lots of bass traps=dulling of the highs...partially reflective traps?

[PaulP]

Originally Posted by DanDan

Of course both Lupo and myself are actually Avatars.

In another life I did woodworking by traditional, hand-powered means and there
was an email list dedicated to this. When I mentioned to my brother-in-law that
I enjoyed being able to talk to an oldtimer cabinetmaker who would share his
experience with me he replied "it's probably some 14 year old kid".

Paul P

[DanDan]

, and I'm a GIRL!

But for imaging at least you need reflections.

Not correct in my experience. In fact the opposite is the case. Some of the most spectacular imaging is heard on binaural recordings played back via headphones. When the side reflecting walls are treated, as in RFZ, the stereo images formed between and even outside the speakers become vivid, almost tactile. Imaging reflections are in the recording not the room.

Control Rooms in my freelance experience have been mostly quite bad. By bad I mean everything sounds different outside in the real world. It is quite common practice to review mixes on three systems in three different locations, to work around this issue. From memory and current practice I find the ones that do translate best, uncannily so, tend to be pretty dead. In fact if I had to do a quick assessment of a mix room I would play back reference tracks on my own headphones, comparing the speaker/room to that. If it is not close, it is not going to work. Many listening spaces have other ambitions, e.g. impress the client. Home and theatre listening is for pleasure. The ambience surrounding the music in such situations is pleasant, but it absolutely obscures detail, including imaging. Conversely there is no way that I would enjoy listening for pleasure only in a successful mix room.

DD

[Yiannis]

Originally Posted by DanDan

yiannis- your vertical scale shows the wobbles caused by the desktop very well. Turn down the microview and you may decide there is no problem. It is certainly not the sonic problem of cloudly low mid. I would suggest we are seeing an image of that in the Log squared and none of us understands it. That pattern appeared in both L and R measurements. I don't think it is a bug or operator error at all. You could try changes of speaker and worktop height, angles, and your own distance perhaps. At the end of the day you may just have to live with your desktop. You would not be alone. Furthermore the wobbles are very small. Very very small compared to you moving your head from side to side!

DD

I must admit that the problem is more visual than audible.

Of course it has nothing to do with my cloudly LM .

I don't notice something is changing by playing music and put/pull the foam on my desk.

Maby a very very minor hi freq definition...but maby is my brain playing tricks.

I can't be sure but the measurements show that there are some reflections I have to take care .

I will try but maby at the end I have to live with them

we'll see.............

[Nordenstam]

Originally Posted by DanDan

PaulP, we have been presented with scenarios of working with ETC. It often involves string, a friend with a panel. We need friends.

Friends are good! =) But it also works fine to work alone with ETC's.

Mirror reflections, single or multiple, are not the only source of problems. The wavelength of light is way small compared to sound. You can't see audio frequent diffraction.

Originally Posted by DanDan

In this thread, the damaging desktop reflection was not noticed or identified as bad, UNTIL it was shown to be so by blocking.

That's not how the history of the thread unfolds. I suggested to look into that reflection in post number 81, as it seemed like an obvious source of problems based on viewing the ETC. Evaluating if it is potentially bad or not is impossible without a working dB scale. Anyway, from the looks of it, it seemed like an obvious place to start. Paul gave a practical example of how to do it in post number 86. The result of those posts can be seen in post number 105, where Yiannis correctly identified it as being a reflection from the work surface.

I wouldn't stop there if it was my room! The change in level is probably not as much as can be had by using thicker absorbents. Try some other stuff, check the ETC again. Find something that is effective and can be used as temporary absorbers for critical listening. Take them off while working. There are also other reflections within 20ms that probably could do with some attention. Hard to know though until the impulse file arrive and we can get a dB scale on the curve!

As for hearing the difference - try playing pink noise through a single speaker and move your head around. Apply treatment and do it again. If the reflection is loud to start with and the absorber is working correctly, difference should be obvious.

Originally Posted by DanDan

They have repeatedly spoken in highly technical, obtuse, often wrong, and always without communicating at a suitable level to be heard and understood. This has caused confusion and doubt, and is wasting a helluva lot of our time.

Tell us what's wrong! If there are factual errors, we'll all benefit from seeing them corrected.

Sorry that you feel it's been a waste of time. That's definitely not the intention.

