Absorption vs. Diffusion

[NLP]

Thanks!

I watch your products and theorys 3-4 years. Also my first studio was built upon your acoustics site, but I havent bond the membrane (plywood) absorbers on the wall. The characteristics arre still impresive -I must admit, but I have built for "security" reasons much bigger and deeper absorbers (20cm thickness).

Now Im interested in pistonic membrane principe (Fraunhofer/dr. Fuchs patent) and I cant get it, why they dont use the limp mass like mass loaded vinyl. Steel plate must be damped with special adhesive (-also limp mass layer?), cause plate (It think so) will otherwise produce unwanted audible vibrations.
So, is mass loaded viny maybe too slow to ineract with vibrations (cause when I was on BBC they told me, that they experiment with bitumen and get brilliant results) !? What do you think Mr. Ethan?

P.S.: I made 4 years ago a bunch of big and small poly diffusors (2 big diffusor wall) in medium sized room, and they were just ok, but I have to move from them at least 3-4 meters to "hear" they are really working, this was kind waste of space. Now I have big QRD type diffusors and that is great improvement!

[Joel DuBay]

Originally Posted by Ethan Winer

Glad to.

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.

I hope this answers your question, and explains why our products are universally accepted by top pros as the best commercial bass traps on the market. Please let me know if I can clarify further.

--Ethan

Great,


In your opinion Mr Winer(edited by DrDeltaM, no stupid namecalling please!), how is a bonded medium "limp mass"?

Is it still "limp" or "limp mass" after it is bonded to the 3" 705 slab with mastic?

[Ethan Winer]

Originally Posted by NLP

What do you think Mr. Ethan?

Without spending a lot of time to review all the relevant details I can't really comment. There are a lot of ways to make bass absorbers, and I'm expert with only a few of them.

I made 4 years ago a bunch of big and small poly diffusors ... Now I have big QRD type diffusors and that is great improvement!

Yes, a QRD type diffusor is far better than a curved surface. At least in smaller control rooms.

--Ethan

[Ethan Winer]

Originally Posted by Joel DuBay

In your opinion Mr Weiner, how is a bonded medium "limp mass"? Is it still "limp" or "limp mass" after it is bonded to the 3" 705 slab with mastic?

Mr. DuBay,(edited by DrDeltaM, no stupid namecalling please!)

If I told you how we make our products, then I'd have to kill you.

--Ethan

[NLP]

Mr. Winer thank you for helpful informations!!!

[Ethan Winer]

> Mr. Winer thank you for helpful informations!!! <

Glad to. It's what I do.

Also, yesterday when I described the types of membranes I've tried, I should have also mentioned that I've tried membranes in both the front and rear, and the rear only. For maximum effectiveness it's important that only the front surface have a membrane. When there's a membrane on the rear too - or even just heavy and dense fabric - the performance is much worse than with a membrane on the front only. At the time I didn't note if having two membranes is even worse than plain rigid fiberglass alone, but it's definitely much worse than with only one membrane on the front.

By the way, that particular test with multiple membranes was done at IBM's acoustics lab we use for official RealTraps testing. These days we have our own test lab at the RealTraps factory that we use for informal comparisons. Note that it's not difficult to do these tests yourself, and my Density Report shows how I do this using the ETF software:

www.ethanwiner.com/density/density.html

The only tricky part, besides needing a very quiet room built with normal construction, is making sure the measuring microphone doesn't move even a tiny amount from one test to another, and being sure you place each set of absorber samples in exactly the same place in the room. With those two simple criteria met, it's possible to get useful information that's valid down to very low frequencies. In fact, you can test reliably to a much lower frequency than the standard ASTM tests acoustic labs charge handsomely for. You won't get Sabins of absorption (though you surely could), but you can compare different materials and different proposed trap designs with a very high degree of confidence.

--Ethan

[Joel DuBay]

Originally Posted by Ethan Winer

Deleted by DrDeltaM for namecalling

Shameful, back to the name calling....oh-well, to be expected.


I believe I was asking you for your "opinion". In fact, I am sure of it. Read my post above where I am trying to engage you in a discussion that will help others understand more about acoustics. And since you are the expert, who better to ask this question?

No one asked you to deconstruct your products here. The question was indeed this:

"In your opinion Mr Winer (edited by DrDeltaM, no stupid namecalling please), how is a bonded medium "limp mass"?

Is it still "limp" or "limp mass" after it is bonded to the 3" 705 slab with mastic?"


