, these folks are in good company, as such contradiction can be found even among those who should know better. On the Web you can find manufacturers of equalization equipment, as well as companies that specialize in acoustics, present “before and after” time-domain graphs that claim to show an improvement in ringing, that actually do not. I’ll show some tragic examples of the type in Part 2 of this piece.


Decay Speed vs. Decay Rate
A quick explanation for those who may have no idea of what any of this is: “Ringing” is a succinct term that refers to the time it takes a bass signal to fade down to the room’s noise floor after the signal stops. Measurements of the decay duration are typically presented in time-domain graphs such as waterfalls and spectrograms.

To start, let's clarify a few definitions. In the following discourse, when I refer to "decay time" I mean the time it takes a signal to fade away, relative to its gain or loudness. For example, an 80 dB signal will quite naturally fade down to the noise floor in less time than a 95 dB signal.

When I refer to "rate of decay" or “decay rate” I mean how fast the sound decays: If we have 85 dB signals in two separate rooms and one fades to the noise floor in 300 ms, and the other in 200 ms, the latter has a faster "rate of decay.”

It should probably be noted at this point that the accepted professional benchmark for determining audio signal decay in a room is known as RT60. RT60 (RT = reverberation time) refers to the time it takes latent reflections to drop 60 dB after the signal has been shut off. Unfortunately, RT60 measurements are mainly relevant in auditorium spaces, not the small rooms where we typically have our systems, for a number of reasons.

For starters, RT60 measurements are accomplished with specialized equipment and measurement devices, not the omnidirectional measurement mics or hi-fi speakers we use with REW and similar platforms. In addition, RT60 measurements typically are not full range and do not factor the highest frequencies, or the lowest, where we are most interested in learning about the in-room behavior of our subwoofers. Furthermore, the waterfall or spectrogram graphs we use will seldom have a full 60 dB of signal from peak to floor anyway. (Note: Here is a good link with more information on RT60 for those interested, including a nifty video showing how the measurements are taken.)

Another problem is that RT60 measurements incorporate both “decay time” and “decay rate,” as you can see from the graph linked above. However, for our purposes we need to look at these two things separately.

So with RT60 off the table as the gauge for defining the low frequency decay behavior of a home theater room, I’m forced to come up with some terms of my own – hence “decay time” and “decay rate.” I don’t pretend that these are legitimate scientific definitions, but hopefully clarifying a difference between the two will help keep the discussion understandable and making sense.

In addition, when you see the term "ringing" being used, there is (again) typically no delineation between the “time” and “rate.” You’ll often see people say things like, “After doing ‘xxx,’ an increase [or decrease] in ringing can be observed,” with no indication if they mean “decay time” or “decay rate.” (I suspect that most of them don't know a difference exists.)

Confused already? Don't feel bad – lacking that background in the relevant sciences myself, it took me years to sort this stuff out. Let's try to untangle it.


That Old Graph Magic
Probably the most common source of confusion on this topic is misunderstanding the effect that signal levels (i.e. gain or SPL) have on a waterfall or spectrogram. Here’s a waterfall graph from a thread at Home Theater Shack some years back:


01-105-db-waterfall-jpg.jpg

Graph 1: 105dB Waterfall


Looks pretty scary, huh? Notice that the signal is peaking at nearly 110 dB. Now, let’s look at the same measurement with the signal reduced to peak at 85 dB:


02-85-db-waterfall-jpg.jpg

Graph 2: 85dB Waterfall


Wow. Just like magic it looks much better, doesn’t it? As you can see, merely reducing the signal level makes for a noticeably “better” waterfall graph, because a quieter signal will obviously fade away quicker than the louder one:


03-gain-and-decay-time-jpg.jpg

Graph 3: Signal Level and Delay Time


But that is not the same thing as improving the decay rate, as you see happening on the right side of this graph:


04-rate-of-decay-jpg.jpg

Graph 4: Signal Level and Rate of Decay



Equalizer “Modaling”
Now let’s look at the relation between room modes and signal level. This probably isn’t the best explanation, but a room mode is a build-up of bass energy that causes a substantial increase in level (gain or SPL) at a certain frequency. As we’ve seen, any increase in signal level nets an increase in decay time: A room mode takes longer to fade away merely because it is louder than the rest of the signal. Again, this is not to be confused with the decay rate.

