Acoustics: Real Traps Vs. Ready Traps ?

[Glenn Kuras]

Originally Posted by Youn

So, you are saying it really becomes a balancing act at some point? Is this because 100% absorption across the low spectrum is unlikely? Do bass traps simply need to be thicker in dimension to absorb lower? Maybe they need to get denser as they approach the room, so higher freqs gradually get bounced back and not sucked in. Just a thought.

I just sorta vaguely remember these types of cases, where folks filled their small room's volume upto 30% or more. they were positive more = better and the before and after graphs were pretty convincing. Was that over in StudioTips forum?

Here is a case study that was done not to long ago..
http://www.sbrjournal.net/currentiss.../Acoustics.htm

[Bang]

Hey Glenn, today is a busy mix day as is the rest of the week so I can't say much past this post. But having a reference mix that you know well is a very important way to help get a sense of a room's acoustics. I have a reference mix which I can blast out of any speaker system and although I won't be exact in knowing the exact db of peak or null, I'll generally know where the problems are. Afterall, you don't put up traps so that you can show off your pretty graph, you put up traps so you can make the room easy to mix music in. That doesn't mean running some noise and measuring isn't important, because it is.

Usually when I join a topic on specific gear or mixing techniques, I'll prove my points by posting a mix. In this case I can't do that. But the thing is, I've heard it with my own ears, and so have many top guys in field. If you're not convinced I can deal with that, but its clear as day to me. If you over bass trap a room, what comes out of your speakers will sound thin and crappy. If you properly bass trap a room, what comes out of the speakers is full and rich. Much of this depends on the room, whether it is isolated, the position of the traps, the kinds of traps, and probably MOST important, where the speakers and mix position are. Some rooms don't agree with "first 3rd of room" others do.... Either way, it was good talking to you, and ring me up when you're in Hollywood.

[Glenn Kuras]

Sure I will give you a call next time I am in town

But with all that said I still would like to see this graph with the bass being sucked out..

Glenn

[Savant]

Ethan: The actual number of sabins measured in a lab will not jive with the actual number of sabins measured in a small room. That was my point. A lab is an idealized situation. If a 72 ft² area of absorbers is placed in a lab and measures 78 sabins at 500 Hz, that's indicative of the performance in a large space, but not exactly. When modeling larger rooms, it is assumed that this is an exact number, but the predictive results clearly show that the same amount of absorption was not, in fact, added to the real-world room. The lab assumes (and delivers, over the standard frequency range) statistical reverberance. The big auditorium where the absorbers are being placed on the wall (in much greater quantities) is not usually quite so idealized.

Take this one step further and make the room very small like a studio room, and the entire concept of sabins goes out the window. Whether sabins/unit or absorption coefficients, the numbers are really only useful for the most cursory of comparisons. Beyond that, the performance is situation specific for both low and high frequencies.

The main reason this happens is because the result - sabins of absorption - is calculated using differences in decay. Since there is no linear relationship between the decay change that occurs in a chamber and the decay change that occurs in a studio room when the same amount of absorption is added to each, the results cannot be the same. There is a volumetric relationship in the purely theoretical sense. But there are other factors controlling the actual results that are largely being ignored when absorption is measured in a small room.

*********

ddageek: I guess we could all get together and do that. However, since - as I mentioned - such standards do exist, the only thing we'd accomplish is a reinvention of the wheel. (Assuming we could all work together!!! )

*********

Others: The argument about too much LF absorption being possible should be clarified a little bit for the contexts of this thread:

(a) If the goal is a "flat" frequency response, then too much LF absorption is probably not likely in most small rooms. But it would be possible.

(b) If the goal is a "flat" time response, then I would argue. Most rooms - even studio control rooms - should not be "flat" in terms of their time response. So, if the goal is an even time response with a slight rise in the low-end, then too much LF absorption is not only possible, but more probable than in the case of (a) above.