I know for sure that the technical stuff is way below some of the posters in this thread. There's probably things I write that makes them shake their head, seeing me for the n00b I am! Some people get it all with more or less effort. Thanks! There's probably also a lot that goes over the head of some people, but they'll hopefully gleam some useful bits here and there anyway. Again, the big winners are those who make the most progress. More power to ya!

Writing so that anyone without any technical qualifications can understand it doesn't seem useful to me. These are technical issues, after all! I'd rather err on the side of too much than too little info.

Originally Posted by DanDan

You need to be fluent in FFT Maths to fly that helicopter.
Many of us think it better to walk that short trip.

Let me once again point out that I haven't used a single technical word to describe ETCs. All the technical talk lately have been on the topic of frequency analysis. Frequency analysis requires Fourier transform. That's typically done using the Fast Fourier Transform. ETC's have nothing to do with Fourier!

Have spent way much time doing all sorts measurements over the years. Macc knows I have a habit of posting graphs in the mastering forum! :D Whenever I wonder about some technical issue, transforming it into a test setup and doing some measurements is usually the first thing that comes to mind. As you may have noticed by the barrage of graphs and illustrations! All the difficult talk about frequency response graphs is because it's a difficult subject that demands a certain level of competence to fully use and understand. I wouldn't like to use frequency response graphs without having access to changing the measurement range, FFT size and windowing options. Preferably also overlapping, hopefully in both frequency and most importantly, time. There are some circumstances where some of the options can be locked due to the operational framework, but most of the time, one needs control over all the parameters to get the most meaningful reading. It's very easy to skew the results in all sorts of ways if due attention is not given to the details. The reason it's so difficult is because it's impossible to get into a pure and clean frequency domain. It requires endless time. We're dying any moment, relatively speaking, so we got to hurry up. Time domain on the other hand is very easy to achieve. It requires zero time. We can live with that! No uncertainty principle to deal with there.


I'm very glad to see that you're open for trying to use it! Despite the wrapping that gets stuck in the throat. :P I think that you may find, with practical experience, that there's a reason why Everest writes in the master handbook of acoustics: "the in-room response graph shown in figure 24-9 is of little value in an environment with multiple reflections". ... "Pinpointing the level and decay times of room reflections, with respect to the direct sound, is best evaluated using a filtered energy-time curve." The graph referred to is the sort of frequency response graph that keeps popping up in this forum(long measurement window, fine resolution).

As for the error percentage inherent in measurements. It was a very loose figure, not a hard number from actual gear. My (individually tested) mic calibration file shows the values to be between is +0.56dB to -0.23dB with most of the values starting with a leading zero behind the decimal point. Almost makes the calibration file extraneous!

Here's a list found online for Radio Shack SPL Meter correction factors(the .cal file format):
10 Hz +20.5
12.5 Hz +16.5
16 Hz +11.5
20 Hz +7.5
25 Hz +5
31.5 Hz +3
40 Hz +2.5
50 Hz +1.5
63 Hz +1.5
80 Hz +1.5
100 Hz +2
125 Hz +0.5
160 Hz -0.5
200 Hz -0.5
250 Hz +0.5
315 Hz -0.5
400 Hz 0
500 Hz -0.5
630 Hz 0
800 Hz 0
1 kHz 0
1.25 khz 0
1.6 kHz -0.5
2 kHz -1.5
2.5 kHz -1.5
3.15 kHz -1.5
4 kHz -2
5 kHz -2
6.3 kHz -2
8 kHz -2
10 khz -1
12.5 kHz +0.5
16 kHz 0
20 kHz +1

9.5dB deviation from in the ten octaves from 20 Hz to 20kHz, with 4.5dB span in the 8 octaves 40Hz to 10kHz. 4.5dB is more than ten percent in any graph that spans less than 45dB.

Never mind.. It's probably not the best point to make. The general idea is true though - measurements comes with uncertainty. Some more than others!


... spellcheck.net is working again! Apologies for the misspellings in the previous posts..

[Nordenstam]

Originally Posted by PaulP

It seems to me that headphones would be best to completely remove your
room from your work, if that is what you want. And you have said that you
like your room fairly dead.

But for imaging at least you need reflections. But they have to be useful
reflections. It is my understanding that you would benefit from having
a more lively room if the life was well behaved. It would enhance the music
you're producing just as much as a bad room would harm it.

