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REW measurements after bass trapping 500 Series Dynamics
Old 12th April 2019
  #1
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REW measurements after bass trapping

EDIT - PLEASE SEE POST 6 FOR NEW MEASUREMENTS, DIAGRAMS ETC

I've just put some acoustic treatment in my room and I was wondering if anyone could have a look at the attached REW file and help me understand what's changed, and if it's looking better?



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There are three measurements in the file - the empty room, the room as I had it before (3 bass traps leaning against the wall, left, right and behind the monitor) and the new treatment (left/right bass traps raised on proper stands, and full bass trapping of the front corners).

(Also I should point out that I stupidly didn't read the FAQ before doing the measurements, so I have both speakers going instead of just one at a time. I think that should be OK for looking at bass though?)

Thanks!
Attached Files
File Type: mdat New GIK Measurements.mdat (9.93 MB, 33 views)
Old 4 weeks ago
  #2
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With the third setup, your room modes are reduced but you now have a deeper hole around 67 Hz. The position of microphone and speakers hasn't changed between measurements?

The frequency response isn't really good though. What mode is the 126 Hz one? You can use this tool to find out.

Out of curiosity, how big are the woofers in your speakers? They seem to roll off quite early.
Old 4 weeks ago
  #3
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Quote:
Originally Posted by johannburkard View Post
With the third setup, your room modes are reduced but you now have a deeper hole around 67 Hz. The position of microphone and speakers hasn't changed between measurements?
I tried to keep the positions the same between measurements - just in case, I've taken a new measurement today and it's not significantly different.

Quote:
Originally Posted by johannburkard View Post
The frequency response isn't really good though. What mode is the 126 Hz one? You can use this tool to find out.
Not sure how to work out which mode it is on that tool - my room has built in cupboards and a chimney breast which make it hard to work out which width measurement to input.

Quote:
Originally Posted by johannburkard View Post
Out of curiosity, how big are the woofers in your speakers? They seem to roll off quite early.
The speakers are KRK V6 mk2. The woofers are approx 6 inches and I believe they drop off below about 55Hz.
Old 4 weeks ago
  #4
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Here are some waterfall graphs of the room untreated and treated (taken today).

It's mainly bass trapping in the the side first reflection points and the 2 vertical corners nearest the speakers. There's also a bass trap propped up behind the computer screen (trying to minimise reflection from window behind desk) and a large picture bass trap hanging on a side wall (not a first reflection point).

I think it's looking quite a bit better other than the increased null around 70Hz?
Attached Thumbnails
REW measurements after bass trapping-studio-no-treatment.jpg   REW measurements after bass trapping-studio-rfz-front.jpg  
Old 4 weeks ago
  #5
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REW problem?

Quote:
Originally Posted by mediumsizeddog View Post
I've just put some acoustic treatment in my room and I was wondering if anyone could have a look at the attached REW file and help me understand what's changed, and if it's looking better?...
I agree with Johann. Not so good yet.
But I think your measurements have some problems...

1. REW sample rate was set to 44.1kHz. The same for Duet?
2. Measurement 3 is distorted. Check levels carefully.


Pls describe your room.
Photo, dimensions? L-W-H
Heavy walls, openings, alcoves, windows, furniture... Pos of mic and speakers.

Best

PS Reason for measuring L & R separately is: We like to see if they are similar.
Broken speaker? Rigid wall to the left, flimsy to the right? etcetera...

EDIT: just saw your new post
Old 4 weeks ago
  #6
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Quote:
Originally Posted by akebrake View Post
1. REW sample rate was set to 44.1kHz. The same for Duet?
You're absolutely right - they were set differently!

I've redone the measurements from scratch. So attached to this post are the REW file, screenshots of before-and-after waterfall plots, a photo of the working position and a diagram of the room, showing the location of the treatments so far.
Attached Thumbnails
REW measurements after bass trapping-studio-diagram.jpg   REW measurements after bass trapping-7a878a23-93f1-46f7-a934-e6ac68fe2ecf.jpg   REW measurements after bass trapping-studio-treated.jpg   REW measurements after bass trapping-studio-untreated.jpg  
Attached Files
File Type: zip New Measurements 16 April.mdat.zip (11.89 MB, 11 views)
Old 4 weeks ago
  #7
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Can you get monitor stands and set up the speakers touching the rear wall (and the window)? Also try to get the tweeters at ear height. Experiment with one speaker to speed up the testing process.

The stereo image seems a bit small from your photo so putting the speakers further away is a chance of getting a wider stereo image.

PS: Nice clean desk.
Old 4 weeks ago
  #8
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Quote:
Originally Posted by johannburkard View Post
Can you get monitor stands and set up the speakers touching the rear wall (and the window)? Also try to get the tweeters at ear height. Experiment with one speaker to speed up the testing process.

The stereo image seems a bit small from your photo so putting the speakers further away is a chance of getting a wider stereo image.

PS: Nice clean desk.
It's difficult to fit monitor stands because of the radiator immediately behind the desk. Also, the window is recessed about 20cm back and not central, so one speaker would end up right by the wall, while the other was away from the window.

I've currently got the speakers spaced so they make a roughly equilateral triangle with my head. The tweeters are at ear height, and there's a GIK 244 standing on the floor right behind the computer screen which hopefully captures some first reflections from the window.

PS - thanks! I'm obsessed with keeping my workspace neat. Plugins were the best invention ever for me!
Old 4 weeks ago
  #9
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I looked at your measurements and treated, the symmetry is pretty good. The left speaker has more of a room mode effect at 76 Hz than the right one. Maybe another panel behind the TV would help?

However, don't expect too much from the 244 panels left and right to your desk. They won't do much at 60 Hz where you would need it.

Any chance you could get two GIK Monster Bass Traps?

Speaking about the frequency response, if you can manage, a spaker with built-in DSP (Genelec 83** series for example) would probably help because the frequency response I think is the worst part of your setup.
Old 4 weeks ago
  #10
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Quote:
Originally Posted by johannburkard View Post
I looked at your measurements and treated, the symmetry is pretty good. The left speaker has more of a room mode effect at 76 Hz than the right one. Maybe another panel behind the TV would help?

However, don't expect too much from the 244 panels left and right to your desk. They won't do much at 60 Hz where you would need it.

Any chance you could get two GIK Monster Bass Traps? h
My next plan was to put a couple of Monsters on the back wall (behind me when I’m sitting at the desk) and maybe a soffit trap horizontally on the floor below them (at the floor-wall corner). Do you think that would help, or are you thinking specifically of the left/right reflection points?

Quote:
Originally Posted by johannburkard View Post
Speaking about the frequency response, if you can manage, a spaker with built-in DSP (Genelec 83** series for example) would probably help because the frequency response I think is the worst part of your setup.
I could always try something like Sonarworks, although I’d like to get as much of the room right as possible first.
Old 4 weeks ago
  #11
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Definitely cover that back wall...you could literally cover it floor to ceiling (even behind the door a bit; use a doorstop on the floor)...if you want some life after, you could then put up some diffusion...do you need the cupboards, is there stuff in them? Could you just fill them with mineral wool? What height is your ceiling? What are the walls made of?

You'll want traps on the ceiling above mix position also. Rear wall and ceiling should be your next targets for panels...maybe soffits on the rear wall if you can afford them...you'll need monster traps at the very least for the rear wall...

A good way to measure your room would be at 1m intervals...in all dimensions...so do ground plane (mic just lying on floor), 1m intervals to ceiling, touching ceiling...for example, start at the rear left of the room and work your way to the front, all on the floor, then 1m out, 2m, 3 etc. etc, then put the mic on a stand at 1m, repeat, then 2m etc.....make sure you name everything systematically!!!...use loopback as reference so you have the distance in the measurement.

you don't have to be hugely accurate in your positions if you're lazy; a wireless keyboard and a few key commands will speed up the process...the places with the biggest peaks will be where u want to put absorption...also you should be able to work out what dimension is causing what.
Old 4 weeks ago
  #12
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Whoa, everyone on this forum says basically the same thing, "BUY bass-trap! The seller is a GOOD guy and TRUSTABLE! blah blah blah".
But brutal honest truth is, it's ABSOLUTELY HOPELESS under 100 Hz!!
This thing is a bunch of CRAP!!
Old 4 weeks ago
  #13
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Quote:
Originally Posted by ignorant View Post
Whoa, everyone on this forum says basically the same thing, "BUY bass-trap! The seller is a GOOD guy and TRUSTABLE! blah blah blah".
But brutal honest truth is, it's ABSOLUTELY HOPELESS under 100 Hz!!
This thing is a bunch of CRAP!!
The advice is correct, the implimentation is flawed. Most commercially available products are NOT bass traps. Then the majority of people buy broadband absorbers or only a few tuned bass traps and wonder why it didnt work. It takes lots of volume to treat the low end, but everyone ignores that part. You'll find most experts recommed DIY and entire walls several feet thick of fluffy insulation.
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Old 4 weeks ago
  #14
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Quote:
Originally Posted by ignorant View Post
But brutal honest truth is, it's ABSOLUTELY HOPELESS under 100 Hz!!
The latest waterfall plots show a definite (albeit small) effect below 100Hz, and even if they didn’t there are still big and useful effects above - the reduction at 130Hz is huge, especially if you take reverberation time into account. And that’s with a pretty small amount of bass trapping, just at the front of the room.

