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130hz standing wave at listening position
Old 7th September 2019
  #1
Here for the gear
130hz standing wave at listening position

Hello all,

Coming through with my first post ever, I'm here to ask for advice on how to get rid of this very annoying standing wave I'm facing. I apologize if I'm breaking rules or doing it wrong.


The frequency is roughly at 130hz, I don't have fitting gear to precisely measure the amount but I'd say it's a +4dB peak. After lots of trial and error I've found out it's my desk that causes this problem. I've verified this by getting it out of the room and playing music and sounds from my monitors. I've also tried replacing the material of my desk, and I've tried replacing the table legs.

The desk is made of chipboard, it's 25mm thick. The dimensions are 80 x 180cm.
Every time I'm playing sound from my monitors (tannoy reveal 501a), when I'm speaking, or even typing this post, I hear the 130hz tone.

My room dimensions are a bit strange. The total length is 3,65m. The height is 2,5m. However on the right of my desk there's extra space that's 1,15m x 40cm.

I've loosely drawn the layout of my room https://imgshare.io/image/img-20190907-102933.yJJUH

It's also relevant that the tone gets lower/disappears when I stand up. Same goes when I put my head below the desk.

Thanks in advance

EDIT: I've placed basstraps in the corners above my monitors, as well as the upper corners behind me.

Last edited by xChimera; 7th September 2019 at 09:39 AM.. Reason: Forgot to include relevant information
Old 7th September 2019
  #2
I have the same issue at 130Hz

Acoustic Treatment - Bigger Room

Mabye I should also check if it's the desk, which has the same size. Do you hear the 130Hz also in the corners or just near the desk?
Old 7th September 2019
  #3
Gear Addict
 

Quote:
Originally Posted by xChimera View Post
Hello all,

Coming through with my first post ever, I'm here to ask for advice on how to get rid of this very annoying standing wave I'm facing. I apologize if I'm breaking rules or doing it wrong.


The frequency is roughly at 130hz, I don't have fitting gear to precisely measure the amount but I'd say it's a +4dB peak. After lots of trial and error I've found out it's my desk that causes this problem. I've verified this by getting it out of the room and playing music and sounds from my monitors. I've also tried replacing the material of my desk, and I've tried replacing the table legs.

The desk is made of chipboard, it's 25mm thick. The dimensions are 80 x 180cm.
Every time I'm playing sound from my monitors (tannoy reveal 501a), when I'm speaking, or even typing this post, I hear the 130hz tone.

My room dimensions are a bit strange. The total length is 3,65m. The height is 2,5m. However on the right of my desk there's extra space that's 1,15m x 40cm.

I've loosely drawn the layout of my room https://imgshare.io/image/img-20190907-102933.yJJUH

It's also relevant that the tone gets lower/disappears when I stand up. Same goes when I put my head below the desk.

Thanks in advance

EDIT: I've placed basstraps in the corners above my monitors, as well as the upper corners behind me.
Try to get rid of that table you seem to have standing in front of the speakers.
Old 7th September 2019
  #4
Gear Addict
 

Quote:
Originally Posted by Lilith View Post
I have the same issue at 130Hz

Acoustic Treatment - Bigger Room

Mabye I should also check if it's the desk, which has the same size. Do you hear the 130Hz also in the corners or just near the desk?
Don't put speakers on that desk.
Old 7th September 2019
  #5
Here for the gear
Quote:
Originally Posted by Lilith View Post
I have the same issue at 130Hz

Acoustic Treatment - Bigger Room

Mabye I should also check if it's the desk, which has the same size. Do you hear the 130Hz also in the corners or just near the desk?
Nope, it's only at the position my head is. I should note that moving sideways makes barely to no difference.

EDIT: the only suggestion I haven't tried yet is to hang up a cloud. That may be what we're both looking for but I'd really like to try more first.

Last edited by xChimera; 7th September 2019 at 01:57 PM.. Reason: forgot info again
Old 7th September 2019
  #6
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A desk is not going to "cause" a 130 Hz standing wave. Standing waves are modal, related only to the hard, solid, rigid boundaries of the room (in other words, the walls, floor and ceiling). Those are the only things that can cause low-frequency standing waves in a small room. It is possibly that the desk might have an effect on such a wave that is being caused by the walls, yes, but the desk is not causing it. It would be better to first find the cause and treat that, rather than treating the symptom.

For the dimensions you gave, there's no standing waves at exactly 130 Hz, but there's a huge bunch of them at 138 Hz: In fact, the 0,0,2 axial, 3,0,0 axial, and 0,2,0 axial all line up almost perfectly, right on top of each other around there (within 6Hz of each other), along with an oblique mode and a tangential mode in among them! Modal nightmare....

Quote:
I don't have fitting gear to precisely measure the amount
Then how did you determine that it is a standing wave, and that the frequency is 130 Hz? If you didn't test properly, then all you can say is that you have an unidentified tone at about 130 Hz. There's no way of knowing that it is a standing wave unless you actually check that it is.