I've read that most control rooms are not dead spaces. They can't be if
you want to be able to play back the music for others to judge.

This is a mighty good point. Perhaps the best post of the thread!

It touches the core issue here - what do we actually want from room acoustics?

If one use a frequency response graph as the sole judgement of listening quality, no reflections can be good reflections! The only way to have a flat frequency response graph is by having a single impulse without any reflections at all. This is exactly what happens with headphone listening. Near-anechoic control rooms was built in the 70's and no one liked it. The extreme/simpleton variant of LEDE, with a totally dead end and a live end, didn't fall in taste either.

Most people prefer a room where destructive interference is minimized while still preserving some life in the room. So how can we approach that goal? Frequency response graphs are not the answer. All reflections, early or late, gives the same seemingly destructive response in those graphs. Large magnitude reflections will of course create more of a havoc in the graph than smaller reflections. So it's true that the graph will look better in a room where the most offending reflections have been removed. But since the only way to get a flat graph is to have an anechoic response, how do we go about creating a listening space with euphonic qualities using such a graph? It will not tell us when we've approached the ballpark area we're heading for. It will not even tell us what direction we're heading in! The graph only tells us if we're heading for an anechoic response or not!

That may suit some listeners perfectly well. I like deadish rooms, but I like a real room better than anechoic room! The imaging in anechoic room is great, but... It's not something I'd like to listen to every day all day. Translation is also a big issue as Paul mentions above.


So how do we go about quantifying where we want to go in regard to room acoustics? The ETC is not only a tool to see the level of individual reflections. The time vs level graph also lends itself well to defining a viable goal for a nice sounding listening room.



This is the aforementioned figure ten from this paper: http://www.rpginc.com/news/library/T...ffCritList.pdf

This picture corresponds directly to every paper I've ever seen on spatial issues. A typical example can be found in Masters Handbook of Acoustics figure 6-11. Have granted myself the freedom to reproduce that graph here. Apologies to Everest if he doesn't like that! Hope it's part of the fair use deal. Don't have a scanner, so here's a photo:


Notice that the graph is an energy time curve. The interesting area according to the graph, is found between curve A and B.

There are many such graphs around. The actual threshold for hearing the reflections depends on the angle of incidence and sound being used. Short click like transients are very revealing of reflections while steady state tones are near unaffected by reflections. Such graphs illustrates viable goals for creating a non-anechoic listening room with great imaging and some euphonic life to them. The common factor of them all is that they come in a time vs level format. The same format as ETC's are using. So the ETC's is not only a tool to check the level of individual reflections, the time/level format is also part of the definition of the goal of treating rooms! This corresponds directly to all information one finds on spatial issues in psycho acoustics, stereophonic techniques, etc.

It's hard to get anywhere without having a predetermined goal to strive for.

[DanDan]

I will be unsubscribing after this last post. The activity has become appropriate to a University Debating society.

Lupo is clearly enamoured with ETC. He also has great difficulty with Frequency Response measurements. This must be difficult when all around us the vast majority of tech specs use FR. Overall there appears to be a over-riding desire to exercise theoretical mathematical and other skills.
The lack of understanding of what a Flutter Echo is suggests a dearth of real world experience.

To finish neatly, from my perspective, I will reiterate some points which don't seem to have gotten through. I will also point out some of the tearing at the edges of the credibility envelope.

I have edition 4 of MHOA. I can't comment directly on V5 which Lupo refers to. But, I will say that much of the later editions has not been written by Mr. Everest, sadly long gone. There are guest writers, there are opinions and there are blatant wrongs. e.g P228 Edition 4. That test, involving measurement, not written by Mr. Everest, does not hold up to duplication of the device or the test.
Let's make our own points here and let them stand or fall on their intrinsic validity. Quotation, perhaps out of context, is as dodgy as it ever was.


ETC in practice requires a friend with a panel just the same as the organic methods.

I have never seen a microphone or any other gears response quoted as a percentage error. Furthermore I have not seen dB and % mixed in this crude manner before. A ratio of a ratio? This is mathematical sleight of hand designed to dupe.
As Lupo admits 'not the best point to make' And as Lupo ignores, the same errors if they did exist, would occur in ETC measurements using the same crappy gear.