However – what distinguishes a room mode from a “regular” peak in frequency response is that it will also display a longer decay rate in addition to the increase in SPL.

What can we do about the huge “sore thumb” signal level of the room mode? Enter the equalizer. An equalizer is merely a device that alters signal gain at specified frequencies.


05-rew-sweep-baseline-vs-rta-filtered-jpg.jpg

Graph 5: Baseline (purple) vs. Equalized Frequency Response (black)


With a parametric equalizer we can set a precise filter – bandwidth, frequency and negative gain value – that counteracts the mode and basically robs it of energy. We can see the effect with this "before and after" that features a nasty mode at 55.7 Hz. Counteracting the mode with a precisely-set parametric filter eliminates its audible and unpleasant “boomy” effect.


06-raw-response-waterfall1-jpg.jpg

07-filtered-response-waterfall1-jpg.jpg

Graphs 6 and 7: Room Mode Before and After PEQ


So by reducing the level (gain) of the mode, the equalizer brought its decay time, as well as its decay rate, back in line with what the room is naturally exhibiting.

Here's another example. In this comparison, a parametric filter was set for a mode at 41.9 Hz. This time with the second graph, the level of the signal after equalization was raised to match the SPL reading the mode was displaying before being equalized. In other words, 41.9 Hz are at the same SPL in both graphs. Naturally, increasing the signal level in the second graph makes it look worse overall (as discussed above). However, we can clearly see that after equalization, the frequency where the mode was located (41.9 Hz) now displays a significant improvement in rate of decay.


08-base-waterfall-graph-at-200-ms-jpg.jpg

Graph 8: Baseline Waterfall

09-waterfall-graph-with-42-hz-filter-at-200-ms-jpg.jpg

Graph 9: Waterfall with 42 Hz Filter


So we can see in both the presentations above that the room mode’s rate of decay has indeed improved after equalization. Please note however, it has not improved beyond the room average. At the of the day, this is the best that can be achieved with electronic equalization. It’s pretty much an iron law.


How Ringing is Significantly Improved
Why is that? The next thing to understand is that ringing is the same to low frequencies as audible reverberation (or echo) is to the upper frequencies. Both have to do with the rate of decay: If you have a room with a lot of hard surfaces, it has a lot of reverberation because the sound bounces around all over the place and takes a long time to fade away. Add some room treatments, furniture, carpet etc. and the reverberation virtually vanishes. Why? Absorption. The furnishings and treatments absorb the sound waves and thereby the reverberation is truncated – i.e. the rate of decay the "live" room exhibited has been radically stunted. It should be self-evident that an equalizer is no cure for a "live" room that has lots of echo and reverberation, nor is any other electronic device.


04-rate-of-decay-jpg.jpg

Graph 4: Signal Level and Rate of Decay


In the same manner, absorption is required to improve low-frequency ringing – by that I mean the signal decaying at a faster rate, irrespective of its SPL. Typically this means bass traps or something similar. An equalizer can only make adjustments in gain levels to problematic frequencies; it cannot absorb acoustical energy. It can make a waterfall graph "look" better to the untrained eye by reducing the signal level of peaking frequencies, but again – that doesn’t necessarily mean there was an improvement in the rate of decay.

So, how do you determine from a "before" and "after" waterfall graph if you have actually realized an improvement in ringing? It’s simple: Just study the spacing between the horizontal lines. Each horizontal line indicates a "slice" (fraction) of time as the signal decays from its "starting point" until it falls to the graph's floor. So, if there is a real and factual improvement in ringing – i.e., if the signal in an "after" waterfall graph is actually decaying faster than in the "before" graph – there will be wider spaces between the horizontal lines.

