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Standing waves get their own thread - lucky little blighters!

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Re: Standing waves get their own thread - lucky little blighters!

Postby Ethan Winer » Mon Dec 20, 2004 6:21 pm

TS,

> A standing wave at another frequency would surely be 'broken up' by the reflection at the opposite boundary, reducing the effect? <

Not really. I've measured peaks and nulls at both modal and non-modal frequencies. For any given frequency you'll be able to find a peak and also a null location in the room. Likewise, for any given location you'll be able to find both peak and null frequencies.

This is yet another reason I dispute that a standing wave is the same thing as a room mode. Again, one is a wave and the other is a propensity to vibrate at a particular frequency. Apples and cauliflowers.

--Ethan
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Re: Standing waves get their own thread - lucky little blighters!

Postby DoeZer » Mon Dec 20, 2004 6:24 pm

Hi slammer.

funny that.

I've had my stuff in a tiny little room for the past few years, completely UNTREATED acoustically, with two dimensions the same (width = height) and opne pretty close (it was 8 x 8 x 7ft) so it should have been a disaster, and have managed to make music that translates well to the outside world and was of release quality (i.e. a label released it, so it must have been ok...))

and my monitors were placed quite high on the wall (say 6ft up, and were angled down... I always felt that the angling down of the monitors was helping cos it was screwing up the angles of incidence etc. but i am not an acoustics theory guru so this could be rubbish. (i dont think so though ;))

im now moving to a bigger room (8 x 8 x 10.5), and am thinking that I might just place teh monitors in the same way again...
I originally placed them like that, not for of any technical/acoustics reason. simply because the speaker wall brackets I got had an adjustable pivot which allows you to adjust the vertical alignment and my Tannoy Reveals were too heavy so it simply tilts down whether i want it to or not..!

anyone got impressions on that?

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Re: Standing waves get their own thread - lucky little blighters!

Postby Paul Woodlock » Mon Dec 20, 2004 7:41 pm

*** Thanks for the support Paul, (I'll wear it always :tongue:) I hope you don't mind me trashing your work but as we're trying the new page, new start approach (courtesy of TS ;)) I'd prefer that we just drop this for now. I'll make my reply to Ethan via PM - as I perhaps should've done initially.

I realise that you also have some valid points to make on this subject but please, for now, limit them to the science. It's not open season on Ethan or anyone else. (Again, I do appreciate the support.) 0VU :) ***
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Re: Standing waves get their own thread - lucky little blighters!

Postby Ethan Winer » Mon Dec 20, 2004 8:35 pm

0,

> I'll make my reply to Ethan via PM <

If you don't mind, it's a lot easier for me to correspond by email. I also check my email much more often than the forums. If you don't mind, please use either the email address listed on my personal site www.ethanwiner.com or the one on the RealTraps site.

Thanks.

--Ethan
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Re: Standing waves get their own thread - lucky little blighters!

Postby Anonymous » Mon Dec 20, 2004 8:37 pm

E,

OK, email it is. It's easier for me too in many ways.

0VU.
Anonymous

Re: Standing waves get their own thread - lucky little blighters!

Postby Paul Woodlock » Mon Dec 20, 2004 8:51 pm

Paul Woodlock wrote:*** Thanks for the support Paul, (I'll wear it always :tongue:) I hope you don't mind me trashing your work but as we're trying the new page, new start approach (courtesy of TS ;)) I'd prefer that we just drop this for now. I'll make my reply to Ethan via PM - as I perhaps should've done initially.

I realise that you also have some valid points to make on this subject but please, for now, limit them to the science. It's not open season on Ethan or anyone else. (Again, I do appreciate the support.) 0VU :) ***

Greetings 0VU

I would have preferred to stick to science.

However Ethan's post I was replying to, contained NO science, and was full of personals, and sentances saying nothing. So how could I reply with science to all that?

:)


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Re: Standing waves get their own thread - lucky little blighters!

Postby Tequila Slammer » Mon Dec 20, 2004 11:18 pm

DoeZer wrote:Hi slammer.

funny that.

I've had my stuff in a tiny little room for the past few years, completely UNTREATED acoustically, with two dimensions the same (width = height) and opne pretty close (it was 8 x 8 x 7ft) so it should have been a disaster, and have managed to make music that translates well to the outside world and was of release quality (i.e. a label released it, so it must have been ok...))

and my monitors were placed quite high on the wall (say 6ft up, and were angled down... I always felt that the angling down of the monitors was helping cos it was screwing up the angles of incidence etc. but i am not an acoustics theory guru so this could be rubbish. (i dont think so though ;))

im now moving to a bigger room (8 x 8 x 10.5), and am thinking that I might just place teh monitors in the same way again...
I originally placed them like that, not for of any technical/acoustics reason. simply because the speaker wall brackets I got had an adjustable pivot which allows you to adjust the vertical alignment and my Tannoy Reveals were too heavy so it simply tilts down whether i want it to or not..!

anyone got impressions on that?