(c) It is possible that the reason many seasoned acousticians find over-absorption of the low-end common is because the absorbers being used are also absorbing the high frequencies. If this is the case, too much of a good thing ("traps") is possible and can indeed lead to too much of a bad thing (dull response on the high end).

(d) It is also possible that the seasoned acousticians are over-generalizing. This is less likely if the acousticians in question were being specifically queried on studios. However, it is common to find cases of over-absorption of the low-end in large rooms.

So, if I were asked, I would say that over-absorption of the low-end is possible. Whether or not it's probable would depend on what kind of situation we were discussing.

The same sort of generalization holds true, I find, for most things in audio and acoustics.

[Ethan Winer]

Jeff,

Excellent post and I agree with everything you said.

(How could I not agree?)

--Ethan

[zak7]

So what is the deal with RealTraps, Ready Acoustics and GIK.?
I want to know the materials that each company use...
Ready acoustic is really a development acoustic company?
Seems that is more like a system..I mean the Owen Corning boards that everybody can get...just they have the bag ready............is GIK the same??

so the question is GIK o Ready Acoustics...I gues the answer is which one looks better!,,if both uses the same materials!

Any comments?

[Ethan Winer]

Zak,

Originally Posted by zak7

So what is the deal with RealTraps, Ready Acoustics and GIK?

I'll be glad to give you my opinions, and I'm sure Glenn from GIK will be glad to give you his too. However, those opinions may not be appropriate for a public discussion forum, so I urge you to email both of us for more information. The same applies to anyone else here who is interested in learning more about these companies, their products, and their ethics.

--Ethan

[Acoustic Cloud]

I would second the notion of PM'ing Nathan and Glenn. They can shed some good light on this subject. Its also good to keep this info out of the forum, very diplomatic.

[Scott R. Foster]

Howdy:

Ready Acoustics was founded to present to market high performance porous absorber products incorporating design elements which allow the greatest posiible versatility both in acoustic implementation and decorative choices, all at modest cost in order to maximize the value to our clients.

http://readyacoustics.com

The flagship product of the firm is the 2x4’, 4” thick Ready Trap, known as the RT424. The RT424 is a broadband absorption panel with a 4" thick core of Owens Corning 703 [other mineral fiber products or even scrims and membranes can easily be incorporated if desired].

The mineral fiber core of a Ready Trap is wrapped in a form fitted ultra suede "Ready Bag" with integral hangers yielding a unit with no acoustically reflective surfaces that is ready to hang on the wall in either horizontal or vertical aspect, or from the ceiling. The unit has a sharp edged clean look and comes in a variety of colors.

Though the RT424 is versatile in that it can be installed in various ways, the recommended installation is in a corner straddling mount – as this type of installation will yield increased low frequency performance. In addition to the RT424, we also sell 2” and 6” version of this unit, though we strongly advise clients to use the 4” version in corner mountings whenever practical as it provides the greatest “bang-for-the-buck” as a broadband absorber in this thickness, and when mounted as recommended. Attached below is a comparison of the 4” RT424 and the 6” thick RT426 in corner mountings.

Additional testing data on these units including full mounting details can be reviewed here:

http://www.readyacoustics.com/index.php?go=acoustics-advice.acoustic-data

The use of OC 703 and the 4" thickness of the RT424 are a result of extensive investigation into both the material handling properties of numerous commercially available mineral fiber products suitable for acoustic applications, and the performance of these materials in various unit sizes. This work and the determinations arising thereby was greatly influenced by the work I have done with my friends Jeff Szymanski and Eric Desart, and others at the StudioTips forum on DIY absorber design and testing. The results of this volunteer collective project created/formalized the SuperChunk DIY corner wedge mentioned previously in this thread.

We also sell the Ready Bags used to make Ready Traps for use by DIY Basstrap makers which spares the DIY guy from frame building and upholstery chores.

