False wall and audio sound

[Sir Terrence the Terrible]

...we are well beyond "answering a question"...It's like this...good ol' Terrence the Interminable tells the poster, "...sure, punch a couple of holes in the wall, pop in the speakers, and you're good to go...".

And this was all I said? Bull old dude This is what I said

If you are speaking of a baffle wall, that will increase bass tremedously, and get rid of some modes and nodes in the room.(that would be standing waves) THX actually recommends this for THX certified rooms. I would not recommend boxing the speakers, that would create resonances that are undesireable. If you build a wall with speaker cutouts for the left, center, and right speakers with acoustical foam surrounding the speakers, you will get pretty good sound.

and this

Installing baffle walls is a common practice in THX certified rooms. I have done at least three installations using baffle walls that I can remember(I am sure there is more), and none of the problems that the individual above me listed ever showed up. While it must be carefully designed, it is doable

Did you forget the increase bass tremedously part? Or how about the carefully designed part? I mentioned the only acoustical issue you get from this mounting, and gave him a simple guidline to work with in terms of mounting. What he didn't ask for was specific construction answers, acoustical issues unrelated to this kind of install, no mention of the need for toe in, and all the other crap you brought to the table. Half the crap you mentioned there wasn't enough information to even address.

I disagree, and stated my position as to why. TtT simply has a problem with that...how dare anyone question his "expurtise"...I purport to be no "exspurt" and my experience(regardless of TtTs opinion) tells me the project isn't a simple one with simple solutions...in fact it could prove to be more trouble than it's worth...simply providing an alternate POV...

jimHJJ(...quite simple really...)

Your position was a position of complete ignorance of this kind of installation. The kinds of acoustical issues you brought up are not issues for this kind of install. If you have ANY experience doing this kind of install, the kinds of issues you raise would be in line with this kind of setup. The rather silly thing that makes me laugh is that you are arguing against something that has been done over and over again. You need to check out more magazines that feature custom installed hometheaters. Several things that you seem to forget constantly is;

He never asked any constructions questions.
He never stated a room size
He never stated a screen size
He didn't say HE would build it
He never mentioned a budget
He never said he was married or had children, a dog, or a horse.
He never asked was the easy or hard to do.

In spite of this, you still brought some of these up with absolutely no information. You call that a POV, or just fishing for a problem in a situation you don't understand. You know, just throw crap out there and see what sticks. Now had you have asked about vibration control, differences between flush mount in a cutout hole and mounting the speakers to the frame, these are issue related to this kind of setup. Not standing waves, not the lack of rearward waves effect the speakers sound, not creating more acoustical problems(because it doesn't) or any of the other non flush/baffle mounted issues you raised. Those issues you raised are problems with in room speakers, not baffle/flush mounting. You may call it a POV, I call it complete ignorance.

It is completely disingenuous of you to come here and represent yourself as the saviour of HVAIC from misinformation. Your created more misinformation and dispelled nothing. You didn't even address my responses to your so called POV

[Resident Loser]

...what you really said was:

If you are speaking of a baffle wall, that will increase bass tremedously, and get rid of some modes and nodes in the room. THX actually recommends this for THX certified rooms. I would not recommend boxing the speakers, that would create resonances that are undesireable. If you build a wall with speaker cutouts for the left, center, and right speakers with acoustical foam surrounding the speakers, you will get pretty good sound.

...and you pretty much would have left it that way if I hadn't put that bug up your @$$...perhaps if you had the forethought to include...

While it must be carefully designed, it is doable

in your initial response, I might have been inclined to let you slide...probably not, but maybe...and anyway, how do you know he wasn't ready to whip out the ol' Sawzall and start on this project simply because you intimated it was a piece of cake and would probably cure cancer and solve world hunger to boot?

Do make a note for future reference YOUR use of the word "if"...conjecture on your part is OK, however if I choose to raise some doubt it is verboten, eh?

I included everything I did simply to counter your overly simplistic answer, sorry you no likey!

