# Over Trapping a Dead Room



## Prof. (Oct 20, 2006)

This is my question...to all the acoustic experts here...

If one already has a room that is very acoustically dead,(in this case a very small room) is not further trapping just going to make it even deader?:scratch:
It seems to me that a very dead room is going to adversely affect the sound quality, virtually taking the life out of the sound so to speak..

I realise that a lot of trapping is going to help to improve the bass side of things, but isn't there going to be some further constraint on the rest of the frequencies?


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## Kal Rubinson (Aug 3, 2006)

Prof. said:


> I realise that a lot of trapping is going to help to improve the bass side of things, but isn't there going to be some further constraint on the rest of the frequencies?


There are bass traps that have minimal effect at the higher frequencies.

Kal


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## bpape (Sep 14, 2006)

It depends on how, where, and with what you've treated the room. 

You can in theory completely cover every surface of the room in narrow band bass absorbtion and have almost zero effect above say 500Hz. Not that this is desirable but it's possible.

Now, realistically, in a small room, one usually needs to use a more broadband solution simply because there is limited amount of space to deal with. On the positive side, modal frequencies in smaller rooms are higher in frequency.

The trick is to determine what the target decay curve should be based on size, usage, construction, furnishings, etc. and then come up with a treatment plan that will address SBIR, modal issues, early reflections, etc. but do so in a way to stay within the target range.

More to your question - if one simply takes some of the say 1 and 2" material in the room and converts it into 4 or 6" material, you're not changing the mid and high frequency absorbtion but you are adding additional low end control in the lowest few octaves.



Bryan


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## Prof. (Oct 20, 2006)

Thanks for the replies...

I was planning on additional floor to ceiling bass traps to the rear corners, but since my room is already dead, I was afraid that it would maker it even deader and start to suck the life out of the overall sound..
It would appear by all accounts, that isn't going to happen.
I will be using 6" total thickness of stacked 703 equivalent..


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## Josuah (Apr 26, 2006)

Plus, a totally dead room means that the only thing you hear is what's coming out of the speakers and should be the most accurate reproduction of the audio. Being in a wide open plain should not have bird chirps reflecting even a little. And if there was supposed to be a reflection, it should come out of the opposite speaker with a delay anyway.

On the other hand, you might think you're the only person left on the planet.


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## Prof. (Oct 20, 2006)

Josuah said:


> On the other hand, you might think you're the only person left on the planet.


That's what I feel now every time I watch a movie..
Living in an isolated rural area where there is not a sound at night, only adds to the illusion :bigsmile:


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## Ethan Winer (Jul 21, 2006)

Josuah said:


> Plus, a totally dead room means that the only thing you hear is what's coming out of the speakers and should be the most accurate reproduction of the audio.


I agree with that. The smaller the room, the more dead you need to make it for good reproduction. A dead sounding room is not the evil many would have you believe. I'm not saying totally dead, but mostly dead. Especially at bass frequencies.

BTW, nice to see you here Kal! :T

--Ethan


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## bpape (Sep 14, 2006)

If you're going to do floor to ceiling 6 inchers, straddle the corner and bond an FSK facing onto the side facing the room. That'll minimize the absorbtion above about 350Hz.

Bryan


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## Prof. (Oct 20, 2006)

Ethan Winer said:


> The smaller the room, the more dead you need to make it for good reproduction.


Is that because the intensity of the waves hitting the walls is greater than in a larger room?


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## Prof. (Oct 20, 2006)

Bryan...If my memory serves me, FSK is some kind of paper facing on the 703 isn't it?
Where would i likely get this paper and how would you bond it to the fibreglass?
I doubt if they've ever heard of it here in Australia..


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## bpape (Sep 14, 2006)

Smaller rooms require proprotionately more bottom end control because the modes are by default closer together and there's also less space for them to spread out and work in the air with other things in the room.

The FSK is a combo of a heavy paper, a mesh, and a foil covering all bonded together. If you can't get it there, look for a heavy 'butcher paper' - that will be similar. Bond with a medium grade spray adhesive like Scotch 77

Bryan


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## Ethan Winer (Jul 21, 2006)

Prof. said:


> Is that because the intensity of the waves hitting the walls is greater than in a larger room?


In a small room the walls are closer so the reflections are stronger. Also, as Bryan tried to say :neener: the modes in a small room are _farther_ apart, which makes them more damaging.

Sorry Bryan! :kiss:

--Ethan


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## Prof. (Oct 20, 2006)

bpape said:


> Smaller rooms require proprotionately more bottom end control because the modes are by default closer together and there's also less space for them to spread out and work in the air with other things in the room.


Thanks for that Bryan...It makes perfect sense now.:T.



bpape said:


> The FSK is a combo of a heavy paper, a mesh, and a foil covering all bonded together. If you can't get it there, look for a heavy 'butcher paper' - that will be similar. Bond with a medium grade spray adhesive like Scotch 77


I have seen a 2" thick fibreglass sheet with what looks like an aluminium facing..
Could that be the FSK material?


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## Prof. (Oct 20, 2006)

Thanks Ethan..:T


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## Prof. (Oct 20, 2006)

I have another acoustic question for you guys if you would be so kind...

There is a ton of information available on the placing of acoustic panels at the first reflection point..but it seems to all refer to the standard setup, with your L&R speakers being either floor-standing or raised just above the bottom of the screen, as is the situation in most theatres...
It is generally recommended that the acoustic panel be placed on the side walls at the reflection points, from floor to a few inches above the height of the tweeter..
But what about speakers that are mounted above the screen?
My tweeters are about 18" below the ceiling!..Surely a floor positioned panel isn't go to be of much help down there..
Should my treatments be more in the wall ceiling corner at the first reflection point?

At the moment I have floor to ceiling suede curtains from the front of the screen, extending about 6' along the side walls, but no panels at the reflection point..
What would you advise?..


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## SierraMikeBravo (Jul 1, 2007)

HI!

You first need to determine if you even need panels at the reflection points. If you have poor off axis response by determination through an RTA, then you should treat the reflection points. Generally, diffusion is the preferred method as absorption can reduce the soundstage. Also, it is more desirable to leave untreated space above the panel so you don't lose spatial imaging. 

However, I guess we should ask these questions. Why is your room acoustically dead? Have you over treated? Too many curtains? You may want to consider removing some of the deadening material if that is the case. The other question is why is your center channel (I am assuming that this is the case) above the screen? I am not sure of your setup, but it is usually undesirable to have such a seperation between your center and your L/R speakers. This will cause panning to no longer be in the same plane.


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## bpape (Sep 14, 2006)

Yes - you'd have to do the 3D trig (or just use the mirror) to determine the reflection location. 

Curtains will help absorbing high frequencies but will not reach down into the vocal range. I'd recommend some panels behind the curtain to extend things in general.

Yes - the foil on the insulation is likely either FRK or FSK (either is similar enough acoustically to do the job).

Bryan


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## Prof. (Oct 20, 2006)

SierraMikeBravo said:


> However, I guess we should ask these questions. Why is your room acoustically dead? Have you over treated? Too many curtains?


