# Diffusion or absorption?



## Martin_Cph (Oct 2, 2009)

Hi all, Hope you can help.

My room is a rather big as it contains my kitchen, my dining room and my living room. Its consists of several rooms, but the main room where the speakers are placed measures 455cm wide by 960cm long, 230cm to the ceiling.

Floor is massive wooden oak planks. Walls are brick; most walls are actually covered with panorama windows. Front wall behind speakers is however plaster/knauff with fiber and paint, and rear wall is all windows and overall both sides are more or less open to either the kitchen or a second living room. However the front area around the speakers does have sides. To the left there is a plaster wall with a glass door (thick glass in massive maghony). To the right a big panorama window covering ¾ from top and down.

A big heavy carpet is placed between the speakers. In the remaining space some midsize carpets are placed strategically. Paintings and minor bookshelves cover only a fraction of the walls. A three seat sofa is placed against the side and 3 meter dining table (60 mm thick massive oak standing on a thin carpet) in the far end. That is pretty much all the furnishing in the rather large room.

My system is on center in the room, and it seems to works well. 

I only listen to two channels and I have no subwoofer located in the room. Stereo imaging and stage size is key for me.

I have in total 9 sheets of 15mm Rockfon acoustics panels produced by Rockwool placed behind the speakers only to adjust the RT60 down a bit. They only work from 500hz and upwards with a Noise Reduction Coefficient around 1.

I have not yet treated the sidewall 1st reflection points as haven’t made up my mind yet. 
Should go for diffusion or absorption? I see many placing multible basstraps i all corners in a room. Doesnt that kill the energy in the music? Maybe great for recording but what about for reproduction?

Should I go for mobile (wife acceptance) basstraps placed on stands with rubber wheels underneath. 
Height two pieces of 703?

Or 

Same height mobile difussors

I currently have a nasty dips in my response around the 50 hertz (not the speaker; Dali MS4), and I would like to have this smoothed out. 

I will naturally upload any measurement you like from REW..


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## bpape (Sep 14, 2006)

Can you post a sketch of the area so we can better see what's happening - or maybe a pic or 2? You'll need to use the post padding thread as you have to have 5 posts I believe before you can do pics.

Bryan


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## Martin_Cph (Oct 2, 2009)

Restrictions should be immediately lifted for donating members...hmm?


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## bpape (Sep 14, 2006)

Sorry Martin. Wasn't paying attention. Not sure if that's even a doable thing. No matter, you have enough posts now.

Bryan


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## Martin_Cph (Oct 2, 2009)

These are my speakers - Dali MS4 without sub - 2 channels only.


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## bpape (Sep 14, 2006)

Not seeing anything. Tried to do an edit on your message in case it was just a link problem but nothing there. Just embed it in your post using the icon that's yellow and looks like a mountain.

Bryan


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## Martin_Cph (Oct 2, 2009)

I see it fine? 

Thanks...I used the postcard icon that lets you write the url/deeplink to the picture..

Funny?


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## Martin_Cph (Oct 2, 2009)

Does the drawing show now?


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## bpape (Sep 14, 2006)

Still don't see it - sorry.

Bryan


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## glaufman (Nov 25, 2007)

Bryan, you still don't see it? I do. Back in the original post?
Or am I missing something?


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## bpape (Sep 14, 2006)

Sry - yes, I can see it now.

Diffusion at the ceiling reflections would be nice but behind the speakers probably won't do much of anything for you. 

Try an experiment. If you move the speakers say 6" closer to the front wall, does the 50Hz dip change any? Shift frequency?

Bryan


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## Martin_Cph (Oct 2, 2009)

So this is what I ended up with; the green curve is the current status-curve.

Moving the speakers closer to the front wall increased the bass again. How can I level this out even more? Any suggestions.

This software is so cool...I must have made more than 100 sweeps during the weekend.:blink:


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## Martin_Cph (Oct 2, 2009)




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## Martin_Cph (Oct 2, 2009)

The 9 sheets of 15mm Rockfon acoustics panels seems to work well in the higer mid-to highs.


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## glaufman (Nov 25, 2007)

If you want it flatter in the bass region, start taking scans from 15-200Hz, with no smoothing, to see the details in what you're getting there. To look at the waterfall, make sure the frequency axis is in log mode.


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## Martin_Cph (Oct 2, 2009)

What kind of settings should I use for the waterfall besides the log scale? Time range and window?


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## Martin_Cph (Oct 2, 2009)

Why are my peaks so high on the waterfall and not on the standard SPL curve?


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## Martin_Cph (Oct 2, 2009)




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## bpape (Sep 14, 2006)

You're recording REALLY loud. Careful of those tweeters. Base level should be about 75db

Bryan


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## Martin_Cph (Oct 2, 2009)

bpape said:


> You're recording REALLY loud. Careful of those tweeters. Base level should be about 75db
> 
> Bryan


WHAT???:sarcastic: 

It keeps telling me that the level is to low when i test before recording. I calibrate using my RS-meter at 75dB. Maybee my seetings are wrong somewhere?


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## bpape (Sep 14, 2006)

Could be 'cause you're a lot hotter than that on the charts. 

Bryan


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## Martin_Cph (Oct 2, 2009)

bpape said:


> Could be 'cause you're a lot hotter than that on the charts.
> 
> Bryan


You lost me here...:sweat:


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## bpape (Sep 14, 2006)

Sorry - bad sentence construction. Was just saying that something was likely set wrong elsewhere since the charts are so different in SPL.

Bryan


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## glaufman (Nov 25, 2007)

Hmmm... something not right... if I understand correctly, REW says the levels are low, but when you run the scan they're up in the stratosphere? Probably flipped a radio button or changed a connection somewhere you don't realize or remember... 
Try re-running the check-levels routine from the soundcard tab in the settings pop-up. When you have the tone playing, take a screenshot showing the VU meters AND all the settings in the soundcard tab and post it...

You have the dial on the RS meter set to 80, right? And you remembered to save the SPL calibration?


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## Martin_Cph (Oct 2, 2009)

I only use the RS meter to check the level from the amp measured at the EMC8000 - this is always set at 75dB. Do I need a calibrationfile for the EMC8000? The soundcard EMU is linear OK.


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## bpape (Sep 14, 2006)

If you have a cal file, that would be great, though it won't address the levels. Something has changed. The difference between your FR plots in post 12 and post 18 are quite a bit. 18 pretty closely matches the waterfall.

Bryan


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## glaufman (Nov 25, 2007)

^^^+1


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