And again, for the gazillionth time...

The rather silly thing that makes me laugh is that you are arguing against something that has been done over and over again.

When what I actually said was:

Once again, you can put your enclosures or drivers in any configuration you chose, but they need to be either designed for the purpose or mechanically/electronically manipulated to compensate for their environment.

Given the choice(and since they make 'em for multiple environments) why would one want to use a speaker optimized for free-field use, when a flusnh-mount or cabinet-mount model is available?...as in the case of PSB. It'll only require that much more tweaking...

Why use the Genelecs which are near field radiators and which should be toed-in, as per spec, completely out of context?

Why put your boots in the oven and expect them to be seen as biscuits?

The answer is simple...HT is simply a medium for laser-totin' mechanical lizards...accuracy simply isn't of paramount concern...it's all nothing but one-upsmanship and old fashioned popcorn makers...and ooh's and aah's...

You didn't even address my responses to your so called POV

There are around 55 posts, roughly half of which are mine...if you don't have all the answers you need, the problem isn't mine...

jimHJJ(...and it really p!$$es you off...)

[Sir Terrence the Terrible]

...what you really said was:



...and you pretty much would have left it that way if I hadn't put that bug up your @$$...perhaps if you had the forethought to include... in your initial response, I might have been inclined to let you slide...probably not, but maybe...and anyway, how do you know he wasn't ready to whip out the ol' Sawzall and start on this project simply because you intimated it was a piece of cake and would probably cure cancer and solve world hunger to boot?

Listen, this is not about you no matter how much you attempt to make it. It is about the posters question, something you failed to answer even after 27 or so responses. Your responses didn't even respond to the basic question that was asked {b}would the false wall effect anything else?[/b]. Your responses brought up issues related speakers out in the room, not flush/baffle mounted. Because of this, it was of no help at all. Of course, this wasn't about the question the poster asked was it?

Do make a note for future reference YOUR use of the word "if"...conjecture on your part is OK, however if I choose to raise some doubt it is verboten, eh?

Do make note of the mistletoe located conviently on my coattails. In the future when raise some doubt, make sure its appropriate to the design that discussed. You were totally off the mark on this one.

I included everything I did simply to counter your overly simplistic answer, sorry you no likey!

The question was simple, the answer was simple. Only an idiot thinks he needs to rewrite the constitution just to answer the question. You included everything you did, because you are not familar with this particular kind of installation. So what you did was throw everything including the kitchen sink,to hide your ignorance(which it did not) and make a feeble attempt to counter my response. Not very effective, and not particularly helpful to the original poster. You are welcomed to challenge anything I say at any time.

And again, for the gazillionth time...



When what I actually said was:

You should have stop right there. The rest of your responses were not helpful,.

Given the choice(and since they make 'em for multiple environments) why would one want to use a speaker optimized for free-field use, when a flusnh-mount or cabinet-mount model is available?...as in the case of PSB. It'll only require that much more tweaking...

How do you know it requires more tweaking, have you tried it? Do you actually have any hands on experience, or are you just guessing? You use the Genelecs because they work, and they are better than what is being marketed as in wall or flush mounted. PSB are optimized in a reflection free anechoic chamber, not a room, not in your room, and not in the posters room. PSB does not have any idea where their speaker is going to be installed.

Why use the Genelecs which are near field radiators and which should be toed-in, as per spec, completely out of context?

They require toe in when the installation requires it. They do not ALWAYS require toe in. Your still thinking inside the box. We use them because they work exceptionally well in this kind of design. Toe in is a recommendation, not a specification must.

Why put your boots in the oven and expect them to be seen as biscuits?

I guess for the same reason why you think a standing wave is a room resonance.

The answer is simple...HT is simply a medium for laser-totin' mechanical lizards...accuracy simply isn't of paramount concern...it's all nothing but one-upsmanship and old fashioned popcorn makers...and ooh's and aah's...