That's a good question..I suppose that considering the room is small, then there is a fair amount of square feet of curtaining..
The front wall is covered with 1" acoustic material with floor to ceiling bass traps..
The screenwall is covered with acoustically transparent cloth..
The theatre recliners are covered with micro fibre material and the floor is covered with a fair thickness of underlay and carpet...Oh and the walls and ceiling are plasterboard with insulation behind..
All in all, adding up to a very dead room.:bigsmile:


SierraMikeBravo said:


> The other question is why is your center channel (I am assuming that this is the case) above the screen? I am not sure of your setup, but it is usually undesirable to have such a seperation between your center and your L/R speakers. This will cause panning to no longer be in the same plane.


The L&R speakers are above the screen, with centre speakers above and below the screen..
I was not able to place the L&R speakers below the screen because on the left hand side behind the screenwall is the equipment rack..
This is what it looks like..








The speakers sit just above the top of the screen, angled down and within the screen boundaries..


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## Josuah (Apr 26, 2006)

Even with good off-axis response, you would want to prevent first-order reflections if you don't want the sound to actually bounce off the other surfaces. Sure, it "expands the soundstage", because the sound is echoing off. And that's going to be really bad if the off-axis response is not good (and tweeters are never good off-axis), but it will still be bad if you're going for accuracy because there's a delay between when the sound first gets to you and when the reflected sound does. And the reflected sound isn't going to be a "mirror" reflection.

Anyway, in case it's not blatantly clear, I prefer no reflections and no expanded soundstage due to reflections.


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## Prof. (Oct 20, 2006)

bpape said:


> Curtains will help absorbing high frequencies but will not reach down into the vocal range. I'd recommend some panels behind the curtain to extend things in general.


Yes, I think that's the first thing I'm going to try..



bpape said:


> Yes - the foil on the insulation is likely either FRK or FSK (either is similar enough acoustically to do the job).


Thanks for that..I thought it might be a similar product..


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## Prof. (Oct 20, 2006)

Josuah said:


> Sure, it "expands the soundstage", because the sound is echoing off.


Yes, that what I get now..I call it an "openess" to the sound, but I can see that it should not be a reflected echo..
One thing I've noticed (which is probably caused by reflected sound interactions) is that I get a gap in the surround sound, between the screen and the surround speakers, particularly noticeable when sound is travelling from front to back along a side wall..and with Tri-pole surrounds, I shouldn't get that..


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## OvalNut (Jul 18, 2006)

> I'm not saying totally dead, but mostly dead.


:bigsmile:
.... That made me laugh, reminded me of a line uttered by Billy Crystal's Magic Max character in The Princess Bride. :filmstrip:

Tim
:drive:


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## salvasol (Oct 31, 2006)

Prof. said:


> ...The front wall is covered with 1" acoustic material with floor to ceiling bass traps...The screenwall is covered with acoustically transparent cloth..


Prof. ... I want to kill my front wall too :bigsmile:

What kind of accoustic material did you use??? ... I'm planning to cover the wall with something (I'm not sure what to use) and then cover that material with speaker cloth or any transparent cloth :dontknow:

The other option is to use panels ... but I prefer to cover the whole wall :yes: :yes: :yes:


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## gullfo (Nov 25, 2006)

for bass trapping - use 4" 3pcf (semi-)rigid insulation (703, mineral/rock wool, recycled cotton, etc). for high frequency use 2". i'd go with the deeper insulation since most folks make the common mistake of only absorbing mids-highs and end up with a bass response problem. take care of the bass first and then work the mids-highs.


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## Prof. (Oct 20, 2006)

salvasol said:


> Prof. ... I want to kill my front wall too :bigsmile:
> 
> What kind of accoustic material did you use??? ... I'm planning to cover the wall with something (I'm not sure what to use) and then cover that material with speaker cloth or any transparent cloth :dontknow:
> 
> The other option is to use panels ... but I prefer to cover the whole wall :yes: :yes: :yes:


I used an insulation material called "Supertel"..It's the equivalent down here for OC703..
I then covered that with black burlap, so you couldn't see it through the screenwall..


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## salvasol (Oct 31, 2006)

Thank you Glenn and Prof. :wave:


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## Guest (Mar 10, 2008)

Ethan Winer said:


> I agree with that. The smaller the room, the more dead you need to make it for good reproduction. A dead sounding room is not the evil many would have you believe. I'm not saying totally dead, but mostly dead. Especially at bass frequencies.
> 
> BTW, nice to see you here Kal! :T
> 
> --Ethan


This just creates the effect of listening to headphones. Much more realistic sound can be had by proper utilization of room reflections.


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## bpape (Sep 14, 2006)

In a larger room that's true. Smaller rooms require proportionately more broadband bass control to tame them. The advantage is that smaller rooms have primary modes that are higher in frequency so they're also a bit easier to deal with.

Bryan


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## Guest (May 18, 2008)

An easy way to determine all of the first reflection points is to perform an ETC (Envelope time curve) measurement of the listening position for each speaker.

Their delay and intensity is easily determined. But there is nothing that states that they will necessarily be the side walls, although that is a very common location. Ceiling and flows, as well as other sources (diffraction) may act as virtual specular sources.

By making a sweep with a piece of absorbent material placed in the path of anticipated reflections - repeating until said path is interfered with - will easily be determined by the disappearance of the said specular reflection in the ETC.

Additionally. all is not lost in a dead acoustic space, as devices such as a reflective 'Haas kicker' may be installed thus creating a defined end to the ISD (Initial signal delay) gap and providing an increased sense of definition to the source.

Also, to add one more observation and to take issue with the aforementioned assumption, a small room need NOT be dead! Adjacent space, be it unused ceiling cavities, crawl spaces, closets and adjacent hallways and rooms can be utilized very effectively to provide addition semi-reverberant tails via the use of phase gratings, thus adding to the sense of perceived space to even the smallest room! 

I might also add that this speaks directly to the all too common race to use far more absorption in a room than is appropriate...where the surgical use of absorption coupled with the liberal use of diffusion is a much more advantageous approach!

There are a variety of tricks available depending upon if you are beginning with too dead a space, or the more common too live space.


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## bpape (Sep 14, 2006)

Some of what you say is true in some environments. In a home theater or any multichannel environment, the target decay time across the spectrum is lower than in a 2 channel environment - though not as dead as something like an iso or vocal booth.

Making statements like that without proper context only confuses people more. Having proportionately more broadband bass control DOES NOT necessarily equate with a room being too dead. There are ways to do it without introducing much of any HF absorbtion (though that would generally be impractical).

I will agree that many times, people just throw too much absorbtion at a problem. Sometimes it's the right amount but not properly balanced across the spectrum. Diffusion - well, in many residential sized spaces, there really isn't enough space for a diffuse field to properly develop between diffusion position and listener position. They can be useful for minimizing slap echo certainly.

Bryan


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## Guest (May 18, 2008)

bpape said:


> ...
> 
> Making statements like that without proper context only confuses people more. Having proportionately more broadband bass control DOES NOT necessarily equate with a room being too dead. There are ways to do it without introducing much of any HF absorbtion (though that would generally be impractical).
> 
> ...


The response was in reference to the claim that: "The smaller the room, the more dead you need to make it for good reproduction". A broad claim with which i, and most folks I know designing rooms would disagree. 

A semi-reverberant diffuse tail and the resultant sense of increased space can definitely be generated via the creative use of 'unused'/adjacent space via the use of phase gratings where a traditional diffusor would be impractical due to the insufficient spacing between the listener and the diffusor- thus presenting a very viable alternative to the use of traditional planar diffusors.