This is clearly evident in the graphs below that show ringing in a room with and without bass traps. Note the dramatic difference above 140 Hz that absorption makes.

10-realtrapsbefore-l-jpg.jpg

Graph 10: Ringing in an Untreated Room

11-realtrapsafter-l-jpg.jpg

Graph 11: Ringing in a Treated Room

Courtesy of Real Traps


You simply can't get this effect with an equalizer – again, it can't absorb acoustic energy. Don't get me wrong, equalizers are great tools for what they do. Personally I love them. I have lots of equalizers. But you have to know and respect their limitations.


Slices and Levels
Obviously it’s easy to use a waterfall graph to gauge the effects of ringing when bass traps have been added, especially if you add a lot of them. However, gauging the effects of equalization is different, because equalizers merely address ringing by reducing the level of a modal peak. For example, let's revisit this graph shown earlier in this post, where an EQ filter eliminated a 55.7 Hz room mode:


06-raw-response-waterfall1-jpg.jpg

07-filtered-response-waterfall1-jpg.jpg

Graphs 6 and 7: Room Mode Before and After PEQ


This time take a closer look at the spacing of the slices seen both outside the circle, and inside where the mode was equalized. Note that the signal level (SPL) of the area below 45 Hz is something on the order of 10-12 dB higher than the signal level above 45 Hz. Yet, the spacing of the slices is virtually the same across the board. This should sufficiently demonstrate once again that once you've eliminated the room modes, you can't equalize to further "improve" ringing. All you're doing at that point is making gain (signal level) changes, not improving the decay rate .

Aside from studying the spacing of the slices, the best way to show if EQ improved ringing in a room mode is gain matching the baseline signal with the equalized signal. Since equalizing the mode will bring a gain reduction at the offending frequency, and hence a better-looking waterfall graph, it’s easy to be fooled into thinking there was an improvement in ringing whether there actually was one, or not. As such, the offending frequency in the “after” graph should be level-matched to the baseline measurement, as seen above in Graphs 8 and 9 above. That will make it easy to see if the decay time of the mode actually improved. This is especially important if you’re using spectrograms instead of waterfalls: Since they have no slices to study, it’s the only way to tell that a mode’s long “tail” has fallen in line with the rest of the graph.

It should be further clarified not every peak in measured frequency response is a room mode, as this graph shows:


12-room-mode-vs-room-peak-jpg.jpg

Graph 12: Room Modes vs. Room Peaks


We can clearly observe from the long decay “tails” that there are room modes at 40, 62, and 90 Hz. But notice the peak at 120 Hz. You can see that it is at a much higher level than the peaks at 40 and 62 Hz, but its rate of decay is significantly faster than those two. This is because 120 Hz is not a room mode. Addressing that peak via EQ would certainly bring an improvement in perceived sound quality, but not an improvement in the decay rate, as would be observed by examining the slice spacing.

This is the situation people face when trying to use equalization to improve ringing where there are no apparent room modes, as you can see below 30 Hz in the next graph. The only "improvement" you'll see will merely be the effect of the signal level being reduced by the equalizer, so you're just chasing your tail. All you’ll get is less bass.


13-low-freq-ringing-jpg.jpg

Graph 13: No Room Modes
 
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Wayne A. Pflughaupt

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Part 2: Expert Disillusionment


Now that we understand how to interpret ringing and signal levels in time domain graphs, we can look at questionable information presented by some whom we might presume to be knowledgeable experts on this subject.

Manufactured Waterfall Malfeasance
The first example comes from the DSPeaker company. DSPeaker sells an automated subwoofer equalizer called the 8033 Anti-Mode. Its very name indicates that it is capable of reducing the effects of room modes. It’s been a while since I’ve seen anyone use this device, but I recall that it had generally good reviews.