D

That seems to back up what my A level physics tells me ;)

If the sound is propagating from the speakers spherically (for the sake of simplicity) there will only be a tiny proportion of the sound that ever hits the walls at 90 degrees in both planes. This will be directly in front of, behind, above, below and to either side of the speakers.

A lot of the research I've done so far says a good initial set-up is to put treatment above, in front of, behind and to either side of... The monitoring position!

That always niggled at me. Why would you ever get standing waves there? Any sound crossing that point has to be going at an angle to the wall other than 90 degrees, unless you wear your monitors like headphones. Wide angles won't exhibit standing wave properties at all, and very narrow angles will lose energy bouncing around before they creep over to you.

The mirror trick, which I picked up on the studiotips website after Paul mentioned it on the Mick-Traps thread, sounds like a much more scientifically valid method of treatment placement.

What's everyone's thoughts on having high monitors angled down? It makes complete sense to me, but as I siad, I have all of an A level in physics.

What are the sonic advanages of having your monitors' tweeters level with your ears? Is it worth it to suffer the hideous mangling of audio that comes with standing waves?
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Re: Standing waves get their own thread - lucky little blighters!

Postby Scott R. Foster » Mon Dec 20, 2004 11:42 pm

TS:

Why would a standing wave created by reflections from room boundaries require normal incidence (90 degree) in order to be iterative?
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.......

Postby Paul Woodlock » Tue Dec 21, 2004 2:57 am

Tequila Slammer wrote:......A lot of the research I've done so far says a good initial set-up is to put treatment above, in front of, behind and to either side of... The monitoring position!

That always niggled at me. Why would you ever get standing waves there? Any sound crossing that point has to be going at an angle to the wall other than 90 degrees, unless you wear your monitors like headphones. Wide angles won't exhibit standing wave properties at all, and very narrow angles will lose energy bouncing around before they creep over to you.

The mirror trick, which I picked up on the studiotips website after Paul mentioned it on the Mick-Traps thread, sounds like a much more scientifically valid method of treatment placement.


Greetings Tequila

Acoustic treatment ain't just about standing waves.

1] Treatment for standing waves at Room Mode frequencies is best treated by broadband absorption in corners. Tri-corners being the optimal placement if you can't do ALL corners. Room mode standing waves NEED two or more boundaries, and in the real world they can affect the freqeuncy response of a room from the bass upto around 500Hz.

2] The mirror trick is used to determine placement of broadband absorption for EARLY REFLECTIONS ( i.e those reflections whose path length is less than around 20 feet ( about 20ms ) greater than the direct sound path length. These reflections are heard by the ear as part of the direct sound and cause reduced clarity and detail, innacurate stereo image/source location. And a 'comb filter' type response. All across the audio bandwidth where the sound is directional.

So... "A lot of the research I've done so far says a good initial set-up is to put treatment above, in front of, behind and to either side of... The monitoring position!" is great advice. As it helps to create an RFZ ( Reflection Free Zone ) at the listening position.

And in particular, with free standing non-soffited speakers, placed close to one or more boundaries, there will be a rise in bass response. This is due to the omnidirectional response of a speaker cabinet at lower frequencies, and the wavelengths of the lower frequencies being large compared to the reflection path length resulting from the boundary. As the wavelengths are so long in comparison the reflected sound will pretty much be in phase with the direct sound, causing an additive increase in level. IIRC you get theoretical 6dB increase in level for every boundary. Which means peeps who place their speakers in a reflective tricorner will get a theoretical increase of 18dB. In practise it will less than this due to real world losses, etc.

You can also compensate for this increased bass response by EQ. In fact many active monitors have tilt and shelving controls to do just that.

As you increase the frequency, so the wavelength and path length become a similar size, the reflections cause interference patterns, which results in a 'comb filtered' response.

So with free standing speakers that are close to walls, floors and ceilings ( unavoidable in small rooms ), LOTS of absorption behind, below, above and at the sides of the speakers is well recommended.

The other option is to soffit mount the speakers, which places the sound source at the SAME PLANE as the wall, thus their are NO reflections from behind the speaker to cause any increase in bass levels or comb filtering at higher frequencies. The other advantage of soffit mounting is to stop sound diffracting at the edges of the speaker cabinet.