Russ Berger has been employing this technique for well over a decade with phenomenal success - transforming many 'studios in a closet' into much larger virtual rooms.


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## Prof. (Oct 20, 2006)

mas said:


> .
> A semi-reverberant diffuse tail and the resultant sense of increased space can definitely be generated via the creative use of 'unused'/adjacent space via the use of phase gratings where a traditional diffusor would be impractical due to the insufficient spacing between the listener and the diffusor- thus presenting a very viable alternative to the use of traditional planar diffusors..


Can someone please explain the constructional aspect of this "phase grating"?.:scratch:


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## bpape (Sep 14, 2006)

In a dedicated space where you have proper isolation from the rest of the house, it's of no use. It's a way to 'loosely' couple an external space from the listening space when you can't physically separate them and hopefully avoid some of the anomolies of the combined space.

Bryan


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## Guest (May 19, 2008)

And example of a phase grating is the Space Coupler made by Russ Berger's pArt Science and marketed by Auralex.

It is simply a macro version of what has been a standard 'device' used in optical circles for ages sized for audio wavelengths. Here is link randomly selected from a google of the commercially available version of the 'device': http://truesoundcontrol.com/products/PSSC22.html?gclid=COT-y5rVspMCFQ7WsgodHh1zow 

And "of No use"? LOL! Perhaps, but only if one is not creative enough to understand its function and application!

In point of fact, it is but one technique that augments more traditional diffusion in a variety of ways. And it is a technique that lends itself to a myriad number of diverse applications once understands the underlying principles! May i suggest one review the use of optical phase grating for use in optics for a primer - and them extrapolate their use for the pertinent wavelengths appropriate for audio! Anyone with a background in physics should recognize their potential instantly! 

In a very small room, a significant problem is that you have but a finite amount of acoustic energy. In a small acoustical space (a term which applies to a very large space - effectively_ any_ home listening room - when a full range response is considered!) you do not have a statistical reverberant field. Anyone doubting that might want to refer to _Sound System Engineering_ by Davis and Patronis, 3rd Ed on pages 177-179. It concerns me that some are still debating what has been established as fact long ago!

While many run to overdamp such a room in a common effort to create what has historically been referred to as an RFZ (reflection free zone) creating an essentially anechoic response (detailed but very claustrophobic and sterile), your focus is on constraining and absorbing the focused specular reflections that dominate the space (in lieus of the statistically random reverberant field). 

This approach does not attempt to diffuse and thus lower the amplitude and also more greatly distribute and 'randomize' the acoustical energy - instead it attempts to effectively 'remove' it via termination in the form of absorption. And what you achieve is a very dead and ultimately sterile room that MANY find cluatrophobic. 

Sound familiar? It should! Such practices are very commonly proposed by folks whose focus is primarily upon the widespread use of absorption as the one stop solution toall things acoustic. (OK, I use a bit of hyperbole here, but I think that many should find that this exaggeration is not too far removed from the truth! ;-)

So, what is the alternative?

In such a small acoustical space, traditional planar diffusors (1 ans 2 space QRDs, etc.) the listener diffusor spacing is insufficient to allow for adequate diffusion - as too close a proximity is predominated by simply lower amplitude specular (focused) reflections.

This problem was initially addressed by Russ Berger by using an acoustical phase grating.

And there are a number of creative ways this technique can be used to afford the desired effect.

Most common is the use of the phase grating to effectively couple the small room with an adjacent 'waste space'. This space may be in the form of a high ceiling - especially above the false ceiling as is so often the case in commercial establishments, or a closet, or a bathroom, or a hallway or even a basement or crawl space. 

The adjacent spaces, be they rooms, high ceilings, or unused 'dead space', are coupled via the use of the phase grating. And this phase grating allows sound to exit the small space, and dependent upon the wavelength and the incident angle, to 'bounce around' in the coupled space - thus resulting in a reduction in gain over time relative to the length of the traveled path. This energy is allowed to return to the small room depending upon its nearly normal (perpendicular) incidence to the phase grating - which at 90 degrees is essentially transparent to sound.

What returns is a much more diffuse sound field which has been effectively attenuated in gain and diffused in time - creating a very nice semi-reverberant tail to the room response - with the benefit of creating a very well behaved sense of largeness and space to the otherwise fundamentally limited room. In other room, we have a very small room that heretofore was dead and we impart a sense of space that would otherwise be difficult to impossible to create. And the result is a superior alternative to a dead room. And these benefits can be obtained without regard to the physical separation between surface and listener required by traditional planar diffusors.

We have effectively taken a lemon and made lemonade. 

Phase gratings can be made rather simplly and elegantly by the end user with a bit of creativity and initiative. They need not be ugly or expensive - quite the contrary!



I will mention that such a technique has demonstrated some rather surprising results when employed in a variety of ways - be they offset from a reflective surface, suspended as ceiling tiles or flown as clouds, and even applied over or offset from absorptive materials - and their response verified by measurements with TEF and EASERA.

And while they can also be used to minimize the effect of coupled spaces (they cannot truly decouple them!!!), their MUCH MORE USEFUL application is to effectively couple the spaces in a controlled and beneficial manner and take advantage of the finite acoustic energy that is wasted by the ALL TOO COMMON use of excessive absorption.

I apologize if I have inadvertently stepped on the toes of of local authorities. But these methods have not only been proven, but they have been employed in a myriad number of listening rooms and studios! And I think that in this case it appropriate to name drop and cite their widespread use by such notables as Russ Berger. A few more could benefit from an aspiration to such prodigious understanding and level of experience!


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## bpape (Sep 14, 2006)

Nice explaination and I understand the theory - however, you kinda made my point for me that you just disagreed with.

Quote:
Most common is the use of the phase grating to effectively couple the small room with an adjacent 'waste space'. This space may be in the form of a high ceiling - especially above the false ceiling as is so often the case in commercial establishments, or a closet, or a bathroom, or a hallway or even a basement or crawl space.
Quote:

A properly isolated listening space does not open up into any other 'dead spaces'. If/when it does, you've lost your isolation and your lower noise floor. Same goes with a false ceiling. Any room with a false drop type ceiling is not providing proper isolation of sound into and out of the space. So, we trade one issue for another.

I'm not saying these are of no use in any situation - they certainly are. However, in real residential dedicated spaces where great care has been taking to isolate the listening space from the outside, where would these be of benefit? Many home theaters are IN the basement so that's not an option. If we 'vent' out into the other part of the basement, then we need to spend even more money by having to isolate an even larger space. Is that cost effective? I don't think so.

Again, I'm not saying overdamp everything. Not saying diffusion has no place either. What I'm promoting is a properly isolated space with a low noise floor, proper addressing of reflections (not just blanketing things), and a balanced absorbtion scheme that provides a proper decay time across the spectrum based on room volume and room usage.

Bryan


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## Guest (May 19, 2008)

Sound transmission through walls and acoustic response within the room are two separate, albeit related, subjects! And they should not be confused.

Many rooms commonly have adjacent spaces - especially in basements! In fact, they would by definition unless they occupy the entire space!

