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Huge standing wave, help needed

sarged

New member
Jun 6, 2016
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I get a huge standing wave of at least 15 dB @ 124 Hz in my listening position.

I use two rear ported monitors 8 inches from the wall on a desk. (can't get any further because I have too little space).

This standing wave is ruining my sound especially if I want to play rock music...

I did some research and converted this frequency to wavelength resulting in 2.74 meters.

This happened to be the exact distance from the floor to the ceiling.

The 'buzz' is mostly observed in the nearfeald.

Here is the graph with frequency response. It's not very accurate but it can be a start.

 

Benedict_Arnold

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Jan 16, 2013
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How about a fake oak beam halfway along the ceiling or one of those things they put in the National Opera?

Failing that, you could always move...
 

MajorFubar

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Mar 3, 2010
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How big is your room, how is it furnished, how is it treated, what monitors are you using. You might have to rearrange your room and introduce some acoustic treatment. These Studio Rescue videos by Francis Buckley are an excellent source of information about the subject.
 

andyjm

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Jul 20, 2012
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A resonant peak around 150 Hz is a common problem - as you pointed out it aligns with standard room dimemsions.

Peaks are relatively easy to fix if you are prepared to go down the DSP route, its the nulls that you can't do much about. If you want to avoid bass traps and the like, you can use a notch filter at the resonant frequency to tidy things up. Not sure what your budget is, but there are a number of DSP room correction products available.

I have a dreadful peak in my listening room at 130Hz, but my processor has room correction facilities and I was able to tame it with a 130Hz notch.
 

sarged

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Jun 6, 2016
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I see.. well the problem is it mainly concentrates near the speakers at the desk, so when I listen music and move a bit around the room - it's not there. If I make 15 dB correction - it's a really ugly thing to do. It will unbalance sound if I move 1 meter away. Unless I was tied up that chair... well DSP is not the way.

What I'm thinking is to put two 0.6m x 1.2m x 50mm rockwood panels, one behind the monitors and another at the ceiling just above the desk. It should reduce different kinds of standing waves and minimize reflections. I can get those quite cheap, just 8 bucks / peace for 80 kg density. I'm looking for a supplier for 120 kg now, which I think will do better but maybe cost more as well.

Though mounting can be an issue. I understand how it can be done, but I'm not a carpenter and I don't have tools. Probably will need to hire some neighbour. I've never used that insulation before though. Can someone advise if those 120 kg rockwood boards are rigid enough to handle easily? and If I don't use any cover, would that stuff scatter all over my room or unlikely so?..
 

sarged

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Jun 6, 2016
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Oh by the way. I think I undestand now why this is happening. The room width also happens to be 2x times the room's height, so it further multiplies this frequency. Unfortunately, I cannot treat the sides of the room, because there is a door and the kitchen... uhm. The door is made of porous material, it is a come kind of cheap ass particle board, so I think it should absorb some of the sound.
 

thewinelake.

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Jan 22, 2016
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120kg anything is not going to be easy to handle!! (Oh, you're talking about density!)

Why rockwood? (I've never even heard of it - is it like celotex?)

Putting foam on the walls/ceiling should help, as would rugs on the floor. Sounds like a case of experimenting.

Width on your plan is 4.5m - not twice the ceiling (sorry, I know I'm being as dense as 120kg rockwood!!!)

...and maybe another option would be to rearrange the room...
 

Muddywaterstones

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Apr 21, 2016
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I read it as Rockwool. Can certainly make panels using this but will probably look fugly in a main living space. Depends how artistic and gifted one is at DIY.
 

RobinKidderminster

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May 27, 2009
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Foam is no good. I have used Rockwool - it does need covering for cosmetic reasons - it doesn't look nice. 50mm may not be enough - you may need to think about corner bass traps. Plenty of advice for DIY and commercial here and elsewhere on the web. GIK are good for advice if you want to buy traps. U mention trying DSP - not sure how u have tried this. An antimode may be much better.

I have an antimode and DIY corner traps. Fairly happy within constraints.
 

sarged

New member
Jun 6, 2016
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Well rockwool, it's like fiberglass but it shouldn't get you itchy... in theory

The width is indeed twice the ceiling btw.

I just found out that the ceiling is pywood, and there is some empty chamber, I guess it's for electric wiring of light bulbs. Multiplying the density to the volume it tells me that each panel of that size should weight 4.32 kilos. I don't know if it will be ok to scew it directly onto plywood ceiling or would that be too heavy, and make it buldge creepily.