So, do you have an "opinion" you are willing to generously share with the acoustics-interested readers of this forum, or would you rather call names for some reason?

I think it is apparent.

Nevermind....




So, Where is the moderator "NOW"? I do sleep some hours per night as well! - DrDeltaM







Joel DuBay
Ready Acoustics

[NLP]

I follow your "mini wars" on other forums almost 4 years (forum.studiotips, John Sayers, AVS...) and want to say that this is childish (fun too must admit).
Everybody have own opinion and I know that is not necessarily (and impossible) to have all things right.
In acoustics axioms changes every few years. You know that.
Please cooperate dont be bantering to each other (maybe because you all have own business interests?).

Mr. deleted by DrDeltaM (look at german dictionary) is Mr. Winer and Mr. deleted by DrDeltaM (everybody understand that) is Mr. DuBay.

So intelligent people must stay on high level communication.

Im not beginner in acoustics and this is the reason why I dont want to "interrupt" you in more expert forums about acoustics (Im not an expert either).

Sorry on my weak english.

Nenad L.P.

[Joel DuBay]

Originally Posted by NLP

I follow your "mini wars" on other forums almost 4 years (forum.studiotips, John Sayers, AVS...) and want to say that this is childish (fun too must admit).
Everybody have own opinion and I know that is not necessarily (and impossible) to have all things right.
In acoustics axioms changes every few years. You know that.
Please cooperate dont be bantering to each other (maybe because you all have own business interests?).

Mr. deleted by DrDeltaM (look at german dictionary) is Mr. Winer and Mr. deleted by DrDeltaM (everybody understand that) is Mr. DuBay.

So intelligent people must stay on high level communication.

Im not beginner in acoustics and this is the reason why I dont want to "interrupt" you in more expert forums about acoustics (Im not an expert either).

Sorry on my weak english.

Nenad L.P.

Indeed.

No war here. JUST VERY good questions that can help further the discussion and understanding of acoustics. No name calling either. I wish I could say the same for others.

[NLP]

OK.

What a pity that administrator delete post from Mr. Scott R. Foster, he made some fine statements.

Can you Mr. Scott "rewrite" that post please.

I have it on my HD but I think that DrDeltaM will be piss** off.

[DrDeltaM]

Originally Posted by NLP

OK.

What a pity that administrator delete post from Mr. Scott R. Foster, he made some fine statements.

Can you Mr. Scott "rewrite" that post please.

I have it on my HD but I think that DrDeltaM will be piss** off.

It's a fine line between posting info and putting competitors products in a bad daylight, which manufacturers aren't allowed to do.
Let people make up their mind for themselves, and not all info about acoustics has to come from a manufacturer of panels.

A rewrite of the post by Scott could be good: keep the general info, stay away from manufacturer-specific stuff, besides the info about stuff you make yourself.

Thanks

[pan60]

Scott R. Foster
start a thread to discus limp mass verses constrained pro and cons.

[pan60]

Originally Posted by DrDeltaM

It's a fine line between posting info and putting competitors products in a bad daylight

A rewrite of the post by Scott could be good: keep the general info, stay away from manufacturer-specific stuff, besides the info about stuff you make yourself.

Thanks

yes please do Scott

[Acoustic Cloud]

Joel, you say there is "no War here"....thats correct, I havent seen Warren on this thread.

Some comments removed by DrDeltaM

[Scott R. Foster]

Hi Pan:

First off, I love your work... you old goat... still playing the pipes on weekends?



As to your request, that's a tall order... a coherent and informative post addressing the claims made with regard to the existence of a "limp mass" layer in a particular porous absorber device... and the related claims as to the resulting acoustic effects... and their suitability for creating a broadband panel... but no reference to the device which is claimed to have this property.

I sincerely regret disappointing you but I don't think I can do that given this forum's rules [which I wish to treat with the respect they deserve].

FWIW you are welcome to talk about Ready Acoustics products and the physics which is underlying of their performance, in any rational and non-violent way that you might desire, as is everyone else - even other manufacturers.

We will never ask that a post be deleted because of such usage. We know that the laws of physics happily abide with our product claims and are delighted to have such discussed with regard to what we make and how the products perform. Also, of course we are always interested in learning more, and open discourse is a great tool in that regard.

If and when other manufacturers grant such permission - and with the allowance of the moderators - I will happy to share my thoughts on the subject claims.