It is relatively simple to treat an adjoining space's surfaces as well as the associated flanking paths for signal transmission instead of simply treating the listening room's surfaces. All it requires is awareness and planning. I am not about to propose solutions while justifying the lack of either. (Also, if the room does occupy the entire space of the basement, I would suspect that a rear partition could easily be constructed that could provide a coupled space that could be used to great advantage without deleterious effects to the main room.)

And within a room, the use of phase gratings offer a very flexible option to achieve the same desired results without the necessary use of adjacent spaces. A prime example is their use on side walls and as suspended/flown partitions.

Still further uses are in addition to absorptive materials when used either placed together or with variable spacing between them. But such applications are beyond the scope of this thread.

I differ in the position that ever since the first iteration of the LEDE concept, absorption has assumed an increasingly greater role for very specific surgical use. No more than is absolutely necessary! And an ETC is a great tool for for most of the necessary use. 

And please understand me, I am not positing them as a one trick do it all pony! They are an additional very useful and valuable tool that offers much flexibility over many traditional tools But they are simply an additional tool that can be used to achieve a greater goal. And preserving the all too finite amount of acoustic energy in a small room without creating a claustrophobic dead space is paramount.

But bottomline, in a small room, given the choice of the use of simply more absorption or more diffusive techniques, the choice is easy! Effective diffusive techniques are definably preferable except for room modes and highly focused high energy near field specular reflections. And the web is dominated by a plethora of far too many over damped rooms and sites advocating the use of still more 'do everything - one size fits all' absorption.

But I will maintain that diffusion in its various forms assumes a much greater role for the overall room response in a small acoustical space. A dead room for use anything other than a special purpose, and with all due respect to those who might think they like them - to use the common vernacular - suck. And this is supported all the way up to the most recent evolution of the small acoustical space models ranging from the latest iteration of LEDE to those posited by Toole and D'Antonio and their implementation of such in places such as John McBride's Blackbird studio.


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## bpape (Sep 14, 2006)

I fully understand the difference between treating the interior of a room and providing isolation of that room from other spaces. My point is that if you deliberately open up another adjoinging space simply to take advantage of grating, you're incurring additional cost to provide the same level of isolation into the other space.

Sorry, but I'll disagree that stopping 100db, 20Hz (or lower) bass is a 'simple' task. The concepts to do so are not hard but the implementation is expensive. This is a home theater forum you're posting in. That type of thing happens all the time. 

Sure, we could use the rest of the basement to expand the space, but then that's (in most cases), 300% more cost to expand the isolation, both structural and airborne to that space (assuming the typical HT takes up approx 25% of the basement). 

I will agree with you that no more absorbtion than absolutely necessary should be used. In addition, the appropriate type(s) of absorbtion should be used and can be combined in such a way that the room can be balanced and not sound dead and lifeless and 'suck'. All it takes is some planning  - and usually not a ton of extra money. If done properly, and space allows, it can be done as part of the architecture of the room.

Bryan


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## Guest (May 19, 2008)

Respectfully, I can't help but feel that with each point, the responses have increasingly assumed a quality increasingly reminiscent of asking the scarecrow the directions to OZ, rather than moving towards a common consensus. ;-)

In another post regarding the a question about the effective use of phase gratings from Auralex (the screen6 system) your response is in regards to overhead treatments for "resonances" focused entirely in the frequency domain of room modes rather than in the time domain and higher frequencies dominated by specular reflections in which a phase grating is definitely appropriate. Where room modes came from in that response, one can only wonder as that is completely non sequitur to the issue!

And in another post you debate the use of the time based ETC response in lieu of using a large acoustical space specific RT60/30 calculation in a small acoustical space where no such reverberant field even exists in order to evaluate early and later arriving specular reflections and the status of the existence (or non-existence) of a semi-reverberant sound field in a small acoustical space.

And a 300% increase in cost to build a partition within an existing or planned home theater space? Wow! I would suggest that is ~299% too high! In fact, for such a deployment, no additional sound transmission treatment would even be necessary. Additionally, if the use of an adjacent space was anticipated from inception, only negligible differences in cost would generally be involved. Again, this has become a common practice not only in studios where sound transmission incurs a much greater penalty than simply the inconvenience of another family member, but also in many home recording and listening environments - especially as one can often utilize an existing adjacent space where music listening or family movie viewing does _not _present some anomalous activity where the rest of the household finds it objectionable! .

I have no problem with your insight, but I would suggest that the continuing issue in the use of diffusive techniques for the control of specular reflections as a preferable alternative to absorption has little to do with sound room modes, transmission problems that should have already been anticipated, substantially increased cost, or the use of calculations/measurements which have little to no fundamental use when the reverberant sound field that which they purport to calculate/measure does not even exist. Especially when extremely accurate atomistic measurements exist to provide very detailed analysis of the behavior within an acoustic space.

Instead, focusing upon a treatment for a specific problem employing optimal measurement techniques and analysis without mixing and creating issues might be more productive - especially when the concern for reader confusion has been expressed. 

Your responses are consistently oriented toward frequency domain approaches to issues which are most productively analyzed and fundamentally treated in the time domain. 

And as such, responses vacillate back and forth without a complete appreciation for the primacy of the time domain issues.

These diffusive techniques have never been proposed for room mode issues, not here nor in the question regarding the use of the Auralex Screen 6 phase gratings. And such responses reflect a misunderstanding for that which they are intended and the fundamental which they employ and do not help those curious about their legitimate use.

These are not speculative techniques of questionable origin. These are proven well established techniques that are actively being employed in some of the highest level designs and installations! And the analytical methods have been increasingly well understood ever since Heyser introduced them in 1967. The only thing that is relatively new is the commercially available product for sale to the general public of a product that had been heretofore employed and constructed for private use. They are now available generally for purchase, or one is free to construct them. 

But in any event, their productive use is predicated upon a valid understanding of the underlying principles and the practical variables governing their effective functional application. And the atomistic ability to accurately ascertain the_ real _components and variables of sound fields dominated by focused speculate reflections as well as tools to effectively address and modify such events in a predictable manner are assets - and tools wherein many would benefit from understanding, as they offer additional very useful tools in the acoustician's toolkit.


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## bpape (Sep 14, 2006)

Not sure what you're reading but I've not at all stayed in the frequency domain - quite the opposite. I've argued for balanced decay TIME across the spectrum. I've argued (agreeing with you) that absorbtion should be kept to the minimial required to address all of the room's issues with regard to reflections, frequency response where applicable, and proper decay time distribution.

You argued to open into another UNUSED space. That WILL require additional expenditures to isolate that space. If you're talking about cutting out a portion of what is already normally small spaces in a residential environment, then the cost would be lower - but it would also cramp the already limited space for speaker and sub placement, seating placement, and enough space for a proper surround field to be presented.

How many homeowners have enough space to build the size room they really want - much less have to make it larger only to chop it off in order to use phase grating when other treatment strategies can address many of the same issues without losing any space? 

As for RT30/RT60 - yes, as I previously stated, they're PRIMARILY used in large space acoustics. However, they can be scaled down to appropriately model smaller spaces if done correctly and consideration is given that reflection times are MUCH shorter than in large spaces - not to mention the fact that low frequencies must be tamed rather than in large spaces where they're allowed and encouraged to develop and propogate. 

I'll give you my personal room and you tell me where it is applicable.