Another advantage of soffit mounting speakers is the increase in efficiency of lower frequencies ( Sound energy that otherwise would radiate in directions other than forwards, now CANNOT, due to the soffit wall. EQ is used to compensate the response, and thus your monitors have more bass head room. Meaning less speaker distortion.

Genelec have the best FAQs on soffit mounting here..

http://www.genelec.com/support/soffit.php

http://www.genelec.com/support/faq/faq20.php

http://www.genelec.com/support/faq/faq19.php



All this though , in regard to real world treatment, is a seperate issue to Room Mode treatment ( trapping ).



What's everyone's thoughts on having high monitors angled down? It makes complete sense to me, but as I siad, I have all of an A level in physics.

What are the sonic advanages of having your monitors' tweeters level with your ears? Is it worth it to suffer the hideous mangling of audio that comes with standing waves?


The sonic advantages of having the tweeters at ear level is to help the clients sitting on the couch at the back of the studio hear a balanced HF. Angle them down and it's likely the client will hear a dull version ;) Important considerations in the real world.

I've actually designed my monitors to angle downwards in my new studio, as I don't have clients and I angled the speakers ( and front soffit wall ) downwards by 10 degrees to optimise the sound at the listening position in regard for other pieces of equipment like computer monitors obsuring the Audio Monitors.


Sorry if my reply has been too much or too long :) I got carried away.


But it is important, IMO, to show that when treating rooms, the innacuracies we wish to treat, are caused by various situations, and different treatments are used for those different situations.

In short(er).... ;)

Room mode Standing waves need TWO or more Boundaries to exist, and have their maximum pressure at those boundaries. They are pretty much independent of speaker placement, although certain speaker placements can excite them more easily ( such as in the case of soffit mounting ). Corners are where maximum pressure of modes from more than one room dimension add together. So corners are where to maximise the efficiency of room mode absorption treatment.

Early Reflection problems are treated by absorbing ay reflections that will end up at the listening position. The Mirror trick is the easiest way to find the spots, although it can be done pretty well by visualisation for those without mirrors ;)

IMO those are the two types of treatment that shoudl be considered first off. And then once the early reflections and room mode standing waves have been tamed you can then start thinking about diffusion to smooth out the LATER reflections in the case of large rooms, or smoothing out any ambience left over in a small room.

Right! that's enough for now.

back to designing my studio build acoustic treatment.

:)


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Re: Standing waves get their own thread - lucky little blighters!

Postby Tequila Slammer » Tue Dec 21, 2004 10:38 am

This is all great stuff! Thanks for taking the time to reply - it's very much appreciated!

:lol:

I understand the difference between simply reflected sound and standing waves. What I still don't understand is why room mode standing waves are independent of monitor position.

As I described in my previous post, the physics of the situation seem to suggest to me that standing waves could only be generated where the speakers are between parallel boundaries.

Assuming the speakers are widely enough spaced apart, that would mean that the only way to create standing waves at the monitoring position would be to be holding a sound source. Or the waves somehow reflecting towards the monitoring position, then changing their angle of incidence suddenly to 90 degrees...

This is assuming that we agree that standing waves are generated by two similar waves travelling in precicely oposite directions - 90 degree reflections at boundaries.

We're also assuming a perfectly cuboid room, I suppose.

So while I understand and/or agree with everything else, I don't see how:

1: Perpendicuar standing waves appear at the monitoring position and
2: Treating above, below and to either side creates a 'reflection free zone'. Reflected sound will be at angles other than 90 degrees, so those placements will surely entirely miss all the reflected sound that would reach the monitoring position!

Treating around the speakers I can see, and treating the diagonals I can also see. Diagonal room modes crossing the monitoring position seems far more likely, and the energy build-up in corners is readily apparent.

I want to stress here, I'm not saying 'you're wrong'. I just want to understand the physics of it... So far the only explanations I've seen have been 'It breaks up standing waves' and 'it works'.

The rest of your post is gold dust :lol:
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Re: .......

Postby Hugh Robjohns » Tue Dec 21, 2004 10:39 am

Paul Woodlock wrote: IIRC you get theoretical 6dB increase in level for every boundary.

Just to clarify here, the close wall loading produces a 3dB step increase in sound pressure below about 200Hz, with another 3dB increase in sound pressure for a second wall forming a corner, and a further 3dB increase for a third wall (floor/ceilng).