However, DSPeaker offers the following graphs to prove that the 8033 reduces room modes. The graphs are actually pretty good in one way, in that the “after” does show wider space between the slices.


14-dspeaker-graph-1-jpg.jpg

Graph 14: DSPeaker Baseline

15-dspeaker-graph-2-jpg.jpg

Graph 15: DSPeaker After Antimode 8033 EQ


However, the explanation they offer is, “The strongest peak at 53 Hz has been countered quite succesfully (sic), and the slow decay mode of 34 Hz has been improved for the first 200 ms. (An) audible difference is obvious...”

Well sure, the SPL was reduced a full 10 dB at 34 Hz and 15 dB at 54 Hz! That alone would “improve” the waterfall “for the first 200 ms.” And certainly the subwoofer is going to sound better, if for no other reason than its frequency response is now smoother.

However, it will also need to be turned up quite a bit to compensate for the severe gain reduction. Anyone who’s been paying attention thus far can predict how this story ends: That’s right, when the sub gets turn up it’s going to completely blow out the so-called “improvement for the first 200 ms” on a subsequent waterfall graph. If the intent of the graphs was to show the equalizer improved ringing from the room modes (which I’m sure it did), it would have required “before and after” measurements that were level-matched.


Spectacular Spectogram Fail
The next two examples come from a respected consulting service. I’m not going to identify them because one of the principals is a really nice guy who offers a lot of help to folks on various home theater forums. However, despite the company’s expertise in room acoustics, their on-line material shows that they do not know how to read time domain graphs.

In an article on the topic of subwoofers and parametric equalizers, these two spectrograms are presented as proof that parametric EQ reduced ringing of a mode at 72 Hz.


16-af-72-hz-before-jpg.jpg

Graph 16: 72 Hz Room Mode Before EQ

17-af-72-hz-after-jpg.jpg

Graph 17: 72 Hz Room Mode After EQ


Personally I don’t like spectrograms as much as waterfalls as a tool for analyzing low frequency time-domain behavior because they’re not as readily intuitive.

However, if you look at the graph below that shows the frequency response before and after equalization, you can see that after EQ the 72 Hz peak has been reduced by 6 dB.


18-af-72-hz-graph-jpg.jpg

Graph 18: Baseline and After PEQ Frequency Response


That by itself explains why the “after” spectrogram looks better. Unfortunately, since a spectrogram does not show the “slices” of time like a waterfall does, it’s impossible to make the determination if EQ has accomplished an actual improvement in the decay rate for the 72 Hz peak, or merely its decay time.

This is relevant because (as noted previously) not all peaks in response are room modes. EQ would / could only reduce the decay rate of a true room mode. If the “after” spectrogram had been level-matched at 72 Hz, we could possibly make a determination, but that key element was overlooked.

Another article from the same party claims that manually-adjusted parametric EQ is superior to digital room-correction (DRC) processing, supported with spectrogram graphs that – once again – confuse a reduction in signal level with an improvement in the rate of decay. The first spectrogram shows decay after equalization with DRC, the second after manual parametric equalization:


19-drc-spectrogram-jpg.jpg

Graph 19: Spectrogram after Digital Room Correction

20-peq-spectrogram-jpg.jpg

Graph 20: Spectrogram after Manual Parametric EQ


And as before, the frequency response graphs show why the parametric “after” spectrogram appears better:


21-drc-freq-graph-jpg.jpg

Graph 21: Frequency Response after Digital Room Correction

22-af-peq-freq-graph-jpg.jpg

Graph 22: Frequency Response after Manual Parametric EQ


We can clearly see that the parametric graph is on average 5 dB lower than the DRC graph. Adding insult to injury, the article explains that manual parametric EQ did a better job at reducing the long time decay between 43Hz and 20 Hz than DRC did. Well sure, the frequency response graphs shows 20 Hz is down nearly 10 dB – no wonder that region “looks” better on the spectrogram.