I’m no expert (hence the thread) but both the REW results and subjective experience point to the fact that it’s moving in the right direction, and certainly not ‘hopeless’.
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Old 4 weeks ago
  #15
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Quote:
Originally Posted by ignorant View Post
Whoa, everyone on this forum says basically the same thing, "BUY bass-trap! The seller is a GOOD guy and TRUSTABLE! blah blah blah".
But brutal honest truth is, it's ABSOLUTELY HOPELESS under 100 Hz!!
This thing is a bunch of CRAP!!
Actually, most people here are not saying that the OP should BUY a bass trap: Rather, the are suggesting that he should BUILD them.

It's easy to do, and they do, in fact, work below 100 Hz. A superchunk, for example, can theoretically work down to 30 Hz or so. Commonly, in real life testing of real studios, they easily work down to the 60's and 50's, and there's some effect at 30. Even a few inches of suitable insulation on the wall or ceiling can have a very usable effect down to below 100 Hz.

So no, it isn't a "bunch of crap" as you so delicately put it.

- Stuart -
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Old 4 weeks ago
  #16
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Quote:
Originally Posted by mediumsizeddog View Post
The latest waterfall plots show a definite (albeit small) effect below 100Hz, and even if they didn’t there are still big and useful effects above - the reduction at 130Hz is huge, especially if you take reverberation time into account. And that’s with a pretty small amount of bass trapping, just at the front of the room.

I’m no expert (hence the thread) but both the REW results and subjective experience point to the fact that it’s moving in the right direction, and certainly not ‘hopeless’.
Exactly. You are definitely on the right track. And you are understanding correctly that time-domain response is more important than simple frequency response. I've never understood why so many people think that flat frequency response is the most important goal to pursue in a studio: it isn't. Flat time-domain response and correct phase response matter more. Flat frequency response is nice if you can get it, but can usually only be achieved with digital tuning, and only AFTER the acoustic issues in the room (time-domain) have been brought under control.

So yes, your 130 Hz reduction in the time domain is far more important than the peak in the frequency domain.

And yes, porous absorption bass trapping (deep, thick, tall, wide) will definitely help to get the low end controlled better, despite what "ignorant" said.

- Stuart -
Old 4 weeks ago
  #17
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Well, the right direction, sort of yes. But direction is not enough.
If you are on the way to Rome from Beijing, I will call it "hopeless" even if you're walking to the west.
Eating that space (including the air gap), blocking cabinets doors, and "After" is still pretty much terrible and that is all.
(Placing is not good ether but primary issue is the tool.)

Room acoustics is just a simple summation of the modes and if trap thingies do not affect desired modes, it's simply does not work, I mean, hopeless.
Commercial basstraps are not tuned because obviously they do not know your room and thereby, needlessly broad and hopeless low efficient, or uselessly humongous.
They claims
"The 244 Bass Trap’s 5.25″ thickness combined with the rigid fiberglass core provides twice the low end absorption over similar foam-based products." (via their catalogue)
and you know? 5.25″ thickness foam is absolutely useless in low end, and doubling useless is, still useless.

The time domain is more important blah blah blah is just bull**** as well because, you know, amplitude/freq + phase/freq is equals to amplitude/time, it's a very primitive (Even some bloke called "ignorant" knows ) knowledge so-called FFT.
That is because you can calculate the IR by measuring swept sine with good SNR, instead of blowing up your speaker.

So, Go tuned, Stay tuned!
Old 4 weeks ago
  #18
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Quote:
Originally Posted by ignorant View Post
Well, the right direction, sort of yes. But direction is not enough.
If you are on the way to Rome from Beijing, I will call it "hopeless" even if you're walking to the west.
Eating that space (including the air gap), blocking cabinets doors, and "After" is still pretty much terrible and that is all.
(Placing is not good ether but primary issue is the tool.)

Room acoustics is just a simple summation of the modes and if trap thingies do not affect desired modes, it's simply does not work, I mean, hopeless.
Commercial basstraps are not tuned because obviously they do not know your room and thereby, needlessly broad and hopeless low efficient, or uselessly humongous.
They claims
"The 244 Bass Trap’s 5.25″ thickness combined with the rigid fiberglass core provides twice the low end absorption over similar foam-based products." (via their catalogue)
and you know? 5.25″ thickness foam is absolutely useless in low end, and doubling useless is, still useless.

The time domain is more important blah blah blah is just bull**** as well because, you know, amplitude/freq + phase/freq is equals to amplitude/time, it's a very primitive (Even some bloke called "ignorant" knows ) knowledge so-called FFT.
That is because you can calculate the IR by measuring swept sine with good SNR, instead of blowing up your speaker.

So, Go tuned, Stay tuned!
I have NO idea at all what you tried to say there: it's seems to be a jumbled mish-mash of apparently unrelated words, as far as I can see. And what little I can make out, bears no resemblance to the science of acoustics.

For example: "Room acoustics is just a simple summation of the modes " Riiiight. Modes really are the leading cause of SBIR. I forgot that. Also, modes cause early reflections at the mix position. Yup. For sure. Everyone knows that. And they also cause the ITDG, and the floor bounce, and comb filtering from the desk, and the diffuse field. Yup. I must have been forgetting all that. ...

Quote:
Commercial basstraps are not tuned because obviously they do not know your room and thereby, . . .
Except for the ones that ARE tuned. Which is quite a few of them, if you look around. You can, in fact, buy many commercial tuned devices to treat specific problems in your room. Some of them are tuned to one frequency (in which case you need to order the one you need), others are tunable (in which case you just need to buy it and tune it!). So your claim is totally wrong (in addition to being mangled).

Quote:
5.25″ thickness foam is absolutely useless in low end,
Except, of course that it isn't useless in the low end at all!... there are a few ways that 5.25" of porous absorption can be used in treatment of fairly low frequencies. In several rooms that I have tested, there's rather useful absorption below 100 Hz, for example, with many porous absorbers. As predicted by theory, and borne out in practice.

Quote:
The time domain is more important blah blah blah is just bull
I'm sorry that you didn't understand that, but it does require some knowledge of acoustics to grasp. I'd suggest that you start out by reading "Master Handbook of Acoustics" by Everest, then maybe move on to "Architectural Acoustics" by Marshall Long, and perhaps even "Acoustic Absorbers and Diffusers", by Cox and D'Antonio. Those three should give you enough basis to figure this out. Time domain graphs really are more useful for understanding the response of a room than frequency response graphs. And of course, as any acoustician will tell you, looking at the phase data is rather important if you plan to use digital tuning to even out the frequency response. But those concepts are probably too advanced for you right now. Don't worry: if you study hard enough for a few years, you'll get there! Then you'll realize that time domain graphs really are more useful than frequency domain graphs, for understanding a room. ETC, for example, is priceless.

Quote:
That is because you can calculate the IR by measuring swept sine with good SNR
... which is, in fact, exactly how all of the data that we are talking about in the various graphs and files, was generated! And good SNR isn't necessary for getting a usable IR from a swept sine. That's one of the advantages of swept sine, actually: it is usable even in an environment that doesn't have such a good SN. So I have no idea what your point was.

On the one had you are blathering about bass traps not working, and on the other you are blithering about acoustic measurement graphs, using terms that I suppose you found on Google, but clearly don't understand at all.

You should probably lay off the bong for a few hours before you post next time: it isn't helping to enhance your linguistic skills.

