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PostPosted: Tue Oct 23, 2007 9:37 pm 
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Eric_Desart wrote:
Glenn wrote:
still want to know what is the most effective type of trapping

:mrgreen: Isn't anyone ???


Some related question marks:
  1. Passive or active?
  2. Narrow or broadband?
  3. Space constraints (how much weighs lesser space needed)?
  4. Cost/result ratio?
  5. Simplicity?
  6. Physical/acoustical comprehensibility, predictability and controlibility?
  7. Technical/acoustical best result independent of cost?
    1. without whatever space constraints?
    2. within the smallest space constraints?
Note that the use of membranes or panels are sensitive (more or less important) to the properties of the walls on which they are mounted (they become part of the system).

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PostPosted: Wed Oct 24, 2007 2:56 am 
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if you can post a complete Excel table mapping out the best absorbers for each of those situations/questions, that would be very handy 8) :twisted:

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PostPosted: Tue Feb 19, 2008 1:00 pm 
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Well this thread is somewhat dead but sooooo interesting… after taking the time to read all replies as well as other posts regarding the issue of Hangers or Superchunks, based on everything I’ve read, the pros and cons, I finally choose to go with the hangers design, eventhough there is no data as to how they work or why they work. And to stay on the esoteric side on things my guts tell me it’s an idea worth trying :shock: . The graph below shows what I intend to do for my rear corner bass trap, based on John’s idea posted earlier on this thread.

A new frame will be built to hold the two layer of 5/8 drywall in place as well as to hold the hangers, that new frame will then be filled with rockwool on both side. Here's a couple of questions for John if he’s still around , or anyone who have some clues about what I’m proposing.

1)When using hangers in a corner like this what would be the spacing between each hangers, I’ve seen 8” to 12” to barely touching ?

2) Does the spacing between the newly added drywall (purple) corner and the inner wall meet is an important factor in the trap performance, if so, how large should it be ?

2)Again, some contradictory info on this, Light pink stuff (1.6pcf) or rockwool (2.5pcf) for the hangers and the inside of the trap.

Regards


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PostPosted: Wed Feb 20, 2008 7:19 am 
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hey there orange,

Looks good, but I have 2 concerns about your drawing.

First, the hangers look close enough together that they are touching. My understanding is that there is supposed to be airspace between them (ie, john settles on 8" to 12" between hangers?)

Second, the new wall-framed "inverse corner" at the back of the room looks to be touching the rear walls, ie, creating a very tiny "room" at the back corner. In John's original drawing on page 1, the new inverse corner did not touch the rear walls, ie, there was space for sound to travel behind it. I don't know enough about this approach to know whether it is right or not, I just saw a discrepancy between the 2 drawings.

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PostPosted: Wed Feb 20, 2008 3:38 pm 
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Hi JWL

Thanks for answering. Well your concern about my drawing are my questions in my previous post. I know i drew them barely touching because i'm not sure of the spacing, i've read 8", 12" and barely touching. Same for the inverse corner wall, my drawing shows a 1" space, John's drawing shows lots of space between the walls, but how much is a lot of space :roll: i mean is it 3" or 12" or did he just draw it like that so it's clear and easy to understand ? I am willing to do whatever it take to built this monster, i just need some clarifications. Now if you know that John go for the 8" to 12" for the hangers i'll go with that without further questions but again is it 8" or 12" or am i being too picky ? :wink:

Sorry if this is anoying...and thanks again for your answer

Regards

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PostPosted: Fri Feb 22, 2008 2:59 pm 
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generally, 12" if you have the space. if you're restricted with the amount of space and need more absorption surface area, i'd go with 8". worst case just a couple of inches. i'd also alternate them so they provide a path into the back corner.


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PostPosted: Sat Feb 23, 2008 3:40 am 
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Hi Gulfo

OK got it, i'll probably go with 8" then. What are the rules for these spacing ?

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i'd also alternate them so they provide a path into the back corner.


Have you look closely to John's design for this trap? It involves building an inversed corner hard wall with dry wall inside the trap, that alone takes alot of space, I am not using all that space for hangers so they can't be placed like in the pict you posted ( although it's a good idea ). Now i'm wondering how large should the "ports" be on each side for this inversed wall.

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PostPosted: Mon Feb 25, 2008 10:14 am 
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no hard and fast rules... if you can use 8" and get the amount of absorption you need, then i'd say use it. if you're space constrained and you have the inner drywall set up, then opt for closer spacing and more even alignment with the idea of trying to get the hangers to provide a face to the opening - which i would think needs to be at least a foot high and a couple of feet across to ensure good flow into the space.

