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Discussion Starter · #1 · (Edited)
Hello there!

I am currently trying to adjust the acoustics in my home-studio (mainly for mixing) and need your help to sort out some issues!
It's a 2,30m x 3,70m room (yes, it's metric, please continue reading) with carpet on the floor (about 2-3cm).
Cieling is about 2,40m high. It also has a small space after the door:

(image here)


My monitors are Mackie MR-5 which are quite fair budget-level monitors placed at ear level, driven by a Motu AudioExpress interface.
I measured the response of one of the monitors and it seems quite flat. I am using a Behringer ECM-8000 for measurements.

Facts about the room:
- when clapping your hands, you can hear a clear metallic ringing lasting about 200ms after the clap.
- opening the room door and breaking the small space helps for this, but not completely.
- when bass is playing loud in the room, I cannot hear specific bass resonnance in the small space before the door.

I have tried placing my traps and absorbers in the following matter:

(image here)


wall traps: 1150 x 575 mm, 50 mm thick, 65kg/m3
corner trap: 575 x 575 mm, 100 mm thick, 65kg/m3
foam absorbers: 1000 x 1000 mm, 70 mm thick, quite light (about 20kg/m3)

- wall bass traps are placed about 8cm away from the wall
- foam absorbers are put against the wall
- closet is open on the right side, filled with clothes

The main problems in the room (according to REW measurements) are two persisting bass frequencies: 130Hz and 150Hz that tend to become too present.

Questions:
1. During adjustment, the "wall" bass traps and foam absorbers are not held firmly at 8cm from the wall, they are simply placed on a supporting object:

(image here)


Does this heavily effect the performance of the traps?

2. Changing the traps and absorbers placement had little effect on the room's bass response, for example covering the window with a bass trap or not has very little effect.
What other factors am I overlooking?
I separated the speakers from the desk they are put on by a block of 15cm of foam and made sure the desk was not resonnating/vibrating heavily with bass frequencies.

3. As mentioned earlier, when clapping your hands, you can hear a clear metallic ringing lasting about 200ms after the clap.
What can cause this?

4. Can you suggest a potentially more effective speaker placement?

Thanks for your help

PS: if images don't show, here are the links in order:
http://imgur.com/FaR8Tw7
http://imgur.com/CMKssOZ
http://imgur.com/5C3QkaG
 

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50mm is going to do very little below a couple hundred Hz. 4" straddling a corner is OK but don't expect it to get down into the last 1.5 octaves. The foam, sorry but pretty much useless unless you want to cut it up into pieces and use high on the walls to help with the slap and flutter.

You would have better luck flipping the setup to face the window wall and keep what's in front of you symmetric left to right. Where you sit will have far more impact than where the speakers are placed - though they can certainly be adjusted to make some improvements.
 

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Discussion Starter · #3 ·
Thanks for the info bpape!

I'm using the foam mainly to taim reflections in the mid/high frequencies. Is that useless?
How do you use the foam high on the walls to help with the slap and flutter?

Also, during adjustment, the "wall" bass traps are not held firmly at 8cm from the wall, they are simply placed on a supporting object.
Does this heavily effect the performance of the traps?

Thanks for your help.
 

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Much of what you're hearing with that metallic zine is up high on the walls. Just cut into strips 12-18" and go around the upper perimeter.

Reflections are much broader than just mids and highs, I would never use anything less than 2" fiberglass. Even 4" will do a better job though with more boundary related phase issues in the 100-250hz range.
 

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Discussion Starter · #5 · (Edited)
Hello,

Thanks for your input guys, I changed my disposition since my first post to something which makes more sense. It also closer to what you guys suggest:
- turned 180° facing the window
- more symmetry.
- use the closet as a bass trap (closet is filled with clothes)

Here is my new disposition:

(image here)


This is how I'm thinking of putting the traps/absorbers. I only possess for now 2 trap panels, the basic foam absorbers and the corner trap.

(image here)


How would you suggest treating the small area at the beginning of the room? Would some sort of thick curtain suffice?

Concerning the hard wood under the speakers, those are positionned on a hard woodden, 2-story desk (with isolation). Would that be enough?
I only have discrete absorbtion issues in mids and highs (a bit at 2kHz and some at 8kHz), but nothing drastic.

Thanks for your help.

PS: images not showing:
http://i.imgur.com/R0sun6Y.jpg
http://i.imgur.com/FbKIzYN.jpg
 

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Skip the foam absorber - not going to do much of anything useful. For the front corners you need to maintain symmetry left to right. 2 flat on the walls in one corner and one straddling in the other will function completely differently.
 

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Discussion Starter · #7 ·
Thank you Bryan for your comments.
"Skip the foam absorber - not going to do much of anything useful"
at all?? I am using the foam absorber here mostly to retain some mid/highs from reflecting on the closet door (1/2 inch light wood). Why is that useless?
 

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It's only dealing with the very very high frequencies. Plus it's only on one side of the rear wall. Still have now unbalanced reflection from the other side.
 

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Discussion Starter · #9 ·
Concerning the unbalanced sound, I will place foam on the other side too. I just can't place it permanently or else the closet won't open...
The foam definitely deals with mid frequencies. Changing the place of the 1m² foam absorber makes a noticeable difference around 2-5k.
Plus, 5cm is theoretically enough to absorb at least some 3-5k, why wouldn't that apply?
 

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If you like it, use it. Just saying that most rooms already have considerably more mid/high absorption than they do lower absorption so using things like this just unbalances the decay time spectrum more.
 

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Discussion Starter · #11 ·
OK, thanks for the clarification.
My room doesn't seem to absorb much mid/highs (despite the carpet floor), but their reverb time is reasonable (under 150ms).

You mentioned earlier:
"Much of what you're hearing with that metallic zine is up high on the walls. Just cut into strips 12-18" and go around the upper perimeter."
Could you explain the theory behind this? (my level of understanding is quite good).
Are there specifically high frequency modes on the cieling perimeter? or is it simply flutter echo with the fact that the carpet floor already absorbs lots of high frequencies?

A detail that might be important:
the wall on the right side (in the drawing) is a thick building wall.
the one on the left side is much thinner and filled with air.
I am wondering if such a wall actually reflects bass frequencies... it certainly contributes to the room modes, but I feel that I should treat the thick wall with more absorbers/traps in order to compensate...

What do you think?

Thank you Bryan for your time and advice, you seem to be the only one here with enough patience to answer my concerns...
 

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Don't do anything on the side walls asymmetrically. While the walls will act differently to a certain extent you'll cause more issues than you'll fix by treating them different.

It's not just highs up high on the walls but that's what your ear is most sensitive to and it's a decent use of the foam instead of throwing it out.
 
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