- Stuart -
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Old 4 weeks ago
  #19
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Quote:
Riiiight. Modes really are the leading cause of SBIR. I forgot that. Also, modes cause early reflections at the mix position. Yup. For sure. Everyone knows that. And they also cause the ITDG, and the floor bounce, and comb filtering from the desk, and the diffuse field. Yup. I must have been forgetting all that. ...
WHOA, you do(n't) understand pretty much everything(!)
In fact, everything you wrote can be calculated from the modes, but NOT the CAUSE of them, it's just the same thing looking from another angle.
Again, this is a very PRIMITIVE knowledge and also a useful technique for reducing costly LU decomposition.
If you don't understand, ask any college student around you! Do some cramming! Or, you look even more ignorant than Mr.Ignorant

Quote:
Except for the ones that ARE tuned.
Commercial basstraps are not tuned because obviously they do not know your room
Well, I need to correct above to below. Sorry for ignorance of Mr.Ignorant!
Ready-made basstraps are basically not tuned, INCLUDING THIS CASE, because obviously they do not know your room
(And strictly speaking, "tunable" is not "tuned", isn't it?)

Quote:
there are a few ways that 5.25" of porous absorption can be used in treatment of fairly low frequencies. In several rooms that I have tested, there's rather useful absorption below 100 Hz, for example, with many porous absorbers. As predicted by theory, and borne out in practice.
Is "fairly low frequencies" is the "low end" for you?
You're saying below 100 Hz, what is the exact frequency?
In this case, the low "end" is below 45Hz. Are You SURE?
Or are you saying to make idiotically huge air space behind the 5.25″ foam?
Or, using back wall vibration?
Anyway, if you could proper "low end" absorption in a proper way (e.g. impedance tube with rigid termination) with bare 5.25″ foam, Not only me, even Mr.Cox would be amazed.
And small wonder, if 5.25″ foam were such a good absorber, WHY his measurement with so-called basstrap, which SHOULD have doubling performance of it, is so appalling?

Quote:
Time domain graphs really are more useful for understanding the response of a room than frequency response graphs.
Yes, we can see some phenomena in CSD or wavelet more clearly, BUT impulse response, i.e. amplitude/time response, is exactly the SAME to amplitude plus phase/frequency response, MATHEMATICALLY.
So, saying amplitude/time response is more important than amplitude+phase/frequency is rather IDIOTIC.

Quote:
So I have no idea what your point was.
What I meant was, you can measure IR by swept sine, thanks to FFT and that is the familiar evidence of above.

Quote:
I'm sorry that you didn't understand that, but it does require some knowledge of acoustics to grasp. I'd suggest that you start out by reading "Master Handbook of Acoustics" by Everest, then maybe move on to "Architectural Acoustics" by Marshall Long, and perhaps even "Acoustic Absorbers and Diffusers", by Cox and D'Antonio. Those three should give you enough basis to figure this out.
Thanks for book recommendation , well...
"Master Handbook of Acoustics", It's cheap at least but increased bulk by adding silly "example"s if I'm honest. I personally don't prefer.
"Architectural Acoustics" contains relatively broad topics but bit shallow, and not for studio acoustics.
"Acoustic Absorbers and Diffusers" is sort of a good book. except for some wrong equations... (e.g. chapter 4.1.1. some were corrected in the 3rd ed though... e.g. table 6.4)

Mr.Ignorant
Old 4 weeks ago
  #20
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Anyone else find it odd that “Mr Ignorant” seems to have joined the forum yesterday just to have this argument? Anyway, thank you to those who gave advice, and sorry the thread got derailed.
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Old 4 weeks ago
  #21
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Quote:
Originally Posted by mediumsizeddog View Post
Anyone else find it odd that “Mr Ignorant” seems to have joined the forum yesterday just to have this argument? Anyway, thank you to those who gave advice, and sorry the thread got derailed.
Yup! He certainly lives up to his name, and very, very obviously has an agenda... sounds like a disgruntled customer of some commercial acoustic product, who bought it, didn't have a clue how to use it, got bad results, and now wants to lash out at everything acoustic.... in his grand "ignorance" of the subject, of course!

It's rather amusing, actually.... And so very obvious! But maybe I'll play his game a little more, and expose even further his "ignorant" nature...

- Stuart -
Old 4 weeks ago
  #22
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Old 4 weeks ago
  #23
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Quote:
Originally Posted by ignorant View Post
WHOA, you do(n't) understand pretty much everything(!)
In fact, everything you wrote can be calculated from the modes, but NOT the CAUSE of them, it's just the same thing looking from another angle.
Again, this is a very PRIMITIVE knowledge and also a useful technique for reducing costly LU decomposition.
If you don't understand, ask any college student around you! Do some cramming! Or, you look even more ignorant than Mr.Ignorant


Commercial basstraps are not tuned because obviously they do not know your room
Well, I need to correct above to below. Sorry for ignorance of Mr.Ignorant!
Ready-made basstraps are basically not tuned, INCLUDING THIS CASE, because obviously they do not know your room
(And strictly speaking, "tunable" is not "tuned", isn't it?)


Is "fairly low frequencies" is the "low end" for you?
You're saying below 100 Hz, what is the exact frequency?
In this case, the low "end" is below 45Hz. Are You SURE?
Or are you saying to make idiotically huge air space behind the 5.25″ foam?
Or, using back wall vibration?
Anyway, if you could proper "low end" absorption in a proper way (e.g. impedance tube with rigid termination) with bare 5.25″ foam, Not only me, even Mr.Cox would be amazed.
And small wonder, if 5.25″ foam were such a good absorber, WHY his measurement with so-called basstrap, which SHOULD have doubling performance of it, is so appalling?


Yes, we can see some phenomena in CSD or wavelet more clearly, BUT impulse response, i.e. amplitude/time response, is exactly the SAME to amplitude plus phase/frequency response, MATHEMATICALLY.
So, saying amplitude/time response is more important than amplitude+phase/frequency is rather IDIOTIC.


What I meant was, you can measure IR by swept sine, thanks to FFT and that is the familiar evidence of above.


Thanks for book recommendation , well...
"Master Handbook of Acoustics", It's cheap at least but increased bulk by adding silly "example"s if I'm honest. I personally don't prefer.
"Architectural Acoustics" contains relatively broad topics but bit shallow, and not for studio acoustics.
"Acoustic Absorbers and Diffusers" is sort of a good book. except for some wrong equations... (e.g. chapter 4.1.1. some were corrected in the 3rd ed though... e.g. table 6.4)

Mr.Ignorant
Ah yes! So very true. everybody knows that SBIR can be "calculated from the modes,", as can first reflections at the mix position... the math is so SIMPLE! It's in every acoustic text book ever written! Right there, on page nothing... It's such common knowledge that modes cause reflections at the mix position, that nobody ever even bothers talking about. Not to mention the huge effect they have on setting the ITDG. Yup.

But seeing this is so basic, maybe you could enlighten us all with the explanation of how room modes cause SBIR? No need to go heavily into the math (after all, it is so well known!). but just a simple description of the physics behind it. And also the physics behind the process that causes room modes to create early reflections at the mix position...

We will all wait breathlessly while you present your explanation....

Quote:
a useful technique for reducing costly LU decomposition.
Right! Because all studio builders just HATE it so badly when there LU's decompose. Nobody wants a pile of decomposed LU's all over their studio floor. Such a mess to clean up!

Quote:
Or, you look even more ignorant than Mr.Ignorant
Now THAT would be a grand achievement! But highly doubtful any living person on planet Earth could attain that.

Quote:
Commercial basstraps are not tuned because obviously they do not know your room
Except, of course, for the ones that ARE tuned... As you would know, if you knew anything at all about acoustics. And since a bass trap is inanimate, it can't actually "know" anything. Nor does it need to: it just needs to be chosen by someone who is not ignorant (of acoustics), and does understand how tuned traps work.

Quote:
Sorry for ignorance of Mr.Ignorant!
Apology accepted, but I have a feeling you'll need to repeat that phrase rather frequently....

