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Are my speakers in a null?
http://www.johnlsayers.com/phpBB2/viewtopic.php?f=3&t=2441
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Author:  Felix Hoo [ Thu Jul 09, 2009 7:02 pm ]
Post subject:  Re: Are my speakers in a null?

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:

Author:  macrylinda1 [ Wed Jul 28, 2010 1:34 pm ]
Post subject:  Re:

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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Author:  knightfly [ Sun Aug 15, 2010 12:44 pm ]
Post subject:  Re: Are my speakers in a null?

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

Author:  tomislav [ Sat Feb 19, 2011 9:54 pm ]
Post subject:  Re: Are my speakers in a null?

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?

Author:  gullfo [ Thu Mar 17, 2011 1:09 am ]
Post subject:  Re: Are my speakers in a null?

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.

Author:  sayyousayme [ Thu Jun 02, 2011 11:50 pm ]
Post subject:  Re: Are my speakers in a null?

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

Author:  gullfo [ Fri Jun 03, 2011 2:04 am ]
Post subject:  Re: Are my speakers in a null?

the blue locations are a good starting point from the model - the actual room response will dictate their final positions.

Author:  JohnTrumpet [ Wed Oct 26, 2011 9:42 pm ]
Post subject:  Re: Are my speakers in a null?

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.

Author:  lindastacy3 [ Sat Oct 03, 2015 5:28 pm ]
Post subject:  Re:

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.

Author:  DanDan [ Sat Apr 15, 2017 5:14 am ]
Post subject:  Re: Are my speakers in a null?

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

Author:  Soundman2020 [ Sat Apr 15, 2017 6:59 am ]
Post subject:  Re: Are my speakers in a null?

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.


- Stuart -

Author:  Sarahk [ Fri May 25, 2018 3:04 am ]
Post subject:  Re: Are my speakers in a null?

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.

Author:  Soundman2020 [ Fri Jun 15, 2018 12:08 pm ]
Post subject:  Re: Are my speakers in a null?

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 -

Author:  knightfly [ Fri Mar 29, 2019 8:06 am ]
Post subject:  Re: Are my speakers in a null?

Since it seems to be fashionable to resurrect dead threads, thought I might as well put up a current link to the Harman spreadsheet being used -

https://www.harman.com/room-mode-calculator (too simple, right?!?!)

BTW, this is more of a "quick and dirty" approach that can help SOME of the problems in a room; NOT to be confused with the herculean efforts by Stuart (AKA Soundman2020) to show us all the REAL way to do a MUCH MORE ACCURATE job, using REW and an inexpensive (but special, and necessary) mic -

viewtopic.php?f=3&t=21122

I'm getting close to taking advantage of Stuart's generosity myself; about a month ago my "production" computer took a massive dump, so far I've not been able to resurrect ANY of my info on its boot drive, even with external interface adapters to turn it into a USB drive. The OTHER drive, a 10krpm WD, responds OK and I can get at any and all files on it - the boot drive spins up but nothing else - it's now a project for a crappy day LATER :horse: And yes, I WAS a bad boy; did NOT keep up with backups, couldn't happen to ME, right??

Anyway, that little "glitch" pushed me to decide to replace that ONE computer with two - one already here, a Win7(64bit) laptop, to be used for networking/portable sound, including REW and a newer measurement mic - opted for the Dayton emm-6; good reviews (incl' Stuart's list) and reasonable price ($68 usd @ amazon) - it'll get used with a Focusrite 6i6, just now ordered, and that interface will likely spend MOST of its time with my eldest grandson (the one EVERYBODY wishes they had :=) - he's 19, already makes me look like I shoulda sold at least a dozen of my guitars and at least a few of my keyboards...

