Room EQ in Damon's room

[damonrpayne]

All measured. Holy huge bump at 20hz!

[damonrpayne]

Low freq waterfall:

So, if I read and interpret this graph properly, the slope that I am mostly looking for is the db strength on the Z-axis for time domain. It would be ideal if the Z vs. dB slope was very steep as this would mean the LF energy is decaying quickly. This is not the case so much below 80hz.

[gaspr]

Can you adjust the Z axis for a longer time window? Might make it easier to understand.

[damonrpayne]

Yes you can, but it means about the same thing to me with a larger time window. I'm formulating a testing methodology now, this is fun. I've had this measurement stuff for 9 months and that's how long it took me to finally say "Ok, time to start tweaking the system".

[DrWho]

125dB?!? Are you measuring the system at maxSPL, or have you not calibrated the SPL measurements yet?

It takes a while to get used to the software and even longer to get

used to doing measurements so I expect it'll be a while until you learn

how to manipulate the scales and data to make it meaningful. Sounds

fishy don't it? []

One of these days we need to sit down and have you send me your impulse

responses so we can discuss over the phone what we're seeing in

the measurements. There are some things to look for to ensure that the

data is meaningful before you go about trying to do before and after

measurements. You especially need to turn off the smoothing of the

frequency response.

[mas]

There is no huge bump at 20Hz. You are discovering the resolution limits.

What are the parameters and windowing values you are using?

There is also apparently something amiss at the lower extreme of the plot.

There should be a foreshortening of the LF display. The length of each successive step in time results in a lose of resolution at the lowest resolvable frequency and a shortening of each step at the LF end. Each successive step will be valid to ~ 1/(windowed time span). Each successive step is shorter with a loss of LF detail.

[DrWho]

Keep in mind that this is REW....free software written by a guy trying to use EQ for "treating" room acoustics.

The default parameters involve a window that starts 150ms before the direct sound arrives and then extends for 500ms afterwards. The window being used is "Tukey 0.25". 256K data points are being taken over a range from 10Hz to 200Hz with a 44.1kHz or 48kHz sampling rate.

[damonrpayne]

So change the window to begin closer to when sound reaches the microphone, and extend how long?

[DrWho]

So change the window to begin closer to when

sound reaches the microphone, and extend how long?

Both ends of the window depend on what you're looking for. Do you want

to see the frequency content of the semi-reverant decay? Are you trying

to see the direct (semi-anechoic) frequency response of the speakers?

How bout verifying crossover transistions?

There is no window setting that yields a frequency response that can be used to validate the quality of the system.

[damonrpayne]

Not looking for quality of the system nor frequency response of the speakers, nor crossover transitions. I believe what I'm looking for is semi-reverant decay. I arrived at this through process of elimination from your choices. I could read about the frequency responses of the speakers, amp, etc. elsewhere without having to measure it. If I understand your leading questions, changing the window to start closer to when the direct sound reaches the microphone would be showing the semi-anechoic frequency response, which would maybe be the measurement least affected by the room? What I am looking for is the measurements that best show me that anything I do in the room has made the final direct frequency response flatter and that sound energy has decayed faster. I believe this means I need to change the window to allow for some reflections to have occurred? Might the starting point and time length of this window need to be based on the size of the room? Am I getting warmer?

I plan on using a combination of LF absorption and mid/hf dispertion to experiment. I plan to check the results with follow up measurements, no more than half a dozen music tracks I know very well, and two or three multichannel movie scenes I know very well.

[gaspr]

Hey Doc...Would it be possible for Damon to record an impulse

response, save the file, then e-mail it to you for you to

convolve it into all the other graphs and charts? Probably a dumb

question but just wonderin...

[DrWho]

Not looking for quality of the system nor

frequency response of the speakers, nor crossover transitions. I

believe what I'm looking for is semi-reverant decay.

In that case, you don't even want to look at the frequency response -

this is what all those wackos mean when they see they don't even bother

looking at the frequency response anymore.

For the treatment of standing waves in the LF, you want to look at the

waterfall plot where you can see which frequencies are ringing. For the

treatment of MF/HF relections, you want to look at the ETC.