Quote:
Ready-made basstraps are basically not tuned, INCLUDING THIS CASE, because obviously they do not know your room
As I pointed out previously, bass traps are inanimate, and therefore don't know anything at all. They also don't need to know anything: It's quite simple of for us non-ignorant folks to identify the modal issues in the room, then choose traps that are tuned to the indicated ranges, from a catalog, for example. The only knowledge that is needed here is that of the non-ignorant studio designer / builder / acoustician. For those if us who are not ignorant of how acoustics works, nor ignorant of the commercially available solutions, it's actually very easy to do this, by checking the catalogues for tuned devices and selecting the one that best matches the already-identified modal issues in the room. Of course, for ignorant people, that is simply out of the question: Some basic intelligence is required, slightly beyond the level of amoeba.

Quote:
(And strictly speaking, "tunable" is not "tuned", isn't it?)
Heheheh! Nice try! Or rather, stupid try... (especially the meaningless double-negative, which actually negates what you tried to say...). Tunable traps are, in fact, already tuned when they arrive. All one needs to do is to RE-tune them to the required frequency... But only non-ignorant non-amoebas can grasp such advanced concepts, so don't feel bad that you were unable to get it.

Quote:
Is "fairly low frequencies" is the "low end" for you?
Well, umm, gee.. I dunno... that seems like something that would be hard for the ignorant to understand.... I guess that it all depends on what the meaning of "is" is....

Quote:
You're saying below 100 Hz, what is the exact frequency?
The exact frequency for what? For how many times an amoeba feeds during a day? I have no idea. But you can probably tell us, from first-hand experience.

Quote:
In this case, the low "end" is below 45Hz. Are You SURE?
Once again, you'll have to be more specific. As I said, that all depends on what the meaning of "is" is....

Quote:
Or are you saying to make idiotically huge air space behind the 5.25″ foam?
Say what? Why do you personally want to stand behind the foam? That does seem to be the best method for obtaining an "idiotically huge" gap...

And no, no air space is needed behind the foam. I guess you never heard of the 3.5% issue... See if you can figure it out.... It's well known by smart acousticians, especially those here at GS, but apparently not so well known by the ignorant...

Quote:
Or, using back wall vibration?
Sounds kinky! Is that legal? But I'll skip on that. My wife would object.

Quote:
Anyway, if you could proper "low end" absorption in a proper way (e.g. impedance tube with rigid termination) with bare 5.25″ foam, Not only me, even Mr.Cox would be amazed
This sentence no verb. Thus, meaningless. But the effect is quite apparent, even in an impedance tube. Of course, real rooms are nothing like impedance tubes, so the effect is even more obvious in reverb chamber tests, and above all, in real rooms! Imagine that!

People who are not ignorant of acoustics know all about this. Including Trevor C. (If you read his books and papers, you'd already know this... So I guess that explains why you've never heard of it.)

Quote:
So, saying amplitude/time response is more important than amplitude+phase/frequency is rather IDIOTIC.
Except, of course, that non-ignorant acousticians talk about this all the time, and don't invent strawmen to support their ignorance. The non-ignorant folks around here all noticed that you left out the key words from what I was saying.

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What I meant was, you can measure IR by swept sine, thanks to FFT and that is the familiar evidence of above.
You do seem to enjoy repeating yourself about this! Is your excitement because you just learned about something the non-ignorant have know for decades? As I already pointed out, swept sine is, indeed, the very reason the OP and others were able to post such detailed data and graphs, with such good SN ratios... Not exactly headline news, so one has to wonder why you are so keen on repeating it, yet again?

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Thanks for book recommendation
You're welcome. Perhaps if you were to actually read them, instead of just googling them, you would be able to learn something concrete about acoustics.

Dissing the three most-recommended books about acoustics, by the authors most commonly cited in research papers, while pretending to know more than all of them together... well, I have to say, that does seem rather pompous, not to mention ignorant...

- Stuart -
Old 4 weeks ago
  #24
Pno
Gear Maniac
...an nice easy read on studio acoustics is Newell's Recording Spaces...kinda book you could read on a train etc.; no MHOA of course, but a good introduction.
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Old 4 weeks ago
  #25
Here for the gear
 

Sorry for the late, apparently HE was refused to post (suspended? or url-tag was wrong? who knows. weighted for whole 12 hours.).
HE might have posted something INCONVENIENT for the moderator but I HAVE LITERALLY NO IDEA WHAT IT WAS.


Quote:
It's rather amusing, actually.... And so very obvious! But maybe I'll play his game a little more, and expose even further his "ignorant" nature...
A "game" should have some unpredictability, in my opinion.
If there are a CLEAR WINNER and a LOOSER (OF COURSE it MUST BE MR. IGNORANT!), it should be called a massacre, isn't it?

Anyway, LET'S PLAY A GAME


Quote:
Ah yes! So very true. everybody knows that SBIR can be "calculated from the modes,", as can first reflections at the mix position... the math is so SIMPLE! It's in every acoustic text book ever written! Right there, on page nothing... It's such common knowledge that modes cause reflections at the mix position, that nobody ever even bothers talking about. Not to mention the huge effect they have on setting the ITDG. Yup.
Well, I reckon that Room Sim component of the REW is (internally) based on the very same theory (limited to the rectangular room so the mode is obvious, no need for searching, Yes, very SIMPLE maths and INSTANT), and of course some of the book I have, such as Vibration and Shock Handbook (chapter 9) are referring to this as well.
(Of course some acoustics textbook, which you may have, referring as well but I mention about this particular book because I am bastard!)
And, as above, this is not limited in acoustics, actually this is a very commonly used technique for thirty years in the structural mechanics, such as prediction of the car NVH.
Obviously, mode number rises up very rapidly in higher frequency region or in the complicated model, so it does not have good performance in some cases, but in the lower region and relatively simple model, this is a very strong tool, especially when you want to change the excitation. (once the modes have found, no heavy recalculation needed for the change of position, pole, etc.)


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But seeing this is so basic, maybe you could enlighten us all with the explanation of how room modes cause SBIR? No need to go heavily into the math (after all, it is so well known!). but just a simple description of the physics behind it. And also the physics behind the process that causes room modes to create early reflections at the mix position...

We will all wait breathlessly while you present your explanation....
Okay, this is 2D floor of this case, note that this is massively SIMPLIFIED model for some SIMPLETON,
and also exaggerated (giving relatively high impedance B.C.) as well for the visual obviousness of the mode summation.

This is the First Rigid mode, Second longitudinal mode, Third transversal mode, then.. , 200th mode.
note the rigid mode(s) = virtually 0Hz isn't handled as the first mode in some case, especially in the acoustics.

pbs.twimg.com/media/D4e4h75U4AgWD93.png 1st
pbs.twimg.com/media/D4e4ki2UUAIAJdS.png 2nd
pbs.twimg.com/media/D4e4k4-UEAEUrYh.png 3rd
pbs.twimg.com/media/D4e4lQKUwAAOS_1.png 4th
pbs.twimg.com/media/D4e4tTqU8AEuotB.png 5th
pbs.twimg.com/media/D4e4t4zUYAA_kUA.png 6th
pbs.twimg.com/media/D4e4uJkUwAAfiui.png 7th
pbs.twimg.com/media/D4e4vY8U4AAuCoh.png 200th
These are nothing particularly novel, Ok?

Where, if you observe single mode, say second mode (longitudinal), and put some acoustic source for forcing excitation, say, 50Hz mono on the somewhere upper left, the pressure would be like this, no surprise at all.
The shape does not change over the frequencies except for the phase, because this is a resonance and you are observing single mode, OK?
But real pressure amplitude and SPL response of some point, for example bit forward from the centre of this room, would vary like this.
pbs.twimg.com/media/D4fF_AUUcAIVifx.jpg 2nd

Then, if you observe another single mode, then.... (The same colour range)
pbs.twimg.com/media/D4fF-vEU8AAuOn0.png 1st (obviously uniform and no contour)
pbs.twimg.com/media/D4fGAKOUUAMvNT4.jpg 3rd
pbs.twimg.com/media/D4fGAo-UEAEDxhm.jpg 4th

Some modes are strongly excited, and the other modes are weekly excited, depending on the modal/exciting frequency, damping, and location of excitation (and in graph, observing location).
SBIR can be seen the selection of the exciting mode in modal region, obviously.
[B]IT IS THAT SIMPLE.[/SIZE]

And the summation of these individual modes is the very frequency response, BECAUSE THEY ARE THEORETICALLY EQUIVALENT.
(note that you should search for the modes in a bit wider region than desired frequency region)
pbs.twimg.com/media/D4fJaCOU4AEEzQ2.jpg Total frequency response

Or spatially, for example, at 50 Hz, you can see the second mode around 42Hz and the third mode around 57Hz are basically dominating, but both of modes are not very strong because away from the resonance frequency, thereby other modes are still affecting.
pbs.twimg.com/media/D4fJaW9U0AEwOvL.png Total pressure distribution at 50Hz
(contour is representing 2nd-7th mode in the same colour range, and gradation is representing actual pressure at 50Hz, i.e. summation of the modes.)
And you know, the low pressure zone is basically where both modes have the same-ish amplitude area with inverted phase.
This is commonly called modal cancellation or something like that.