Another advantage of soffit mounting speakers is the increase in efficiency of lower frequencies ( Sound energy that otherwise would radiate in directions other than forwards, now CANNOT, due to the soffit wall.

This is only true if the soffit mounting enclosure is sufficiently massive to contain the low frequency energy. In other words, the soffit enclosure has to be constructed from bricks/concrete and be very solid indeed. Constructing a false wall from timber is not sufficient as the LF energy will simply be disipaited in causing the structure to vibrate.

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Re: Standing waves get their own thread - lucky little blighters!

Postby DoeZer » Tue Dec 21, 2004 10:48 am

so it seems there's some general agreement that placing them up higher and angling them down can yield better results... obviously soffit mounted and angled being better again, but even without I think it makes sense no?

although it makes your mirror test alot harder surely, cos its harder to track the actual line of reflection with the cones tilted...

I had planned in my new place to get the classic speaker stands , fill them with sand etc etc... I may just use the same wall mounted speaker brackets I had the last time and angle them down, maybe put them a bit further away from the corners than I had them.

The thing with wall mounted speakers (into a concrete wall)... there really is NO structural vibration whatsoever, even with low low bass and loud. BUT!!! the downside is that they are quite close to the wall (about siz inches away...) meant I had to stuff a sock into the bass ports at the back in order to reduce bass mess!!! worked quite well i must say ;)

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Re: Standing waves get their own thread - lucky little blighters!

Postby Tequila Slammer » Tue Dec 21, 2004 11:03 am

DoeZer wrote:so it seems there's some general agreement that placing them up higher and angling them down can yield better results...


No... I like the idea a lot, but want to learn more. Paul does it by necessity, due to desk placement.

Personally I don't think being able to monitor from the rear of the studio is a concern.

I want to know if anyone can confirm that angling them like that gives theoretically better results. I'd have to buy new stands to even try.



although it makes your mirror test alot harder surely, cos its harder to track the actual line of reflection with the cones tilted...



I thought the mirror test was simply 'seeing the monitors from your monitoring position' (as a theoretical spherically radiating source I suppose) rather than getting snarled up in cone angles...
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Re: Standing waves get their own thread - lucky little blighters!

Postby Eric Desart » Tue Dec 21, 2004 1:48 pm

Seeing the Moderation of Hugh now in the other thread, I do understand now that there is no place for me here.
I enter this now, not really expecting this to be read in function of content.

I really tried to keep this post without emotions representing the dry facts.
The facts are still as correct, but it's difficult to be emotionless, when people hurt you by plain lying.
I think I'm entitled to set some things straight.
Being Dutch: sorry for spelling, gramatical errors and possible wrong words.

OVU or other moderators. Before doing anything. Read this in it's entirity, not only words but content.
What you read is not a scientist's words but the scientist himself.
I strongly believe this post fights for integrity and truth in favor of the acoustic comunity.


OVU wrote: true or untrue?
Is "Look at the FAQ second in the list on my article page" banned on RO (assuming that refers to recording.org)? A straight, one word answer will suffice. If you want to explain the one word answer then fine but please answer first then keep to the point in any explanation. If it is true I'd be very interested to know why. If not then I sincerely hope that Eric will apologize and retract the comment.


I DON'T lie, I hardly know how to, even when telling the truth brings me in trouble.
And if I should sin, being human, I hate myself for it. My first rule in live is honesty and genuineness.
I don't have to proof anything. I don't sell a thing.
I don't become an inch better or worse by creating suggestive pictures.
And when I tell something I clearly try to distinguish (and tell it as such), between the things I know, assume, or conclude in analogy with.
I show the reader my own own uncertainties and certainties.
And when I feel to have sinned, I'm the one most bothered by it, not ashamed to rectify my own words.

Reply to the rightful concerned above quote by OVU related to Ethan's FAQ.

http://www.recording.org/ftopicp-164508.html#164508
Recording Org Management Posted: Sat May 22, 2004 9:07 pm wrote:From the Editor and Administrators of Recording. ORG.

"Recording dot Org" is not responsible for and does not condone the contents of Ethan Wieners "FAQ".

Well known and accredited acousticians who hold P.H.D.'s, have voiced concern to the administrators of this web site with regards to the content of Ethan's FAQ, as to it's accuracy and with the methods used to measure coefficients, room response and conclusions arrived at.

signed, The Administrators of RO


Since then (May 2004] ANY reference by Ethan to his FAQ is banned.
In the period between Sept 22, 2004 and oct. 18, 2004 Ethan tried to re-enter a few times the acoustics world-wide known reference/link:

Ethan Winer anywhere one can think off wrote:
See the Acoustics FAQ, second in the list on my Articles page:
www.ethanwiner.com/articles.html


This certainly wasn't an easy decision for RO management, with commercial interests, in a Forum which was known (before Ethan's current EQ Forum) as Ethan's Forum. Ethan himself presented this Forum as HIS's not RO's.