New products from our firm to be presented for market this Spring include our new Chameleon Traps which are designed to allow clients a larger variety of aesthetic choices through the use of a perforated steel frame available in a variety of colors which can be implemented using any of our fabric colors… or using the client’s choice of fabric. Thus panels can be color coordinated to virtually any studio or theater design scheme. Attached below is an exclusive Gearslutz sneak peek of the Ready Acoustics Chameleon Trap.

The Chameleon Trap will be available soon from our web site as either a finished product, or as a frame kit which the DIY client can use as is or paint/powder coat to precisely match his taste, and add any fabric cover desired. Chameleon frame assembly is easy – just insert the mineral fiber core of choice wrapped in the fabric of choice, close the frame, and mount the unit. Any look you desire without carpentry or upholstery skills required.

Also this quarter we will be releasing the NEST corner mounting system. These products consist of a corner mounting bracket which allows easy installation of acoustic panels in corner mountings precisely as recommended for optimum acoustic performance.

The Ready Acoutics Corner Mounting Bracket [RCMB] of the NEST system will work with any of our panels, including the RT424, RT426, and Chameleon Trap, or for that matter with any 2’ wide format panel whether factory made or DIY. In addition to mounting the panel in optimal position, the RCMB also provide the means to mount a 12" wide by 4” thick nested porous absorber panel behind the main panel yielding absorptive performance rivaled only by the aforementioned SuperChunk design, but doing so with a fraction of the material costs for the user. A picture showing the elements of this system is attached below.

Ready Acoustics is an avid supporter of the DIY acoustics community. Thus, as with all our products, the NEST system will be available both as a complete finished product, and as components to allow client to assemble their own units meeting their design goals, decorative requirements, and budget.

Please visit our web site to contact us with any questions you may have.

http://www.readyacoustics.com/index.php?go=acoustics-advice.what-do-i-need

[Glenn Kuras]

Originally Posted by zak7

So what is the deal with RealTraps, Ready Acoustics and GIK.?
I want to know the materials that each company use...
Ready acoustic is really a development acoustic company?
Seems that is more like a system..I mean the Owen Corning boards that everybody can get...just they have the bag ready............is GIK the same??

so the question is GIK o Ready Acoustics...I gues the answer is which one looks better!,,if both uses the same materials!

Any comments?

Hey zak7,

As Scott pointed out:

>We also sell the Ready Bags used to make Ready Traps for use by DIY Basstrap makers which spares the DIY guy from frame building and upholstery chores.<

Our product is made from 8 pound mineral wool. We build the panels with a wood frame to the back to keep the trap from sagging over time and make it pretty easy to mount (just like a picture frame). Also we put a plastic frame to the front to keep all the edges as sharp as possible.

If you would like you can drop me a email to go over any room set up or questions on what might be best for your room.

Good luck in your search.

Glenn

[sekim]

GIK

I'm pleased with my purchase.

[bpape]

In addition, our panels have a built in air gap in the back so you can have the advantage of the additional spacing with the clean look of a panel mounted flush to the wall.

Bryan

[the chod]

in relation to materials used.

what is a limp mass membrane ?

what material can it be made of ?

and what is its function and how does it work/function

thanks

[Ethan Winer]

Originally Posted by the chod

what is a limp mass membrane ?
what material can it be made of ?
and what is its function and how does it work/function

We use a type of plastic. The purpose of a membrane is to increase absorption at bass frequencies, and also reduce absorption at mid and high frequencies. This way you can put enough traps into a room to truly fix the bass problems, without sucking the life out of the room as can happen with foam and plain rigid fiberglass. I have 42 RealTraps in my 25 by 16 living room, and the bass response is fantastic yet the room is not too dead at all.