All of this is based on your personal experience? Or are you just complaining that the industry has grown past your knowledge. Have you ever heard any custom installed theaters. Is your opinion educated, or just some more ranting and raving because you just don't get it?

There are around 55 posts, roughly half of which are mine...if you don't have all the answers you need, the problem isn't mine...

jimHJJ(...and it really p!$$es you off...)

You call those answers? It was more like crap on the wall that is not even appropriate for this kind of installation. You don't know what pisses me off. I certainly am not bothered by the musing of an old man well past his time, with no current information on current audio technology. Remeber the question waswould the false wall effect anything else?
. You offered nothing to answer that question nor to this discussion

[Resident Loser]

...I provided ALL the info I that did (kitchen sink included) to counter your overly-simplistic response. PERIOD, end of story...sorry you no likey.

My take(and consequently MY response) on the "false wall" was as I outlined in text AND as I presented in those .jpegs. PERIOD, end of THAT story...

I guess for the same reason why you think a standing wave is a room resonance.

You mean it's not?!?!? Funny thing, these folks seem to think so:

http://www.indiana.edu/%7Eemusic/ete...standing.shtml

http://hyperphysics.phy-astr.gsu.edu...es/standw.html

I'll guess you have some new and revolutionary take on what currently comprises a standing wave in the scientific community...Oh, do 'splain Lucy...

For example you have a room whose dimensions are AxBxC...you have a loudspeaker whose low-end FR is limited so that the interaction, in that room, insofar as standing waves is concerned, is nil or negligible. Given the fact that as we move up in frequncies the wavelengths become shorter...so if we shorten a room dimension so that now it will line up with the wavelength of a lo-end freq the loudspeaker is more capable of producing, something is probably going to happen...nodes or anti-nodes...but something. Caveat emptor...

jimHJJ(...or as in your case "cabeza empty"...)

[Sir Terrence the Terrible]

...I provided ALL the info I that did (kitchen sink included) to counter your overly-simplistic response. PERIOD, end of story...sorry you no likey.

Not end of story, you provided that information because you didn't know what you are talking about. Its funny, you still don't. Simple question requires simple answer. Get that simpleton?

My take(and consequently MY response) on the "false wall" was as I outlined in text AND as I presented in those .jpegs. PERIOD, end of THAT story...

Unfortunately it didn't even come close to describing what the poster wanted.. Sorry YOU is wrongy. Speakers boxed in a free standing solid wall, get the concept? You wanna try again, and please put the speaker IN THE WALL.

You mean it's not?!?!? Funny thing, these folks seem to think so:

http://www.indiana.edu/%7Eemusic/ete...standing.shtml

http://hyperphysics.phy-astr.gsu.edu...es/standw.html

I'll guess you have some new and revolutionary take on what currently comprises a standing wave in the scientific community...Oh, do 'splain Lucy...

You still do not get it.

These standing wave modes arise from the combination of reflection and interference such that the reflected waves interfere constructively with the incident waves. An important part of the condition for this constructive interference for stretched strings is the fact that the waves change phase upon reflection from a fixed end. Under these conditions, the medium appears to vibrate in segments or regions and the fact that these vibrations are made up of traveling waves is not apparent - hence the term "standing wave".

In the case of a loudspeaker in a baffle there is no rear wave colliding with incidental waves in opposite directions coming at the listening position. There is a single incidental wave coming from the front baffle(which the ears hears first), and reflections from the back wall arriving MUCH later(which the ear interprets as another event). In the case of a speaker out in the room(can anyone say proud to the wall) you have the front wave arriving first, and close arriving second waves reflected off the front and side walls near the speaker arriving next. These waves are 180 degrees out of phase with each other. Notice in the text where is says An important part of the condition for this constructive interference for stretched strings is the fact that the waves change phase upon reflection from a fixed end.. In order for a standing wave to be audible there must be a flip in phase. This can only happen if the speakers sits IN FRONT of the wall, and you hear a combination of the direct, and later arriving reflected signals. That is what creates standing waves. If there is no combining of incident, and later arriving reflections, then there cannot be a audible standing wave. Installing a speaker in a baffle wall supresses any late arriving reflections that would be out of phase, so only the incident wave is heard. Hence, no exciting of standing waves. Since the speaker is closer to the baffle wall, it places the speaker in a high pressure zone which accounts for the boosting of the bass. Much like what you get when you push a sub against a single wall. Room resonances can occur at all frequencies, standing waves are a low frequency occurence period. Not the same thing Methuselah