You can transform this frequency response to the time response as well, Of course you can see the reflection, ITDG, and so on.
BECAUSE THEY ARE THEORETICALLY EQUIVALENT.
video.twimg.com/tweet_video/D4fJzVNUIAAexPp.mp4 Time response
(blurred looking is due to higher frequency limitation, in this case, 800Hz. again, not have a good performance in higher frequency.)


OKAY? This is the VERY BASICS OF THE MODE THEORY.
IF YOU DON'T KNOW THIS, YOU WERE JUST AN IGNORANT, IT IS OK, AND IF YOU LEARNED, YOU AREN'T ANYMORE.
BUT IF YOU DON'T UNDERSTAND THIS, EVEN I'M TRYING THIS HARD FOR EASY EXPLANATION,
REMEMBER, YOU ARE NOT JUST AN IGNORANT ANYMORE, BUT AN IMBECILE.



So, the mode is the easiest way (at least in my opinion) of grasping low frequency phenomena.


Quote:
Nobody wants a pile of decomposed LU's all over their studio floor. Such a mess to clean up!
YES, absolutely! it does cost helluva lot, seriously!


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Now THAT would be a grand achievement! But highly doubtful any living person on planet Earth could attain that.
Well, maybe it is.


Quote:
Apology accepted, but I have a feeling you'll need to repeat that phrase rather frequently....
What frequency should I do?


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Except, of course, for the ones that ARE tuned... As you would know, if you knew anything at all about acoustics. And since a bass trap is inanimate, it can't actually "know" anything. Nor does it need to: it just needs to be chosen by someone who is not ignorant (of acoustics), and does understand how tuned traps work.

Ready-made basstraps are basically not tuned, INCLUDING THIS CASE, because obviously they do not know your room
As I pointed out previously, Bass Traps are inanimate, and therefore don't know anything at all. They also don't need to know anything: It's quite simple of for us non-ignorant folks to identify the modal issues in the room, then choose traps that are tuned to the indicated ranges,
Yes, ranges. It must be relatively strongly damped for getting the range and damping means losing efficiency, otherwise, it will be useless in most of the rooms.


Quote:
Well, umm, gee.. I dunno... that seems like something that would be hard to decide.... I guess that all depends on what the meaning of "is" is....
The exact frequency for what? For how many times an amoeba feeds during a day? I have no idea. But you can probably tell us, from first-hand experience.
Once again, you'll have to be more specific. As I said, that all depends on what the meaning of "is" is....
If 45Hz is not the "low end" in this case, it is not the "end", HA-HA.
Or, if thread starter says (s)he want to treat the "low end" problem, do you SERIOUSLY think the "low end" is bloody 90Hz or something, and recommend 244 which of course literally hopeless around 45Hz?
(I do not meant the "low end" of product's performance, in which case, high frequency only absorber can claim the same thing and it sound a bit silly.)


Quote:
And no, no air space is needed behind the foam. I guess you never heard of the 3.5% issue... See if you can figure it out.... It's well known by smart acousticians, especially those here at GS, but apparently not so well known by the ignorant...
This sentence no verb. Thus, meaningless. But the effect is quite apparent, even in an impedance tube. Of course, real rooms are nothing like impedance tubes, so the effect ix even more obvious in reverb chamber tests, and also real rooms.
Yes, you're correct, I do not know 3.5% thingies so I googled.
Well, actually I don't need this kind of guessing because I can do PROPER wave based calculation.
Anyway, 5.25" is roughly equals to 3.5% wavelength of 90 Hz, so what?
5.25" foam is completely useless for 45Hz, an octave down problem, and doubling useless thingies so-called basstraps, can not treat it as well, and as above (thread starter's example).


Quote:
Except, of course, that non-ignorant acousticians talk about this all the time, and don't invent strawmen to support their ignorance. The non-ignorant folks around here all noticed that you left out the key words from what I was saying.
If someone really says that the time response is more important than MATHEMATICALLY EQUIVALENT THING, well, so-called non-ignorant acousticians are actually ignorant acousticians.


Quote:
You do seem to enjoy repeating yourself about this! Is your excitement because you just learned about something the non-ignorant have know for decades? As I already pointed out, swept sine is, indeed, the very reason the OP and others were able to post such detailed data and graphs, with such good SN ratios... Not exactly headline news, so one has to wonder why you are so keen on repeating it, yet again?
Yes, because I'm ignorant! Ahh! Ahh! (playing the "Ignorant song")


Quote:
Dissing the three most-recommended books about acoustics, by the authors most commonly cited in research papers, while pretending to know more than all of them together... well, I have to say, that does seem rather pompous, not to mention ignorant...
I'm not dissing, bit of gentle criticizing for the first cheapie but not for the rest.
Architectural Acoustics is meant to providing wide information, rather than digging down for one theme. This is what it is.
And, about Acoustic Absorbers and Diffusers, wrong equations are wrong, even if widely read or the author is an authority, period.

Mr. BuyBassTraps
Old 4 weeks ago
  #26
Here for the gear
 

Sorry for the inconvenience, it was the url-tag.
just D&D to the tab-bar of your browser.
Old 4 weeks ago
  #27
Lives for gear
 

Quote:
A "game" should have some unpredictability, in my opinion.
I must admit that your opinion is, indeed, the most unpredictable game I have ever come across!

Quote:
If there are a CLEAR WINNER and a LOOSER (OF COURSE it MUST BE MR. IGNORANT!), it should be called a massacre, isn't it?
One question then; Since you have already been massacred, why wont you just lay down and expire?

Quote:
Okay, this is 2D floor of this case, note that this is massively SIMPLIFIED model for some SIMPLETON,
and also exaggerated (giving relatively high impedance B.C.) as well for the visual obviousness of the mode summation.

This is the First Rigid mode, Second longitudinal mode, Third transversal mode, then.. , 200th mode.
note the rigid mode(s) = virtually 0Hz isn't handled as the first mode in some case, especially in the acoustics.

pbs.twimg.com/media/D4e4h75U4AgWD93.png 1st
pbs.twimg.com/media/D4e4ki2UUAIAJdS.png 2nd
pbs.twimg.com/media/D4e4k4-UEAEUrYh.png 3rd
pbs.twimg.com/media/D4e4lQKUwAAOS_1.png 4th
pbs.twimg.com/media/D4e4tTqU8AEuotB.png 5th
pbs.twimg.com/media/D4e4t4zUYAA_kUA.png 6th
pbs.twimg.com/media/D4e4uJkUwAAfiui.png 7th
pbs.twimg.com/media/D4e4vY8U4AAuCoh.png 200th
These are nothing particularly novel, Ok?

Where, if you observe single mode, say second mode (longitudinal), and put some acoustic source for forcing excitation, say, 50Hz mono on the somewhere upper left, the pressure would be like this, no surprise at all.
The shape does not change over the frequencies except for the phase, because this is a resonance and you are observing single mode, OK?
But real pressure amplitude and SPL response of some point, for example bit forward from the centre of this room, would vary like this.
pbs.twimg.com/media/D4fF_AUUcAIVifx.jpg 2nd

Then, if you observe another single mode, then.... (The same colour range)
pbs.twimg.com/media/D4fF-vEU8AAuOn0.png 1st (obviously uniform and no contour)
pbs.twimg.com/media/D4fGAKOUUAMvNT4.jpg 3rd
pbs.twimg.com/media/D4fGAo-UEAEDxhm.jpg 4th

Some modes are strongly excited, and the other modes are weekly excited, depending on the modal/exciting frequency, damping, and location of excitation (and in graph, observing location).
SBIR can be seen the selection of the exciting mode in modal region, obviously.
[B]IT IS THAT SIMPLE.[/SIZE]

And the summation of these individual modes is the very frequency response, BECAUSE THEY ARE THEORETICALLY EQUIVALENT.
(note that you should search for the modes in a bit wider region than desired frequency region)
pbs.twimg.com/media/D4fJaCOU4AEEzQ2.jpg Total frequency response

Or spatially, for example, at 50 Hz, you can see the second mode around 42Hz and the third mode around 57Hz are basically dominating, but both of modes are not very strong because away from the resonance frequency, thereby other modes are still affecting.
pbs.twimg.com/media/D4fJaW9U0AEwOvL.png Total pressure distribution at 50Hz
(contour is representing 2nd-7th mode in the same colour range, and gradation is representing actual pressure at 50Hz, i.e. summation of the modes.)
And you know, the low pressure zone is basically where both modes have the same-ish amplitude area with inverted phase.
This is commonly called modal cancellation or something like that.