--Ethan

[the chod]

can it be a solid material or floppy [limp] and thin?

does it need a air gap between it and the fibre glass?

can you use polythene like the ones used by painters to cover things from getting paint everywhere and does it need to be thin
or what about cling film?

and does it need to be glued to the fabric
or the fibreglass.

is frk backing the same thing?

i still dont understand how it helps, does it vibrate in sympathy with bass frequencys and then the fibreglass absorbs it?? i understd that it will reflect higher frequencys .

thanks again mr winer

[Glenn Kuras]

Not only are you a smart guy, but come to find out you and Gavin Haverstick (from Auralex) play in a ROCK band.

CD Baby: RIVETSHACK: Rough and Changing

wow Jeff did you guys record Dry Flowers in the River Bank reverb room?

Glenn

Originally Posted by Savant

Ethan: The actual number of sabins measured in a lab will not jive with the actual number of sabins measured in a small room. That was my point. A lab is an idealized situation. If a 72 ft² area of absorbers is placed in a lab and measures 78 sabins at 500 Hz, that's indicative of the performance in a large space, but not exactly. When modeling larger rooms, it is assumed that this is an exact number, but the predictive results clearly show that the same amount of absorption was not, in fact, added to the real-world room. The lab assumes (and delivers, over the standard frequency range) statistical reverberance. The big auditorium where the absorbers are being placed on the wall (in much greater quantities) is not usually quite so idealized.

Take this one step further and make the room very small like a studio room, and the entire concept of sabins goes out the window. Whether sabins/unit or absorption coefficients, the numbers are really only useful for the most cursory of comparisons. Beyond that, the performance is situation specific for both low and high frequencies.

The main reason this happens is because the result - sabins of absorption - is calculated using differences in decay. Since there is no linear relationship between the decay change that occurs in a chamber and the decay change that occurs in a studio room when the same amount of absorption is added to each, the results cannot be the same. There is a volumetric relationship in the purely theoretical sense. But there are other factors controlling the actual results that are largely being ignored when absorption is measured in a small room.

*********

ddageek: I guess we could all get together and do that. However, since - as I mentioned - such standards do exist, the only thing we'd accomplish is a reinvention of the wheel. (Assuming we could all work together!!! )

*********

Others: The argument about too much LF absorption being possible should be clarified a little bit for the contexts of this thread:

(a) If the goal is a "flat" frequency response, then too much LF absorption is probably not likely in most small rooms. But it would be possible.

(b) If the goal is a "flat" time response, then I would argue. Most rooms - even studio control rooms - should not be "flat" in terms of their time response. So, if the goal is an even time response with a slight rise in the low-end, then too much LF absorption is not only possible, but more probable than in the case of (a) above.

(c) It is possible that the reason many seasoned acousticians find over-absorption of the low-end common is because the absorbers being used are also absorbing the high frequencies. If this is the case, too much of a good thing ("traps") is possible and can indeed lead to too much of a bad thing (dull response on the high end).

(d) It is also possible that the seasoned acousticians are over-generalizing. This is less likely if the acousticians in question were being specifically queried on studios. However, it is common to find cases of over-absorption of the low-end in large rooms.

So, if I were asked, I would say that over-absorption of the low-end is possible. Whether or not it's probable would depend on what kind of situation we were discussing.

The same sort of generalization holds true, I find, for most things in audio and acoustics.

[Savant]

Originally Posted by the chod

can it be a solid material or floppy [limp] and thin?

Limp and thin (usually around 1/8 inch).

does it need a air gap between it and the fibre glass?

No.

can you use polythene like the ones used by painters to cover things from getting paint everywhere and does it need to be thin
or what about cling film?

It's likely neither of these are thick enough, but you're on the right track.

and does it need to be glued to the fabric
or the fibreglass.

Won't make much difference if it's glued and it's usually sandwiched between two layers of fuzz.

is frk backing the same thing?

No. FRK is "Foil Reinforced Kraft" paper. Basically like aluminum foil paper. It won't do the same thing, but it will do something.

i still dont understand how it helps, does it vibrate in sympathy with bass frequencys and then the fibreglass absorbs it??