For example you have a room whose dimensions are AxBxC...you have a loudspeaker whose low-end FR is limited so that the interaction, in that room, insofar as standing waves is concerned, is nil or negligible. Given the fact that as we move up in frequncies the wavelengths become shorter...so if we shorten a room dimension so that now it will line up with the wavelength of a lo-end freq the loudspeaker is more capable of producing, something is probably going to happen...nodes or anti-nodes...but something. Caveat emptor...

First, and once again, you are mixing up room deminisional resonances and standing waves. Room deminsional resonances are resonances based on room deminsions. A room that is 14ft long will have a room resonance of 40hz. This resonance is not out of phase, but in phase when arriving at the ears Standing waves are a different animal altogether. They come from the interaction of a series of reflections combining with a incident wave and flipped out of phase and only occur in a speakers omnidirectional radiation pattern which are in a speakers low bass frequencies(which excludes baffle/flush mounted designs). Two different animals that when combined together(can anyone say proud to the wall) makes things alot worse than if you have a single incedental wave with a boost in bass of about 3db.

Did the poster mention that he wanted to shorten the room deminisions? No! A free standing baffle wall does not shorten a room's deminisions. It cannot since it is not attached in anyway to the orginal rooms walls. Hence FREE STANDING. You have not change the fundemental deminsion of the room, there is just a barrier there. This would break up any side to side room modes, especially a wall 2-3ft thick.

The reality is without room deminsions from the poster, your weak attempt at saving your face is useless.

jimHJJ(...or as in your case "cabeza empty"...)

In your case "don't know ya stuff". Surf the internet, find a link, and thinks ya got it. NOT!!!

[Resident Loser]

...you wouldn't get it if it were on your kitchen table in a big, brown bag marked "IT"...

For all the kiddies in the peanut gallery, let's start with a few definitions and/or references:

http://www.atis.org/tg2k/_standing_wave.html

"Standing wave: In a transmission line, a wave in which the distribution of current, voltage, or field strength is formed by the superposition of two waves propagating in opposite directions, and which wave is characterized by a series of nodes (maxima) and anti-nodes (minima) at fixed points along the transmission line. Note: A standing wave may be formed when a wave is transmitted into one end of a transmission line and is reflected from the other end by an impedance mismatch, i.e., discontinuity, such as an open or a short. Synonym stationary wave."

In this instance, even though the energy we are transmitting is an acoustic wave and our "impedance mismatch" is a wall, this definition is still applicable.

And then from:

http://www.crutchfieldadvisor.com/IS...cs.html?page=2

...in a nutshell:

"Standing waves and room resonance modes

Any time you have a pair of parallel reflective surfaces (like room walls, or the floor and ceiling), you're going to experience some degree of a phenomenon known as standing waves. Standing waves distort the bass and lower midrange frequencies from 300 Hz on down... Standing waves are created when sound is reflected back and forth between any two parallel surfaces in your room. They affect frequencies below 300 Hz...A room's primary or "axial" resonance modes are based on the room's three main axes: length, width, and height. These resonance modes create bass peaks and dips of up to 10 dB throughout the room!"



http://www.audiovideo101.com/diction...nding-wave.asp

"Standing Wave
Low frequency anomaly or distortion created when a certain frequency is reproduced whose size has some special relation to the room or object it is produced in (wavelength the same size as the room dimensions) resulting in the room or object resonating with the sound and increasing the strength of the sound (the sound wave does not diminish and may instead increase as it interacts with its surroundings). The end result of a standing wave is a very loud signal greater than that presented by the original signal. The sound wave is essentially amplified by the space in which it exists."


