gedlee said:
I heard what you said but there's a discrepancy between the measurements and the physics (as you explained it). In the end I couldn't care less why something works as long as it works. We need as much broadband low frequency absorption as we can get. So why not use an ordinary steel plate glued between ordinary foam when it just works?
Best, Markus
markus76 said:
Markus
Thats fine, it was you who dragged this out into a claim for a new absorber "because it was patented". All I said was that there isn't anything new which seemed to offend you. And I didn't get the physics wrong.
Soongsc
LF absorption is very much relevent to the topic of multiple subs. Along the way of this discussion the critical importance of the need for LF absorption sometimes gets lost when people start to think that multiple subs solves everything - it doesn't. It's a good approach and when one combines good LF absorption into the equation its almost ideal. But let us not think that we don't need LF absorption because we have multiple subs. When comnbined together they are vast improvements on the notoriously poor LF performance of most systems.
Matt
The foam that I use for the plug would be ideal for a backing layer for a piece of high mass/area materal that was not too stiff. It should be glued to the foam with the highly damped soft polyurethane that I use and referenced some time ago. This would make a great panel damper.
gedlee said:
Thankfully this foam is easier to get and less ridiculously expensive when purchased in sheets. I will say though, 4" thick sheets won't be that cheap. Maybe I can get 2" for less?
Materials with the appropriate stiffness and mass would seem to be quite heavy, no? One thing I'm wondering about here is supporting such big pieces without having further support. If done in a manner that allowed relatively free movement, could "stand-offs" be used to offer necessary additional support.
pjpoes said:
Yes, this is a design difficulty. The sag from the weight will be fixed by the weight / area which has to be correct for the resonant frequency to be right. Some sag of the panel will be unavoidable. You might be able to use standoffs, but they will stiffen the panel and reduce its effectiveness. The best thing would be to design for the sag, which should be predictable and build it so that when hung it sags to the right location.
Getting the stiffness of the foam should not be a big problem.
Sheldon said:
All good points, but practicality gets in the way. I just recommend "suspending" the panels with glue that also works as a damping mechanism. This kills two birds ... Ceilings are good choices, I do that, but its very difficult to impliment. And you really want the absorption somewhat distributed or certain modes may not "see" it.
Hi,
this can be misunderstood. You do not dmit to any errors?
No, there is not. You know this and you try to say this, but you use a mistakeable verbalisation.
I prefer this:
The decay around the resonance frequency becomes dominant above the decay at other frequencies.
I think, this comes next to the facts and is also understandable by non-PhDs (so by me, I am only a bloody graduated engineer, nothing that could compare to a real PhD (also, I am awfully drunk at the moment, but that was the purpose of this evening).
Bye
Baseballbat
this can be misunderstood. You do not dmit to any errors?
No, there is not. You know this and you try to say this, but you use a mistakeable verbalisation.
I prefer this:
The decay around the resonance frequency becomes dominant above the decay at other frequencies.
I think, this comes next to the facts and is also understandable by non-PhDs (so by me, I am only a bloody graduated engineer, nothing that could compare to a real PhD (also, I am awfully drunk at the moment, but that was the purpose of this evening).
Bye
Baseballbat
Sheldon said:
unfortunately the ceiling isn't available in mine, but maybe in others. I have unusual shaped vaulted ceilings with multiple recessed lights and two ceilings fans. It leaves very little ceiling space to mount a bass absorber, and they would have to hang at a strange angle relative to the ceiling. It's probably a great options for others, all the better if you have suspended ceilings to hide them in, but I think walls will have to be my option.
I got a price on some perforated metal, I'm going a different route. a 6" wide strip of perforated metal rolled for cheaper packaging, with enough to do 1 trap, was 130 dollars. Then a steel front panel was another 120 dollars. I'm going to have to look for surplus materials or get more creative. Drywall's cheap, maybe I should try that instead.
Baseballbat said:Hi,
this can be misunderstood. You do not dmit to any errors?
No, there is not. You know this and you try to say this, but you use a mistakeable verbalisation.
I prefer this:
The decay around the resonance frequency becomes dominant above the decay at other frequencies.
I think, this comes next to the facts and is also understandable by non-PhDs (so by me, I am only a bloody graduated engineer, nothing that could compare to a real PhD (also, I am awfully drunk at the moment, but that was the purpose of this evening).
Bye
Baseballbat
I put this post down to "not my language" and "I'm too drunk!" and let it go at that.
Hey Markus - all these Germans are going to give you a bad reputation!
Baseballbat said:
this can be misunderstood. You do not dmit to any errors?
You know, this one grinds at me. I DO admit errors when I make them. But should I admit to an error when its not mine? Would that make any sense? I did not see any concrete proof of any error on my part that I should admit to. Someone said "Your worng!" - I should admit an error simply on those grounds? Please!