But as noted repeatedly, you can’t really tell if the rate of decay has been improved from a spectrogram without level matching. So the whole exercise is pretty pointless and proves nothing.

This is a textbook example of the situation I described at the beginning of this piece, where people say “xx” gets an improvement in ringing without making a distinction between decay time and decay rate. Without that clarification, all they’re really saying is “The ‘after’ graph looks better.”


Conclusion
It should be clear that much confusion and misunderstanding persists regarding signal levels in time domain graphs, even among those who should know better. But now you, dear reader, are more knowledgeable than many “experts” on this topic.
 
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dengland

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I am in the middle of trying to understand my room's response and trying to treat my room (bass traps at this point). Thanks for the explanation above.
 

tonycdk

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You are correct in thinking of using tuned bass traps. This is really the only way to address resonant modes (other than active cancellation). If you have the space very thick broad-band absorption helps to some degree.

To give you an idea of what can be achieved in a relatively small room I am attaching a waterfall of one of my subwoofers, in my room at the listening position. The room fundamental is at about 23 Hz.
Sub-woofer Waterfall 2.jpg
 

torgeirs

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Very good response at the measurement point! Would be nice to se the results of measurements 30 cm to the side. And 40 dB scale
(Bet they are not so pretty, but they could still be very good:-))
Recomend REW room simulator and changing position. See how the response changes. This can also be experienced by playing a fixed bass frequency and moving yourself around the room
 

dlalli

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Thank you so much for this article as I needed to expand my knowledge on waterfalls . Coincidentally, I ordered acoustic panels and plan on rearranging furniture in my theater space then measuring and rerun the miniDSP & Audyssey. Now I will have a better understanding of the before and after measurements , especially the waterfall graphs

I suppose the next question is how do you determine room treatment & panel placement? Experiment With moving them around?
 

Wayne A. Pflughaupt

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Thanks for the kind words! The company you ordered the panels from should be able to assist you on placement.

Regards,
Wayne
 
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dlalli

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tonycdk

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Very good response at the measurement point! Would be nice to se the results of measurements 30 cm to the side. And 40 dB scale
(Bet they are not so pretty, but they could still be very good:-))
Recomend REW room simulator and changing position. See how the response changes. This can also be experienced by playing a fixed bass frequency and moving yourself around the room

The measurement was made many years ago. I can't remember exactly when but the file, which I considered as non-essential, was lost in a major computer system failure. At the time I was only interested in a 30 dB range but I am sure that extending the range would start to show low level garbage of sorts since four of the six room constraining surfaces are concrete. I did measure 15 cm closer to the speakers and 15 cm to the side without significant changes to the frequency response (of course significant is subjective) but I never checked on the waterfalls.

It is obvious that I use DSP corrections in my system (I use Acourate processing). I actually have five sub-woofers in my multi-channel system, one for each channel, each one of which is corrected to the same band-pass filter (attached front three channels measured frequency responses for info). They are also set for the same sensitivities and time-aligned at the listening position.

Figure 5.  Final Subwoofer Measurements.png



I expect to be doing another system calibration in October so will try to remember to do some more extensive measurements if I have the time. Just in case you are wondering I use Earthworks QTC 50 microphones.

Tony
 
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Sacenti

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Thank you very much for this article Wayne, as I needed to expand my knowledge about waterfalls. I am looking for information on how to interpret the parameters of the table generated in the T60 graph of REW, I cannot say when the measure is good or bad of the variables shown by REW in the table in the attached figure ... why did it change color, precision? Clarity, EDT, Topt, etc ... I would like you to help me understand a little more about what the REW writes and how to use it in the assessment of the acoustics of the room. The REW tutorial does not address this issue very deeply or I did not find the version of the tutorial that explains this You are very didactic when explaining things ... I follow your post, always well grounded and elaborate, congratulations on your willingness to help others who want learn ... in this acoustic and psychoacoustic area that I have worked for years, we learn from crumbs collected here ... I read somewhere that through EDT and its decay of 10 dB in the first 100ms you can judge the quality of the room - living or ideal or dead - would you know to explain anything about this? My suggestion for your next post as always shining in the exhibition. Thanks again for your attention and dedication you add a lot of value to the REW forum.
 

