Auralex kits...??

[Einar]

Hello all...

I recently modified my recording space and set up a seperate mix/control room... I just started using it a few days ago, and untreated it doesn´t sound good at all (as you can imagine, bare walls and everything!)

I came across these Auralex kits on music123 and was wondering if thats any good to make my room workable..??
(I ain´t got a big room-treatment budget as of yet, so I´m trying to do a quick fix until I go for the real deal)

http://www.music123.com/Auralex-Studiof ... 5.Music123

http://www.music123.com/Auralex-Wedgies ... 1.Music123

Have a nice weekend !!

[jwl]

Hi Einar, those Auralex foam products will do a good job of taming room reflections if you want to deaden the room. They won't give you much if anything in the way of bass trapping.

You will want to come up with a strategy to add some bass trapping to the room. Dead and boomy is still tough to mix in....

[knightfly]

Einar, you may find that a little DIY can save you over foam kits and give you better results - check out some of these projects

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=5930

Good luck... Steve

[Indyjoe]

Yeah, those foam kits are expensive. Take a look at this stuff:

http://www.foamandupholstery.com/Noise_ ... or%20Chart

Joe

[Ethan Winer]

I'm leery of any vendor that doesn't offer absorption data. Especially if they are so ignorant they call their foam "sound proofing."

--Ethan

[myfipie]

Ethan,
If you go to the bottem of that page it has the following

"NRC stands for Noise Reduction Coefficient. This is a standard and commonly used method to calculate the ratings of the ASTM C423 test on noise reduction foam. This method covers frequencies between 125 and 4000HZ. The higher the NRC rating, the more sound the material can absorb."

Ok thats nice, but then there are no test numbers.

Glenn

[Ethan Winer]

Ok thats nice, but then there are no test numbers.

Right, NRC is useless for music applications because it addresses speech frequencies only.

[lovecow]

Right, NRC is useless for music applications because it addresses speech frequencies only.

Wow. That's a bit strong. There's plenty of music with content between 88 and 5656 Hz. (These are the bottom and top frequencies included in the 125 and 4000 Hz octave bands, respectively.) That's about F2 to about F8 for those of us with a music theory background. Even if you take the actual frequency range of the NRC (about F3 to about F7 - see below), it's still a significant range for musical applications - not completely useless, IMO.

(Just bustin' your chops, Ethan. Because if I didn't do it, who would? )

Regardless, I would agree that NRC is not as quite as useful as the octave band absorption coefficients because it's the arithmetic average of the bands between 250 and 2000 Hz. If one material has an NRC of 0.20 and another has an NRC of 0.90, I would lean towards the latter if maximum absorption is my goal. However, if one material has an NRC of 0.80 and another has an NRC of 0.85, then the comparison is difficult to say the least!

(Of course, a material with an NRC of 0.20 could, in theory, have better LF performance than a material with 0.90. I would be remiss if I didn't acknowledge that. However, in the course of comparing materials, other characteristics are usually taken into account, e.g., am I comparing a resonant absorber to a piece of acoustical foam, or am I comparing two different densities of mineral fiber?)

This link has more details, and is coincidentally mostly on-topic, at least with regards to the thread title.

[Ethan Winer]

(Just bustin' your chops, Ethan. Because if I didn't do it, who would? )

Heh, who else? let's see:

Glen, Joel, Eric, Scott, Bert ...



BTW, point taken. From here forward I'll refer to NRC as mostly useless.

--Ethan

[lovecow]

BTW, point taken. From here forward I'll refer to NRC as mostly useless.

Well, as you may have gleaned from my posts over the years, I'm no fan of absolutes. NRC is no exception. For the record, I'm not a huge fan of NRC...or STC, or IIC, or any other single number rating. But they serve a purpose, albeit a diminishing one in the information age.

The point we're both making, I hope, is that for recording studios, NRC is not going to tell anyone much of anything about the usefulness of something like a "bass trap."

[Eric_Desart]

Just some thoughts.

Some of these concepts, also in the ISO world are relative recent.
These concepts are valuable IF used where they are designed for.

That relates to geometric acoustics and in this world were absorption still dominates the market (industry, utility buildings, offices and so on).

If you speak about an industry hall(s) 2000 to 3000 m2 is not large.
If office buildings, supermarkets, shopping malls are build, we speak about thousands of square meters floor surface.

If people build a home studio that varies between 20 and 60 m2.
200 m2 are real pro studios already.
That these ask a specific approach is logical, but they don't make these concepts designed for MUCH larger markets and applications, useless or even outdated.
Studios are only minor fraction of acoustics.

When I mounted absorption (baffels = steel framed mineral wool absorbers) at DAF TRUCKS Oevel (Belgium), years back (before I knew the net), that were > 12,000 pieces. If I did the post building in Rotterdam (The Netherlands) that were several thousands of absorbers. Floating floors in the EU buildings in Brussels > 10,000 m2
Here people wonder if they can do with 8, 12 or 20 absorbers. More becomes already a lot.

All these concepts and notions are good and not useless, just this relative new home and semi-pro studio business calls for its specific approach since the approach is different and modal dominated.