http://www.axiomaudio.com/archives/b...e_theater.html

...Pariticularly the following:

"Choose the Correct Room Shape

If possible, avoid square rooms, because deep bass sound waves really misbehave in square rooms. They produce “standing waves,” which result in areas of extreme bass emphasis and no audible bass. Trying to fix the standing-wave problem after the fact is virtually impossible. Instead, select a rectangular shaped room with the dimensions (length, width and height) not evenly divisible by a common denominator. For example, don't choose a room 24 x 16 x 8 ft.; instead lay out dimensions of 23 x 13 x 7 feet. That way, you'll minimize standing waves."

There are more. They basically say the same thing...anyone interested can Google "audio standing waves" or "definition of standing waves"...don't take my word for it, check and see...We are not afraid! At least I'Mnot.

Anywho, back at the ranch...

In the case of a loudspeaker in a baffle there is no rear wave colliding with incidental waves in opposite directions coming at the listening position...

etc.

We aren't talking about "rear waves"...can you say red herring?...All loudspeakers attempt to eliminate (as in infinite baffle, acoustic suspension) or use/control (as in transmission line, bass reflex, ported)those...standing waves are a product of frequency vs. room dimensions REGARDLESS OF SPEAKER TYPE...free-field...in wall...in ceiling...in your shorts...If the conditions are right, standing waves ARE a reality as long as there are two(or more) parallel reflecting surfaces...sooo, bada-bing, bada-boom, bada-bite-me...

Did the poster mention that he wanted to shorten the room deminisions? No! A free standing baffle wall does not shorten a room's deminisions. It cannot since it is not attached in anyway to the orginal rooms walls. Hence FREE STANDING. You have not change the fundemental deminsion of the room, there is just a barrier there. This would break up any side to side room modes, especially a wall 2-3ft thick.

According to your initial "IF"y response, that's what you responded with...simply build a "baffle wall" and hide your PSBs...If that doesn't change a dimension or two I can't think of what would...'twern't 'til I voiced my objections that we got any sort of clariciation (as vague as it was) on the matter...cheez-and-crackers, do you actually think the folks who may have been following this object lesson in futility are as dumb as you are? Let's simplify matters...

Post #1. Pooor HAVIC asks a question...

Post #2. TtT provides the infamous and simplistic "stickin' 'em in a wall is bettr'n canned beer" response...

Post #3. RL says no, no ,no...not so simple...because...

TtT scrambles for the smoke and mirrors...

jimHJJ(..."save face"?...)

[GMichael]

You guys are so great. I would be bored as h.ll if it weren't for this thread.

[Resident Loser]

...from the Yogi Berra school of thought...

Room deminsional resonances are resonances based on room deminsions.

...and you can observe a lot by just watching...

BTW, all that text you posted with the reflected and incidental waves wasn't an ad for Bose speakers...it was an explanation of standing waves with regard to strings and air columns...destructive and non-destructive interference are simply points where sound is either augmented or cancelled(e.g. in-phase or out-of-phase) on a vibrating string or column of air...IT HAS NOTHING TO DO WITH early or late reflections from a loudspeaker. Nice basket of apples and oranges you got there fella...do try to read(and understand) ALL the links within the links provided, it tends to make more sense that way...

In order for a standing wave to be audible there must be a flip in phase

B..b...b....but if there is a flip in phase, and it's a stationary wave...th..th...th....then it's out-of-phase and nothing is audible...QUICK!...somebody get MIT on the line the laws of physics are NOT immutable???? RUN FOR YOUR LIVES...THE SKY IS FALLING!!!!

No, no...sorry it's just TtT mis-reading and mis-applying those dang diagrams again...

This can only happen if the speakers sits IN FRONT of the wall, and you hear a combination of the direct, and later arriving reflected signals. That is what creates standing waves.