    ++++++++++++++++++++++++++++++++++++++++++++++++++++++
    From: Ethan Winer
    Subject: Re: studio foam alternative
    Newsgroups: rec.audio.pro
    Date: 2004-03-06 05:54:10 PST

    Matt,

    You want rigid fiberglass. It's 2-4 times better than foam, yet it costs
    less! Go figure. But you'll want to wrap it in burlap or some other fabric
    for appearance and to keep the fibers in place. For the complete story see
    the Acoustics FAQ, second in the list on my Articles page:

    www.ethanwiner.com

    Also note that my Acoustics forum has moved from recording.org to the much
    classier EQ Magazine site:

    www.musicplayer.com/ubb/ultimatebb.php?ubb=forum;f=26

    --Ethan
    ++++++++++++++++++++++++++++++++++++++++++++++++++++++
    From: Ethan Winer
    Subject: Acoustics forum
    Newsgroups: rec.audio.pro
    Date: 2004-03-06 06:01:24 PST

    Folks,

    Please forgive the blatant self-promotion, but I sometimes see the wrong
    link posted here.

    My Acoustics forum has moved from RO to the EQ Magazine site which is much
    more professional. Here's a direct link:

    www.musicplayer.com/cgi-bin/ultimatebb.cgi?ubb=forum;f=26

    --Ethan
    ++++++++++++++++++++++++++++++++++++++++++++++++++++++
Interesting to note: that the related RO Forum had 3 moderators. It shows how Ethan sees himself, completely ignoring his 2 colleague moderators, Recording.Org itself and others.

In a message where I pointed to the fact that THE FAQ was back, Ethan got immediate support from RO management entering a message were they declared that Ethan had guaranteed RO management that his FAQ was corrected (which were publicly discussed over and over).
Also guaranteed was that all references to the RealTrap web site were removed from this same FAQ (which included as well numerous errors).
RO distinguished between the RealTraps site and the FAQ. As long as the FAQ didn't link to the site it was OK for RO.

Kurt Foster in name of RO management - Posted: Fri Oct 01, 2004 8:59 pm wrote:..... Ethan has revised his FAQ to correct some errors and to remove marketing content.
As long as Ethan's FAQ does not have any links to RealTraps or marketing content, it is not SPAM, therefore I have told him he can post links to it.
If anyone has a problem with the content, let's hear it ........


A few messages proved Recording Org management that Ethan had plain deceived them.
Posted: Sat Oct 02, 2004 9:12 am Subject: how to put fabric directly on 703
http://www.recording.org/ftopicp-181063-.html#181063
Posted: Sat Oct 02, 2004 8:59 am Subject: My basement soundproofing experience!
http://www.recording.org/ftopicp-181062-.html#181062
Posted: Sat Oct 02, 2004 10:25 am Subject: Need help matching monitor to a room
http://www.recording.org/ftopicp-181067-.html#181067

Since then the FAQ is gone/banned again, Ethan tried couple of times more, and seeing the fact that Ethan never appeared there anymore I only can assume that RO management, not keen to be deceived, made Ethan clear that not only his FAQ but he himself wasn't welcome anymore.

Summary:
The FAQ is banned for close to 7 months with a very few in-between exceptions (part Sept/Oct), related to Ethan's deception of RO, but which was clearly corrected by RO management once they knew and checked.
This must have been difficult for RO management: publicly restoring Ethan and his FAQ based on Ethan's personal guarantees, and then reversing that same decision when confronted with Ethan's deceit.
I can't judge if Ethan and/or his FAQ was officially banned, or that he was very strongly advised.
Anyhow, very shortly after the above messages RO deleted the complete thread in which Ethan's FAQ was officially re-instated. And the ones knowing Ethan, know that it's close to impossible to keep Ethan away only if it was to prove he's untouchable.

When I said in my first extensive SOS message that Ethan's site is a handy orchestrated deceit of site visitors, without any sense of responsibility, including plain physical abuse, than I know what I say and take full responsibility for my words.

If one knows me as being hush towards Ethan, then one sees the frustration of trying to correct all those misleading points. And as I said Ethan is an Expert, and I do mean that, but not in acoustics.
He reads what he can use, systematically ignores the rest and knows how to handle people.
Truth for Ethan is a commodity.

