gedlee said:
How about waterfall data form some seats? At least that would provide an insight into frequency response, reverberation time and modal behavior of your room.
Best, Markus
Unless speaker size is too limited, I would think the goal is to not excite room modes. I know that some people will think this will sound weird like in an anechoic chamber. But this would be due to other problems like insufficient speaker low frequency SPL, polarity issues, low background resolution capabilities, etc.
Not all people are going to make the same assumptions when reading these threads. Basically, I would never assume EQ is used unless explicitly mentioned and for specific conditions in a disscussion only. This is because I think EQ will mess up the onset transients of the original signal, which is audible under certain performance characteristics of a system. When we participate in discussion like these, people are going to nit-pick, we just have to accept it as a fact of life and keep our spirits up when it happens.😀
Not all people are going to make the same assumptions when reading these threads. Basically, I would never assume EQ is used unless explicitly mentioned and for specific conditions in a disscussion only. This is because I think EQ will mess up the onset transients of the original signal, which is audible under certain performance characteristics of a system. When we participate in discussion like these, people are going to nit-pick, we just have to accept it as a fact of life and keep our spirits up when it happens.😀
Generally low frequency noise are more common even in seemingly quiet places. Absorption data normally requires subtracting the reflection from the original source. This is very difficult to do at low frequencies due to the wave lengths involved.markus76 said:
markus76 said:
Markus
My software does not do waterfalls, thats one reason that you don't see them from me. And, like Todd, I have my doubts about them as tools. They make pretty pictures, but if they are not useful to me I don't have much interest in developing the technique.
I do intend to post measurements of my room when I get the chance, but time in not something that I have lots of these days. I started teaching a class in Physics at the local University and that is eating up a lot of my time.
So there was another possibility -that the energy shifts in frequency... which is what they are saying about the rc-1. That the resonance is shifted lower into the bass region.
If the drywall resonates at bass frequency (~100 hz) when mounted on rc1, but the normally mounted drywall resonates at a significantly higher frequency (all a guess based on what I am gathering, can someone confirm this?)
My question stemming from above: is damping the drywall with the CLD more successful for the rc-1 mounted than normal mounted, if your only purpose is to absorb bass frequency produced in the room?
I think the tough part of getting to the bottom of this, for us, is that we really need to be able to compare between the 2 (or more) methods, in the same space etc, to see the difference the approaches make. This would be a very cost prohibitive experiment for anyone not commercially selling these things where there is expectation to recoup on investment.
If the drywall resonates at bass frequency (~100 hz) when mounted on rc1, but the normally mounted drywall resonates at a significantly higher frequency (all a guess based on what I am gathering, can someone confirm this?)
My question stemming from above: is damping the drywall with the CLD more successful for the rc-1 mounted than normal mounted, if your only purpose is to absorb bass frequency produced in the room?
I think the tough part of getting to the bottom of this, for us, is that we really need to be able to compare between the 2 (or more) methods, in the same space etc, to see the difference the approaches make. This would be a very cost prohibitive experiment for anyone not commercially selling these things where there is expectation to recoup on investment.
So from the green glue site they show a reverb time calculation to reflect absorption.
Single drywall resonance figures from Green glue site:
http://www.greengluecompany.com/soundAbsorption.php
5/8" is around 100 hz
1/2" is around 125 hz
rc1 pushes it down to about 80 hz
isomax clips push it down to about 40 hz
They don't show the absorptive effect of CLD combined with the decouping, just some figures as to the isolation -so I asked them to!
-Tony
Single drywall resonance figures from Green glue site:
http://www.greengluecompany.com/soundAbsorption.php
5/8" is around 100 hz
1/2" is around 125 hz
rc1 pushes it down to about 80 hz
isomax clips push it down to about 40 hz
They don't show the absorptive effect of CLD combined with the decouping, just some figures as to the isolation -so I asked them to!
-Tony
TRADERXFAN said:
The RC-1 lowers the resonance significantly.
The answer to your question is absolutely yes. CLD works by absorbing energy generated in its damping layer by shearing this layer. The greater the shear the more energy is absorbed. When mounted rigidly, the shearing has to be much less because the wall cannot flex as much, its stiffer. This may be good for sound transmission but not for sound absorption. The limp hanging wall is free to bend significantly and as such its energy absorption will be much much higher than it is for the rigid mount. BUT, this may result in a less than desired sound transmission, especially at the walls resonance frequency. If the net sound transmission is greater or less than is a guess. Bassed on my experience there is a band of frequencies that leak through the walls at very LFs. If this is better or worse than a rigid wall I don't know. I do know that the LF absorption in my room is very high and the HF absorption is very low. This is what I wanted and this is what I got.