You've got the basic idea.

******

Studio designer and author Philip Newell is a big proponent for limp mass membranes in low frequency absorbers. Just about any of his books discuss their construction, as well as their application. The best, by far, is Recording Studio Design.

If you're wanting more theory, Cox and D'Antonio get into the nuts and bolts of membrane absorbers in their book, Acoustic Absorbers and Diffusers: Theory, Design and Application.

[Savant]

Originally Posted by myfipie

Not only are you a smart guy, but come to find out you and Gavin Haverstick (from Auralex) play in a ROCK band.

I believe the proper verb here would be "played." Gavin and I still get together and jam from time to time, but the distance between KS and IN has forced my reluctant resignation from Rivetshack.

wow Jeff did you guys record Dry Flowers in the River Bank reverb room?

Not really. I was playing around a lot with the Acoustic Mirror plug-in for Vegas/Sound Forge at that time. The effect was either "Ginormous Church" or "Parking Garage." I have found that that song scares small children...

[Scott@RealTraps]

Originally Posted by Bang

I and lo and behold, it sucked up too much bass and the quick mix he did was way bass heavy in the 100-200Hz area, which is an awful area to be heavy in.

Are you ABSOLUTELY CERTAIN that the problem wasn't related to a null in that particular spot in the room? Or that the problem wasn't related to something else?

What type of acoustics analysis were you using, and at what resolution?

For example if you were using 1/3-octave pink noise testing (which is a very popular way to test rooms for many people), this is actually not fine enough resolution to get a clear indication, as you can often miss huge nulls, or even peaks that might be averaged in, etc. to the over all frequency response curve.

What was the effect on the decay times at that frequency? Did you test in more than one part of the room?

I've certainly seen situations in which adding a fairly significant amount of bass trapping in a given room resulted in an overall sound that was better in many ways, but certain things actually sounded a bit worse. The reason for this phenomenon is often that certain room resonances that were causing various wide bandwidth peaks were actually masking other problems (such as smaller peaks or, more often, deep nulls with a very narrow bandwidth).

In those cases, it may be (as just one hypothetical example) that you did a very nice job of addressing the room modes related to the length and width of the room, but did not as adequately address the room modes related to the height of the room.

The idea that bass absorption (or even high or mid frequency absorption) can actually attenuate the direct sound emanating from your speaker drivers is preposterous, and completely flies in the face of physics (not to mention common sense logic). This is a very commonly held misconception, even amongst a few "respected" acousticians, it would seem.

What it CAN do is attenuate what is often referred to as "room gain", which is basically the resonance of the room related to the reflected soundwaves. It is uneven "room gain" due to the reflected sound that causes room coloration. Once you get to a point of 100% absorption, you cannot attenuate the reflected sound any more than it already is attenuated, and the absorbers certainly aren't going to be attenuating the sound wave that travels directly through the air from your speakers (or an instrument or voice, etc.) to your ears.

We're talking about passive absorption, here, not some kind of magical sound magnets. ;-)

Let me paint a more common sense picture for you, here. In acoustics (and indeed as the example is given with regard to the calculation of absorption coefficients), we consider an open window to the outdoors (with no surfaces nearby that would reflect sound back into the room) as "perfect" or 100% absorption.

Now . . . taking this a little further, to something most people probably can relate to more direct experience . . .

If you were to take your monitoring system and set it up out in the middle of a huge, flat field (let's say the Bonneville Salt Flats, or a similarly flat piece of wide open land) with no buildings nearby, on a windless day, if you sat down at the standard listening distance and equilateral triangle arrangement, etc., what frequencies from the direct sound of your speakers do you think would be attenuated, due to the (near) perfect absorption at all frequencies of that wide open space?

Assuming a windless day at moderate temperatures and humidity levels, the fact of the matter is basically that the only coloration of the sound you would be getting at the listening position under those conditions would be a result of any early reflections that might occur off the ground between the speakers and your ears.