Direct related to the acoustic content of this thread.

I further refer to:
1) Angelo Campanella, one of US's Top Acousticians, seating in ASTM, ASA and representing American acoustic interests in ISO. He is a member of NCAC, INCE and an AIA-Columbus affiliate.
http://www.campanellaacoustics.com/angelo.htm

2) Dr. Noral Stewart another Top acoustician and active member in ASTM and ASA.
http://www.stewartacousticalconsultants.com/people.html

3) Chris Whealy who created some very interesting, not easy spreadsheets related to room modes, absorption and more.
http://www.rmmpnet.org/members/ChrisW/index.html
The spreadsheets on this site are among the most valuable on the net related to the covered topics.

In this very thread I showed that I warned others not to fall in Ethan's trap, which BTW is even out of context and just a matter of common use of concepts.
As such Ethan can't use his traditional side jumps to make him look clever, he provokes by telling that he corrected a significant misconception of Jeff and me (this relates to exact the point I warned others for).
As such Jeff and me substitute the others which don't bite. It shows even better, if he can point out he teaches well-known acousticians.

This all is as recent of June 2004
This is what Angelo replied, in the Usenet's alt.sci.physics.acoustics newsgroup

Note that Angelo replies to Ethan
Angelo Campanella Jun 3, 2004, 8:38 am (GMT+/-?) wrote:Ethan Winer wrote:
> In fact, this poll was prompted after discussions with several professional
> acousticians who argued that modes and standing waves are exactly the same
> thing and that the terms can be used interchangeably

Anyway, the term 'modes' might mean either the capability of a room to resonate, or the actual presence of sound at one or mode modal frequencies, aka standing waves.
The term 'standing waves', to me, implies only that the sound is there. ......
This topic has been beat to death here. Can we get onto something else?


Ethan is so proud he knows a definition, where US's top acoustician clearly shows how those terms are or can be used in practice, that Ethan over and over, makes this a main topic everywhere standing waves come up, while not even supported by the answer he got.
So this discussion relates to the common use of notions versus a more correct definition where is distinguished between the property and the result.
As Angelo points out, those notions are often used interchangeable, while the underlaying concept is never misinterpreted. And any acoustician clearly knows the difference between both.
For one or the other strange reason Ethan believes he teached the acoustic world something.
This discussion is not about concepts but linguistics and practical use of notions.. Yet Ethan makes it his main topic, thereby confusing anyone.

Here Chris W. replies rather hush on a question of Ethan:
Chris W Jun 2, 2004, 12:20 pm wrote:... A standing wave is the consequence of a room being excited at one of its modal frequencies.
Turn it around the other way - a room's modal frequencies are the set of frequencies which, when excited, will cause standing waves.


Due to the rather hush tone of Chris (who knows Ethan) Dr. Noral Stewart replies in defense of Ethan:
Noral Stewart wrote:> A standing wave is the consequence of a room being excited at one of its
> modal frequencies. Turn it around the other way - a room's modal
> frequencies are the set of frequencies which, when excited, will cause
> standing waves.
Perhaps Ethan did not say it as eloquently, but it seems to me that this is essentially what Ethan was saying.


Ethan's very vague question left a lot for interpretation (standard style having a way out in any direction).
So I corrected this referring to Ethan's FAQ and articles, and which is as well very clear from this very thread, with statements as:
Ethan Winer wrote:In fact, this is further proof that standing waves have nothing at all to do with room modes.

While in the same thread:
Ethan Winer wrote:It's not spurious at all. I never said room modes and standing waves are unrelated.

And his FAQ: http://www.ethanwiner.com/acoustics.html#sb1

Yet Ethan shamelessly replies towards Chris completely ignoring my response:
Ethan Winer wrote:In fact, by the time you got to the end of your post you said, "A room's modal frequencies are the set of frequencies which, when excited, will cause standing waves."
And as Noral pointed out, that's precisely the distinction I was making.

Chris, a clever guy just gives a standard definition. Note this is all as recent as June 2004.
Ethan proud to know this definition now too, provokes anywhere people by statements as the above, just to provoke people to say that room modes and standing waves are the same, where he than proudly can show the distinction between the 2 concepts.
That therefore he must start with complete nonsense statements doesn't bother Ethan.
And how both concepts are commonly used is made clear by Angelo, meaning that the topic itself has nothing to do with not understanding the concepts itself by other acousticians.

About reflections:
Angelo Campanella Jun 4, 6:54 pm (GMT+/-?) wrote:Ethan Winer wrote:
> ... As I see it, simply boundary
> interference - comb filtering - is the primary mechanism ...