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PostPosted: Thu Feb 28, 2008 11:46 am 
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Hi Gulfo, Thanks for taking the time to answer my post your valuable input is always greatly apreciated.

Quote:
no hard and fast rules...


Well i am always looking for "hard" rules granted but not ...fast... ?:wink:

I am definitely going to try the inverse drywall corner, after reading your last post i think that what i am going to do is this : hangers inside the corner spaced appart at 4" or 8" and the ones outside very close from each other, and hang them in a way that air can easily reach the ports each side of the corner. In other words perpendicular to the ports. Those two ports will be 12" wide all the way from to to bottom. I guess this is what you mean and maybe it was john's idea too. If john could just chime in....

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PostPosted: Wed Mar 19, 2008 7:11 am 
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i also have a question about the length and width of the hanger panels.
i have heard of homasote being used for the core of the hanger, and i have found 1/2" 4'x8' panels of it.
my control room ceiling is 11' tall, and there will be a couch in front of the bass trap in the back of the room.

is it cool to have the hangers this length (8')?

should i try to center them in the space between floor and ceiling or hang them relatively close to the ceiling?

also, should they be hung from the ceiling from the center of the board so that it can pivot, or be mounted out to the sides to prevent them from twisting?

any advice would be greatly appreciated! thanks.


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PostPosted: Fri Mar 21, 2008 2:33 am 
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Quote:
is it cool to have the hangers this length (8')?


Yes, from what i've read so far bigger and deeper will be more efficient in the very low freq range.

Quote:
also, should they be hung from the ceiling from the center of the board so that it can pivot, or be mounted out to the sides to prevent them from twisting?


Hang them so they cannot twist.

Quote:
should i try to center them in the space between floor and ceiling or hang them relatively close to the ceiling?


Centered

You may also lined the walls surrounding the hangers with absorbent material. Keep in mind that the orientation of the hangers should be parralell to the sourounding walls where possible.

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PostPosted: Fri Mar 21, 2008 3:07 am 
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orangenumerik wrote:
Quote:
should i try to center them in the space between floor and ceiling or hang them relatively close to the ceiling?


Centered


I mostly stay out of these individual things. And I still have a problem not understanding how they work.

But I don't believe this is right.
Only I can't prove it, as little as you can prove the opposite.

This isn't meant in a bad way, I really mean what I say here.
Normally the further you bring absorption in a really free-hanging field the worse low frequent absorption becomes.

And I've read some sentences here from whoever, but they are all without any measurement to substantiate this.
Forgive me if I add to uncertainty. I immediately draw back and stand corrected if some data substantiates otherwise.

An analogy with suspended ceilings: you increase cavity and your low frequent absorption improves. You increase cavity that much that it looses a logical controlled wavelength relationship with the fixed boundary and the total absorption diminishes again with the emphasis in the lows.

If distance control shouldn't play a roll you could as well see the height underneath the ceiling as the cavity, since sound does not recognize a floor from a ceiling.

With baffels I have the same experience.

But I admit these hangers are some strange things. But I also believe that a lot of never measured assumptions are made trying to fill in the gaps.

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PostPosted: Sat Mar 22, 2008 5:50 am 
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Hi Eric

I'm always impress with all your post, they're always detailed and based on a clever reflexion of the given situation. My hats off to you. Now as for these hanger thing, most of the things said onthis thread (beside yours) are based on unverified but somehow mostly agreed on what one should do to built these hangers. I just hope that some readers do not take this as the absolute truth. Most things read here are based on personal experiences and reasearch based on what's been done before and seem to work. Keeping that in mind i am fully aware that no-ones can explain why these hangers seem to work. But still, i want to built one. This very un-scientific process is more like a collections of mostly used design or way to go than real undeniable data.

regards

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PostPosted: Sat Mar 22, 2008 9:40 am 
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Erik,

I wasn't advising against the use of hangers as principle in themselves. It's an accepted approach here. And there are lots of happy people here with their constructions.

I was clearly limiting my comment to your word centered (related to the hanging height between ceiling and floor).

I don't say the have to be direct against the ceiling, but hanging them completely in a free field centered between floor and ceiling sins with about any analogy I know.

Hence I wasn't trying to question the use of hangers. Just the word "centered" triggered me here.

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PostPosted: Sat Mar 22, 2008 10:35 am 
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looks like i'll have to get Eric the 2nd edition Newell book :wink: which actually includes a whole section devoted to detailed hanger analysis (acoustic wave guide = board covered with insulation - sounds like a hanger :-)) including absorption and pressure measurements - oddly enough it occurs in front of the hangers as well as behind...

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