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PostPosted: Thu Jul 09, 2009 7:02 pm 
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Location: Florida, USA
Ok forgive my noobnest.. but how did you

1) derive the width of the rectangular boxes coming down from the waveform? :?:
2) derive where the rectangular boxes start from the waveform? :shock:


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PostPosted: Wed Jul 28, 2010 1:34 pm 
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knightfly wrote:
If your room's length includes the depth of the rear trap, then your speakers would be in a null front to back that's the 4th harmonic @ 138 hZ; Width-wise, your speakers are as good as they can get - you forgot to list the height of your speakers or your head, so I can't say about any nulls in the vertical axis.

Your head is in another null of the same 4th harmonic of length, or 138 hZ - you should try moving your head rearward by about 4-6", and your speakers forward by about the same.

Heightwise, neither your ears or your woofers should be at 48", they should be either 40-42" high, or at 56-58" high. It's likely that the 40-42" will be more practical.

Hope that helps... Steve

Each woofer is 44 inches from the wall.
The center of each is 51 inches apart.
The center of each is 45 inches from the floor.
The woofer is 36 inches from the front wall.
I am sitting 6' 2'' from the front wall(this was the only measurement I had correct).


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PostPosted: Sun Aug 15, 2010 12:44 pm 
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Hey guise, haven't been here in ages but here's an updated link to the harmon spreadsheet

http://www.harman.com/EN-US/OurCompany/ ... ulator.xls

Grab a copy before their archives get redone by somebody's trunk monkey... Steve

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PostPosted: Sat Feb 19, 2011 9:54 pm 
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Location: Sibenik, Croatia
as I understand this I could just use this image you made and scale it up to fit my room?
then I would just need to measure where are the green spots and I would be good?


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PostPosted: Thu Mar 17, 2011 1:09 am 
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as a general rule, the modes are 1/2, 1/3, 1/4, etc of the wavelength supported by the room boundaries. attached is a quick and dirty (imperial) grid set for mode spacing and generic 1/3 / 1/4 spacing which can help for a rough estimate. if you soffit mount properly, many of the speaker placement issues go away. if not, then the mode locations are a good starting point for identifying places to start with your speakers, absorption, etc. dividing the 1/3 and 1/4 down to 1/6 and 1/8 are also useful for hanger and cloud placement etc.


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PostPosted: Thu Jun 02, 2011 11:50 pm 
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Location: South West Wales, Carmarthenshire
Hi all

I took a stab at doing this and here's my result:

Attachment:
Room Mode Plot of Positions for Forum.JPG


I do have one question..... The areas I have filled with turquoise - are they ok for speaker placement as well? My thoughts are that in those spots, they are not in modal strong points (like the green squares), but also they will allow me to have the monitors up close to the front wall, which will minimise SBIR issues.

Any thoughts?

Cheers

Max


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PostPosted: Fri Jun 03, 2011 2:04 am 
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the blue locations are a good starting point from the model - the actual room response will dictate their final positions.

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PostPosted: Wed Oct 26, 2011 9:42 pm 
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Location: Warwickshire, England
There's one thing I don't understand about the results from this technique - how come, in a symmetrical room, they are not symmetrical? This will surely skew the results depending on whether you align the 'length' graph with the left or the right hand wall, and the 'width' with top or bottom.


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PostPosted: Sat Oct 03, 2015 5:28 pm 
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knightfly wrote:
If your room's length includes the depth of the rear trap, then your speakers would be in a null front to back that's the 4th harmonic @ 138 hZ; Width-wise, your speakers are as good as they can get - you forgot to list the height of your speakers or your head, so I can't say about any nulls in the vertical axis.

Your head is in another null of the same 4th harmonic of length, or 138 hZ - you should try moving your head rearward by about 4-6", and your speakers forward by about the same.

Heightwise, neither your ears or your woofers should be at 48", they should be either 40-42" high, or at 56-58" high. It's likely that the 40-42" will be more practical.

Hope that helps... Steve


I think you are right. We should follow your instructions.


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PostPosted: Sat Apr 15, 2017 5:14 am 
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Location: Cork Ireland
Quote:
The woofer is 36 inches from the front wall.

I suggest this is probably causing deep FWBIR nulling. http://www.mh-audio.nl/CancellationFreq.asp
DD


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PostPosted: Sat Apr 15, 2017 6:59 am 
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DanDan wrote:
Quote:
The woofer is 36 inches from the front wall.

I suggest this is probably causing deep FWBIR nulling. http://www.mh-audio.nl/CancellationFreq.asp
DD

You are replying to a post that is nearly seven years old, Dan.


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PostPosted: Fri May 25, 2018 3:04 am 
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Hey I realize this post is a little late but I would say your speakers are in a null. I'd recommend using computer software to help you more accurately map out where to place your speakers. I'm sure you figured out how to resolve the problem.


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PostPosted: Fri Jun 15, 2018 12:08 pm 
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Quote:
Hey I realize this post is a little late
Yep. About a decade and a half too late, actually....


Quote:
but I would say your speakers are in a null
How did you figure that out? And a null for what frequency?


Quote:
I'd recommend using computer software to help you more accurately map out where to place your speakers.
Which software? In what way would you use it to determine if he is in a null or not? Please explain....

But before you do that: Please read the forum rules for posting (click here). You are STILL missing something rather important, even after being warned about it several times...

- Stuart -

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