You can transform this frequency response to the time response as well, Of course you can see the reflection, ITDG, and so on.
BECAUSE THEY ARE THEORETICALLY EQUIVALENT.
video.twimg.com/tweet_video/D4fJzVNUIAAexPp.mp4 Time response
(blurred looking is due to higher frequency limitation, in this case, 800Hz. again, not have a good performance in higher frequency.)


OKAY? This is the VERY BASICS OF THE MODE THEORY.
IF YOU DON'T KNOW THIS, YOU WERE JUST AN IGNORANT, IT IS OK, AND IF YOU LEARNED, YOU AREN'T ANYMORE.
BUT IF YOU DON'T UNDERSTAND THIS, EVEN I'M TRYING THIS HARD FOR EASY EXPLANATION,
REMEMBER, YOU ARE NOT JUST AN IGNORANT ANYMORE, BUT AN IMBECILE.


So, the mode is the easiest way (at least in my opinion) of grasping low frequency phenomena.
Well, that was a rather long and very useless explanation of nothing! Mildly amusing, but lacking any significance at all.

One more time: You originally said: "Room acoustics is just a simple summation of the modes ..." Since that statement is completely and totally wrong, I challenged you to show how modes are the root cause of normal room acoustic problems, such as "SBIR, ... early reflections at the mix position ... the ITDG ... floor bounce ... comb filtering from the desk ... and the diffuse field". Instead of admitting that your originally claim was wrong, since modes have no bearing whatsoever on any of those phenomena, in your great ignorance (!), you doubled down, saying; "everything you wrote can be calculated from the modes". But, of course, you failed to do that. Instead, you googled some basic info on modes (so as not to appear too ignorant, I suppose...), and posted a bunch of links that don't work, and a bunch of pointless disarticulated waffle about basic modal response, concluding with the outstanding non-sequitur: "SBIR can be seen the selection of the exciting mode in modal region, obviously." Hooo boy.... where do I even start with that? Hint: SBIR is not related to room modes at all. It happens in situations where there are no modes at all... Oooops!

Clearly, you have no idea what any of those phenomena actually are! Instead of trying to show that modes really are the cause of SBIR and desk comb filtering (etc), you waffle and bluster and point us at a rather simple and somewhat flawed room mode simulator!

Then you muffle and mush through some more mangled words, and come up with another gem: "both of modes are not very strong because away from the resonance frequency"... well gee, if the ode is far away from it's own resonant frequency, I guess that means it isn't a mode! Sheesh!. And again: "This is commonly called modal cancellation or something like that". Really. Fascinating. So two modes on the same axes can cancel each other, leaving no mode at all. Wonderful.

But it gets better! Not content with arriving at this new low in acoustic BS, you then come along with this: "You can transform this frequency response to the time response as well, Of course you can see the reflection, ITDG, and so on. BECAUSE THEY ARE THEORETICALLY EQUIVALENT." So let me get this straight: If I add up all the room modes, that will show me the ITDG, and it will also show me the early reflections at the mix position. I've always wanted to do that: string together a whole bunch of smilies, but I've never had an appropriate situation to do so before. But this one certainly is appropriate! In fact, nothing else fits your drivel EXCEPT that string of silly emoticons! I finally understood why you don't provide your name or any other identifying data: Your massive shame and embarrassment would be so overwhelming if anybody from your real life would ever see your posts here!

Quote:
OKAY? This is the VERY BASICS OF THE MODE THEORY.
You say that as though you just discovered that summing modes gives the steady state frequency response: as though it were some grand epiphany on your part. Something exciting. You do realize that this is the kind of stuff taught in any introductory class to acoustics, right?

And of course has no bearing at all on SBIR, ITDG, early reflections, comb filtering form the desk, or any number of other issues that are not in the least related to modes, and in fact can occur in situations where there are no modes at all...

I can do nothing better than post your own words, since they certainly are very fitting: "BUT IF YOU DON'T UNDERSTAND THIS, EVEN I'M TRYING THIS HARD FOR EASY EXPLANATION, REMEMBER, YOU ARE NOT JUST AN IGNORANT ANYMORE, BUT AN IMBECILE."

Quote:
This is commonly called modal cancellation or something like that.
So you don't even know what your alleged effect is called, and you want to teach professional studio designers and acousticians how to build rooms?

Quote:
So, the mode is the easiest way (at least in my opinion) of grasping low frequency phenomena.
Except, of course, for the array of low frequency phenomena that I mentioned (including SBIR, reflections, etc.) which are not related to, nor can they be calculated from, the modal response of the room.

Quote:
What frequency should I do?
Several gigahertz, apparently.

Quote:
Yes, ranges. It must be relatively strongly damped for getting the range and damping means losing efficiency, otherwise, it will be useless in most of the rooms.
You should have your kitchen blender checked: it seems to be spewing out meaningless jumbles of words again.

Quote:
Or, if thread starter says (s)he want to treat the "low end" problem, do you SERIOUSLY think the "low end" is bloody 90Hz or
As I said, that all depends on what the meaning of "is" is.... but you have not defined "is" yet, so there's no possible answer.

Quote:
do you SERIOUSLY think the "low end" is bloody 90Hz or something, and recommend 244 which of course literally hopeless around 45Hz?
Strawman much? At what point in this thread did I "recommend 244" as you claim? Please show us the point where I did that... (I'll save you the trouble: it didn't happen. I never did any such thing....).

Quote:
(I do not meant the "low end" of product's performance, in which case, high frequency only absorber can claim the same thing and it sound a bit silly.)
You certainly do sound a bit silly, yes. Definitely in the "high" end... As high as a kite, apparently.

Quote:
Yes, you're correct, I do not know 3.5% thingies so I googled.
Well, actually I don't need this kind of guessing because I can do PROPER wave based calculation.
Anyway, 5.25" is roughly equals to 3.5% wavelength of 90 Hz, so what?
... and you missed the point entirely, once again. Seems to be a habit of yours: In fact, missing the point seems to be your most highly honed skill.

Try again.

Quote:
45Hz, an octave down problem, and doubling useless thingies so-called basstraps, can not treat it
On the other hand, in real life on Planet Earth, there are many bass trap designs that can and do treat 45 Hz problems. And lower too. Your claim is not only demonstrably wrong, but also ignorantly imbecilic. If your claim were true, then no studio on the planet would have flat response at 45 Hz. Yet many of them do. Even humble home studios...

Quote:
If someone really says that the time response is more important than MATHEMATICALLY EQUIVALENT THING, well, so-called non-ignorant acousticians are actually ignorant acousticians.
Strawman much? Way to totally misunderstand, and once again misrepresent what was actually said. But do keep on digging your hole deeper and deeper. Hopefully, it will soon collapse on you, relieving the rest of us from having to shovel away your blithering gump.

Quote:
Yes, because I'm ignorant! Ahh! Ahh!
Finally, you said something that everybody on GS can agree with.

Quote:
Architectural Acoustics is meant to providing wide information, rather than digging down for one theme.
Like I said: Maybe if you read it, you'll learn a bit about what the rest of us are discussing here...[QUOTE]

Quote:
wrong equations are wrong, even if widely read or the author is an authority, period.
Based on your accusation that a single type in a book invalidates the entire book, I would say that the sum total of all your typos in just a single sentence you have written here, must invalidate your entire existence!


Quote:
Mr. BuyBassTraps
No thanks. I never do buy them: I prefer to design them and build them myself. Which is what most of us here are urging the OP to do: just install DIY bass traps that will treat his 45 Hz problem, effectively and efficiently.