Alex from Oz said:
I would compare those measurements with what you can find on the Green Glue site. I don't know how effective a membrane would be in a drywall CLD unless it was bonded to the leafs (drywall).
Is this stuff covered on both sides with a PSA (pressure sensitive adhesive)? I'm not sure even if that would work well unless you could adhere it before mounting by applying pressure with a roller.
When you attach drywall the pressure points are on the studs where the screws are but much of the shear-action takes place between the studs. Unless you have a good coupling in this area (mid-way between studs), then I think the membrane would be less effective than it could be.
gedlee said:
What's wrong with waterfall diagrams? Newer software works great. Use Room EQ Wizard which is free and easy to use. You should be able to show useful low frequency waterfall data within minutes:
http://www.hometheatershack.com/roomeq/
Best, Markus
MartinQ said:
I was hoping for something that was either more economical or more readily available, or both.
The principles for all of these glues are the same. Its a polyurethane based adhesive (there could be some other binders) that does not harden completely. It is then mixed with a thickener like micro-ballons from 3M. The ballons act as the friction medium (by rubbing together) in the relatively non friction binder creating a very well damped bond. This is exactly what I do for all my CLD parts in my speakers. When mixed yourself it can be lower in cost than the commercial Brands. Five gallons, which goes a long way, and when mixed costs about $200, or $40 a gallon. Quiet glue actually looks like a good deal when bought in bulk at $259 for five gallons.
gedlee said:
I know these 'glues' are both water based. The Green is latex based and the Quiet is an acrylate. It seems that Quiet uses baking soda as a filler. I wouldn't think that micro-balloons would be a good filler for friction generation, but perhaps they are when encased in a viscous substance.
markus76 said:
Hi Markus, I dont think waterfalls are useless, but you have to consider time vs frequency resolution when looking at them. For instance the ones I plotted looked different to some of the earlier posts. Why? Could be in part because I (actually mlssa) has set the frequency resolution to be high(er) and thus the time resolution is low(er). So you have to constantly keep that in mind. Also, the first time I saw a modal "crest" appear seemingly out of nowhere half way down a waterfall, i realized it may be too much information. In that case it is modes exchanging energy with each other, I believe. Interesting, but hard to hang your hat on. And that's just windowed fourier transform waterfalls. There's a whole plethora of other analysis methods, based on wavelets, Gabor, Wigner-Ville, and other, which give different tradeoffs in resolution (BTW these may be better resolution-wise than a simple fourier based CSD). But interpretation is always an issue. For example the Gabor spectrogram can give better time/freq resolution tradeoff, it can have negative energy components. What do you do with that? It does tend to get complicated.
Todd, why make it more complicated than it needs to be? Looking at a waterfall generated with REW gives you a visually very exact representation of the major aural problems like modal ringing and high reverberation time. And it makes data from different rooms comparable (which Earl refuses to do for unknown reasons).
Best, Markus
Best, Markus
markus76 said:
Markus
Thats not fair. I didn't "refuse" to do anything. But given my limited time availability I do reserve the right to do those things that I think are the most important - which is not necessarily what you want me to do. Your priorities are not my priorities. And I don't think that it's reasonable to criticize me when I don't jump to your bidding.
Well, you're the one always talking about the high LF absorption of your room so it's perfectly normal to ask how this can be shown. I think it's not fair to answer "The effect of LF absorption on the sound field is in my books.". Which means, "You first have to pay me, then I'll prove it". That's odd. If you claim something then you have to prove it.
Answering my last post took you probably the same amount of time as downloading and installing REW 🙂
Best, Markus
P.S. Answering this post will take you probably the same time as setting up REW and your mic.
Answering my last post took you probably the same amount of time as downloading and installing REW 🙂
Best, Markus
P.S. Answering this post will take you probably the same time as setting up REW and your mic.
That's not what I intended but sounds consequential if you really don't want to deliver some real world data that supports your approach (now).
Best, Markus
Best, Markus
markus76 said:
Well, at least your using the same resolution in comparing different rooms, that's good. But still, other than just seeing where the modes are (which for modes with significant energy you can pretty much do with a steady state), the question is what to do with all that data (other than oohing and ahhing at it
). It gets down to decay time for each mode i assume (assuming you dont run into some of the anomalies I have, like "holes" and non-uniform decays). So the $64,000 quesiton is whether this information is useful, as oppossed to just the steady state energy in each mode. And, if you are going to look at the fine structure of the decay then you get into the interaction of program material and room response. When you get this figured out, let me know. Its fascinating stuff!