And I'm sure you do have the equipment do check properly! You have a pair of good speakers, and I assume you have at least one reasonably good mic. So all you would need to do is this: How to calibrate and use REW to test and tune your room acoustics Yes, that says to use a special mic, but for a simple issue like this you could use pretty much any mic: you don't need high precision here: all you need to do is to identify one problem so you can fix it. You are not trying to treat your room in detail, nor are you trying to tune it with precision: you just want to identify one modal issue. So any mic will work for this.

Quote:
It's also relevant that the tone gets lower/disappears when I stand up. Same goes when I put my head below the desk.
If it is modal, then that sounds like it must be your 0,0,2 mode at 137.8 Hz. ...

Of course, it might not be modal at all: it might just be some form of resonance that seems to be modal. But REW will help you figure that out too.


- Stuart -
Old 7th September 2019
  #7
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Synthpark's Avatar
Quote:
Originally Posted by xChimera View Post
I've loosely drawn the layout of my room https://imgshare.io/image/img-20190907-102933.yJJUH
Your desk is quite large for this kind of room.

When I installed my desk in my previous room, which was larger than yours (around 33 square meters), a 50 Hz mode suddenly disappeared at listening position. I had to properly install bass traps to get the frequency back. What I want to say: a desk can have a big impact on bass, especially when it is as big compared to room dimensions as in your case, with a rather low ceiling. The whole modes calculation cannot be made like in an empty room, the vertical modes shift and do not behave the same. In adddition the table is placed in the front where SBIR effects apply. In other words: The outcome is rather unpredictable and needs careful experimentation with bass treatment, as well as speaker placement.

cheers
Old 7th September 2019
  #8
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akebrake's Avatar
 

Quote:
Originally Posted by xChimera View Post
...The frequency is roughly at 130hz, I don't have fitting gear to precisely measure the amount but I'd say it's a +4dB peak. After lots of trial and error I've found out it's my desk that causes this problem...
Probably but not entirely. At least some change in the response.

Genelec have added a Desktop EQ (dip filter) in many of their
more expensive "nearfields".

See this 2004 AES paper from Goldberg, Mäkivirta & Varla
Availible on their home site > academic papers.
EDIT: Pic2 Text from 8351 User manual
Best

https://www.genelec.com/sites/defaul...irta_varla.pdf
Attached Thumbnails
130hz standing wave at listening position-desktop-lf-.jpg   130hz standing wave at listening position-8351-desktop.jpg  

Last edited by akebrake; 8th September 2019 at 07:47 AM.. Reason: Info added
Old 7th September 2019
  #9
Quote:
Originally Posted by xChimera View Post
Nope, it's only at the position my head is. I should note that moving sideways makes barely to no difference.

EDIT: the only suggestion I haven't tried yet is to hang up a cloud. That may be what we're both looking for but I'd really like to try more first.
I did some tests again and write later in my thread. It's for sure the floor -ceiling 002 mode in my case. My head is almost sitting in the pressure maximum of that mode. Moving up or down with my head and it's getting better. Moving backward also, but that's because of the asymmetric rear wall.
Old 8th September 2019
  #10
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Quote:
Originally Posted by Soundman2020 View Post
A desk is not going to "cause" a 130 Hz standing wave. Standing waves are modal, related only to the hard, solid, rigid boundaries of the room (in other words, the walls, floor and ceiling). Those are the only things that can cause low-frequency standing waves in a small room. It is possibly that the desk might have an effect on such a wave that is being caused by the walls, yes, but the desk is not causing it. It would be better to first find the cause and treat that, rather than treating the symptom.
Yeah I didn't mean it actually CAUSES my issue, I just pointed out that moving it out of the room gave improvements.

Quote:
Originally Posted by Soundman2020 View Post
For the dimensions you gave, there's no standing waves at exactly 130 Hz, but there's a huge bunch of them at 138 Hz: In fact, the 0,0,2 axial, 3,0,0 axial, and 0,2,0 axial all line up almost perfectly, right on top of each other around there (within 6Hz of each other), along with an oblique mode and a tangential mode in among them! Modal nightmare....
It makes me happy that you seem to know what it is I'm fighting, and it frightens me that you're calling it a modal nightmare. I am by no means an expert on acoustics, just a very enthousiatic producer. I'm not familiar with words like modes or axials.

Quote:
Originally Posted by Soundman2020 View Post
Then how did you determine that it is a standing wave, and that the frequency is 130 Hz?
I used an EQ to roughly measure which frequency is so booming in my room. I have quite the trained ear. I should've used the word ''roughly'' more often in this post.


Quote:
Originally Posted by Soundman2020 View Post
And I'm sure you do have the equipment do check properly! You have a pair of good speakers, and I assume you have at least one reasonably good mic. So all you would need to do is this: [u][i][b]
I have a Scarlett CM25 MkII. I will try what the link you sent suggests.

