703 vs. 705

Hi again, I'm still looking for a solution for my control room issues. It's definitely the side walls, and I've decided that the middle section of the slat resonators are too heavy for me to keep lifting in and out when I want to see through the windows. So, I'm looking for a replacement for that part. Now here's the tricky bit: it NEEDS to be reflective at high frequencies, at an angle, as the slats are now. But, it also needs to be lighter, and more effective at killing frequencies around 100Hz. I CANNOT mix in the room the way it is now. Senn. HD280PROs are more honest in the low end than my room is :shock: . So, I was playing around with 703FRK, and found it to be slightly (2-3dB) more effective than the slats were, but still not effective enough. I got to thinking, and remembered Ethan's article on acoustics, and how it mentions 705 as being more effective at lower frequencies than 703. But then I read an article somewhere (not sure where, I've been bouncing all over the place today) that said otherwise. I looked it up on the OC site, and it shows 703FRK as being more effective than 705FRK at every posted frequency except 1000Hz. Who do I believe? My goal is to create an EFFECTIVE trap centered around 110Hz to fit where the middle slat resonator was (see my other thread for pictures). Face length is 6 ft. Depth is 18in. at its deepest. Height is around 2ft. 6in. Oh, and it needs to be relatively light so I can remove it while tracking. And reflective at high frequencies. Did I say light :D ? Is this possible? It's either this or ripping out all my treatments and starting from scratch, which is a REALLY unattractive option at this point. I have neither the time, money, or energy to be doing that, but will if absolutely necessary. I appreciate all the help and information. Richard

looked it up on the OC site, and it shows 703FRK as being more effective than 705FRK at every posted frequency except 1000Hz. Who do I believe?

Those are actual lab test results from OC. Believe them. Andre

Richard, > My goal is to create an EFFECTIVE trap centered around 110Hz < You'll get great results with either 703, 703-FRK, 705, or 705-FRK. What matters more than the density or facing is simply having a panel that's thick enough. I'll also point out that lab tests vary all over the place. Even in the same lab on the same day. Likewise for my tests! But mine were at least done on the same day one after the other. I don't know if the tests OC did were. For all we know they could have been done ten years apart in two different labs. I assure you that will give far more variance than the tests I did. --Ethan

Thanks for your reply, Ethan. You'll get great results with either 703, 703-FRK, 705, or 705-FRK. What matters more than the density or facing is simply having a panel that's thick enough. Well, I tried using 6 inches of 703-FRK anywhere from 12" off the wall to right on the wall, and, while it helped, didn't cure the problem completely. I still wound up with about a 10dB hole with quite a wide Q, wider than it was with the slat resonator that was originally there. Basically means that the bass is only represented by a peak at around 55-60Hz, because the speakers I'm using for the test (Event TR6s) drop off around 50Hz. I usually use Blue Sky System Ones, which includes a sub, but didn't want the sub placement to effect the tests. But, now I'm getting side tracked. I'm thinking now of building a membrane trap for the two side walls. Would that be more effective than naked 703-FRK? If so, what thickness of plywood would you suggest for that frequency area (100Hz or so)? What kind of bandwidth do those traps have? Thanks very much. Richard[/i]

Ethan Winer wrote:

<snip> I'll also point out that lab tests vary all over the place. Even in the same lab on the same day. Likewise for my tests! But mine were at least done on the same day one after the other. I don't know if the tests OC did were. For all we know they could have been done ten years apart in two different labs. I assure you that will give far more variance than the tests I did.

Lab test are done per official standards. AVare's reply is correct. Ethan's tests are open to a hundred question marks. A complete thread is spend on it, which as standard Ethan completely ignores. Ethan you question all lab tests as per pro standards (if they don't suit you) substituting them by hobby software not able to average 2 measurements, a relative y-axis hiding the peaky behavior (unknown by Ethan at the time of execution, and only discovered by others, resulting from discrepancies in the measurement series, in the related thread), and a representation impossible for laymen to judge. Can you please stop confusing people on the net? And try to listen to yourself for once? PLEASE? - PLEASE? Richard, if you find official measurements of material, that's the best info one will get, unless someone makes new comparative measurements in a lab (not a bedroom, labeled lab), which are official certified controlled environments, with as official certified procedures, methods and equipment. The same lab procedure, questioned here by Ethan Winer, is explained on his site (when related to his own products and the quality of related measurements): http://www.realtraps.com/art_measure.htm

RealTraps / Ethan Winer wrote:

US labs that perform acoustic tests are certified by NVLAP, a department of the US Government's National Institute of Standards and Technology. Testing of acoustic materials is defined by ASTM, an international organization that establishes standards and practices used by acousticians and their companies. By ensuring that its members follow exactly the same rules and guidelines, materials tested to ASTM standards in different facilities can be compared with confidence.

Hence comments about exactly the same seem to depend on the purpose rather than the procedure in itself. Since measurements appeared on the net less favorable for RealTraps, following comment was, relative recent, integrated in another page: http://www.realtraps.com/data.htm

RealTraps / Ethan Winer wrote:

One popular lab is known to report on the high side, and some acoustic product vendors use this lab intentionally just to get larger competitive absorption values.

This is science with an elastic ........ ("is known" is to be understood as: "is assumed/suggested by EW, whether substantiated or not"). A vague 'out of context' misrepresented example then is given which in no way is related to the statement itself. Hence I assume that: Quote: "materials tested to ASTM standards in different facilities can be compared with confidence." is only valid for competing measurements with lower absorption values. The Owens Corner measurements (OC 703, and so on) are executed as per the above NVLAP quote of RealTraps, and are measurements as per the standard absorption coefficient (closed patch) measurements.