17x21x8 room. Drywall ceiling - decoupled. Cavity above filled with insulation. Bedroom above that. Walls decoupled using DC-04 iso clips. External solid door with seals. Double drywall with Green Glue. Separate HVAC system. Soffiting on both side walls - 10" high, 18" wide to run HVAC and cabling without piercing the sealed envelope of the room any more than required. These are fully insulated and also double drywalled with Green Glue.

Right and front side of room built within 6" of concrete foundation. Rear half of left wall butts to a stairwell that lead up and door at top is within 2' of a bedroom door. Door in the middle of the left wall. Front half of the left wall butts to a bathroom that is below a bedroom.

Rear wall butts to the HVAC/mechanicals area with high velocity, high efficiency system (loud fan). I have 2 rows of seating appropriately placed to minimize modal issues and approx 4' behind the 2nd row to allow good surround from the rear speakers. 4 seats front row, 4 seats rear row. 7.1 surround system. Front projection screen - 100" diagonal - 16:9 AR.

So, where do I simply chop off space? Where do I expand out into? Nowhere. This is not at all an uncommon situation. I could make the room narrower but that cramps walkways and reduces usability of the space. I would make the room shorter, but then rear row gets too close to the rear surrounds - unless you're proposing (hope not) that the rear surrounds go behind the phase grating in the 'other' area. I could use the ceiling space above and lose my isolation. I could use the bathroom next to the front but that would throw things out of symmetry - not to mention blowing isolation to the master bedroom above the bathroom (and costing me more money to isolate that additional space) - thereby limiting when and how I can use the space.

Again, nobody is saying there isn't a place for this type of thing. I've never disagreed with that. What I said was in typical residential spaces where isolation is required and space is at a premium, there is very rarely a good use for them and I'll stick with that. Just like if you're in a 12x15 room, typical diffusion doesn't work very well. Just like in a smaller room, it requires PROPORTIONATELY more broadband BASS control to deal with both frequency and time related issues. Now, if you're upstairs or in the basement and you don't have any isolation concerns or the room was already finished and you're not tearing down, then they may absolutely be of benefit.

Or, if you have a huge space to start with that allows you to build the size room you want AND section off another portion of an adjoining space, then that's great. But, that's by far the exception and not the rule in the real world - at least not the residential one.

To those reading along - a poll. How many of you would have additional space to give up to do phase grating either by making your existing space smaller or by giving up additional space and spending more money?

Bryan


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## Guest (May 20, 2008)

The initial purpose of my post was to present an additional useful and proven technique designed to enlarge the toolbox of techniques that can be of great benefit in any room, and in small rooms _in particular_ as an alternative to over damping and the use of more traditional planar diffusion which is quite capable of creating a more semi-diffusive sound field and the accompanying sense of a much larger room than is evidenced by dimensions alone.

The technique employed in much smaller rooms than the example is valid and well proven.

And judging from both the tread originator's response and still other’s questions regarding the technique in other threads (see the thread regarding the use of the pArtScience Screen6 product marketed by Auralex), many here are not familiar with the technique(s) in general nor the product in particular.

But rather than explore the use of such a technique, we are instead entreated with the _repeated_ statements including but not limited to statements to the effect that they are not effective for the primary treatment of room modes (was there ever any suggestion that they were?!http://www.hometheatershack.com/for...king-into-buying-screen6-package-auralex.html And such a response indicates a fundamental misunderstanding of the technique!) and that there might also be situations, especially where someone has already designed and constructed a room where such a technique is now introduced as an afterthought, where the use of a loosely coupled space (just ONE of MANY potential and valid uses) might not be an optimal choice. 

Ordinarily my response to such an observation might be “of course” – there are few one-trick ponies that are optimal in all circumstances. My personal feeling is that this ‘insight’ is a ‘given’ not requiring anything but an assumed common sense acknowledgment. …Rather on the level of a profound “Duh”! 

But your concluding subjective assumptions are simply not supported by _proven_ fact.

Likewise, I guess that implies that I might want to disregard the use of a retrofit V8 engine for use on the new Schwinn bicycle I purchased… Oh well… I rather suspected that the combustion engine was an anomaly with limited application - yup, they are of little if any potential use. On the other hand, the limitation _just might_ be in my incomplete and erroneous assumptions based on fundamental ignore-ance of factors.

But again, physically small rooms offer very real opportunities for this proven technique! 

In trying to introduce a heretofore unfamiliar technique using a classic tool, it seemed appropriate to explore the potential uses of the technique thereof, especially as such interest was explicitly expressed!

What does fascinate me, however is the repeated counterpoint continually feeling the need to repeatedly point out that that the technique is “in typical residential spaces where isolation is required and space is at a premium, there is very rarely a good use for them and I'll stick with that.”

Great . Stick with that. You made your point many posts ago. Unfortunately, your continued subsequent posts fail to offer any addition insight into their constructive use, instead returning the recurring mantra of using more absorption to the exclusion of more advanced diffusive techniques which afford the creation of a greater sense of space – something absorption CANNOT do. In any event, your ‘feeling’ is at odds with the proven real world application of the technique providing a real alternative to over damping in very small rooms by some very prominent acousticians!

I might suggest that proven real world objective use trumps one’s subjective ‘feelings’ based upon speculation. And as such, it bears further investigation and understanding instead of self-righteous dismissal.

In the mean time, for those not so adamant in their dismissal of the technique, it would be useful for others to explore the use of the technique that has been proven very useful in spaces MUCH smaller than your proposed 17x21 foot room! In fact, in the majority of proven applications, such a room (while still a small acoustical space) would be considered huge!

And again, we are not referencing and citing the imagined use of such a technique by someone not savvy enough to know about that which they propose, but a PROVEN technique employed over a 20+ year period by the pre-eminent acoustical designer in the business! 

So you indeed DO have a choice. You can propose a red herring poll which misstates both the factors and tradeoffs aimed at others unfamiliar with the technique and subject to your continued denigration, or you can open your mind to a technique which heretofore has been rather limited to all but the most advanced and skilled practitioners in the industry – due in part to both the unawareness of end users and to a commercially available product for those who are either unable or unwilling to fabricate such an easily designed and constructed treatment. 

Obviously deviation from the ‘party line’ is discouraged here. But if anyone is actually curious or interested in the use of such a technique you are welcome to PM me and I would be glad to explore the potential of the use of this tool (again – one of many which can be used synergistically in an acoustical space) to achieve your desired goal – ESPECIALLY in a room where you are unable to make it as large as your dreams might wish!!! 

In the meantime I will be sure to inform Russ of the fundamental limitations of this technique and how inappropriate it is for use in physically small rooms! I am quite sure he will be amused. It won’t be the first time we have learned of the limitations of a proven technique! This reminds me of Lipshitz and Vanderkooy’s dismissal of the concept and performance underlying the implementation of the technique introduced in a SynAudCon tech topic by Ken Wahlenburg’s PZM microphone!!! Oh well, just another failed concept! LOL! 

It’s a another reminder of the all far too common occurrence whereby those in positions of prominence may indeed be wrong, but _never_ in doubt!




