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PostPosted: Sat Feb 13, 2010 10:45 pm 
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Joined: Wed Feb 10, 2010 8:30 am
Posts: 3
Location: France
Hi all, Sorry for the topic title, i really had no idea what to put.

Its been a while since im browsing inside this forum, filled with tons of great informations however i didnt seem to find anything about my particular problem.
I expose it to you first, then i give all infos needed.
The problem i have, from what i could gather, is a standing wave between my floor and my ceiling at 132/133Hz it gives me a real peak in the sound, i can deal with nulls, but not with peaks, especially at this frequency.
here is how it looks with RoomEqWizard:
Attachment:
req.jpg

And here is how it sounds like in the room when i move myself in it:
Attachment:
sanstit1ef8.jpg


I dont care much for the 47Hz peak, as it sounds really less anoying than the 133 one, my main concern is the 133one.
----------------------------

Now all the infos
:(everything will be in cm, im from france, if needed i can translate everything in imperial)

I am renting a place (this is an important fact, as it means that there is absolutly no way i can make any kind of big work in the room, no new wall, no holes etc) and of course as its not designed for acoustic environment, each opposit walls are parallels :( .

I already have acoustic panels (6 panels of 120*60 and one of 75*60 disposed as shown in plan below)

Here is how it looks with dimensions and placement of window and door:
Attachment:
plan.jpg


Front (without speaker and desk):
Attachment:
plan1.jpg


and back:
Attachment:
plan2.jpg


And one detail about the ceiling, there is no right angle to it, the ceiling is like this:
Attachment:
ceiling.jpg

in "round" shape (this is not my room, just an picture to show you)

Speakers are Foxtex PM0.5MKII so with bass "hole" (dunno the english word for that sorry) on the front, their middle spot between tweeter and boomer is at 108cm from the floor on speaker stands. that same spot is at 65cm from the front wall.

The bookcase you see on the rear wall is a ikea style bookcase 80cm wide, 200cm high, and 27cm deep.

On the floor i have wood, with concrete under it, i have no idea what is between those two, but i guess not much.
The ceiling is in concrete painted.
And all walls are...(from what i can guess) in concrete too with wallpaper on it (kinda thick one though) but they sound hollow (i know, probably makes no sens for you...but im sure its not gypsum à 100%) except the rear wall which is definitly concrete and sounds full.

what you see under the window is a radiator, big metal stuff, height is 60cm , its 90cm wide, and 18cm deep and its 16cm from the floor

----------------------------

So, this was to situate a little the location.
As i said before, what im looking for is a temporary solution, i know i would need to change completly the configuration of the room to get a decent sound, and from all the read i had in this forum, i know exactly what to do and how to do it to get my room to sound good and i will when the place im in won't be a rental.

Here are the solutions i tried to bring to solve the problem:

First, making acoustic panels, they are full of rockwool at around 50Kg/m3, it really made the sound better for mid and mid/high frequencies but almost no effet on my particular problem (as its a floor/ceiling thing)

Tube, i tried to figure out a way to make a resonating tube so it would cancel the bad frequency, but i think i did it wrong, everything online is in english and in inch of foot, not as easy as it seems to make translations in mathematical context.
So i tried a 64cm long tube and 10cm diameter, but unless i put the tube in front of my ears, it has no effect what so ever in the room..
I wanna try a longer and wider tube, but i dont know how long and how wide since i find everything and its opposit online on this subject :/

I also tried to move my listening position front and back, no effect.

i was thinking of making new acoustic panels to suspend on the ceiling, but...im not sure this would solve my problem completly, maybe just attenuate it.

My budget is really low, less than a 200€, the smaller the better, im not looking to spend too much in this since probably my next place would have different problems and obviously the solutions i would make for this room wouldnt apply in the next one..

The room is mainly for mixing/mastering, i make absolutly no recording in it.

Hopefully i gave enough information, if more are needed, i'll be glad to provide.

My question is: What should i do? what would be the most efficient and less costy thing to do in my room to get rid of that annoying peak, the rest i can live with, but this one its impossible.

Thank you for your time!!


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PostPosted: Sun Feb 14, 2010 12:07 am 
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Joined: Wed Dec 06, 2006 6:22 pm
Posts: 144
Location: Berlin, Germany
hello Lafronde,

Lafronde wrote:
i was thinking of making new acoustic panels to suspend on the ceiling,

mr sayers sometimes recommends a cloud with a solid back.
try a search on this.

and indeed the 132/132Hz you mentioned is your 0,0,2 axial mode.
also you should have a dip @ 67Hz right in the middle of the height (must be a few
cm above your head/listening position @ 128cm)

I guess sooner or later someone with more knowledge will chime in and give you proper
tips.

so long,
carsten


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PostPosted: Sun Feb 14, 2010 2:35 am 
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Joined: Sat Aug 25, 2007 10:54 am
Posts: 3802
Location: Exit 4, Alabama
Reads like a great solution to me Carsten. I don't know how anyone else could give a better tip then what you just did.

Brien

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Brien Holcombe
Sound: You can't stop it, you can only try to contain it.


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PostPosted: Sun Feb 14, 2010 3:55 am 
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Joined: Mon Jan 27, 2003 12:46 pm
Posts: 5449
Location: Australia
yup - that's the solution - we had a similar problem in Jamie's studio and the angled solid backed cloud fixed it.


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PostPosted: Sun Feb 14, 2010 8:54 am 
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Joined: Wed Feb 10, 2010 8:30 am
Posts: 3
Location: France
Thank you for your answers!!


I didnt know it was more efficient to actually close the back of it...
Closing it with 3mm plywood would be the way to go?

ill just push your kindness a little more, I thought about this few min ago, would this be effective that way? (i found few cloud panels design, but nothing on where to put it precisly...or i didnt search good enough)

Attachment:
cloud.jpg

(Size of panel correspond to the 70Kg/m3 glasswool panels i could find here, they would be 135*60*4cm and i'd put two times 3 layers)
I've put the longest side as width, but maybe it should be length?

If this is wrong could anyone direct me to an appropriate thread on how big it should be and where is the best to place it?

Thanks again for your help!

EDIT, i read that John is speaking of "the angled solid backed cloud"
What should be the right angle for it?


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PostPosted: Sun Feb 14, 2010 9:37 am 
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Joined: Mon Jan 27, 2003 12:46 pm
Posts: 5449
Location: Australia
build it like this:

Attachment:
Lafronde.jpg


Attachment:
Lafronde.skp


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PostPosted: Mon Feb 15, 2010 2:20 am 
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Joined: Wed Feb 10, 2010 8:30 am
Posts: 3
Location: France
Thanks a lot John!
That's more detailed than i would dare asking for :yahoo:

I'll be sure to make a thread for the building of those in appropriate time!
Thanks once again, im really looking forward to hear my room after them!


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