Repeat, I believe we were wrong about the FM ETC vertical scale. I believe it is regular dB. In the post illustrating the desktop reflection we see the response level start at -20dB. The desktop reflection kicks in at -55 to -75. Even within the first 20mS this is hardly significant. The human body causes a much greater disturbance than this, as would a slight change of head angle. The exercise revealed a desktop, in front of our eyes all the time, a known cause of reflections which would always be addressed. If it were a problem! In this case it is not a mixing desk, it is not large, and it is broken up with keyboards. It is not and never was a problem.

With the utmost respect, I reckon most readers here want to find out how to treat their room. With this goal in mind many of us are interested in any approach which shows promise. I have tried ETC (I repeat) with no success, during a thesis on small room treatment. I have achieved the same, if not better, removal of offending early reflections and flutter using eyes, ears, hands, and brain. I have repeatedly asked, and only Lupo has demonstrated actual uses of ETC. However not one of the two examples has had real world significance. Therefore, for the purposes here. i.e Treating small rooms, without having the 'benefits' of Engineering Level Maths and the Software to go with it, I will claim that the simpler graphs of Waterfall, Frequency Response, and perhaps Decay, are enough to indicate problems.
That is of course after all the normal certain treatments are done.
Look at a dinner plate under a microscope and you may never eat again.

DD

[Nordenstam]

Originally Posted by DanDan

Lupo is clearly enamoured with ETC. He also has great difficulty with Frequency Response measurements. This must be difficult when all around us the vast majority of tech specs use FR.

Have no problem with frequency response graphs and other charts used as tech specs in a normal system. Normal in that it does not have a time delay as one of its ingredients. It works great to describe equalizers, amplifiers and other similar processes. Comb filtering is not possible in such systems.

Would however not trust a FR graph of a reverb unit with the delays/reflections of the reverb actually running. Frequency response graphs (usually/should) show the response to a single test signal. With the reverb delays/reflections included in the measurement, this is no longer true. It's the test signal plus copies of it. Even though it may be a digital delay or reverb, guaranteeing a perfectly flat frequency response of all the delays/reflections in themselves, the sum of the many flat test signals across a stretch of time is not flat. Comb filtering is the result of superpositioning several copies of a signal. What would such a FR measurement tell us about the quality or sound of the reverb unit? Checking the frequency response resulting from superimposing several copies of the same signals doesn't work the way checking the response of a single signal does. I doubt you'll find any technical specs for flangers, choruses, delay boxes and reverbs as a FR graph that gives the sum of both original sound and the time delayed output of the unit.

The typical FR graphs of a room is the result of measuring an EQ+reverb system. The EQ is the source/amp/speaker response and the reverb is the room itself. FR measurements works well to describe the source part. By using a fitting 1-2 millisec window, only the source is observed, with all room reflections discarded from the measurement range. This gives the frequency response as it emanates from the speaker. If the window is made longer, one is no longer looking at the frequency response of the single original test signal system. It's the superposition of several copies of the same signal. A night and day difference from testing EQ's, amps etc.


Was serious when I said that I have to test everything.. RMAA is great for technical measurements on normal audio processes. Loaded up an impulse response reverb and ran the test signal through two way different rooms. It looks like this:



This deserves that confused emoticon:

A frequency response measurement doesn't work as one may expect when it's dealing with time effects. It's not supposed to be used that way.


The graph above is locked. It is what it is. There's no way to do anything about it, like selecting a more useful measurement window. The program is not meant to be used with several copies of the test signal mixed together. It's for measuring normal gear, not for acoustics or simulated acoustics(delays and reverb effects). Ran a REW friendly impulse through the same reverbs (to get the timing right) and had a look at it in REW, an acoustics oriented measurement tool. The resulting frequency response from superimposing many reflections depends, as always, on the amount of time we're looking at.

Here's the FR of the first 15 milliseconds, drum room being red and the opera hall purple:



25 milliseconds:



50 milliseconds:



100 milliseconds:



and lastly 500 milliseconds:



(all with 1/24 octave smoothing and Tukey 0.25 window shape)


This is why I don't get any useful information when someone posts a frequency response graph of their room. REW defaults to the 500 millisec window. That's good in a way as it shows the total response of most of the reflections. Things doesn't change much when going from 500 to 1000 millisec, much less than going from 50 to 100. It does however bear no relation to what we hear as humans. The ear/brain integrates a time window around 15 to 50 milliseconds, with 15-25 being typically quoted numbers. The 15 and 25 millisec windows above are closest to the human perception of the responses. They are both valid representations of the frequency response within the given measurement parameters. How are we to know which one to believe?