Maybe it could be altogether to rearrange the room, but I'm out of ideas.
 

sarged

New member
Jun 6, 2016
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Muddywaterstones said:
I read it as Rockwool. Can certainly make panels using this but will probably look fugly in a main living space. Depends how artistic and gifted one is at DIY.
Well, my room is already fugly like SH** I will probably move out in the future. The only cool thing about it is my computer and the speakers of course. :)
 

sarged

New member
Jun 6, 2016
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RobinKidderminster said:
Foam is no good. I have used Rockwool - it does need covering for cosmetic reasons - it doesn't look nice. 50mm may not be enough - you may need to think about corner bass traps. Plenty of advice for DIY and commercial here and elsewhere on the web. GIK are good for advice if you want to buy traps. U mention trying DSP - not sure how u have tried this. An antimode may be much better.

I have an antimode and DIY corner traps. Fairly happy within constraints.
If I were too choose between the panels and 2 bass traps in the corners, what would be more impactful, considering my specific room? There is one problem though about corner traps is that the door is very close to the wall - only 5 inches, so I'm not sure if I can fit it there. Also the trap in the kitchen would have to be fire resistant.
 

RobinKidderminster

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May 27, 2009
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Suggest throwing some quilts into corners just to see if things improve. Rockwool is fire resistant I think. 4kg is not a great weight over a decent area.
 

andyjm

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Jul 20, 2012
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LF resonance will laugh in face of absorbent panels. I am afraid you will need bass traps or similar to make a difference. It will be impossible to get a small room to sound good everywhere. You may find you have to choose one area for listening and put up with sub optimal sound elsewhere.
 

thewinelake.

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Jan 22, 2016
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Are those acoustic foam panels with pyramids any good?

how about applying a 5mm layer of blu-tac to all non-window surfaces?
 

BigH

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Dec 29, 2012
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Do you have any isolation under the speakers.

Really 6.5 inch woofers on a desk is not a good way to position speakers. Isolation as used in studios may help. I did try to warn you in your previous post.

Oh Rockwool is not a board its like wool so you will need to contain somehow in a frame, you can't just screw it to the ceiling. Probably needs to be 100mm thick.
 

BigH

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Dec 29, 2012
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RobinKidderminster said:
Suggest throwing some quilts into corners just to see if things improve. Rockwool is fire resistant I think. 4kg is not a great weight over a decent area.
I don't think they have quilts in Philippines, its a hot country.
 

sarged

New member
Jun 6, 2016
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BigH said:
Do you have any isolation under the speakers.

Really 6.5 inch woofers on a desk is not a good way to position speakers. Isolation as used in studios may help. I did try to warn you in your previous post.

Oh Rockwool is not a board its like wool so you will need to contain somehow in a frame, you can't just screw it to the ceiling. Probably needs to be 100mm thick.
I've just ordered a piece of acoustic foam 18x18x2 inch. That I will cut in two and use as isolation pads for the monitors.
Let's see if that will change anything but I don't even hope it will make any real difference.

Well there are two types of rock wool. boards and blankets. I suposse blankets are kind of soft and boards are rigid. especially at 120 density they should be... maybe it depends on the brand also?
 

BigH

New member
Dec 29, 2012
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sarged said:
BigH said:
Do you have any isolation under the speakers.

Really 6.5 inch woofers on a desk is not a good way to position speakers. Isolation as used in studios may help. I did try to warn you in your previous post.

Oh Rockwool is not a board its like wool so you will need to contain somehow in a frame, you can't just screw it to the ceiling. Probably needs to be 100mm thick.
I've just ordered a piece of acoustic foam 18x18x2 inch. That I will cut in two and use as isolation pads for the monitors. Let's see if that will change anything but I don't even hope it will make any real difference.

Well there are two types of rock wool. boards and blankets. I suposse blankets are kind of soft and boards are rigid. especially at 120 density they should be... maybe it depends on the brand also?
Yes I see you can get in a firmer material, not sure you can just screw these to the ceiling, maybe need more support, they are designed to go in walls or between roof rafters. They will need covering also, as don't look good and bits may fall down. I'm not convinced the ceiling is the problem, as you say its only when you are about 1m away. Bass traps behind the speakers may help more.
 

Benedict_Arnold

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Jan 16, 2013
661
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And not really having more to add than the more informed comments above...

How do you measure all this?

Where do you get the kit and softeare?

He much does it cost?
 

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