#1925129 - 04/10/08 03:25 PM
Found the problematic peak and which corner it lives, now?
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Emre Yazgin
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Registered: 04/10/08
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On carefully studying the methods Ethan suggested I have checked the room modes, then confirmed the big peak at 124 hz by the SPL and test CD method obtained from Ethan's website.
5 minutes ago I have also produced a 124 hz test tone via computer software and by testing all corners with an SPL meter found that the biggest problem is in the right bottom corner of the room.
My question, is the corner bass trap method the best method for eliminating the bass buildup in that corner? Or should I go for something more tuned like a helmholts resonator?? Any other ideas?
Thank you so much in advance.
Emre
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#1925178 - 04/10/08 05:24 PM
Re: Found the problematic peak and which corner it lives, now?
[Re: Emre Yazgin]
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Speaker Boy
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Registered: 02/04/08
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Loc: Santa Barbara, California
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Are you making a recording studio or are you just an audio nut like me?
You dont want or need to build a helmholtz resonator. 124hz is not that low and a 4" thick 703/705 panel placed across the corner should absorb pretty well.
I am sure you have plenty of problems at other frequencies so the broadband absorption of rigid fiberglass will be useful. You should try to keep your room as symetrical as possible. Try to put panels in the right and left vertical corners at a minimum.
This link has lots of good data and explains almost everything.
http://www.ethanwiner.com/acoustics.html
Here is a link for building panels(you want to use 4" fiberglass so scale the measurements accordingly)
http://www.instructables.com/id/Make-accoustic-panels-for-your-recording-studio-or/
It you want to save a lot of money you can use rockwool(Roxul,Fibrex) or ultratouch cotton. But they are less rigid than the rigid fiberglass and are harder to work with.
You should also treat the first reflection points of your room. This will greatly increase your soundstage, eliminate comb filtering, and improve your imaging.
Jeff
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#1925242 - 04/10/08 08:24 PM
Re: Found the problematic peak and which corner it lives, now?
[Re: Speaker Boy]
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Emre Yazgin
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Hi and thanks for the reply. I am both an audio nut and a young audio engineer. Therefore both  I have just moved into a new apartment, its a big room for UK standards and also because the ceiling and walls are all seperated with plasterboard or a similar material they are probably acting as natural absorbers, therefore when
I insepected with an RTA software I didn't find lots and lots of problems, just one significant null and one peak at 124 hz.
I have 8 slabs of rigid mineral wool of 60kg/m.cube. I think I should use them according to your directions. Thanks once again.
Emre
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#1925619 - 04/11/08 05:44 PM
Re: Found the problematic peak and which corner it lives, now?
[Re: Emre Yazgin]
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Speaker Boy
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Can you post a graph of you frequency response?
Jeff
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#1926776 - 04/14/08 08:40 AM
Re: Found the problematic peak and which corner it lives, now?
[Re: Speaker Boy]
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Emre Yazgin
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Ive purchased the ETF 5 for this purpose and I am now seeing that the deviation of dBs is much more than the test Ive done using Ethan's test samples!? There was max 10-12 dBs of deviation between the peaks in the manual SPL meter test, however with the ETF sweep test the deviation is much larger! I am not even sure which one is correct, or if my methodology is wrong!?..but the problematic peak and nulls are at the exact same frequencies in both cases.
I am posting the ETF screen.
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#1926778 - 04/14/08 08:43 AM
Re: Found the problematic peak and which corner it lives, no
[Re: Emre Yazgin]
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Emre Yazgin
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#1926905 - 04/14/08 11:20 AM
Re: Found the problematic peak and which corner it lives, no
[Re: Emre Yazgin]
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Speaker Boy
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This graph is more what you would expect from an untreated room. The ETF sweep test is more characteristic of how your room responds to music. So this graph is the correct one.
The good news is the worst frequencies are above 100hz(Rigid Fiberglass will work fine). The bad news is your peaks and nulls are bad enough that you might need more than 8 slabs of rigid mineral wool. Try the 8 slabs in the corners and see how your response changes. You should buy some more mineral wool to treat your first reflection points. 2" thick will work for the reflection points. But thicker is always better.
Jeff
Edited by speaker_boy (04/14/08 11:23 AM)
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#1927919 - 04/16/08 06:01 AM
Re: Found the problematic peak and which corner it lives, no
[Re: Speaker Boy]
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Emre Yazgin
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Thanks for the reply eff, when mentioning "use all 8 slabs" do you mean I should build 8 panels ? Because I was thinking to combine 2 slabs for each panel so that they are 10cm thick each. Also do you think a regular panel put diagonally in the corner is better than cutting the slabs triangular and building it like readymade corner bass trap shape?
Cheers,
Emre
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#1928527 - 04/17/08 12:36 PM
Re: Found the problematic peak and which corner it lives, no
[Re: Emre Yazgin]
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Speaker Boy
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For right now you can combine 2 slabs together to make 4 panels. Then measure your response again. Most likely you will need more panels in more corners to get the response you want.
Building corner wedge traps will absorb more bass and go lower than just placing a panel diagonally across a corner. Here is some data showing the difference. NOTE: Any data below 100hz is not considered to be reliable.
http://forum.studiotips.com/viewtopic.php?t=536
As you can see the corner wedge has about 25% extra absorption (50% at 60hz). But the corner wedge uses three times as much material. Here are four reasons to used a corner wedge IMO.
1. If cost is no object. You just want to best response and want to do all you can to get there.
2. If you can't treat very many corners so you need to get the most out of the corners you are treating.
3. If you have major problems below 80hz. Getting rid of 50hz peaks is not easy. Panels across most of the corners might not be enough.
4. You like the clean look of the wedge across the corner.
I have corner wedges for my two back corners. But I meet all four of my criteria. I spent about $125 in ultratouch cotton to treat the two 8ft corners. My listening position is so bad that even with these corner wedges here is my response.
http://forums.musicplayer.com/ubbthreads...rue#Post1917333
Another setup is to put a 12" wide panel behind your panels. Shown here
http://forum.studiotips.com/files/double-corner_645.jpg
This setup only uses two more slabs per corner. But gives some low freq gain.
Jeff
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