Here are the rooms in time/level view:



Don't think I'm overestimating the audio engineering community when I presume that anyone reading this can get the general idea of the rooms by looking at the graphs above.

The waterfall is also very revealing:


(1000ms length and window)

I hear the hearts of the waterfall lovers pounding. :D Sure, it's great! It doesn't tell the whole story though.


Further inspection of the early reflections in the ETC reveals more about how these rooms sounds in respect to imaging:



The red drum room have many high level early reflections. The opera hall have a clearly defined initial time gap. To get similar early reflections in the concert hall as in the drum room, would require the use of reflecting gobos on stage close to the source. The effect on the resulting sound is far from subtle. This is usually not done in concert halls. Though there is usually a conscious effort to leave some (relatively) early reflections in the room. Most concert houses have a large space with two single reflectors giving a distinct echo around 20ms or so. These are typically splayed walls on the sides of the stage. Have a look next time you're in a concert hall! It's something about that initial signal delay ended by a burst of energy that the brain seems to like a lot.

Early reflection management is a very important part of room acoustics. The waterfall does not give such info. Here's the shortest waterfall possible in REW, 300ms length and 50ms window:



The impulse responses used in this example can be downloaded here: Free Reverb Impulse Responses - Voxengo - it's the "scala milan opera hall" and "small drum room" files in the 3rd reverb pack. These can be loaded into room measurement software (REW is free cross platform) and/or played in any of the free IR reverb plug ins/programs around. Beware that some programs expects the impulse to start at some other time than zero. The impulses can also be altered as usual in wave editors, allowing to see and hear the response of changes in level of the reflections. Fun to play around with!

Originally Posted by DanDan

ETC in practice requires a friend with a panel just the same as the organic methods.

Not if using a realtime ETC. Or, measure, place absorber, click mouse for new measurement. No problem working alone.

Or get TEF and all the distances and directions will be served on a plate!

Originally Posted by DanDan

I have never seen a microphone or any other gears response quoted as a percentage error. Furthermore I have not seen dB and % mixed in this crude manner before. A ratio of a ratio? This is mathematical sleight of hand designed to dupe.

Am not deliberately trying to obfuscate the subject. Multimeters, oscilloscopes etc are usually specified with percentage errors. DB's, percentages, whatever, it's all describing the same underlying numbers. I hope that everyone understands what I mean by saying that 4.5dB is the same as 10% of a 45dB range graph. The point was that all measurements comes with errors. It's part of life. Some measurement equipment gives better precision than others and some measurement methods are more susceptible to being influenced by certain errors than others.

Originally Posted by DanDan

As Lupo admits 'not the best point to make' And as Lupo ignores, the same errors if they did exist, would occur in ETC measurements using the same crappy gear.

Frequency response errors will affect FR graphs much more than they affect time domain levels. Only smallers part of the total energy amount is being affected, hence only a small portion of the total energy level (time domain) will be affected.

Testing this is easy. I used white noise at -10dBFS RMS. By applying a -5dB q.71 100Hz parametric eq, the level changed to -10.14dBFS RMS. By using a more severe change with three bands, -5dB 1oct at 100Hz & 10Khz and +5dB 1oct at 1kHz, the level changed to -11.5dB RMS. That's a pretty bad frequency response, plus minus 5dB bumps and dips. The overall energy level (in the time domain) only changed by -1.5dB RMS.

Originally Posted by DanDan

Repeat, I believe we were wrong about the FM ETC vertical scale. I believe it is regular dB.

It doesn't practically work out when translating the numbers to the real world. The graph indicates a total dB range that is physically impossible.

Here's the full picture again:


About 180dB span from top to noisefloor. As I wrote some pages ago, with the noise floor taken to be 0dB SPL (extremely quiet!), a peak level at 180dB higher than this would equal an intensity of 1 million watts per square meters. One million times the watt/area that is the threshold of pain. We usually listen to 0.0003 W/m^2 at 85dB SPL. I doubt the speakers and amps used is in the two digit million wattage category. It would be hard to utilize it too. Fabrics and other things would burst into flames and any living creatures within a certain radious would die from the extreme pressures involved. The gross manner in which humans succumb to such pressure fluctuations have been described earlier. Yiannis is thankfully still breathing! Ipso facto 180dB non summarum.