If you want, you can export your impulse response so that we can

manipulate and label the graphs for you. Actually choosing treatments

is an area that I have practically no experience with so I can only

share what I interpret others say needs to be done. The nice thing

about impulse responses is that they contain all the info needed to

describe the entire behavior of the system (assuming they are obtained

correctly). So someone with better software can come along and

manipulate the data in more meaningful ways.

[IndyKlipschFan]

At some point I am a firm believer in what do you like and, do you enjoy how it all turned out?

We can tweek our rooms to no end..... And in that end, they might seem flat as desired, or perfect graph wise..... but also life-less too.

I wish you all good luck!

Roger

[mas]

At some point I am a firm believer in what do you like and, do you enjoy how it all turned out?

We can tweek our rooms to no end..... And in that end, they might seem flat as desired, or perfect graph wise..... but also life-less too.

Roger, this comment is not directed towards you, but rather to the forum in general.

Many seem to have the idea that the time based measurements have little or no correlation to a subjective experience. And this is absolutely false. The fact is that they are tied inextricably to psycho-acoustic perception.

Conversely, there remains a preoccupation with 'flatness' and various responses in the frequency domain that have absolutely little or no correlation to psycho-acoustics and the subjective experience.

Likewise, in the example above, a CSD (cumulative spectral display)/waterfall plot is NOT the proper tool to indicate diffusion nor a semi-reverberant field. It will ONLY indicate resonances.

More often than not many rush to tweak by positing solutions before knowing what the problem is. And far too many have already 'treated' their rooms. Ironically few can discuss exactly what the problems were and how they were addressed and why or how a real problem was mitigated. How many of those rooms even employed real diffusive treatments?

I do not doubt that folks can easily move problems around and make things "different". In fact, I would maintain that without a systematic approach based upon a firm theoretical, conceptual, and practical knowledge that many ARE simply moving problems around. It is precisely this potential for mis-application of well intentions that concerns me.

Just as I eschew, on the one hand, the refusal to acknowledge real strides in acoustical understanding, on the other hand, I just as vigorously resist the seeming rush to discover a quick easy solution in a web site that promises a solution in a box or room analysis from a drawing. And one need only look as far as the treatment of one of Klipsch's listening room and its transformation into an essentially dead and claustrophobic experience.

And the unfortunate thing is that, unless such a result is desired (hey, I can't account for someone's personal taste), such a result is a result of misguided ignorance. It is a result of someone doing that which they do not understand, despite their thinking that they do.

It is NOT the result of the knowledgeable application of valid principles. And for anyone to suggest otherwise is to simply serve as an example that the ignorance of such concepts persists.

Much is well know as to how to treat an acoustical space. Various steps and measurements are necessary. You don't proceed blindly or emotionally. And for those who seek to achieve a precise result without using the tools that assist a knowledgeable practitioner as a precise roadmap of what needs to be done, and as feedback to verify the appropriateness of actions taken. And for all of those who seek the easy way, the shortcut without the prerequisite knowledge or 'hassle' of measurements, stop now.

Its really not too hard, nor too expensive to make the necessary changes. But it doesn't happen simply as a result of spending money and running to find ready made canned solutions, regardless of how fancy a website looks nor how spectacular their promises. And it won't be accomplished with a test D, and SPL meter, or a fancy SPL meter called an RTA or with an equalizer. And if you consider these items critical, take this as a sign that you need more education.

So, if your goal is a "flat" response (note that few even state a domain or criteria), or if your result is a "lifeless" room, or if anyone blindly follows a measurement without knowing exactly what it shows (assuming it is even valid!) and does not understand the underlying concept, take a bow, as you don't have a clue, and you would be wise to stop before proceeding further.

But if you are willing to learn, and to unlearn many old and and very prominent yet misleading commonplace notions, much is indeed possible. And the irony is that this understanding will also cause you to change many other assumptions regarding the rest of your system as well.

[damonrpayne]

What methodology do you propose following mas? Does it have a name? Where is it published? What's the concrete advice?

[IndyKlipschFan]

Roger, this comment is not directed towards you, but rather to the forum in general.

Many
seem to have the idea that the time based measurements have little or
no correlation to a subjective experience. And this is absolutely
false. The fact is that they are tied inextricably to psycho-acoustic
perception.