For others who are not so convinced regarding the limited use and general inappropriateness of such a technique in a physically small room, especially as this technique has been repeatedly and successfully employed by some of the world's foremost acousticians for over 20 years, here are a few links to articles referring to the phase gratings as well as a few applied uses of the technique. The articles are cursory in nature, while the actual validity of the concept in physics is not, but you will get a feel for a few applications that might provide options for your anticipated use.

http://www.auralex.com/partscience/spacecoupler.asp
http://www.eqmag.com/article/room-tuning-with/may-06/20482
http://www.prosoundweb.com/news/0506/rbdg_scottie.php
http://www.gcpro.com/tozzoli_21_auralex.html


But in one respect we do agree. Don't use this technique to mitigate LF room mode issues! LOL! ...At least not with an ~3 inch deep phase grating! ;-)


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## bpape (Sep 14, 2006)

I don't see an answer to my question from you. Where do I use this in my very typical situation?

You're correct, a V8 has little to no use on a Schwinn bicycle. It's great in a sports car or a truck though. Just because someone says it's of no use on a bike, it's faulty logic at a minimum to extrapolate that to mean that there is no use in any application.


When you inform Russ, have him read the whole thread - not just your misinterpretations of what I wrote. I NEVER said the technique was not valid nor useful. Also make sure that he reads 3 of my posts about balancing the time domain and where you ignored it and insisted I was talking only about frequency response. Lastly, please point out where I said phase grating should never be used in small rooms.

How is asking people with real rooms if they have or would be willing to give up additional space inside or outside their rooms misleading? How does one go about implementing phase grating without doing one or the other - or - blowing room isolation? I'm all ears if you can explain how to do it.

I guess I shouldn't bother asking these questions as you continue to ignore answering them and insist in toeing your own 'party line' and trying to impress throwing around other's names. 

This discussion is going nowhere. You refuse to look at the reality of real world residential spaces. I refuse to endorse the tradeoffs required to implement it in the vast majority of those same spaces. IF you can design from scratch, yes, it could be of use and I've said that probably 6 times now but you don't want to acknowledge that. The very fact that you would even consider a drop ceiling in a space which requires isolation gives me pause.

And then at the end we're agreeing that we can't deal with modal issues? How DOES one deal with that then if the 'typical and commonly accepted' absorption is not employed? ... and don't twist that to make the room dead and 'sucky'. I'm talking about bass absorption here. These could be faced 'soft' absorbtion, sealed membrate absorbers, Helmholz resonators, etc. Oops, another question.

Oh, and one more. How does one effectively use this when RSIC-1 and hat channel is used to provide isolation in a wall? I'm assuming those are the cavities you're referring to with your 3.5" cavity comment and the some of the pics you linked to. 

These are really not meant to be smart-a$$ed questions. If you can show me how to make use of this technique given the situations I've stated, I'm all for it. I'm always willing to learn new things. I thought I gave you the opportunity to do that by fully describing my personal space and limitations. To this point, you've chosen not to. It's obviously that you've done a lot of research and have a good understanding of phase grating and how it works. My assumption is that you also have done the research and have a good understanding of how to implement it without incurring other issues.

I too would encourage folks to explore this technique and see if it will work in your situation. If the opportunity presents itself, it can certainly be an effective option. I don't know how many more times and how much clearer I can state that. Every room is different. There is no one right solution that fits every room. There is no one single correct type of treatment that will deal with every situation. 

All I originally asked that started all of this was that when techniques like this are suggested, they should be suggested and proposed in context and with an understanding of the potential limitations and tradeoffs and the realities of the spaces in use by most of the reading audience. If this was a forum for professional studios, that would be a completely different topic and audience, a completely different set of issues (no bedrooms to deal with, generally not 15-20Hz at 100db+ subs cranking out, etc.)

Bryan


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## Prof. (Oct 20, 2006)

mas said:


> And example of a phase grating is the Space Coupler made by Russ Berger's pArt Science and marketed by Auralex.
> 
> It is simply a macro version of what has been a standard 'device' used in optical circles for ages sized for audio wavelengths. Here is link randomly selected from a google of the commercially available version of the 'device': http://truesoundcontrol.com/products/PSSC22.html?gclid=COT-y5rVspMCFQ7WsgodHh1zow


Thanks for the link..That shows it pretty clearly...but not practical in my theatre..


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## Guest (May 20, 2008)

Please be aware that this use pictures is but ONE of MANY potential uses. And that the application pictured is one of the more limited and site specific uses!

I am not a salesperson for this, nor did I wish to do anything more than to discuss the potential and the physics fundamentals behind such technologies as well as the myriad ways that it might be employed - but then i never anticipated the overwhelming tendency to focus on the negatives without an understanding of the technology and its uses!

You might check out the screen6 implementation package to get an overview of a larger package that attempts to address many of the factors commonly encountered with respect to specular reflections and the contribution to the creation of a semi-reverberant diffuse sound field in a small acoustical space.

Here is but one of many sites: http://www.truesoundcontrol.com/products/SCREEN6.html

Unfortunately, the potenital applications are _myriad_ - increased by one's understanding of the physics afforded by the various topopologies!


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## Guest (May 20, 2008)

deleted dbl post


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## Guest (May 20, 2008)

I don't see an answer to my question from you. Where do I use this in my very typical situation?


Let’s see. I have seen no test data, no ETCs, no convolveable IRs, nor anything to even identify the issue(s) needing to be addressed, let alone a performance/response baseline or a target/goal to be achieved. But what is the answer!? What should I buy? Indeed! This is worse than napkin analysis. The even scarier fact is that so many are more than willing to specify specific actionable answers!

You're correct, a V8 has little to no use on a Schwinn bicycle. It's great in a sports car or a truck though. Just because someone says it's of no use on a bike, it's faulty logic at a minimum to extrapolate that to mean that there is no use in any application.

LOL! Few I know would attempt to analyze what is _obviously_ intended as gross hyperbole! But they _would_ explore the fundamental physics and the subsequent potential for applications based upon a fundamental understanding of a technique. May I suggest that ‘a bit’ more effort might be spent on the latter.

You are the one who responded to the proposed use of the Screen6 product with the completely non sequitur response regarding the technique displaying a fundamental assumption that an utterly unrelated phenomena such as room modes were the issue:
:
_Poster:“I am mounting it above my theater seating. It looks quite simple, but I wouldn't even know where to start to build a set.” 
Your response: “What is it you're trying to accomplish? Normally, for things overhead, it's absorbtion to tame vertically based resonances.”_

Let’s see. What might they be trying to address? Not that we need explore this when we can simply make the leap to room modes and to a dismissal of their effectiveness in this regards – especially when we are assuming their application on a lateral ceiling surface!! Of course that is where is always(sic) reasonable for one to begin addressing room modes! And for a ceiling surface treatment with a phase grating Yeah, right!

So let’s make a blind stab here! What might phase gratings be useful for? How about diffusive treatment in lieu of absorption? Would that work? It most certainly could, but since we are all dealing with the abstract speculative realm devoid of any apparent response measurements, and a response that reflects (there’s a pun!) no apparent experience or familiarity of the technique in but ONE of the myriad possible applications, one is not surprised to see the concept simply dismissed here!

But we were never able to progress to the physics of phase grating, so sizing, spacing, proximity, and the various topological variations were never explored! But gee, just tell me where and how to use it in 25 words or less before my attention span wanes! LOL!