EDIT: It's definitely 130 hz. 138hz doesn't sound nearly as booming on listening position as 130hz

Last edited by xChimera; 8th September 2019 at 12:09 PM.. Reason: did more testing
Old 8th September 2019
  #11
I put two 12 cm thick and 60×120 cm Rockwool absorbers on the floor and measured ca. 110 cm below the ceiling, which is my ear height when sitting on the floor. I measured a decrease of ca. 5 dB at 130 Hz. So a panel on the ceiling should improve it I guess, if it is the ceiling floor mode. Thinking about Basotect which is very lightweight.
Old 9th September 2019
  #12
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Synthpark's Avatar
Quote:
Originally Posted by xChimera View Post
EDIT: It's definitely 130 hz. 138hz doesn't sound nearly as booming on listening position as 130hz
I can only repeat myself: in a small room like that it is a little naive to think that all mode frequencies within 100-200 Hz with big furniture will exactly behave like in an empty room. Effective room dimensions and wave propagation are affected, by the desk, by the wardrobe etc.

Last edited by Synthpark; 9th September 2019 at 09:36 AM..
Old 9th September 2019
  #13
Here for the gear
Quote:
Originally Posted by Synthpark View Post
I can only repeat myself: in a small room like that it is a little naive to think that all mode frequencies within 100-200 Hz with big furniture will exactly behave like in an empty room. Effective room dimensions and wave propagation are affected, by the desk, by the wardrobe etc.
Replacing the desk with a smaller one is not out of the question. Do you think there's another way to deal with this? More acoustic treatment for example?
Old 9th September 2019
  #14
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Synthpark's Avatar
Quote:
Originally Posted by xChimera View Post
Replacing the desk with a smaller one is not out of the question. Do you twhink there's another way to deal with this? More acoustic treatment for example?
Yes, of course. Acoustic treatment is the way to go. I would just not expect problem frequencies to appear where expected.

What is also a bit of a problem is the asymmetry.
Old 9th September 2019
  #15
Gear Addict
 

Quote:
Originally Posted by Lilith View Post
I put two 12 cm thick and 60×120 cm Rockwool absorbers on the floor and measured ca. 110 cm below the ceiling, which is my ear height when sitting on the floor. I measured a decrease of ca. 5 dB at 130 Hz. So a panel on the ceiling should improve it I guess, if it is the ceiling floor mode. Thinking about Basotect which is very lightweight.
Has basotect the same efficiency as the same thickness of mineral wool?
I know Basotect as damping in speaker cabinets sucks.
Old 9th September 2019
  #16
Quote:
Originally Posted by bert stoltenborg View Post
Has basotect the same efficiency as the same thickness of mineral wool?
I know Basotect as damping in speaker cabinets sucks.
It's comparable with Termarock (the more dense Rockwool). For the ceiling I choose Basotect, cause it's very light weight.

I will stretch two wires from wall to wall and just lay the 2 or more basotect panels on the wires. I think this solution is more flexible than directly attaching the panels on the ceiling and you don't have to drill holes in the ceiling.
Old 2 weeks ago
  #17
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Update:

I've replaced my desk with a shorter one, like Synthpark suggested. This one is 160cm long while the previous desk was 180cm long.
Sadly this didn't change much. I'm at wit's end
Old 2 weeks ago
  #18
Is it loud on the floor too and at what distance does it get weaker? Pretty sure it's your floor ceiling 002 axial mode.
Old 1 week ago
  #19
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Synthpark's Avatar
Quote:
Originally Posted by xChimera View Post
Update:

I've replaced my desk with a shorter one, like Synthpark suggested. This one is 160cm long while the previous desk was 180cm long.
Sadly this didn't change much. I'm at wit's end
Hi

I didn't suggest to do this or anything else concretely.

All I was saying is that the table has its own influence on such a small room, probably shifting resonant frequencies.

Replacing one desk with another which is 12% shorter will most likely not do anything.

In the process of replacing the table:
Did you actually measure the room WITHOUT table, using the same mic position? This would have given more insight!

cheers
Old 1 week ago
  #20
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Quote:
Originally Posted by Synthpark View Post
Hi

I didn't suggest to do this or anything else concretely.

All I was saying is that the table has its own influence on such a small room, probably shifting resonant frequencies.

Replacing one desk with another which is 12% shorter will most likely not do anything.

In the process of replacing the table:
Did you actually measure the room WITHOUT table, using the same mic position? This would have given more insight!

cheers
Yeah didn't mean to imply that you actually suggested that, I just interpreted that might have been the issue (desk length)

As explained in the first post, I found that the tone disappears when the desk is not in the room. My monitors are on stands.
Old 6 days ago
  #21
Lives for gear
Quite normal to have a bulge around that area with a desk. Constructive interference due to path differences. Sorry! Remove desk, EQ it out, raise or lower monitors, learn to live with it - I think those are your best options. Reflections and room modes can still be contributing but to me it does just sound like typical desk reflections.
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