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Crazy 130hz Null. will a ceiling cloud help?
Old 4 weeks ago
  #1
Gear Nut
Crazy 130hz Null. will a ceiling cloud help?

I don't need a perfect flat response, i know with the resources i have in space and and money that it's just not possible, that being said, I recently decided to measure my room and it's crazy how much of the 130hz is canceling out. it's no wonder why I tend to mix bass guitar much louder than it needs to be



I have 8 2'x4'x4" panels that i keep moving around the room mostly in first reflection points and as bass traps. my ceilings are 7' height high, my desk is on a side of the room, not center (due to doors and closets and drums). After seeing this chart I started looking for where the frequencies are hiding, and after standing up on my chair i found the 130hz.

Will one of my panels panels placed in the first reflection point on the ceiling, in between my listening position and the monitors help drastically? or will it not do much? I also have Sonarworks reference which helps a lot, but i'd rather get closer to the real deal.

I know i'm not giving exact measurements, but i don't need exact results. I guess my basic question, is, what can cause a 130hz null, and how can i help it. I can't really move my monitors much but i tried and it didn't make a difference vertically or if i pointed them to a completely different wall.
Old 4 weeks ago
  #2
Lives for gear
 

Quote:
what can cause a 130hz null, and how can i help it. I can't really move my monitors much but i tried and it didn't make a difference vertically or if i pointed them to a completely different wall.
Hard to say for sure what that is without further investigation, but very likely it's your floor bounce: that normally ends up somewhere in that region for most rooms. If so, you might find that it isn't very audible! That sounds like a crazy statement for such a deep dip, but try this: set up REW to do slow sweeps from 60 Hz to 300 Hz, repeatedly in a continuous loop, close your eyes so you can't see the frequency it is making, and just listen: Do you hear a huge drop off part way through the sweep? Or do you just hear the peaks at +/-78 and +/-150 with some slight variation in other places? If you can honestly say that it's hardly noticeable, then don't worry about it. It looks ugly. but if you can't hear it, then is it really an issue? And if it is floor bounce, you can't really treat it either, other than putting something in between to block it partly, such as a desk with a console on it. Now, if you CAN hear a huge dip clearly, then it might not be floor bounce, so you'll have to investigate further. It could be modal, or SBIR, or some other form of reflection.

- Stuart -
Old 4 weeks ago
  #3
Gear Nut
Thanks, i'll give that a try when i can make some noise. my floors are carpet so i was hoping that wouldn't have been the issue, though i'm aware carpet wont stop bass much.

I have done a similar test with sin waves between 100-300hz, and the drop off is very noticeable, at around 120- 130 it almost feels like half the volume is coming out. If i stand up on my chair it is noticeably louder, it feels like the tone is just sitting up there in the air..
Old 4 weeks ago
  #4
Lives for gear
Can be floor effect, or room modes (null).

Dimensions of the room?
Old 4 weeks ago
  #5
Lives for gear
Floor effect :

From my calcul (so in theory) for a floor effect at 130Hz, Distance between you and your speakers should be around 150cm.
And if your speakers are around 120cm (height from floor) and your ears are at same level (120cm).

Room mode :

If your ceiling is 230cm, and your speakers are positioned at half that distance (so about 115cm)...it can be your 0-0-2 room mode.

Let us know
Old 4 weeks ago
  #6
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Synthpark's Avatar
Quote:
Originally Posted by iamdro View Post
I have 8 2'x4'x4" panels that i keep moving around the room mostly in first reflection points and as bass traps.
You can try with 16-20 inch blocks with low flow resistivity material instead of thin panels.

Last edited by Synthpark; 4 weeks ago at 12:42 PM..
Old 4 weeks ago
  #7
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akebrake's Avatar
 

Quote:
Originally Posted by JayPee View Post
Floor effect :

From my calcul (so in theory) for a floor effect at 130Hz, ...
I would like to add to that comment:
The dip is centered at 122,5 Hz. (not 130)
And with an untreated ceiling we have a ceiling bounce also.
Plus wall bounces (SBIR) and modal nulls adding to that dip as suggested by Stuart.

Quote:
Room mode :
If your ceiling is 230cm, and your speakers are positioned at half that distance (so about 115cm)...it can be your 0-0-2 room mode.
Ceiling hight 7ft (2.13m) and mode 0.0.1 @ 81Hz. Mode 0.0.2 @ 162 Hz. (two nulls like pic 2)

If the woofer is positioned halfway between floor and ceiling it’s positioned in a peak of 162Hz and will drive that mode quite efficiently.
It would be heard then, but I guess other reflections & modal nulls will cancel that peak.


@ iamdro

We don’t know the exact spkr listener positions and the other dimensions of the room... A rough sketch would be fine.

(Sometimes I enjoy myself with drawings like the ones below to illustrate my points)

Best
Attached Thumbnails
Crazy 130hz Null. will a ceiling cloud help?-iamdro-floor-bounce.jpg   Crazy 130hz Null. will a ceiling cloud help?-iamdro-mode-0.0.2.jpg  
Old 4 weeks ago
  #8
Gear Nut
Quote:
Originally Posted by akebrake View Post
I would like to add to that comment:

We don’t know the exact spkr listener positions and the other dimensions of the room... A rough sketch would be fine.

(Sometimes I enjoy myself with drawings like the ones below to illustrate my points)

Best
This is the best i could do. i'm not an artist.



I have 6 Owens corning 703 4" panels 2'x4' mostly in the first reflection points/ as bass traps in the corner and also some aurelex foam spread around to help with flutter echos.

My basic question is, do I place one above the listening position, or is it futile and not going to make a difference?
Old 4 weeks ago
  #9
Gear Head
 
Mark Alpine's Avatar
Wouldn't it be better to move the desk towards the wall on the right hand side?
Old 4 weeks ago
  #10
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akebrake's Avatar
 

Unsymetrical spkr placement.

Quote:
Originally Posted by iamdro View Post
This is the best i could do. i'm not an artist.

That sketch is perfectly fine and will (partly) explain your ”crazy 130Hz null”.

With the Right speaker close to the corner, and the Left ≈5 ft away from that corner, your L& R freqency responses are totally different
and the L+R is unpredictible.

This spkr/ listener position is very difficult (impossible?) to fix.

On the positive side, your room dimensions (ratio) are quite good.
Well, ceiling hight a bit low...

1. For a start: Move the speakers to the right wall (sketch 2) to get a symetrical L/R position. (Note: Sketches are not to scale)

2. Take some REW measurements and upload mdats here.
Always measure L/R speaker separately. (L+R optional)

3: Add as large, thick, corner, rear wall and ceiling trappings you can afford.

Best
Attached Thumbnails
Crazy 130hz Null. will a ceiling cloud help?-iamdro-orig.jpg   Crazy 130hz Null. will a ceiling cloud help?-iamdro-plan1.jpg  
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