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DanDan

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Well the Titanic was designed by Experts........ ;-)

REW is advancing and adding features at a rate of Knots. New features are appearing frequently. I have been wondering what is the point of the Spectogram when the Waterfall seems to be working well, and is very intuitive. But various friends have praised the Wavelet view in particular.
I look at it now and then, play with it. Below I have engaged the 'Normalise' tick box. OK, nice looking graph, pretty intuitive. The 'Normalise to Peak at each Frequncy' should show any before and after Eq or treatment graphs on a level playing field afaik. Note the peaks do not all start at zero though.....
This could be useful in aligning multi driver speaker systems.

34435




These Graphs increasing require an understanding of the measurement processes which they describe. Full Science. REW has become what I would call a full blown Acoustic Laboratory. Perhaps the most complete software available. But to use it as intended and understand it's outputs..... I am afraid it has ascended to the rarefied heights of Academia.

The BBC Research and Development Dept had 'the budget of a small country' Their work is available free.
One IMO interesting qualifier for a Studio was that any 1/3 Octave Decay figure had to be within 10% of both neighbours. Secenti, you can trust 'Aunty'
Many Acousticians seem to faour the ETC graph. Perhaps because it was the first, and because the wonderful graphics we see now were not possible back then. But the ETC delivers a lot of information. It shows the 'liveness' of a room. A best fit line can show up a great even Decay or deviations from it. Third Octave Filtered ETC can show the Rate and indeed 'Quality' of Decay in bands long considered to represent audibility.

To be honest both I and my computers are struggling to keep up here. But perhaps this is a Meteor trail worth following. From a brief look, I suspect the relatively new RT60 Decay feature is probably the best Decay Tool available anywhere. Once I figure the Wavelet, that newer feature is on my 2 Learn list.
 
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Sacenti

New Member
Joined
Jul 2, 2017
Messages
38
Wayne e DanDan, em primeiro lugar, agradeço a atenção dada ao meu pedido e, em colaboração, encontrei uma dica muito boa sobre a interpretação dos gráficos REW incluindo ETC segue o link: https://www.avsforum.com/threads/simplified - rew-setup-and-use-usb-mic-hdmi-connection-including-requer-técnicas-e-como-interpretar-gráficos.1449924 /
Se você já conhece essa abordagem "jevansoh", desconsidere-a, caso contrário, use-o como um complemento para tudo o que você sabe sobre REW. Nunca postei sobre meu trabalho sobre outras formas de ouvir música de 2 canais, estou fazendo essa citação pela primeira vez, iniciei meus estudos sobre correções de sala nos anos 90, quando usava apenas um vinil de Bruel Kjaer com faixa de ruído rosa de terça de oitava + um medidor de SPL também do Bruel - naquela época não havia internet - e hoje com o REW - uso há cerca de 8 anos - fiz pesquisas sobre formas de reproduzir músicas gravadas em 2 canais PCM em uma sala de home theater. Eu pesquisei e testei vários métodos, apliquei nas salas de amigos e meu quarto também - meu laboratório. Reuni conceitos de reprodução desenvolvidos pelo pesquisador e professor de psicoacústica irlandês Pulkki, além dos conceitos de Floyd Toole - bíblia de cabeceira, outros rudimentos aprendidos com os ensinamentos de Beranek e do Dr. Gueddes, pesquisas da Harman, etc ... para encurtar a história cheguei depois de muitos testes em uma forma convencional de ouvir o estéreo convencional, convertendo 2 canais estéreo PCM em 10 canais (F + W + H + SR + SRB + C + SWs) aplicando os conceitos de triangulação de pontos de Pulkki e adicionando precedência (5 a 7ms) aos canais envolventes com níveis diferentes. O resultado é muito perceptível a ser ouvido, trazendo mais naturalidade ao som - imagem ampla e envolvente - qualidades que se busca no sistema estéreo convencional, mas quase sempre gastando muito para um bom resultado. A vantagem método multicanal com precedência é que você só precisa de um sistema estéreo regular, para os outros canais, você pode usar alto-falantes e amplificação mais simples para o efeito desejado ... Estou informando sobre esta experiência para compartilhar com os interessados em como alinhar, transformando seu AVR multicanal em um sistema muito melhor para ouvir música de dois canais ... Se você já conhece este layout ou sabe de alguma comunidade que usa essa configuração multicanal com precedência e nível, por favor, gostaria de seus comentários ... Estou simplificando as informações nesse momento de curiosidade, ficarei a disposição caso tenha interesse sobre o meu experimento. .. Obrigado e saúde! (Desculpe pelo meu Google em inglês)