Passive absorbers do not create a vacuum or otherwise change the physical properties of the air between the direct sound from source and your ears. They just help to reduce the amplitude of the reflected waves, thereby reducing the acoustic distortion caused by phase relationships between the direct sound and reflected sound at any given spot in the room.

While that isn't completely flawless analogy (of which there are very few in acoustics anyway!), hopefully it at least breaks some things down to a more easily understandable perspective.

Mind you, with the above analogy, I'm not at all advocating that we should be mixing in anechoic chambers. I certainly wouldn't want to!

But I wanted to point out the problems with this commonly held misconception, and point out that, because bass waves are so big, and require so much mass, etc. to absorb completely, it would take a HUGE amount of bass trapping to create an anechoic condition with regard to bass waves, whereas mid and high frequencies can reach that point much more quickly.

This is why so many people get hung up thinking that too much absorption can "attenuate the highs and mids", because so often where full spectrum broadband absorption is used, you will get to that "anechoic" condition in the highs and mids LONG before you reach the point at which you have anything close to an anechoic condition in the low end. And that's why the perceived sound of the monitors (or instruments or voice, etc.) in the room ends up sounding dull if the absorption is not used in a careful, balanced manner.

[Ethan Winer]

Originally Posted by the chod

can it be a solid material or floppy [limp] and thin?

Below is a bit more, which I just found from an old post here at Gearslutz.

--Ethan

Our bass traps are built from double density (705) rigid fiberglass, and we bond a plastic limp mass membrane between the fiberglass and the front fabric. Years ago we used 705-FRK fiberglass, but the plastic we use now is much more effective as a membrane to increase bass absorption, and it doesn't reflect the highest frequencies as much as the paper-based FRK facing. We did extensive research several years ago and determined that this particular membrane and fabric combination provides as much bass absorption as is physically possible for a given panel thickness.

The exact construction and bonding method are proprietary, but I can tell you that the fabric is also part of the system. The fabric we use is custom made for RealTraps to our specifications, and it has a specific weight and density that works in conjunction with the membrane. The fabric itself is not reflective - we use the same fabric for the "HF" versions of our traps too - and the weave is tight enough to ensure that no fibers can leak out into the air. It's actually quite an amazing fabric! It does not shrink or stretch over time, nor does it sag, wrinkle, or discolor. The downside for us is we have to order huge quantities at a time to warrant a production run from the manufacturer. This is why we offer only four colors rather than a large selection as is typical of panels that use Guilford of Maine fabric. But the fabric we use is much more appropriate for absorber products than the Guilford stuff.

As a system, MiniTraps and MondoTraps provide a curve of absorption versus frequency that is ideal for most rooms. To the best of my knowledge, no other bass traps available match this curve. Most either absorb too much or too little at mid and high frequencies. Our approach lets you install as many traps as possible in a room to sufficiently flatten and tighten the low end, but without killing all the mids and highs as can happen with lesser products like foam and plain fiberglass. As you may know, I have 40 RealTraps in my 25 by 16 foot living room. With all those traps the bass is incredibly tight and focused, yet the room is not at all dead sounding. Rather, the mids and highs are perfectly controlled. Indeed, several of my recording engineer friends bring over their important mixes to play on my living room and home studio systems, as a final QC check for good translation.

[Ethan Winer]

Originally Posted by Savant

Studio designer and author Philip Newell is a big proponent for limp mass membranes in low frequency absorbers.

So Jeff, are you now saying that I was right all along, for all these years, and those who said my company's bass traps are "peaky" due to the use of a membrane were wrong?

Of course, I knew I was right, but thanks for finally confirming!

--Ethan

[the chod]

Originally Posted by Scott@RealTraps

Are you ABSOLUTELY CERTAIN that the problem wasn't related to a null in that particular spot in the room? Or that the problem wasn't related to something else?