No, not really...THAT'S called "Stereo Everywhere" and I think Bose may have the copyright on that...Actually, it's the passengers on the ship leaving the dock that are responsible for standing waves...

jimHJJ(...and pal (generic) yo' ship done sailed...)

[Sir Terrence the Terrible]

Room resonances are not created randomly. They have to be stimulated by a sources located near the rooms boundary's. A speaker on a stand in the middle of the room will not excite or drive any of the a rooms modes. A speaker on a stand against the front wall will excite a room resonances associated with the length of the room(front to back), but is not likely to excite any room modes associated with floor to ceiling, or side to side boundaries as it is not efficiently coupling with these boundaries. A speaker against the front wall and on the floor will couple efficiently with both the floor to ceiling and front to rear axial modes. A speaker on the floor and in a corner will excite ALL room modes efficently and cause AUDIBLE standing waves to be heard if you are situated near the room boundaries. Certain condition must be met to make standing waves audible. Your sources must be near room boundaries, and so do your ears. Once you decouple either from the boundaries of the room, room modes and nodes are not efficiently driven, and become less audible.

The reason standing waves are a problem at frequencies below 300hz is because this is the frequency that speakers begin to couple with the room boundaries more efficiently. As the dispersion pattern of the speaker becomes more omnidirectional, the better chance the speaker has of efficiently coupling with the boundaries of the room and stimulating a room modes. A speaker that never becomes omnidirectional will not efficiently couple with the room boundaries.

How does this relate to what the poster ask? The poster wants to erect a stand alone wall(that is decoupled from every room boundary except the floor) and flush mount his speakers in that wall. RL says this will create more acoustical problem and will likely stimulate standing waves in the room. He suggest that it might be better just to install them "proud" with the wall as if that will make acoustical problems go away. Wrong, it will make them worse. The poster has a sub, and it is likely it will produce all of the deep bass from the system. Since the poster has a Yamaha receiver it is likely the crossover point to the sub is 90hz. The posters main speakers are tall and narrow baffled tower, that are pretty deep in depth. The drivers are 6.5" woofers. If placed in front of the wall as RL suggests, it is likely at sometime before 90hz that this speakers output will become omnidirectional, and bass frequencies would begin to wrap around the cabinet and engage the rooms front wall. This will excite the room front to back axial mode. The fact that the speaker sits on the ground already will excite the rooms floor to ceiling axial mode. There will also be early and late arriving reflections that smear imaging, and changes the frequency response of the speaker at the ears. Hardly less problems

The poster did not say how wide this stand alone wall would be, but he did suggest up to 3ft deep. The wavelengths of the bass would have to be pretty long(deep bass)to wrap around this baffle wall, and engage the rooms front to back axial modes. They would have to be VERY long to engage any of the rooms natural boundaries. Since the poster has a subwoofer, it is not likely his main speakers that are in the wall would produce any bass with wavelengths long enough to engage any room mode. The speaker never radiates in a omnidirection pattern, not at any frequency it will likely be producing. That means no early and late arriving reflections, and no stimulating of the room axial modes and nodes. The baffle wall will create a boost in the mid bass, and the speaker is on the floor which will excite the rooms floor to ceiling mode. Both of these CAN be eq'd(especially the baffle wall boost since it is in phase with the direct output of the speaker itself). What RL proposes would require more acoustical foam and eq than baffle/flush mounting. The monolith wall is not near any boudaries, so it would be pretty hard to stimulate or drive any of the rooms modes.

RL, you just cannot mention standing waves as a stand alone issue. Standing waves and room modes have to be stimulated by the source. The closer to the room boundaries you locate the source(and your ears) the more profound standing waves become. If you limit the dispersion pattern of the speakers at bass frequencies(a baffle/flush mounting will do just that) then you decrease the chances of the speaker to interact with the rooms boundaries. Thus you do not stimulate or drive the rooms modes.

Your contention that baffle/flush mounting would be worse is not true at all. What you suggested would require twice the work to get right, not to mention more acoustical control. Your suggestion has more chance of exciting room modes than mine.