Richard, > I still wound up with about a 10dB hole with quite a wide Q < At what frequency? You mentioned 110 Hz above, but didn't say if that's where you have a null or some other problem. Thick rigid fiberglass in corners is very effective at 110 Hz. Also, understand that you'll never get any room perfectly flat unless you line every surface with insulation three feet thick. So we do what we can to make things as good as possible, and then move on. A 10 dB null is not the end of the world, and if that's your worst problem you're better off than 99 perent of the world. But really, the solution is always to add more bass trapping. The more you have, the flatter and tighter the low end will be. It's that simple. Without knowing the size of your room and how many traps you have now, and where they are, it's impossible for me to be more specific. --Ethan PS: You can safely ignore the lunatic ravings above.

Ethan Winer wrote:

PS: You can safely ignore the lunatic ravings above.

:wink: :wink: :wink: Ethan, yet another thread lead to a solution based on merit, from a guy who wins on science, arguments, maturity, being always friendly, and never being offensive????? Ethan I'm grateful to you for your continuous generous help confirming my points.

Not to be a prick or anything, but could we maybe stay on topic just a bit here? I appreciate ALL advice, and I can work out what I want to pay attention to or not. That said, Ethan - the most major issue I'm having is about a 10dB null from around 65Hz to 130Hz, centered at 110Hz or so. You can see pictures, graphs, test info, etc. here. It's not too deep over most of that range, but at mix position it's quite hard to hear any bass at all, and it's near impossible to mix effectively. I know it's never going to be perfect, but I would expect it to be a bit better. The reason I'm looking at panel traps is that the slat resonators that are currently there are too heavy for me to move in and out of position when I want to use the windows, and aren't really as effective as I'd like. I need whatever I put there to be reflective at high frequencies, or else I'm going to be surrounded by 703, and the room really didn't sound so good when I tried that. Thanks again, Richard

Alright, I'm going to build a panel (membrane) trap for the sake of testing. It may not be what I end up with in the long run, but without trying it for myself I won't know. If I build it such that it's spaced off the wall at an angle, can I build the back to act in a similar way to the front? In other words, would that be like spacing a panel of 703 off the wall so that sound can get to the back of it? Or does it not work like that?

Panel traps work by sound PRESSURE, not VELOCITY (at least from an exterior point of view, such as your sound) - the sound pressure excites the front panel at it's resonant frequency, then the movement of the panel tries to move the interior air back and forth through the internally mounted absorbent. Losses occur because of the force required to move the front panel itself, which turns the sound pressure into heat; further losses occur when the internal air is restricted in its movement through the absorbent, due to the air friction within the interstices of the absorbent material, also turning the energy into heat. Although a panel trap doesn't need to be hermetically sealed to still WORK, (air being a relatively stiff medium, it can't "get out of the way" fast enough NOT to still allow approximately the same physical response) the formula is based on a sealed trap - so if you tried to build a NON-sealed trap, you'd need to build and test in order to get close to your target frequency. Angling a sealed trap across a corner might improve its ability to target the same range of frequencies in two axes instead of mainly the one it is perpendicular to, but otherwise would NOT function the same as corner-mounted porous absorbers. Guys, (you know who you are) I have no problem with well-documented argument, but have a BIG PROBLEM with name-calling. My memory isn't nearly as bad as it's apparently thought to be. 'Nuff said? :evil: Steve

OK, I'm not sure my explanation of what I'm thinking of doing was clear (and I'm not sure this is going to help). I'm thinking of a panel built in this fashion: plywood (either 1/8" or 1/4"), small air gap, 703 (2" or 4"), small air gap, plywood, with a frame around the edge to form a box (see crappy paint drawing attached). The trap would be placed off the wall so sound could get to the rear side. Ethan's plans show an air gap between the insulation and rear surface of the trap (in his plans it's the wall). Is that necessary for the trap to work? Or can it be done this way?

Oh, also, Steve, could you point me in the direction of that formula to determine target frequency? Thanks a lot, this is all somewhat new to me, Richard

http://www.johnlsayers.com/phpBB2/viewtopic.php?p=41713 Sorry but I'm totally out of time and have to run, will try to answer your other questions in a day or two if no one else does... Steve

Ethan, your last two posts contribute nothing other than fueling the fire, pissing me off, and NOT helping answer the question; that's why they're gone. Please stick to the subject matter.

Steve, > your last two posts contribute nothing other than fueling the fire, pissing me off, and NOT helping answer the question < My intent is not to piss you off. But when one person is a perpetual school yard bully, it's only fair that everyone realize it. This is not about two guys arguing. It's about one guy attacking others (not just me) so many times that he is finally banned from a forum for his bad behavior. If I behaved as badly as he does, I'd expect to have that revealed too. --Ethan

I'm PUBLICLY INVITED BACK TO THAT FORUM. Even within couple of days and explicit repeated a few weeks after (without any question from my side, neither direct, nor indirect). Hence that forum didn't feel well themselves with this situation, which had completely nothing to do with you and even less with this thread. Hence, you're traditional method of discrediting people not supporting you, even when completely not related and out of context, shows the real you. But if you think this is important, why don't you speak about yourself and the forum you're banned of for years already without allowance to return, even after emailing people, including the owner?