What type of acoustics analysis were you using, and at what resolution?

For example if you were using 1/3-octave pink noise testing (which is a very popular way to test rooms for many people), this is actually not fine enough resolution to get a clear indication, as you can often miss huge nulls, or even peaks that might be averaged in, etc. to the over all frequency response curve.

What was the effect on the decay times at that frequency? Did you test in more than one part of the room?

I've certainly seen situations in which adding a fairly significant amount of bass trapping in a given room resulted in an overall sound that was better in many ways, but certain things actually sounded a bit worse. The reason for this phenomenon is often that certain room resonances that were causing various wide bandwidth peaks were actually masking other problems (such as smaller peaks or, more often, deep nulls with a very narrow bandwidth).

In those cases, it may be (as just one hypothetical example) that you did a very nice job of addressing the room modes related to the length and width of the room, but did not as adequately address the room modes related to the height of the room.

The idea that bass absorption (or even high or mid frequency absorption) can actually attenuate the direct sound emanating from your speaker drivers is preposterous, and completely flies in the face of physics (not to mention common sense logic). This is a very commonly held misconception, even amongst a few "respected" acousticians, it would seem.

What it CAN do is attenuate what is often referred to as "room gain", which is basically the resonance of the room related to the reflected soundwaves. It is uneven "room gain" due to the reflected sound that causes room coloration. Once you get to a point of 100% absorption, you cannot attenuate the reflected sound any more than it already is attenuated, and the absorbers certainly aren't going to be attenuating the sound wave that travels directly through the air from your speakers (or an instrument or voice, etc.) to your ears.

We're talking about passive absorption, here, not some kind of magical sound magnets. ;-)

Let me paint a more common sense picture for you, here. In acoustics (and indeed as the example is given with regard to the calculation of absorption coefficients), we consider an open window to the outdoors (with no surfaces nearby that would reflect sound back into the room) as "perfect" or 100% absorption.

Now . . . taking this a little further, to something most people probably can relate to more direct experience . . .

If you were to take your monitoring system and set it up out in the middle of a huge, flat field (let's say the Bonneville Salt Flats, or a similarly flat piece of wide open land) with no buildings nearby, on a windless day, if you sat down at the standard listening distance and equilateral triangle arrangement, etc., what frequencies from the direct sound of your speakers do you think would be attenuated, due to the (near) perfect absorption at all frequencies of that wide open space?

Assuming a windless day at moderate temperatures and humidity levels, the fact of the matter is basically that the only coloration of the sound you would be getting at the listening position under those conditions would be a result of any early reflections that might occur off the ground between the speakers and your ears.

Passive absorbers do not create a vacuum or otherwise change the physical properties of the air between the direct sound from source and your ears. They just help to reduce the amplitude of the reflected waves, thereby reducing the acoustic distortion caused by phase relationships between the direct sound and reflected sound at any given spot in the room.

While that isn't completely flawless analogy (of which there are very few in acoustics anyway!), hopefully it at least breaks some things down to a more easily understandable perspective.

Mind you, with the above analogy, I'm not at all advocating that we should be mixing in anechoic chambers. I certainly wouldn't want to!

But I wanted to point out the problems with this commonly held misconception, and point out that, because bass waves are so big, and require so much mass, etc. to absorb completely, it would take a HUGE amount of bass trapping to create an anechoic condition with regard to bass waves, whereas mid and high frequencies can reach that point much more quickly.

This is why so many people get hung up thinking that too much absorption can "attenuate the highs and mids", because so often where full spectrum broadband absorption is used, you will get to that "anechoic" condition in the highs and mids LONG before you reach the point at which you have anything close to an anechoic condition in the low end. And that's why the perceived sound of the monitors (or instruments or voice, etc.) in the room ends up sounding dull if the absorption is not used in a careful, balanced manner.

very well explained! makes a whole lot of sense