Conversely, there remains a preoccupation with
'flatness' and various responses in the frequency domain that have
absolutely little or no correlation to psycho-acoustics and the
subjective experience.

No offense taken... Really I am serious here... but we can test it, tweek it to no end... but at some point some test will go against another we will rely on this and that Mas... And feel we do not have a great system at all anymore.. by all means, use what your knowledge, and others knowledge and what they did before you... (The more power to you rule..) A good ratio for instance in building the great symphonic halls that have stood the test of time do so on some very good math as well. I do not deny that at all.

"Just as I eschew, on the one hand, the refusal to acknowledge real
strides in acoustical understanding, on the other hand, I just as
vigorously resist the seeming rush to discover a quick easy solution in
a web site that promises a solution in a box or room analysis from a
drawing. And one need only look as far as the treatment of one of
Klipsch's listening room and its transformation into an essentially
dead and claustrophobic experience."

True... Simple solutions off of the computer are not always the best. And how do you test it anyhow to really know what you have changed? I wish someone in a perfect world at Klipsch would have the balls to just say, if you use XYZ THX Syetem (speakers) the ideal room is this measurement.. They can't for obvious sales reasons.. (I guess anything other than that size... would then be said to not be optimal. LOL) But be honest, if you or for many of us... Including builders and designers had a clean sheet to design your or our basements "killer home theater" and someone at Klipsch said, The XYZ series is killer in a 20w x 30L 10 foot high ceilings room for instance... Place the fronts here.. Sides here... and rears here... We all would know that is the ideal tried and true and designed room then to get that "Optimal" liistening experience Klipsch had in mind for us..

"But if you are willing to learn, and to unlearn many old and and
very prominent yet misleading commonplace notions, much is indeed
possible. And the irony is that this understanding will also cause you
to change many other assumptions regarding the rest of your system as
well."

Also true... I hear a 100 dollar glass jar of tuned galss marbles goes a long way to bring eternal calmness and peace too? hahahaha.. NOT !!!!

[mas]

Many

seem to have the idea that the time based measurements have little or

no correlation to a subjective experience. And this is absolutely

false. The fact is that they are tied inextricably to psycho-acoustic

perception.

Conversely, there remains a preoccupation with

'flatness' and various responses in the frequency domain that have

absolutely little or no correlation to psycho-acoustics and the

subjective experience.

No offense taken... Really I am serious here... but we can test it, tweek it to no end... but at some point some test will go against another we will rely on this and that Mas... And feel we do not have a great system at all anymore.. by all means, use what your knowledge, and others knowledge and what they did before you... (The more power to you rule..)

No.

The tests do not conflict in any manner.

But ultimately you may encounter either environmental constraints that you simply cannot, or are not willing, to alter, or you impose your personal preferences which may run counter to what psycho-acoustical testing says is the norm for most folks - in other words, you just may prefer a room that is more dead than spacious sounding. Or you or your wife simply may not allow you to apply diffusion to the walls, or you may simply like or be unable to alter) your 6 foot wide "Z" shaped room complete with constantly running window air conditioning unit and complete with fully tiled floors and walls and a concave ceiling for your home theater. ;-O

Additionally, such testing can easily be applied to the hardware as well: significant signal offsets (in time) between drivers maybe identified and corrected,;diffraction effects of cabinets identified and corrected (as they appear as separate sources and are readily apparent in impulse and ETC tests); resonances, be they mechanical or acoustic may be identified and corrected; internal cabinet reflections adversely impinging upon dynamic drivers can be identified and corrected; polarity issues are readily identified and corrected; minimum phase response regions are readily identified; not to mention the potential for in depth analysis and investigation of the complex impedance at all frequencies and time via Nyquist and Heyser spirals and the applicability to everything from electrical source load investigations of loads such as cables, crossovers, speakers, as well as summed loads of any combination thus indicating what the source really sees (and it ain't 8 ohms folks!!!!!!!!!!!), and the list goes on.

But the real significance is that you are able to actually see what is happening. And you are able to ascertain the effect of any adjustments made. And the previous issues are all well documented (with the partial exception o the Heyser and Nyquist spirals and analysis of he complex impedance, simply because it is so new!), so you aren't wandering around in a region without precedence.