Moral of the story: If one encounters a dynamic range in excess of 120dB, alarm bells should go off!

(the numbers above are not meant to prove my ability to operate the SPL calculator at Audio calculations in English - acoustics calculator convert audio formulas microphone formula sound studio free audio calculator recording studio acoustic audio engineering online education sound calcs energy calculations - sengpielaudio - guess I'm not the only one to find the range of the dB scale to be amazing!)

Originally Posted by DanDan

Therefore, for the purposes here. i.e Treating small rooms, without having the 'benefits' of Engineering Level Maths and the Software to go with it, I will claim that the simpler graphs of Waterfall, Frequency Response, and perhaps Decay, are enough to indicate problems.
That is of course after all the normal certain treatments are done.

Waterfalls are great for low end treatment. Decay graphs, if you mean energy decay curves, is similar to ETC's. As seen above, frequency response graphs as measured across several time shifted copies of a signal is far from simple to deal with.


.. Please don't quit the discussion quite yet! You're leaving a too big question.

As my previous post was going into, we need a goal to get anywhere with acoustic room treatments. I'm silly at times and it's very possible that I'm missing out on something big here. Just can't see how FR graphs can aid in creating anything but anechoic response! People generally don't like that sort of room. Any real room having any reflections at all will have a deviation from flat FR as observed across a large stretch of time. Most people are interested in minimizing destructive interference while still preserving some euphonic reflections. How can one use FR graphs to aid in that goal? It would be most enlightening if you can address this issue. As it is now, it seems to me that it's a path that can only remove the reverb from the eq+reverb equation. That's not why people chose listening rooms over headphones.


PS: am not out to "get" you Dan! This is not about you, this is about measurements in general. There's nothing personal in this.


Best regards,

Andreas Nordenstam

[DanDan]

Andreas, although I left I took a peek . Believe me I have no personal issue here. Your contributions in other posts have been very illuminating to me and to others. On the topic of ETC however you appear evangelical. You are quite prepared to go to the ends of the earth and over the edge into the nether regions in order to drag in innaccurate and inappropriate analogies in order to score imaginary debating points.

It is a fact that I have studied the practical treatment of small rooms repeatedly. It is a fact that I now practice this professionally. It is a fact that I have tried any tools I found available, including ETC. Within this restricted context of small room treatment, ETC has done nothing for me. Other simpler, faster methods have met with great success. No amount of imaginative debate, or creative graph manipulation will make these facts vanish. Such activity merely strengthens my view that you are of a highly technical nature, the sort of person I would employ perhaps when doing research, or designing of a new structure. I would love to see you driving Odeon or the other big programs. However, many of us use FM. I don't know if you are familiar with the Mac way of doing things. It is broadly speaking point and shoot. We trust, and are generally rewarded, that the developers know this and get the under the bonnet stuff right.
I have never found a reason to use the Windowing controls in FM.
I get my FR and Waterfalls easily and quickly. I use them comparatively, I don't recommend absolute measurement. I find this very useful and it helps me get a an accurate defined measured result. I would have no problem whatsoever doing the same job with brain, eyes, ears, hands, no helpers.

That vertical scale again. Yes it is confusing. Some of the views are not believable. It is possible to move these curves by hand, but it may be a bug, who knows?
However, when viewed positively, i.e. trying to get the best out of it, a good policy with any tool iMHO, I see a result. A result consistent with the waterfall, thus credible to me. In yiannis post 105 above the same ETC has a perfectly believable vertical scale. This is the third time I have pointed this out. The overall level is -20. The desktop hits between -55 and -75. Quite believable, quite real I guess. This is a very very dead room and the desktop is not a problem.

Note that ETC was not in early versions of FM. It was included later, and I really wish it wasn't. In the same post 105 above the desktop reflection is clearly visible in the Impulse Response. Thus why the ETC? Clearly Chris of FM thought the same until the usual pressures to have the same or more features as the competition. This begs the question as to why he included Log squared, Minimum Phase, tools for speaker design, and so on. With the greatest respect, I believe he too thinks in Maths.
My personal wish is that FM would have been trimmed down, made even simpler.
A real Pro version including Building Acoustics and more would be very welcome.