Unless and until that happens, belowlisted are some generic concepts which may help you form your own opinions on the matter. I am sorry to be so limited in my reply, but it is the best I can do at this time, in this venue.

=======================================================

The term "limp mass" refers to the use of a dense material [massive] attached in a way such that it is left free to vibrate [limp]. A common material used to make such constructs is MLV [mass loaded vinyl]. If you mount this material in a fashion such that it is free to vibrate, it is called a "limp mass". If you firmly attach it by doing something like gluing it to a panel, it is still massive, but it aint limp - it is constrained. If you use a material that is lightweight, it won't be massive and thus will do very little to absorb sound energy.

If you do both [neglect to use a material with any appreciable mass, and constrain it by gluing down across a panel], then the construct is neither limp or massive.

The concept of a porous absorber with exaggerated peaks and dips in its absorption performance is the antithesis of broadband.

A perfect broadband absorber would have a flat line of measured absorption all the way across the band from lows to high.

Adding elements to a porous absorber which resonate [such as a limp mass], or which cause an gross entrance impedance jump [like a felt liner with a plastic film backer glued across the pane] will cause peaks and dips in the absorption measured across the band.

This effect can be beneficial [and is in some circumstances such as the an reference earlier in this thread to causing HF reflection from a porous absorber] but one must be careful to not overdo the effect lest one create a circumstance where resonances in the added layers become defining in the device's absorption curve.

In that case, you will need to be very careful that peaks and dips in the absorption curve of the device match the needs of the particular room where it will be used.

I hope that helps.

[warhead]

Originally Posted by Acoustic Cloud

"no War here"....thats correct, I havent seen Warren on this thread.

I've got 5 kids, so cannot participate in threads where the words "limp mass" are used.

War

[Joel DuBay]

Originally Posted by warhead

I've got 5 kids, so cannot participate in threads where the words "limp mass" are used.

War

Excellent.

[Joel DuBay]

Originally Posted by Acoustic Cloud

Joel, you say there is "no War here"....thats correct, I havent seen Warren on this thread. It just seems like you're kinda stupid..sorry for lack of a better explanation.....


More meds, or less meds.....current dose seems to not be working....at least properly....

Mmmmm. Classy......



I am sorry you feel the need to continue to call people names. As you already know, I don't subscribe to the idea that this particular method of posting actually helps, and I don't engage in the same. You can keep trying to get me to do it, but I assure you, it is futile.


I truly hope your day and week get better. Damn shame you are having a bad day today.

Oh, oh, oh...... by the way; are you another one of his "paid" forum posters who just takes swipe after swipe at folks he doesn't like? If so, I am sorry to hear it. If not, then your continued name calling (even in threads where you aren't contributing) is a mystery.




Now, can we talk about acoustics once again?




Have a nice day.







Joel DuBay
Ready Acoustics
www.readyacoustics.com

[Acoustic Cloud]

Originally Posted by Joel DuBay

Mmmmm. Classy......



I am sorry you feel the need to continue to call people names. As you already know, I don't subscribe to the idea that this particular method of posting actually helps, and I don't engage in the same. You can keep trying to get me to do it, but I assure you, it is futile.


I truly hope your day and week get better. Damn shame you are having a bad day today.

Oh, oh, oh...... by the way; are you another one of his "paid" forum posters who just takes swipe after swipe at folks he doesn't like? If so, I am sorry to hear it. If not, then your continued name calling (even in threads where you aren't contributing) is a mystery.




Now, can we talk about acoustics once again?




Have a nice day.







Joel DuBay
Ready Acoustics
www.readyacoustics.com

So then, you dont call people names? Joel. You cant spell Ethans last name?!? Is it the way you spelled it? "Weiner" was an accident? The pseudo nice guy you keep trying to sell yourself as, crashes pretty regularly it seems.

Also Ethan and Glenn have spent alot more time here helping people with questions than I have EVER seen you do. Just calls them as I sees them son.

Oh, oh, oh...... by the way; are you another one of his "paid" forum posters who just takes swipe after swipe at folks he doesn't like? If so, I am sorry to hear it. If not, then your continued name calling (even in threads where you aren't contributing) is a mystery.


Yes, they all pay me, you figured it out. I like the OH OH OH Arnold Horshack impression as well. If you feel you are getting to many "swipes" as it were, maybe the duck rule applies in this particular matter, hmmmm?

[DrDeltaM]

Thread closed for now