But none of it is contradictory. It is simply that the traditional electronic measurements and frequency domain measurements do not provide sufficient resolution and detail of the acoustic phenomena. So we were stuck looking at complex summed signals and trying to guess what component of the sum was doing what. We lacked the ability to see the individual behaviors and sources of the behavior in a sufficiently atomistic manner to both isolate and identify component behavior. The behaviors are rather well understood. But without being able to identify the "what and how", we were stuck making wholesale changes in the hopes that the shotgun approach did more good than harm while most likely any good was a result of simply changing more things for the good as we also changed other things for the worse. But now we are able to avoid this, and focus on the bad and make changes that are specific to the situation.

So, I think many still fail to understand the significance of time domain analysis. And I mean using REAL time domain analysis tools. ...Not simply the same old stuff that simply present spiffy displays that look like some of the time domain tool displays. And there are plenty of such pretenders around.So it demands that real tools be utilized.

But it bothers me that many still feel hat ultimately the measurements are contradictory or simply nonsense. The fact is the tools and measurements are just that: tools. They can be employed intelligently or stupidly. And the tools do not magically make an idiot smart (although they can inadvertently help). But likewise, if you lack an understanding of the principles, I shudder to think what monstrosity one can achieve. (frankly we just saw such a system from ole' Morris the Cat!!! Oh, sory, Romy!)

But the tools we now have available for our use have the ability to greatly advance the effectiveness of any changes that we decide to make. And they also have the ability to expose the many design compromises made for practical or financial reasons of a product, combination of products, and the products in an acoustical environment. And they afford us the ability to analyze, isolate, and to provide real feedback regarding the effectiveness of any changes that we might make as we attempt to modify and correct for such compromises.

Which now means that, one, folks need to better understand the significance and what is happening in the various domains and their relationships, and we need to find appropriate tools sufficient to allow us to examine the issues. And, as much as I wish it were true, the most capable tools are not free. And you definately get what you pay for in terms of elegance, sophistication, design and capabilities. The industry dominate tools are TEF, EASERA and SMAART. And in the lower teir Praxis and a few others.But you are looking at a minimum investment of ~$1000 before the various necessary accessories! And below that is one that I think just might work for the majority here. But that is not to say that you need to go broke.

But I dare say selecting the tools requires more than a web search for 'free' software tools that promise the world in their marketing blurbs.

And if anyone is interested in going further, PM me and leave your personal contact info and a good time to call. We may have a plan.

BTW: Ratios, etc. were an attempt to predict behavior in the age prior to modeling and measurement. You will find that they have become rather passe in the age of sophisticated modeling and auralization programs such as EASE and CATT-A. We no longer have to guess as we already have a good idea of the performance behavior before any construction begins..

[mas]

True... Simple solutions off of the computer are not always the best. And how do you test it anyhow to really know what you have changed? I wish someone in a perfect world at Klipsch would have the balls to just say, if you use XYZ THX Syetem (speakers) the ideal room is this measurement.. They can't for obvious sales reasons.. (I guess anything other than that size... would then be said to not be optimal. LOL) But be honest, if you or for many of us... Including builders and designers had a clean sheet to design your or our basements "killer home theater" and someone at Klipsch said, The XYZ series is killer in a 20w x 30L 10 foot high ceilings room for instance... Place the fronts here.. Sides here... and rears here... We all would know that is the ideal tried and true and designed room then to get that "Optimal" liistening experience Klipsch had in mind for us..

Hmmmm.

False.

The proper measurements correctly applied can easily determine not only problems, but also the effect of modifications. That is one of their primary strengths.

An optimal room? Just one? And are you assuming that we can say all folks prefer the same acoustics? (I can certainly aim for what is considered an acceptable optimum, but I can guaranty there will be someone here who will wine and cry about it!)

And while they are at it, why not just ONE ideal speaker. Of course you will have to redesign your house to incorporate it, but hey...

I can understand your frustration, but I think you are looking in the wrong place for a solution. (Likewise we could say that we should supply the room and that Klipsch should design the speaker to compliment the space via controlled polar coverage Qs and the like...so it is a double edged sword...)