The fact is, depending upon the desired goal, there are a plethora of potential uses for phase gratings. And many ways to achieve the same or similar issues. Additionally they can be used for a variety of final results, be they increased diffusion or enhanced LF absorption of absorptive panels. Of course, we have not even explored the options afforded via direct mounting versus offset mounting versus oblique offset mounting (at an angle relative to the reflective or absorptive surface), etc. etc. etc.

Do they have practical use on the ceiling or lateral side walls directly applied to the surface? Sure. Are they optimal? Let’s see, I could speculate based upon an emotional basis or we could have say, an ETC to indicate whether the side wall or ceiling is even the source of the early or later arriving offending specular reflection… Obviously some have no need for such objective information to pass pronouncements!

Could they be installed on either or both surfaces with a small gap between then and the surface, thus modifying the response characteristics? Sure! Would this increase their diffusive signature? Sure! But hey, they have already been dismissed – especially as their function relative to the mitigation of room modes precludes their use! (On the other hand, others never would have considered them for such a use!)

Or, perhaps based upon actual measurements, we have a need to increase the absorptive characteristics of an existing treatment. Could they be used to advantage? Sure. Not that they are the only way or the most preferential way to do this, but they are certainly an option considering one’s aesthetic and technical requirements! 

Or, consider a room, say in a cathedral or vaulted architecture so common now days. Would such a phase grating offer substantial benefits in the development of a very well behaved semi-reverberant diffuse tail and at the same time mitigate what are often some potentially nasty specular reflections of the angled surfaces? Of course! But then, most would run for absorption and while addressing the reflection, also lose the option to increase the diffuse response ‘tail’ (refer to an ETC). Of course such a use would increase the apparent size of the room acoustically instead of further deadening and ‘shrinking’ it. 

And this, as well as offset mounting elsewhere, would have the exact same effect as adding a very loosely coupled space.

Oh, and lighting can be placed above the grating allowing for wonderful ambient and direct lighting effects while at the same time rendering the light sources ‘invisible’ at all but near normal incident angles – meaning, unless you are directly below them looking up!

But hey, why diffuse if we can absorb. LOL!

Gee, and all of these real possibilities and we haven’t even punched a hole anywhere! Nor have we explored their use in a room of fixed height as a suspended ceiling (and the gap need not be large) allowing for easy access to wiring, utilities, etc. Oh, and the grating can be covered with an acoustically transparent skin to augment the aesthetics as well as to obscure that which one might otherwise like to keep hidden!

Of course, if such a room, any room, has a closet, space under a stair well, a hallway, or any adjacent space not normally considered useful acoustically and which does not impinge on your playing the sub at 130 dB while the baby next door is trying to nap, we haven’t even touched upon such a practical and beneficial topology!

Each room is different. For each ‘basement home theater that you mention where you dismiss the various techniques, I can site one that is of optimal benefit! And that was the purpose of mentioning the technology! …Precisely to expand the potential use of appropriate tools for application towards an enhanced response. But never mind folks, some may not find it useful – and hence the need to counter each post with the reminder that it may not solve all issues in EVERY situation – as if folks might be silly enough to do so!

Additional knowledge and the options it enables can be a dangerous tool, and we certainly wouldn’t want folks running amuck considering options not heretofore on the approved list! Especially as they are not proposing additional absorption in a very small room!

Far more possibilities exist, assuming one has a basic understanding of the physic principles employed.


When you inform Russ, have him read the whole thread - not just your misinterpretations of what I wrote. I NEVER said the technique was not valid nor useful. Also make sure that he reads 3 of my posts about balancing the time domain and where you ignored it and insisted I was talking only about frequency response. Lastly, please point out where I said phase grating should never be used in small rooms.

Oh, I know that you find them very potentially useful, and amazingly the only time you mention this is as a qualification to your rebuttal and dismissal of the technique in every mentioned application. After all, as you have mentioned, your 17 x 21 room is far too small for the application of such techniques! LOL!

And, if I might, I will stick my neck out and offer a guess at Russ’ response. Being the very classy individual he is, he will most likely shrug his shoulders and allow for each individual’s freedom to do whatever they like…for whatever reason – reasoned or not.

How is asking people with real rooms if they have or would be willing to give up additional space inside or outside their rooms misleading? How does one go about implementing phase grating without doing one or the other - or - blowing room isolation? I'm all ears if you can explain how to do it.

Gee, assuming one can spare the same amount of precious space that some of the hallowed absorptive panels might occupy, I think I have mentioned just a few of the possible applications above that might be employed. And far more are possible!

I guess I shouldn't bother asking these questions as you continue to ignore answering them and insist in toeing your own 'party line' and trying to impress throwing around other's names. 

You know, the fact is that these concepts whose applicability to small rooms are so easily dismissed and deemed inappropriate for the use in small rooms by yourself have been proven over and over again by some whose credentials and knowledge are not so easily dismissed as simply some posted on the forum. Credence to the idea, objectively verifiable results, as well as standing in the acoustics community, does count just a bit!

And party line! ROF****! This hilarious comment reflects a preconceived notion that couldn’t be further from the truth!

This technology was initially suggested simply as an additional alternative to the too oft used perennial favorite recommendation to “just use more absorption” which can be used to advantage, but which DOES have the disadvantage of being a detriment to the perceived spaciousness of a small room! Its just one more valuable tool. But it amazes me to see the degree of adamant dismissal! Methinks thou doest protest too much! Oh yeah, now remind me that it might possibly be used somewhere – of course just not in a proverbial “Home Theater”!…LOL!

This discussion is going nowhere. You refuse to look at the reality of real world residential spaces. I refuse to endorse the tradeoffs required to implement it in the vast majority of those same spaces. IF you can design from scratch, yes, it could be of use and I've said that probably 6 times now but you don't want to acknowledge that. The very fact that you would even consider a drop ceiling in a space which requires isolation gives me pause.

And then at the end we're agreeing that we can't deal with modal issues? How DOES one deal with that then if the 'typical and commonly accepted' absorption is not employed? ... and don't twist that to make the room dead and 'sucky'. I'm talking about bass absorption here. These could be faced 'soft' absorbtion, sealed membrate absorbers, Helmholz resonators, etc. Oops, another question.

And one not aspect not even breached in the use of the said technologies! How one can even confuse the two issues of room modes and specular reflections and diffuse semi-reverberant sound fields and their distinct solutions is fascinating to me! As, like it or not, it reflects a fundamental misunderstanding regarding the proposed technique, its uses, and your preconceived assumptions regarding it! After all, why would one respond to the purpose and use of the Screen6 product by a concern for room modes?! LOL! Talk about an intellectual snipe hunt!...

You are the one who has repeated brought up the subject of room modes. Oh!

(The true irony is that a phase grating CAN be used to increase the efficiency of LF absorption. And it can also be tuned to a degree. But it does afford one just one more potential tool. But this was NEVER a focus of the technology from my perspective and it is far beyond the scope of this discussion – well from my perspective anyway! Despite your repeated non sequitur criticism of the technique relative to the suppression of room modes!)

Oh, and one more. How does one effectively use this when RSIC-1 and hat channel is used to provide isolation in a wall? I'm assuming those are the cavities you're referring to with your 3.5" cavity comment and the some of the pics you linked to. 

Again, you assume incorrectly, as has become an ever popular occurrence! 