And you still have not show us your theory on how to calculate SBIR from the sum total of the room modes. Or your theory on summing room modes to show what the ITSG will be. Nor your theory on using modes to show what the early reflections at the mix position will be like. Or your theory on using modes to calculate the floor bounce.

So please do go ahead, and show us how this all works. Since you claim to be a greater acoustician than Long, Everest, Cox, D'Antonio, Hidley, Sayers, Newell, Toole combined, there's a whole bunch of us eager students just sitting here, waiting excitedly for you to show how we can use modal response to predict SBIR and ITDG!

Please don't keep us waiting any longer! Just show us already! You say it is so simple, so basic, but you don't want to show it: Why is that?


- Stuart -
Old 4 weeks ago
  #28
Here for the gear
 

Quote:
One more time: You originally said: "Room acoustics is just a simple summation of the modes ..." Since that statement is completely and totally wrong, I challenged you to show how modes are the root cause of normal room acoustic problems, such as "SBIR, ... early reflections at the mix position ... the ITDG ... floor bounce ... comb filtering from the desk ... and the diffuse field". Instead of admitting that your originally claim was wrong, since modes have no bearing whatsoever on any of those phenomena, in your great ignorance (!), you doubled down, saying; "everything you wrote can be calculated from the modes". But, of course, you failed to do that. Instead, you googled some basic info on modes (so as not to appear too ignorant, I suppose...), and posted a bunch of links that don't work, and a bunch of pointless disarticulated waffle about basic modal response, concluding with the outstanding non-sequitur: "SBIR can be seen the selection of the exciting mode in modal region, obviously." Hooo boy.... where do I even start with that? Hint: SBIR is not related to room modes at all. It happens in situations where there are no modes at all... Oooops!
Well, I never said "room mode", because I'm mentioning about the modes of the whole model, which includes what you need to know, such as desk, or structural vibration, and again, as I mentioned in #19 , modes are not cause of them, it's just the same thing looking from another angle.



Quote:
Then you muffle and mush through some more mangled words, and come up with another gem: "both of modes are not very strong because away from the resonance frequency"... well gee, if the ode is far away from it's own resonant frequency, I guess that means it isn't a mode! Sheesh!.
YES, there are modes. The only point is negligible or not.
As I mentioned, "you should search for the modes in a bit wider region than desired frequency region"

Quote:
And again: "This is commonly called modal cancellation or something like that". Really. Fascinating. So two modes on the same axes can cancel each other, leaving no mode at all. Wonderful.
If there are two excited modes, which has different distribution, there will be modal cancellation IN SOME WHERE, but it does not mean cancelling out entire modes.


Quote:
But it gets better! Not content with arriving at this new low in acoustic BS, you then come along with this: "You can transform this frequency response to the time response as well, Of course you can see the reflection, ITDG, and so on. BECAUSE THEY ARE THEORETICALLY EQUIVALENT." So let me get this straight: If I add up all the room modes, that will show me the ITDG, and it will also show me the early reflections at the mix position.
Quote:
And of course has no bearing at all on SBIR, ITDG, early reflections, comb filtering form the desk, or any number of other issues that are not in the least related to modes, and in fact can occur in situations where there are no modes at all...
Again, not the "room mode", it's a mode of entire model.
If you gave sufficient B.C. , of course the modes are affected and EXACTLY THE SAME thing happens.
But as I mentioned above, searching gets heavy in high frequency, so not cost efficient.
SBIR is OK because usually primary dip is not in particularly high frequency.
But, determining of ITDG or comb filtering needs relatively high frequency (imagine, inputting IR file in 2kHz sample rate...), you can do it THEORETICALLY, but in 3D simulation, it is not realistic.


Quote:
Clearly, you have no idea what any of those phenomena actually are! Instead of trying to show that modes really are the cause of SBIR and desk comb filtering (etc), you waffle and bluster and point us at a rather simple and somewhat flawed room mode simulator!
"simple"?
Again, the morel is simplified because simulating of full mid-sized room in 3D model roughly has several million dofs and will take days (I'm not joking, it is that heavy), even in under 1kHz with relatively fast workstation.
But, if you can do this rather simple FE simulation, basically you should have understood everything I wrote and can do a lot about acoustic simulation.
DO YOU REALLY CAN DO THIS "rather simple" SIMULATION? And, if you could, can I give you SOME BASIC PROBLEM?
(ANSWER NEEDED, BECAUSE IF YOU COULD, YOU CAN EXPLAIN YOURSELF NOT AN IMBECILE.)
But I bet you that you can not, because you even don't understand the "mode".

"flawed simulator"?
Well, in that case, literally a lot, lot of academic researches are affected. that is literally a disaster, Ha-ha.




Quote:
So you don't even know what your alleged effect is called, and you want to teach professional studio designers and acousticians how to build rooms?
Well, some acousticians and some of the slutz call it mode cancellation as well, so, "or something like that".


Quote:
You should have your kitchen blender checked: it seems to be spewing out meaningless jumbles of words again.
It is basically the same to putting sponge into bass-reflex port, you know. Simple mas-spring-damper foundation.
If you damped the mode, you get broader response, but lose efficiency, it is the nature or the law of physics.


Quote:
Strawman much? At what point in this thread did I "recommend 244" as you claim? Please show us the point where I did that... (I'll save you the trouble: it didn't happen. I never did any such thing....).
Of course you don't. Because, as I said, that so-called basstrap thingies are useless to the low end of this case.




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... and you missed the point entirely, once again. Seems to be a habit of yours: In fact, missing the point seems to be your most highly honed skill.


Try again.
Point it out, Try again.


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On the other hand, in real life on Planet Earth, there are many bass trap designs that can and do treat 45 Hz problems. And lower too. Your claim is not only demonstrably wrong, but also ignorantly imbecilic. If your claim were true, then no studio on the planet would have flat response at 45 Hz. Yet many of them do. Even humble home studios...
"The 244 Bass Trap’s 5.25″ thickness combined with the rigid fiberglass core provides twice the low end absorption over similar foam-based products."
It's not my words, but they claims on their own homepage.

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Strawman much? Way to totally misunderstand, and once again misrepresent what was actually said. But do keep on digging your hole deeper and deeper. Hopefully, it will soon collapse on you, relieving the rest of us from having to shovel away your blithering gump.
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time-domain response is more important than simple frequency response. I've never understood why so many people think that flat frequency response is the most important goal to pursue in a studio: it isn't. Flat time-domain response and correct phase response matter more.
Time domain response is exactly the same thing to amplitude+phase/frequency response, so at least you do not understand maths.

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Based on your accusation that a single type in a book invalidates the entire book, I would say that the sum total of all your typos in just a single sentence you have written here, must invalidate your entire existence!
It is irrelevant to me, he had done some mistakes, and I pointed.

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And you still have not show us your theory on how to calculate SBIR from the sum total of the room modes. Or your theory on summing room modes to show what the ITSG will be. Nor your theory on using modes to show what the early reflections at the mix position will be like. Or your theory on using modes to calculate the floor bounce.
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Please don't keep us waiting any longer! Just show us already! You say it is so simple, so basic, but you don't want to show it: Why is that?
Well, you can find in my explanation, if you aren't an imbecile, and further more, in the book I mentioned.
I am bastard but not an evil, so I do not recommend cheapies. Actually this book is good.
Personally I've never saw an acoustic textbook referring to deep in the theory of mode analysis, because it is just a tool for them (I'm not mocking), but this book spend pages.
This is what I call the "Handbook".
SBIR, ITDG, floor bounce, blah blah blah are found in both of frequency and time analysis, which can be internally calculated by this mode theory.

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So please do go ahead, and show us how this all works. Since you claim to be a greater acoustician than Long, Everest, Cox, D'Antonio, Hidley, Sayers, Newell, Toole combined, there's a whole bunch of us eager students just sitting here, waiting excitedly for you to show how we can use modal response to predict SBIR and ITDG!
how we can use? exactly the same to frequency data and time data.
As I explained in figure, just search the modes, adding excitation to the summation of the found modes, get the frequency data, transform to the time data.
BECAUSE IT IS EQUIVALENT!


Mr. BuyBassTraps
Old 4 weeks ago
  #29
Pno
Gear Maniac
"Time domain response is exactly the same thing to amplitude+phase/frequency response, so at least you do not understand maths."

LOL.