Here is a suggestion. If you want an optimal room, it can certainly be had.(Actually, if all you want is an optimal listening room, I can draw you one. ) But it is not for Klipsch to dictate THE room. There are myriad considerations to be made. Do you want one completely outfitted with say, RPG systems? Great, what's your budget? Its easy for me to design an ideal room for you that may cost as much or more as the rest of your house!

But now they are to dictate your taste and use too? And I guess that this room will be a dedicated listening room, and not a multi-purpose room? As as you determine use, the design criteria change as well. Specifying a monolithic room is a bit like specifying the ideal house that accommodates all uses and all families. Come over here, we have your "ideal" house...one size fits all.

And with all due respect, THX would not even be a consideration! ...No more than I put STP stickers on my car to make it run faster.But if you want to hang a big THX poster in the hall outside he room, it probably won't hurt anything.

The point is that there are great rooms that can and are being designed everyday. But they aren't being designed with an SPL meter and a fancy RTA with a test CD.

And I would suggest that more people beginning to learn and to be open to the new time domain principles and applied test gear would be a good place to start rather then to lament someone not telling you what room would be best for you.

[DrWho]

What methodology do you propose following

mas? Does it have a name? Where is it published? What's the concrete

advice?

Since Mark got sidetracked, I'll tell you what he told me and see where that goes...

Basically, the methodology he is proposing is called "LEDE". I

hesitate saying this though because any free information you find on

the

internet regarding LEDE is the old version and effectively false - I

think that is also why Mark rarely uses the term (since incorrect

information from other sources is bound to lead to confusion).

What you need to do (at least according to Mark) is

read the latest research by the guy that introduced the LEDE concept in

the first place. Was it Patronis? I'm so bad with names. All I know is that SAC is the organization actively

researching the concepts - and better yet, they even provide

educational seminars. You can become a member of the society and gain

access to all the latest research (via PDF):

http://www.synaudcon.com

D'Antonio is also a part of that research, who is also the guy that started RPGinc:

http://www.rpginc.com/

I mention this because the technical articles provided on that website are applying the same modern LEDE principals.

As far as keeping things practical, we first need to get meaningful

data. It's crazy, but if you show Mark an ETC of your room he'll be

able to tell you how it sounds without you telling him anything about

the system. Really, once you understand what the ETC is showing you,

it's almost intuitive what kinds of treatments are needed - or at least

where they should go. But that's why Mark gets so hung up on the

understanding of measurements (not to mention it is so exceedingly

frustrating when people with no experience challenge the validity of the measurements).

Anyways, you're not in that annoying group Damon so I can only hope

Mark will chime in with some practical information for your situation.

You're really best off if you catch him on Skype where he doesn't need

to be so defensive with how the information is presented. In fact, if

you're willing Mark and I are looking for a room to use as a

demonstration of the concepts (so lots of measurements of before and after).

[IndyKlipschFan]

I think your missing my point here too.

The proper measurements correctly applied can easily determine not only

problems, but also the effect of modifications. That is one of their

primary strengths.

I agree...

What I asked for was a ideal room size to be listed for a dedicated HT. Certainly materials used... what the other equipment is... makes a huge difference too.

An optimal room? Just one? And are you assuming that we can say all

folks prefer the same acoustics? (I can certainly aim for what is

considered an acceptable optimum, but I can guaranty there will be

someone here who will wine and cry about it!)

Yes, this is what I am asking for.. 3M has 2 room sizes they push with a pre set of speakers and amp they like.. go out on that edge a little.. go for it. You can't please everyone Mas... Just as I may love a panting by Monet. another sees all dots and can't grasp the French impressionist style at all.

THX is a certification to standards.. your right, not a sound format. (I bet 7 in 10 do not know this too...LOL)

Yet they, (THX) will design and certify your room to THX specs... LOL.

The point is that there are great rooms that can and are being designed

everyday. But they aren't being designed with an SPL meter and a fancy

RTA with a test CD.

Of course not... Most SPL meters for use in the forums is just to match the SPL output.. A real time RTA meter gives us a live representation of the frequency response based on the sound or pink or white noise sent to it through our speakers... A test CD just again shows us where we are..... maybe..

Again, I like you Mas.. Not looking for a fight here.... but really those STP stickers make your car run faster.. wow... never knew that! LOL.