Only in 1997 ISO INTRODUCED a new single number rating for absorption (alpha w where w stands for weighted) which is a bit a counterpart of your NRC, but a bit more extensive (weighting curve). (I can't remember when I first heard about it, must be arround 92 to 95).
As such this has little to do with the availability of calculation means, but a different target group, where the studio world is only fraction of the market.
http://webstore.ansi.org/RecordDetail.a ... 654%3A1997

[lovecow]

Thanks, Eric! While ISO's αw uses curve-matching, it's still better than NRC. (And better than the ASTM's relatively new "SAA," which is just like NRC, only it includes the 125 and 4000 Hz bands. ) Designating materials with an αw that includes the appropriate shape indicator(s) would be a much more useful single-number metric, when single-number metrics are appropriate. (Which largely excludes studios, unfortunately.)

Thankfully - more applicable to recording studios - companies like RPG are developing new and better ways to quantify the low frequency performance of absorbers. For some time, RPG has been using combinations of the ISO reverberation room and impedance tube measurement standards to measure absorption down to 50 Hz. IMO, their results are by far the closest anyone has yet come to the elusive objective quantification of LF absorber performance.

Many published low frequency absorption coefficients are non-sense<sic>, becasue the accuracy of the absorption efficiency
decreases at low frequencies in standard ISO 354 and ASTM 423 tests, due to inadequate diffusion. Therefore, additional
testing has been carried out at the Fraunhofer Institute in large scale impedance tubes with a cross section of 1.6 x 1.2 m
and a special approach monitoring the decay times of the lowest axial modes in a 5x4x3 m room, with and without the
sample present on one of the opposing surfaces.

Source (PDF).

All the best,

[Ethan Winer]

NRC is not going to tell anyone much of anything about the usefulness of something like a "bass trap."

Heh, isn't that exactly what I said originally?

[Ethan Winer]

Many published low frequency absorption coefficients are non-sense<sic>, becasue the accuracy of the absorption efficiency decreases at low frequencies in standard ISO 354 and ASTM 423 tests, due to inadequate diffusion.

Well whack me with a baseball bat. This is exactly what I've been saying for - what? - at least three years now! This also is the whole point of my article in the current issue of Sound and Vibration, which I'll link publicly in a few days as soon as the next issue comes out. Further:

a special approach monitoring the decay times of the lowest axial modes in a 5x4x3 m room, with and without the sample present

WTF? This also is exactly how I did my Density Report that was soundly ridiculed by many of the "experts" in attendance here. But after Dr. Pete discovers this is actually a pretty good way to assess absorption at very low frequencies, now it's acceptable!

I have $100 that says Dr. D'Antonio learned this from my writings.

Thanks for posting that PDF Jeff, it's a keeper.

--Ethan

[lovecow]

Many published low frequency absorption coefficients are non-sense<sic>, becasue the accuracy of the absorption efficiency decreases at low frequencies in standard ISO 354 and ASTM 423 tests, due to inadequate diffusion.

Well whack me with a baseball bat. This is exactly what I've been saying for - what? - at least three years now! This also is the whole point of my article in the current issue of Sound and Vibration, which I'll link publicly in a few days as soon as the next issue comes out.

The relative accuracy of reverberation room methods for LF absorption tests has never been up for debate. (If you feel it has, then perhaps you misunderstood...) In fact, the inaccuracies have been know about at least as long as the standards have been around. After all, they never included low frequencies to begin with due to the known erratic behavior of testing rooms in the modal region. I can point you to some publications to that effect from the middle of last century if you like.

Also, I read your article. The RPG reference above pertains to the use of extant standardized methods to measure LF absorption, which was not discussed in your article. (You made brief mention of the standards and their inadequacy for LF absorption testing, but did not delve into it much further. Which - FWIW - I thought was fine given what appeared to be the intent of the article. I'm always a fan of authors that stick to what they know.)

a special approach monitoring the decay times of the lowest axial modes in a 5x4x3 m room, with and without the sample present

WTF? This also is exactly how I did my Density Report that was soundly ridiculed by many of the "experts" in attendance here. But after Dr. Pete discovers this is actually a pretty good way to assess absorption at very low frequencies, now it's acceptable!

I think you are mistaken. A 5x4x3 m reverberation chamber (read: laboratory) was used for the RPG measurements. The "density" tests you refer to were not conducted in a such a room. Also, the decay at the lowest axial modes was monitored to (partly) arrive at the LF absorption results. The "density" tests you referred to utilized a swept-sine testing methodology (but with no mention of whether the ISO standards for absorption testing using alternate signals, like swept-sine, were followed), and did not report absorption results.

Further, the RPG results not only utilized the modified reverberation method, but also incoporated impedance tube measurement results from standardized laboratory tests.

With all due respect, I think you're making this about you...and it's not about you.

I have $100 that says Dr. D'Antonio learned this from my writings.

Doubtful. Most of Dr. D'Antonio's research - which I've known about for at least 10 years (and it was already around long before I got around to reading about it) - was conducted long before your "writings."

(FWIW, I remember him talking about his research and methods during that AES workshop a few years ago in direct rebuttal to your statement that there was no standard method to test LF absorption.)
(Of course, if nothing else, consider the fact that Modex products were around at least several years before RealTraps...)

************
In short, while RPG's methods may appear similar to your own, it's only on the surface. Your tests and articles are interesting, but do not provide a way of attaining objective, repeatable, reproducible results. RPG is utilizing extant measurement standards, and applying them in a way that has great potential to provide objective, repeatable, reproducible test results for LF absorption.

Finally, this was not meant to be a critique of you or your methods, "writings," "tests," and so forth. As I wrote above, I think you're making this about you. Stop making this about you.

(I mean no ill will, Señor Winer. )