This is a totally stupid thing to say in response...if you're considering a loudspeaker for example, that has lets say an uneven frequency response, but decays in the time domain equally to the rest of its response, and rolls off equally throughout its dispersion, then you have a very simple problem that can be corrected by EQ very successfully. However, if the notable elements of this uneven frequency response have different rates of decay, eq can only alleviate the problem, the ringing will remain, only the magnitude of its excitation will be reduced. Of course gets much more complicated when you're talking about rooms...but anything that rings is a major problem, because it cannot be treated with EQ...and, lets say in a pure acoustic setting, even if you're an exceptional musician and you hear that the room resonates with certain notes, you still cannot correct for that just by playing softer, as the room has taken away your control of decay...even if you're playing really slow, and paying the utmost attention to the room, and trying to correct that, with your touch and timing, you're still only doing it for the position of your ears...**** knows what's happening elsewhere...nothing worse than an instrument, or a room, that rings incongruently to what the excitation is trying to achieve; you're ****ed...
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Old 4 weeks ago
  #30
Lives for gear
 

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Well, I never said "room mode", because I'm mentioning about the modes of the whole model, which includes what you need to know, such as desk, or structural vibration, and again, as I mentioned in #19 , modes are not cause of them, it's just the same thing looking from another angle.
Oh brother. Just keep digging... your hole must be half way to China by now.

Hint: Even if you could measure every single mode of every single object in the room, including the the room itself, the structure, the desk, chairs, sofa, console, light fittings, flower pots, and even the people, it would STILL tell you NOTHING AT ALL about SBIR, or early reflections, or ITDG, or comb filtering, or any of the other issues. Because they are all totally unrelated to modes of any kind. There simply is no connection between any of those, and any type of mode.

One more time; Even if it were possible to measure all of those mode, and manipulate the numbers in an amazingly wonderful mathematical equation that somehow "adds them all up", that would STILL not predict anything at all about SBIR, for example. Because there is no connection!

With each new post, you just continue to demonstrate more and more that you don't have a clue what you are talking about.

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As I mentioned, "you should search for the modes in a bit wider region than desired frequency region"
But I thought you told us that there is "no need for searching", because the modes are be predicted accurately by the model, and measured perfectly? So why would you need to search for them in a region that is NOT at the frequency where they should be? So you are saying that if a room is 12 feet long, then I should NOT expect the first axial mode at 47.1 Hz? That instead I should look for it at 35 Hz, or 59 Hz, or 937.4 Hz? Then why did you say that there is no need for searching, but now you say that there IS a need for searching"?

Curious...

On the one hand you say that everything about the modes is related to everything about the room in a perfect mathematical relationship, but now you say that the modes won't actually be where they are supposed to be according to the math... Hmmm....

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Fascinating. So two modes on the same axes can cancel each other, leaving no mode at all. Wonderful.
If there are two excited modes, which has different distribution, there will be modal cancellation IN SOME WHERE, but it does not mean cancelling out entire modes.
Ahhh! Ok. So, two axial modes on the same axis will cancel each other out, but they wont' actually cancel each other out. Got it. So maybe you could explain how the 3rd axial length mode and the 8th axial length mode could to that (cancel each other out but without cancelling each other out)....
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Again, not the "room mode", it's a mode of entire model.
heheheh! I love it how trolls who don't have a clue have to move the goal posts after they get called out for glaring ignorance... but then move the goal posts into the region of abject stupidity instead!

But let's see where this goes, and how far you need to push your goal posts before you fall off the planet entirely (after all, it is flat, you know?)

Please show how you would calculate every single mode of every single object in the room, including the room itself, the structure, the desk, chairs, sofa, console, light fittings, flower pots, and even the people, and use that to calculate SBIR, or LBIR, orr ITDG, or cob filtering at the mix position, or early reflections at the mix position.

Once again, we will wait breathlessly for your equation that takes all of this into account.

Oh wait! I forget that you'll probably also need to include the modes of the spider hiding in the corner, because modes are in corners, where spiders live, and also the modes of the dust motes laying on the floor, because I'm sure that in your demented imagination, even those will have a huge impact on LBIR, SBIR, ITDG, etc.

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If you gave sufficient B.C. ,
B.C. = Bull Chit? I think you seem to have plenty of that. It seems to come from you in an endless supply, so please do assume that your calculations will have PLENTY of B.C. in them. We can all agree on that.

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But as I mentioned above, searching gets heavy in high frequency, so not cost efficient.
What do you mean by "high frequency"? And "heavy"? How much does a frequency weigh on your planet?
Is "high frequencies" the "fairly high end" for you?
You're saying above 1000 Hz, what is the exact frequency?
In this case, the high "end" is above 4 kHz. Are You SURE?
Or are you saying to make idiotically huge modal measurements behind the 5.25″ foam?
Or, use back wall vibration to find the weight of a frequency? Or a mode?



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SBIR is OK because usually primary dip is not in particularly high frequency.
(The saying is true: ignorance knows no bounds)... Now, since you say that it is possible to use your "modal analysis of the room, desk, chair, console, and furniture" method to predict SBIR, please go ahead and do that. Show the B.C. equation you will use, and show the results. I'll make it easy for you: What is your SBIR prediction for a room measuring 11' x 9' x 8', with a simple apple crate for a chair, measuring 20" H x 19" W by 16", and a simple wood plank for a desk, 2" thick, 5ft long, and 3ft wide, 28" above the floor, on the room center line, and 4ft from the front wall, resting on four 1" diameter solid steel legs, one at each corner. There is no other furniture in the room, and no acoustic treatment. No doors, no windows. Assume that the walls, floor and ceiling are all 1m thick concrete, to make it even easier for you. Standard temperature and pressure.

So, with that simple situation, it should be a piece of cake for you. Since you seem to be the world's leading expert on calculating SBIR, ITDG, and comb filtering, from modes alone, please go ahead and do that: Show us the equation you would use to calculate those from the information given, and show us the results. And since you say that it "gets heavy in high frequency", please do ignore the "High frequency" (whatever that is...)

That's all.

you made the claim, so it is up to you to demonstrate that you are correct.

In other words: put up, or shut up!



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But, determining of ITDG or comb filtering needs relatively high frequency
Strange... and here's the rest of us thinking that ITDG and comb filtering occur across the entire spectrum... How silly of us!

It's REALLY good to know that I only need to consider from 2K up for comb filtering at the mix position, and ITDG, in all future rooms I design! That will make it SO much easier! For all these years, I've been doing it wrong... and so has every other studio designer and acoustician on the planet.... This is revolutionary! According to you, we do not need to consider the entire bottom 6 octaves of the musical scale any more when designing rooms! Wow! So COOL!



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[YOU :] Well, I reckon that Room Sim component of the REW is (internally) based on the very same theory, limited to the rectangular room so the mode is obvious, no need for searching,...
[ME :] ... and point us at a rather simple and somewhat flawed room mode simulator!
[YOU :] "simple"?
Are you saying that the mode simulator in the REW Room Sim window tab is an ADVANCED room mode simulator? Wow! Who knew?

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Again, the morel is simplified because simulating of full mid-sized room in 3D model roughly has several million dofs
Really? You can see all of that in the REW Room Sim window? I guess I must have an older version (even though it's just from last week), because there's no 3D display in mine. Which button should I push to get the "multi-million dof 3D model" view? I can't seem to find that on the control panes...

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basically you should have understood everything I wrote and can do a lot about acoustic simulation.
To be honest, I think nobody on this thread understood a single thing you said, because all of us live in actual reality right here on planet Earth, and you seem to be living in Bong City on planet Troll Waffle, floating around in fairy dust and unicorn tails....

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But I bet you that you can not, because you even don't understand the "mode".
I kind of think that if we studio designers didn't understand modes, our clients would have noticed by now....

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"flawed simulator"? Well, in that case, literally a lot, lot of academic researches are affected. that is literally a disaster, Ha-ha.
I'm floored by your flawed! I really didn't know that the REW Room Sim window was relied on so extensively by academic researchers.... Maybe you can point out some leading books and peer-reviewed papers, where they present their results using REW Room Sim?

One question: Just how deep do you plan to dig this hole of yours? What do you plan to do when you pop out in China, and they throw you back in again, in order to not drastically increase the average ignorance level of their population?


- Stuart -

Last edited by Soundman2020; 4 weeks ago at 05:45 AM..
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