A Drum Room has a very different purpose to an Opera hall, even sampled ones.
A drum room provides support for the drums. The clusters of very early reflections add bloom and resonance, literally, to the drum sounds. A reflecting surface nearby feeds back into the drum, causing long sustain, more volume and so on. I would typically place drums in a corner for the bass boost. This 'bloom' is far from image enhancing, the opposite in fact.

The 20mS 'Kicker' in Opera and Orchestral halls has another purpose entirely. Such halls as we well know are generally disastrous for drums.

I do not go along with the assumption that things are better now than in the 70's. Loudness, MP3, jeez.
A lot of the 'developments' have been artist led. The 'feeling' of discomfort in 'dead' rooms has driven designers to provide more lively rooms. I see no evidence that this yields better results.

The ubiquitous notion of a later arriving bloom of ambience from behind is also worth questioning.
Our ears don't hear particularly well back there. So how loud, how clear, and how important is that late bloom? Or is it just another 'feeling"


In conclusion. I suggest we terminate this banter focussed on ETC, however fascinating and entertaining.
It is not getting towards any conclusion and there is plenty else to consider. The same amount of energy could be put into other posts, where we could both learn, and help others learn or simply get their rooms better. When I think about it, the same amount of energy would probably have put a dent into The Loudness War, MP3, Global Warming, the Middle East etc. :-)

CU there, DD

[johndykstra]

Hey guys,

If you don't mind, I have a thought.

It occurred to me last night, that there always seems to be the same faces around here. A certain percentage of us are devoting an excessive amount of time researching, building, and talking about acoustics. Broken down to the evil underbelly of human desires, this says one thing...money.

Granted, it never starts that way. Most of us start lurking around the acoustics forum to start treating our home projects, or improving our commercial facilities...whatever. The point is, anyone can look at the how I built my bass traps thread, read Ethan and Glen's FAQ's, and from that be able to build a pretty decent sounding room; one that anyone should be proud of. To do this, whether aware of it our not, you are going to need to manipulate principles of what the ETC does. A reflection free zone. Most of us will clap and use mirrors. Why? Because it's easy and proven effective. And for personal use, probably enough. Done.

Why would anyone spend upwards of 6 hours a day on here looking into acoustics? I started down this road because my career is appointment based, and I don't need many more than 10 actual hours of work a week to make a decent living... I am blessed. This started as research to build my band's rehersal space and studio. The more I read about acoustics, the more it excites me. The more I challenge myself with new concepts, the more everything I've encountered with my decade plus experience with live sound and recording starts to make sense, on a completely different level. I have SAC to thank for this. Before my first scuffle with him, I was content with the FAQs. So after all I've said about you, thank you... truly. I'm sure we haven't scuffled for the last time, and I hope that's the case. I often get defensive and confrontational when I don't understand something... you are very good at bringing that out in me.

What's my point. The ETC, if nothing else, is a tool to verify results. You can explain to anyone (in about 30 minutes) the hows and whys of a RFZ, and when and at what level we want to start seeing some ambience right? It's taken you a half hour to illustrate the concept on a very fundamental level to someone who doesn't spend their free time learning about this. Now, if you create this result for him, using mirrors, without the ETC, he just has to trust you that you've given him what you set out to do. But, if along with the explanation, you show him what it will look like on a graph, you can PROVE to him that you have done your job.

Let's face it, with the time some have dedicated to learning, at some point, you're going to run out of personal spaces to treat. And if you treat your personal spaces to an amazing degree, other people will take notice. This is where the money comes in. I'm starting to be approached by local colleagues to come and help. I'm not ready, and I've made them aware of that. We (the band) are undertaking a new control room, as some of you already know... I've been reading at a fury pace, and soaking everything I can. Books by Sedaris have been replaced by Everest as my night time reading. While I used to play online poker with my free work time, I now troll around acoustic sites. If I can achieve with this design what I think I can, I may just throw my hat in the ring... my hunger for this can not be quenched with the limited area of personal use... after all, I have a lot of free time... again, blessed.

With my limited understanding of measurement software, I can at least see the benefits of verification. And if used often enough for verification alone, at some point it's bound to reveal mistakes. We are all human right?

Andre, Lupo, Dan, Collo, Rod, GE, John, Victor, Paul, SAC, Ethan, Glen, Frank, Tiny, Brian,... this is starting to feel like an acceptance speech, sorry. You guys are all amazing.

