Your flimsy waveguide will be vibrating at the forcing frequency if it remains linear. If it becomes non-linear then you will see some harmonics. If there is an impulsive component to the forcing then you may see some activity at resonant frequencies. You will not see noise. What you posted looked fine to me and I suspect others (the labelling of the harmonics did not but that is a separate issue). I deleted my last post to Earl on this subject and am now content to let him believe what he wants (as well as what to use for a constraining layer, how to brace cabinets, etc...).
how is this advancing the debate?
looks like black bag rhetoric technique - hiding the "evidence" by deleting the post - and then alluding to the invisible "proof"
seems like a lot of work for someone who "am now content to let him believe what he wants " - and wasn't trying to score points
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If you read the thread you will see a set of measurements showing the effect of substantially reducing the motion of a flimsy waveguide, a simple explanation given for what was going on, confirmed indirectly by Andrew Jones, confirmed indirectly by the KEF Blade distortion measurements, plus no doubt a few things I have missed. Earl's response was that he doesn't believe it. Fair enough but unless he contributes something of substance there is no debate to advance.
On the topic of CLD, Some of the gents on another forum argue there are very few, if any replacements for Green Glue. Am I reading this right?
https://www.gearslutz.com/board/studio-building-acoustics/925363-green-glue-alternatives.html
https://www.gearslutz.com/board/studio-building-acoustics/925363-green-glue-alternatives.html
They are talking about studio walls (big things that move a lot). It won't necessarily work well for cabinets (small and move a small amount) in the same way that CLD for car bodies and computer casings does not necessarily work well either. The principles are the same but the effective damping material is likely to be different.
They talk about shearing, and that this only happens for materials that don't set. It seems like the material used on the horn walls in this thread are an adhesive though, which sets...
The horn walls were light and flimsy. Anything that provides stiffness, never mind damping, is going to improve things.
The point of CLD is to change the deformation of the damping material from mainly extension without the constraining layer to a stronger shearing with the constraining layer. Damping materials tend to work better in shear. If you look at commercial system they tend to use something like 3mm of stiff rubber as the damping material (e.g. section here)
Does the viscosity vary with frequency, or with layer thickness / mass of materials adhered by it?
Has anyone taken this test to see where their perception of distortion audibility is?
Listening Test
This is a complex question, which is why I think most have avoided it.
First lets deal with "dynamics" - there is no real definition of this term. You will hear lots of opinions, but no accepted definition in objective terms. So we can't discuss that one.
Linear distortion of a signal is usually frequency response. It has the same effect on any signal. It cannot create new frequencies -tones - that were not there in the first place.
Nonlinear distortion has to do with a system changing with sound level, excursion, hundreds of causes. New tones can be created in a nonlinear system and given high enough nonlinearity and enough time of action and nonlinearities will generate all kind of new tones, new harmonics and IM on created tones, etc., leading to chaotic behavior, i.e. noise. So a system that is nonlinear enough can generate noise.
The perception of "small" nonlinearities - small because there isn't much point in studying large nonlinearities since they all just sound bad, so no one has done that - has been studied extensively. I have a couple of AES preprint and papers on the topic and several papers on posted my website.
There is also the nonlinear perception of a linear system. Things like diffraction are linear, but they are more audible at higher SPL levels. This adds a whole other level of complexity to the problem.
Thank you for this Eldam, it is best I hear this from a Frenchman. When I pronounce voilà I use the short 'v' as in viper, short that I have almost finished before I begin to make sound. The harder accent comes down to the 'o' and the 'oi'. In English this sounds like 'wa', but when pronounced well there is a 'v' in front almost like it is a silent 'v'.
At first your words confused me as some European languages pronounce 'w' as if it were almost 'v'. This is unusual in English as I know it.
Do they speak English in NZ? (I think that is correct! Or is it AUS?!) 🙂
PS. One of the places that I most want to see, but have not!!
PS. One of the places that I most want to see, but have not!!
NZ is a beautiful place. They speak almost the same as we do in Australia. Their vowel pronunciation is unique (almost as if they rotate the five of them) eg: their 'i' sounds like our 'e' etc. I'd make a similar distinction with US pronunciation, your 'o' sounds like our 'u', for example.
If you can put our accent aside, I think Australian english is closest to English english, at least traditionally.
If you can put our accent aside, I think Australian english is closest to English english, at least traditionally.
I've been to Sydney and Brisbane a couple of times. Liked it very much. Its about 1/2 way between the US and England culturally. Nice compromise.
They are different things. Isolation requires a soft spring so that the resonant frequency of the mass being isolated is well below the frequencies you want to isolate. CLD is about getting a high degree of damping at the expense of using some of the thickness for this purpose rather than carrying load.
In practice damping is not only provided by forces that can be represented as viscous which is one of the main difficulties in simulating it with a high degree of accuracy. The damping varies significantly with frequency and, unfortunately, it tends to be weakest for the lowest frequency cabinet modes which are usually the ones we want to suppress most. It also varies with thickness: thick provides more material to do the damping but each lump of material is strained less. The stiffness and thickness of the constraining layer also has an effect with the constraining layer typically being about 50% the thickness of the base layer if the materials are similar but the desire to maximise stiffness for a given thickness may push things towards thinner constraining layers.
I am tempted to wonder if xrk's base case is so bad, 5mm of untreated foam, that painting on some damping while playing music brings dramatic sonic improvements as he describes. Is it the bad base case behind the discussion?
I am sorely tempted to suggest major *linear* distortions in the base case. Would be interesting to see completely ungated, unsmoothed FR and impulse response in an anechoic chamber, for his untreated 5mm and treated CLD horns.
At least they would be able to explain the audibility of the improvement, unlike HD.