The depth referred to is the depth of the phase grating! Go figure! But then, this does assume that one has a basic understanding of what a phase grating is and how it functions! Sorry to be so blunt, but hey, you are the one issuing challenges based upon utterly erroneous assumptions that display your fundamental misunderstanding of the technology! And yet you demand specific applications to a napkin based room!

These are really not meant to be smart-a$$ed questions. If you can show me how to make use of this technique given the situations I've stated, I'm all for it. I'm always willing to learn new things. I thought I gave you the opportunity to do that by fully describing my personal space and limitations. To this point, you've chosen not to. It's obviously that you've done a lot of research and have a good understanding of phase grating and how it works. My assumption is that you also have done the research and have a good understanding of how to implement it without incurring other issues.

Sure…and “smart” would be assuming information not in evidence. Hey, I get my witty digs as well… The fact is that your attempts at rebuttal are so couched in preconceived notions as to eliminate all possibilities of your understanding or applying the concepts! You have repeatedly rejected and dismissed that which you even understand! 

I do not consider it responsible to simply jump to specifying specific uses of products to others without a more thorough understanding of a situation. I’m sorry, I guess it is a character flaw and I lose lots of sleep because of it. But at least others aren’t running about spending big bucks on a suggestion based upon canned answers. 

Sure, I can do cursory napkin analysis – the same analysis that many vendors perform in the process of specifying specific pricey applications! – but I don’t except as conceptual discussions and as a springboard to explore potential avenues for resolution of yet to be verified real problems! I am glad to suggest general approaches based upon basic ray tracing and generally accepted best practices for bass traps, etc. But I would never tell someone remotely to go out and invest big bucks in such a configuration without on site TEF/EASRA measurement – before and after installation!

And if ‘doing’ a large acoustical space, we would also include EASE modeling and auralization coupled with before and after TEF/EASRA measurements and subsequent tweaking and proof of performance measurements. 

I too would encourage folks to explore this technique and see if it will work in your situation. If the opportunity presents itself, it can certainly be an effective option. I don't know how many more times and how much clearer I can state that. Every room is different. There is no one right solution that fits every room. There is no one single correct type of treatment that will deal with every situation. 

You know, this paragraph that I would hope all assume as a matter of all too (un) common sense, would have been sufficient mentioned once in this thread – or for that matter as a preamble to the entire forum. I assumed this. Unfortunately your responses and repeated objections have not. And I suspect your negative responses have suppressed more than a few who might otherwise have wished to explore a greater understanding of, and the potential that such a technique can offer. 

And this statement would make even more sense had an opportunity to actually explore the necessary behavioral characteristics upon which the determination of its applicability to a situation could have been actually performed! Hey, but why confuse folks with facts and understanding when you have opportunity to dismiss the applicability of the technique for use in small rooms!!! (Not to mention that that Russ Berger fellow must be a fraud!)

If nothing else, the fact that such a technique is readily employed by principles such a Russ Berger is FAR smaller rooms than your example should speak for something. Unfortunately I guess you would find his application of the technology, overwhelmingly employed in homes, as a mistake as well. Oh, but such valid and proven references constitute name dropping in your mind. 

All I originally asked that started all of this was that when techniques like this are suggested, they should be suggested and proposed in context and with an understanding of the potential limitations and tradeoffs and the realities of the spaces in use by most of the reading audience. If this was a forum for professional studios, that would be a completely different topic and audience, a completely different set of issues (no bedrooms to deal with, generally not 15-20Hz at 100db+ subs cranking out, etc.)

Whatever!

In order to progress to a discussion of limitations, it is customary to explore the underlying physical (as in physics!) concepts, and also to introduce an example of the both the product and some of its potential uses. Unfortunately, your rebuttal began before we even had a chance to present said critical analysis. And your continued ‘encouragement’ of such a discussion has been detrimental to the attempt to do exactly that – including limitations! 

And I am fascinated by your distinction between ‘professional studios’ and home theaters. While the design end goals and parameters may vary, the physics of the techniques and tools available to achieve a particular end do not! 

My initial focus was exactly to present the potential for, and to enlarge the awareness of those interested, regarding a very fundamental and potentially useful technique. Unfortunately, we never got even close to understanding the physics behind the technique, let alone the incredible leap to specific case studies where the use of a technique to achieve a particular response characteristic might be explored – despite your recent demands for specific applications to the most general situations (as if simple dimensions and descriptions of soffits define the acoustical environment!) without an understanding of the underlying physics contributing to the performance of the technique. Oh…

I had hoped to explore the physics and applications of such a technique. Unfortunately you made not one attempt to further such a discussion. And to that end, you utterly failed to contribute to an understanding of how and where such a technique can be most applicable and beneficial in a small room. But you were inadvertently correct in one assessment: “This discussion is going nowhere” - as insured by your initial dismissal of the applicability of a technique with which you have repeatedly demonstrated your misunderstanding. 

Thanks. Unfortunately your dominating a thread takes precedence over the active contribution to the greater understanding of a technology that is apparently new to many. 

But we did learn that “There is no one single correct type of treatment that will deal with every situation.” Duh!!! Has everyone written that down? I fear for anyone for whom such an insight is not fundamental to ALL of life’s endeavors.





But keep on measuring RT60’s in small acoustical spaces for non-existent reverberant fields - Unless you are concerned with reverberant fields above ~77.792 kHz!!!! in your 2906 ft^3 room with a target RT60 at or near 1.6!!!!! Always a useful realm to explore!)(especially if you prefer their use to ETCs in analyzing and addressing actual specular reflections relative to their gain and arrival times, as well as diffuse characteristics in a small room! 

That reference will result in quite a few chuckles for many!


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## bpape (Sep 14, 2006)

Still no answers to my questions. Only more misquoting and misinterpretations. Where did I say my 17x21 room was too small? What I asked was where in that space I could use phase grating without losing isolation or space inside the room. You again choose not to answer. I was not looking for a specific recommendation for the space.

As for my repeated hang up with room modes. I mentioned it once in the context that modes were higher in frequency in smaller rooms. I mentioned it again asking you a question as to how you would propose to deal with modal issues if not via absorption. Again, no answer.

As for RT60, yet again, you're misquoting me. What I said was that you could use similar yet scaled down analysis to work in smaller spaces where you don't have a truly reverberant field yet still are working toward a balanced decay time across the musical spectrum. This is specifically done to avoid overdeadening a room. 

Never said you can't do this in a small room. Never said anything of the kind. What I said was that in most (not all - never said all) residential spaces, there aren't adjacent spaces to use without losing isolation and space inside the room is at a premium already. In the example you showed with the drum kit - sure - great application. No seating to worry about, no 7 channel surround system to consider, no worries about 6-8 different seating locations trying to be balanced, etc.

Yes - the tools available to us are largely the same in a home theater and a studio. However, there are certainly limitations in a residential environment that don't exist in most studios. 


If we can be civil for a minute. I would invite you to start a new thread about the topic of phase grating in general where the physics and applications can be discussed. That would be good for everyone. I'll stay completely out of it. The last thing I want to do is stifle creativity or different thinking. I'll apologize to all if that's the way I'm coming across. This was not my intention. My intention was simply to try to balance application of a specific type of treatment and reality for common consideration. When I hear someone say "just use an unused space like a bathroom next door", red flags go up. 

I'm done.

Bryan


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