Comb filtering; true.
Also, A plane wave of a single frequency, on reflecting from a wall, also reates "standing waves" in the wall vicinity.
But in that case the colloquial expression is "interference pattern".
Can we distinguish standing waves as being being only in a closed room, or at least between parallel walls?

Note the word PLANE here, which is VERY important in this text.
A plane wave hardly occurs in studios unless in modal standing waves. A traveling wave with a behavior close to a plain wave are waves radiated by a source at a relative long distance as e.g. the back wall where the spherical propagation by the radius of the sphere resembles a plain.
real 90 ° sound incidence occurs mainly with standing waves related to room modes and only fraction of the spherical propagation of the traveling waves.

Angelo Campanella Jun 6, 8:03 am (GMT+/-?) wrote:
In the case of modes and standing waves, it is apparent that each may imply the other, but that implication alone soon will not satisfy the users (us).
At the moment, I am favoring the concepts that: Modes mean the 2D or 3D pattern of the motion, especially at system resonance.
Standing waves mean the array of waves within a bounded space.
At least two bounds are needed (e.g. two parallel walls; one is not enough).


All the above messages by Angelo are known by Ethan. Since Angelo is one of the people defining those definitions for Standards, valid for anyone, his opinion is utterly important.

Addition:
It's important to distinguish in Room acoustics between:
1) Modal behavior/Standing waves:
Standing waves are independent of the propagation direction of the source radiation.
Defined by the room sizes and acoustic properties.
The strength of excitation defined by the coupling of the source with the mode defined by the position of the source within the modal pattern and the phase relationship with the standing wave.
2) Traveling waves:
Propagation directly related to the directivity and radiation pattern of the source.
Here the sound is governed by geometric acoustics.

There is much more, but that's why I need to make a page, not being forced to repeat it over and over again.

I saw following comments in Ethan's reply:
I do apologize to SOS but there is no gentle way to respond to this.
Ethan is it possible for you to write 1 single page without lying?

I NEVER contacted RO to become moderator, neither in any direct, nor in any indirect manner .
What they knew from me was what I wrote openly in any forum for all to see.
CAN YOU PLEASE KEEP YOUR SICK FANTASY FOR YOURSELF.
They CONTACTED ME, AFTER THEY DECIDED TO GET RID OF YOU.
YOU EXCLUSIVELY HAVE TO THANK YOURSELF FOR THAT.
THIS IS FIRST CONTACT EVER I HAD WITH RO. AND THAT WAS 10,000% THEIR INITIATIVE - NOT MINE
    ----- Original Message -----
    From: "Kurt Foster"
    To:
    Sent: Thu, January 01, 2004 4:44
    Subject: Your posts at RO

    > Eric,
    > SNIP >
    > We may need someone to take his spot. Would
    > this interest you?
    > Kurt Foster
The him relates here to Ethan.

Ethan you systematically and shamelessly abuse the fact that I'm bound to confidentiality to spread your lies on the net, knowing you provoke people.
I do not ask now, but DEMAND a public apology.

Also Later when your Faq was banned from RO: I never wrote neither Chris nor Kurt. They decided that from themselves. based on several complaints as I can read in the related post, AND NONE originating from me. They didn't ask me, I didn't ask them.
They banned your FAQ for what it is, based on complaints they got and they certainly were and are right.

You have a very sick way don't you, to get rid of anyone and anything which jeopardize your guru status, don't you?
What I had to say back then, now and always I do in the forum.
So can please try, for once in your live, to stick to the truth?

Ethan Winer wrote::I have already shown they are not the experts they claim to be, by proving beyond all doubt that a standing wave is not the same thing as a room mode. I have also shown that standing waves occur at non-modal frequencies, which is another thing Eric had disagreed with before but can no longer dispute. I have a long list of other technical gaffs and errors made by Eric Desart. I see no point in listing them all here, but I will if you really want me to. Bear in mind that for two years now these "experts" have denied that basic quarter-wavelength comb filtering occurs at a single boundary.
If Eric continues to insist that a standing wave is the same thing as a room mode, I ask him directly to explain this:

Summary: A bunch of nonsense covered by my comment: For Ethan truth is a commodity to be used in function of circumstances.