My new main system is a Dell, originally bought from Costco - not a complete screamer, but core i7/3.6 gHz, Win 10 Pro; now with 32 gb ram, added firewire card, the original 1 tb drive will get relegated to storage and a pair of 1 tb SSD's added for recording/rendering. It has a separate nvidia graphics card with 4 gigs ram, both DP and HDMI ports (both going to their respective 28" Samsung UHD monitors, and the MB mounted HDMI is going to a third, 22" monitor for a "3 piece desktop" - all 3 monitors will get mounted to a 4 monitor VESA rack that clamps to rear center of the desk, sitting high enough for a hardware mixer NOT to block them, and rearward enough from a pair of my original K-Rok passive monitors - those worked really well with a Yamaha dual 8" powered sub in this room several years ago...

In addition to the Focusrite for me and "super kid", I also ordered 2 new MOTU interfaces, the 24Ai and the 8pre-es - these will give a total of 24 balanced line ins, 8 mic/line pre's and 10 analog outs, ignoring any ADAT stuff.(all on the BACK panel where they belong) - Motu's newer line have the "AVB" bus, basically gigabit Ethernet for musicians - latency around a couple milliseconds, bunch more whistles and bells, check it out on motu's site so you don't hafta skim thru a dozen MORE pages here :=)

Now, the NOT quite so cool part - for the next couple YEARS, all this cool stuff (and more) needs to get crammed into a spare bedroom, while I figure out how I'm gonna do (and pay for) adding a 12'x48' addition onto my shop, tearing out a couple walls, building an outer frame(s) so my (finally, after 3 decades) old studio can go from a total of 432 square feet, to 1152 square feet, with room for ALL my toys (some of which were bought over 10 years ago, and are still in their boxes - and no, I have NOT yet slashed my wrists, sometimes anticipation just hasta be enough :roll: )

The "sorta" good news - that spare bedroom, altho small, isn't a TOTAL disaster (or won't be, when I move 1 desk and 3 HUGE bookshelves out of it) - I've attached a basic axial mode shot (my 20 yr old roomtune still works, for what it is)

Attachment:
RoomTune-SteveBR-sm.jpg


- also, there's a 4.5'wide closet in the CENTER of what will be the back wall (behind mix position) that will likely get a pair of sliding rockwool "doors", open to get at stuff and closed to make noise :=)

This project is also turning into the kick in the ass I've needed to get around to tossing a bunch of antiquated crap (no, not me I hope) that I've hung onto for 'way too long - hoarders and small houses are Dante's version of Hell (Abandon all hope, ye who enter here - )

Gotta go, more crap to ditch; I hope everyone's well... Steve

Author:  Gregwor [ Fri Mar 29, 2019 4:34 pm ]
Post subject:  Re: Are my speakers in a null?

Quote:
Now, the NOT quite so cool part - for the next couple YEARS, all this cool stuff (and more) needs to get crammed into a spare bedroom, while I figure out how I'm gonna do (and pay for) adding a 12'x48' addition onto my shop, tearing out a couple walls, building an outer frame(s) so my (finally, after 3 decades) old studio can go from a total of 432 square feet, to 1152 square feet, with room for ALL my toys (some of which were bought over 10 years ago, and are still in their boxes - and no, I have NOT yet slashed my wrists, sometimes anticipation just hasta be enough :roll: )

The "sorta" good news - that spare bedroom, altho small, isn't a TOTAL disaster (or won't be, when I move 1 desk and 3 HUGE bookshelves out of it) - I've attached a basic axial mode shot (my 20 yr old roomtune still works, for what it is)

- also, there's a 4.5'wide closet in the CENTER of what will be the back wall (behind mix position) that will likely get a pair of sliding rockwool "doors", open to get at stuff and closed to make noise :=)

This project is also turning into the kick in the ass I've needed to get around to tossing a bunch of antiquated crap (no, not me I hope) that I've hung onto for 'way too long - hoarders and small houses are Dante's version of Hell (Abandon all hope, ye who enter here - )

Gotta go, more crap to ditch; I hope everyone's well... Steve

Woah! He's back!

Time for a design thread from you is it!???

I'm very excited to this unfold!

Greg

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