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While the piling up of frequencies at or above 150Hz is certainly worse than lower (and almost always is), this does not negate the need for decay time control down that low. Also, look at the offending frequencies that are piling up. They're almost all primarily interactions between the length and width multiples. Addressing the fundamentals of those dimensions will help the multiples also.

Also, remember 2 things:

- Predictions are very useful and should be paid attention to - but they're just predictions. Real world measurements will almost certainly be very different.

- ModeCalc only addresses the axial modes of a room. Axials are by far the most powerful of the room modes. However, the tangentail and oblique modes of a room are MUCH lower in frequency. They can also easily pile up on each other and on the axials to turn somewhere that looks innocent enough into a place where you have many different things piling up on each other. Please don't get me wrong. I'm not trying in any way to minimize ModeCalc or it's usefulness. It's very handy to get a quick look at the main axial issues in a room.

- Calculations of a rooms modal issues look at the information in a void. They do not take into account the position of the speakers, the subwoofer, or the listening position(s) - all of which can be used to your advantage (or against you) to address frequency response related issues to a certain extent.

I'm not trying to minimize the use of ANY room mode calculator. I simply want to make sure that you don't make decisions on how deep your absorbtion NEEDS to go based simply on an axial modal analysis that looks like most of your modal overlap happens above 150Hz. This will ignore the issues I stated above - not to mention the general decay time issues that will be present in pretty much every room.

Bryan
 

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Discussion Starter #42
Scott,I think I will cut large openings in my triangle tops and just cover it the same way with the material.

Bryan and Scott ,thanks for sharing your expertise, your informative posts have been very helpful .
 
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Quick question. for bass traps is it necessary to run the foam trap up the lenght of the wall to the ceiling? or just lay one on teh ground?
 

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What a great thread!!! Wow, thanks Scott and Bryan for the truly professional (if somewhat dizzying :rubeyes: ) help.

My question regards my room which has strange "corners"--meaning that my back L is about an 11' angle wall with a fireplace in it, my back R has a 4' closet on it (meaning 2 corners) and my front R has a door close to it with the SVS parked there, and the front L has a double door right to the corner. Overall room size is 15D x 27W x 8H.

I'm a newbie so I don't know how to post a pic!

So, if I were to use a "corner" trap--where would it be? and how effective could it be (especially considering that the one backwall corner actually faces away from the SVS).

Much thanks for the help!

Phil
 

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This is a great thread. Just wanted to put in my $.02.

Corner traps are easy, even I, with no juxtaposed thumbs (but a brother with tools!) managed a pair, and they work great (and augment the performance gains from sub eq). Mine are combo oc703 and acoustical cotton in a minimal framed enclosure found in this thread:

http://www.hometheatershack.com/forums/home-audio-acoustics/736-corner-traps-wall-treatments.html

If I can do it, so can anyone lurking here. And they work great. So do my diy oc703 wall panels.

Even the wife can appreciate the difference.

Another tip of the hat to Ethan, Bryan, Scott and others who preach the gospel on this subject. :T
 

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I had forgotten those pics - still get a kick out of the Marshall logo!

Bryan
 

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Discussion Starter #50 (Edited)
I finally finished my second pair of corner traps and as hoped they did bring about further improvements.The biggest improvements are most apparent when listening to music with bass guitar and acoustic bass.Midbass is much tighter and more detailed sounding with much less overhang. This was the frequency range I really wanted the traps to be most benificial and they did'nt disapoint.

Adding the traps along with the previously built acoustic treatments certainly has been the most bang for the buck tweak that Ive done.My room is small but I was able to fit quite a bit of treatment into it without it taking up much space or making it look too ugly.(although my Wife may not agree with that last statement)

Here is a list of treatments.

2 corner traps in the lower front corners.

2 corner traps in the upper rear corners

2 8" thick rockwool panels behind the main speakers(for SBIR reduction)

2 3" rockwool panels at the side wall first reflection points

several small 2"fibreglass panels on the upper rear wall to reduce reflections.

Im soon going to be removing the thick pile carpeting and replace it with a harwood floor.This will probably make the room much more lively so I may need to treat the ceiling.But That may be a bit of challenge.
 

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That's exciting F1--could you post some pics of your "treated" room for us?
Thanks,
Phil
 

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Nice job, F1. You inspire us...
 
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I am building 88" 24x17 corner traps. I was wondering if you have any tips on stretching the fabric. I built frames last night and will order some 703 and GOM over weekend.
 

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Discussion Starter #58
Hi crg,I bet those large traps will work great.
As far as tips , I just started on one side and secured the fabric the full length of the frame with an electric staple gun.I then pulled it as tightly as possible to the one side then stapled it.Then the top then the bottom.Im not sure about the GOM but the fabric I used was very strecthy so it was easy to get tight so that there were not any wrinkles.

Good luck and when you get them done be sure to post some pictures.
 

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Discussion Starter #60
Wow those are huge,I wish I had the space for something that big.NicelyDone.

btw your helper is a little cutie.
 
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