Wayne and DanDan, first of all, I appreciate the attention given to my order and, in collaboration, I found a very good tip on the interpretation of REW graphics including ETC follows the link: https://www.avsforum.com/threads/simplified - rew-setup-and-use-usb-mic-hdmi-connection-including-requires-techniques-and-how-to-interpret-graphics.1449924 /
If you already know this "jevansoh" approach, disregard it, otherwise use it as a complement to everything you know about REW. I never posted about my work on other ways of listening to 2-channel music, I'm doing this quote for the first time, I started my studies on room corrections in the 90s, when I used only a Bruel Kjaer vinyl with a pink noise strip from Tuesday octave + an SPL meter also from Bruel - at that time there was no internet - and today with REW - used for about 8 years - I did research on ways to play music recorded on 2 PCM channels in a home theater room. I researched and tested various methods, applied it in friends' rooms and my room too - my laboratory. I gathered concepts of reproduction developed by the researcher and professor of Irish psychoacoustics Pulkki, in addition to the concepts of Floyd Toole - bedside bible, other rudiments learned from the teachings of Beranek and Dr. Gueddes, research by Harman, etc ... to shorten the story I arrived after many tests on a conventional way of listening to conventional stereo, converting 2 stereo PCM channels into 10 channels (F + W + H + SR + SRB + C + SWs) applying Pulkki's point triangulation concepts and adding precedence (5 to 7ms) to the surrounding channels with different levels. The result is very noticeable to be heard, bringing more naturalness to the sound - a wide and immersive image - qualities that are sought in the conventional stereo system, but almost always spending a lot for a good result. The advantage of multi-channel precedence is that you only need a regular stereo system, for the other channels, you can use speakers and simpler amplification for the desired effect ... I am informing you about this experience to share with those interested in how to align, transforming your multichannel AVR into a much better system for listening to two-channel music ... If you already know this layout or know of a community that uses this multichannel configuration with precedence and level, please, would like your comments. .. I am simplifying the information in this moment of curiosity, I will be available if you are interested in my experiment. .. Thanks and cheers! (Sorry for my Google in English)
 
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FargateOne

Member
Joined
Jun 5, 2017
Messages
109
My AV System  
Preamp, Processor or Receiver
Rotel 1562
Additional Amp
Bryston 3B3 for fronts mains
Universal / Blu-ray / CD Player
Cambridge CXU
Front Speakers
B&W 804 D2
Center Channel Speaker
B&W HTM4D2
Surround Speakers
B&W 705
Subwoofers
SVS PC-2000
Other Speakers or Equipment
10 PEQ filters/channel in receiver with REW
Video Display Device
Samsung UN55ES8000
Dear Wayne, thank so much for this "paper"
 
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