I for one think, that the more we argue, the more we all learn.

Sorry for all of that, just how I'm thinking right now.

-John

[johndykstra]

I just read that back, and it really sounds like a proclamation that "I have arrived". Please don't read it as such. I clearly have a LONG way to go, and have no allusions of being a professional.

I guess I simply wanted to state, that from the outside looking in, i can see merits to ETC.

Humbly,

John

[PaulP]

Originally Posted by dykstraster@gmai

It occurred to me last night, that there always seems to be the same faces around here. A certain percentage of us are devoting an excessive amount of time researching, building, and talking about acoustics. Broken down to the evil underbelly of human desires, this says one thing...money.

I was expecting you to say just about anything except money .

I have a hard time imagining that there would be much interest from people
where I live for having me show them how to achieve good acoustics in their
homes. And if there were, I would not feel comfortable proposing they install
some corner superchunks, RFZ panels and a cloud. I find these terribly ugly
to tell the truth (though clouds can be attractive). I can appreciate the
improvement they can bring to the acoustics of a room and they would
satisfy my technical side, by I can't imagine many people being able to
accept them visually.

And the few studios nearby (I have no idea how many there might be)
would certainly wonder who the hell I was if I walked in a started making
suggestions.

Of course I'm speaking about some imaginary point in the future as right now
I don't even have enough experience to do my own space...

There are still quite a few McMansions going up around where I live so
that perhaps there could be work as a consultant to a buider but this
would still require that the homeowner be aware that acoustics are
important. The work would then have to be integrated into the structure
of the building itself for it to be acceptable visually. I've seen a few
examples of this sort of thing on the net and it's quite obvious that this
is a very expensive undertaking.

So I'm in the "in it simply out of intellectual interest" camp but who knows,
if I ever succeed in treating my space in manner that is both effective and
attractive I may think otherwise.

Paul P

[johndykstra]

No, I hear you, but my situation is a bit different.

I've been a house engineer at a rock club for nearly a decade, and a few clubs before that. I've met and become friends with countless bands, many of whom produce their own recordings. Inevitably, there's that one guy in the band, and for hours before the show we end up talking recording. Over the course of the last year or so, those conversations have started to drift from "what type of mic", to "let's talk about your room", as this is the area I have started to devote my energies toward. Naturally, the number of people that pay attention to acoustics, is a macrocosm of how things work at Gearslutz. 1200 people viewing "all about the gear", 160 viewing "studio construction and acoustics". There's a decidedly poor shift in priorities, and when you get me going talking sound, my arms begin flail in an attempt to help visualize and eyes get wide... as I see who ever it is I'm talking to begin to understand. Granted, I would NEVER knock on the door down at Electrical Audio and present myself as someone who can help. That's just silly. But I know a bunch of dudes I can help, and several have already asked for it. I have no intentions of becoming a studio designer getting rich. I already have a solid career. But I can see taking a laptop over to Joe Six pack's house, running an ETC, and showing him what the problems are, help him correct them, and run it again. Why? Spending more time with other musicians, get to keep building things (which I absolutely love doing), keeping fit, drinking beer (getting less fit), drawing on sketchup, and yeah, I guess making a little extra coin.

Win win as far as I see it.

[PaulP]

Originally Posted by dykstraster@gmai

Spending more time with other musicians, get to keep building things (which I absolutely love doing), keeping fit, drinking beer

Those are worth more than money thumbsup

Paul P

[Nordenstam]

Howdy folks!

An update on the strange looking pattern in this pic:




Got the impulse from Dan in the email and found the solution to the mystery pattern. It's truncation distortion!

Here's the impulse file in close up:


As can be seen, the data is so low in level that it's dominated by truncation distortion when it gets to 60ms or so.

The weird thing is that both FM and REW creates imaginary data after the 120ms point where there is no data what so ever in the room measurement! Arta did not do this. One nasty trick, IMHO, worth keeping an eye on!

The waterfall also looks normal in my programs, none of the 20ms repetition of data follow by the cliff like drop.
Here's a waterfall from RplusD:


And here's the ETC of the room (from ARTA) showing the D R Y room:

[Yiannis]

Hi Lupo,

so how would you describe the freq response of this room?

I already know Dan's opinion which I also respect, but I would like yours too.

Is there something that makes my LMF cloudy and unfocus?

speakers are 1031 A with HF tilt at -2.