The typical GURU:
Ethan Winer wrote:Paul,
> I would contend that the peaks and dips you are hearing at those frequencies are FAR MORE LIKELY to stem from the path length differences of reflections v. direct sound, path length differences of reflections v. other reflections, etc, etc rather than standing waves. <

Absolutely not. They are entirely due to and caused by comb filtering off the various room surfaces. You remember those pesky 1/4 wavelength peaks and nulls, right? In fact, this is further proof that standing waves have nothing at all to do with room modes.
--Ethan

Paul's description is PERFECTLY CORRECT as well physically as well mathematically, and except for the word standing waves Ethan doesn't see what Paul is saying.
Paul is EXACTLY describing comb filtering in its basics. For Ethan the word comb filtering is lacking so it must be wrong.
Paul your description can directly be taken over in any physics book related to interference and superposition of waves in function of room acoustics. And the discussion about the use of the notion standing waves can be seen in Angelo's replies.
It's the path length difference, which is related to the phase shift, which further defines the interference causing anything between constructive and destructive interference.
This description is correct. One even doesn't need a wall. Once one has 2 or more sources with equal sound this description applies. Any reflection is nothing more than a mirror source, giving the same effect as if this were 2 or more sources free in space. The only difference with reflections is that the possible absorption can influence the calculation, but in principle the approach is 100% identical.

Ethan's way of thinking:

In my recent first message I clearly explained the Foam by Mail fraud:
http://acapella.harmony-central.com/forums/showthread.php?s=7c03a51e23f07d26e45e4391f248c3b8&threadid=741521&perpage=20&pagenumber=2
Just read Ethan's and my replies on that page.
This thread is referred in:
http://www.soundonsound.com/forum/showt ... mber=58407 - 05/12/04 09:46 AM
It's proven that FBM is a FRAUD; It's 99% sure that indeed that derived the absorption values directly from the Auralex measurement.
In this message Ethan suggest he does Auralex a favor (a poisoned apple) in return to Auralex's site adjustment

This was the original text on the RealTraps site before those SOS posts:
RealTraps before wrote:
"Most important here is the huge disparity between the published data for corner foam versus what we actually measured in a real acoustics lab."

We also include the manufacturer's published data for the brand of foam we tested so you can see how it compares with other brands of corner foam. Since most acoustic data is, at minimum, shown as octave bands down to 125 Hz, you can directly compare other corner foam with the particular brand we measured, to see how well they would perform when tested in corners. Top

What's most important here is the huge disparity in the first table (highlighted in white) between the published data for corner foam versus what we actually measured in a real acoustics lab. Please understand, this is not due to deceit or trickery - rather, it merely underscores the points made in The Numbers Game article.


This is the text after Ethan's poisoned apple he offered Auralex in the SOS thread:
RealTraps after wrote:"Most important here is the huge disparity between the published data for corner foam versus what we actually measured in a real acoustics lab."

We also include Foam By Mail's published data so you can see how it compares with other brands of corner foam. Since most acoustic data is, at minimum, shown as octave bands down to 125 Hz, you can directly compare other corner foam with the particular brand we measured, to see how well they would perform when tested in corners. Top

What's most important here is the huge disparity in the first table (highlighted in white) between the published data for corner foam versus what we actually measured in a real acoustics lab. Please understand, this is not due to deceit or trickery - rather, it merely underscores the points made in The Numbers Game article.


Just objectively analyse this:
Ethan misleads anyone based on data he knows is falsified. Yet in his mind others are responsible.
He knows the published FBM data are falsified, but his recent poisoned apple does harm the foam industry even more by suggesting that other products in function of corner absorption can be deviated by this huge disparity between the measured and published data.
Yet he knows that the published data are derived Auralex numbers, and his measured numbers are measured based on acoustic JUNK foam. Summarized he uses to Fraud by others to build huge part of his site around, distributes false press info and articles, but feels no responsibility whatever to whoever.
His use of mixing Sabine numbers with absorption coefficients is PLAIN physical fraud.

When I bring this site to court for FALSE ADVERTIZING I WIN, NO DOUBT whatsoever.
Even when I forget the foam industry, HE DECEIVES ALL SITE VISITORS.

This is the STANDARD manner his site is made.
The cynical part is that he states: >Please understand, this is not due to deceit or trickery - rather, it merely underscores the points made in The Numbers Game article<
This has completely NOTHING to do with the Numbers Game and ANYTHING with Deceit or Trickery.

I give up.
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The important thing is not to stop questioning. Curiosity has its own reason for existing ............... Albert Einstein

Re: Standing waves get their own thread - lucky little blighters!

Postby Tequila Slammer » Tue Dec 21, 2004 2:08 pm

Yes Eric. All very nice, but what do you think about the idea of downward pointing angled monitors to reduce the effect of standing waves at the monitoring position?

:headbang:
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Tequila Slammer
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