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Time to give up on the 80Hz null?
Old 30th June 2012
  #1
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ludwigvanlee's Avatar
 
🎧 15 years
Time to give up on the 80Hz null?

So I've got my small room that is 10 by 10 and the surface of the walls are about 50% covered with 2" or 4" absorbers and 50% of the corners, including all the tri corners have bass tube traps on them...

And I've still got a nasty 15 db null at 80Hz..

I don't even have much room left for much more treatment since it is getting really cramped and I can't really move the monitors anywhere else due to being cramped soo here are my last options..

let me know what you guys think would make the biggest difference or would be the best option

1) Replace the 5" thick twin size mattress that is covering the entire large window behind the mix position with thick absorbant fabric

2) buy a subwoofer

3) place some absorbant material on the large wooden surface drawers that take up 50% of one wall

4) keep on buying bass tube traps until I can't move around
Attached Thumbnails
Time to give up on the 80Hz null?-6-30-waterfall.jpg   Time to give up on the 80Hz null?-6-30.jpg  
Old 30th June 2012
  #2
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
I would try to move the mix spot forward or back a bit to see if things improve first. Needless to say if a room has the highest peak and lowest dip of 15db in the low end it is considered VERY nice and to have a room your shape to get to that point is actually not easy. Also keep in mind that it really is about the decay times which yours seem to be well within tolerance.
You can always keep putting in treatment but the best of rooms out there are not much better then what you have now and those start out with a much better shape.
Old 30th June 2012
  #3
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ludwigvanlee's Avatar
 
🎧 15 years
Hey Glen,

thanks a lot for the response.. I tried moving the measurement mic and the biggest difference is moving closer to the wall, which I already did..

when my listening position was a little more centered, the dip increased about 5 db.. back and forth didnt affect so much..

so do you think the only way I'm really going to be able to hear the 80Hz is using EQ on the output and possibly a sub?
Old 30th June 2012
  #4
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Jens Eklund's Avatar
 
🎧 10 years
I think you need to gain some understanding of what it takes to absorb (effectively) frequencies below about 100 Hz. Not only do you need to treat large areas, but the absorber also either needs to be very thick if velocity based (4” total depth is nowhere near enough), or you need to use pressure based absorbers and regardless of type used; they need to be placed at a surface related to the modal/SBIR –related problem that your trying to fix. If you haven’t already experimented with position, you definitely should.

Yes, your room dimensions aren’t great but I think you could do better than that, and although agreeing with Glenn that FR response is not the only important factor; decay times are as or possibly more important assuming the variations in the RF response are not very big but in this case the variation is a bit too big to call it “ok” just yet (in my opinion), even considering the unfortunate room dimensions, but it naturally depends on how much time and money (and space) your willing to lose.
Old 30th June 2012
  #5
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ludwigvanlee's Avatar
 
🎧 15 years
Hey Jen

The 2" and 4" are just for the early reflections..

for bass treatment, i use these type of tubes.. which are about 14 inches in circumference

i have 7 of them in my room already and they've done wonders for the decay times.. bass is much tighter in my room but .. i just cant hear anything at 80Hz!!!

I can probably fit all of 3 more for the corners and an additional 2 more that would just be at the sides or behind the mix position between the two speakers.. but ive read that putting bass traps outside of corners are very ineffective and shouldnt even bother..?
Attached Thumbnails
Time to give up on the 80Hz null?-bass-tube.jpg  
Old 30th June 2012 | Show parent
  #6
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Glenn Kuras's Avatar
 
🎧 15 years
Quote:
Originally Posted by ludwigvanlee ➡️
Hey Glen,

thanks a lot for the response.. I tried moving the measurement mic and the biggest difference is moving closer to the wall, which I already did..

when my listening position was a little more centered, the dip increased about 5 db.. back and forth didnt affect so much..

so do you think the only way I'm really going to be able to hear the 80Hz is using EQ on the output and possibly a sub?
I would not eq...

Just to clarify 4" of rigid fiber glass straddling corners will absorb 80hz with out any problems.
Old 30th June 2012 | Show parent
  #7
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Quote:
Originally Posted by ludwigvanlee ➡️
Hey Jen

The 2" and 4" are just for the early reflections..

for bass treatment, i use these type of tubes.. which are about 14 inches in circumference

i have 7 of them in my room already and they've done wonders for the decay times.. bass is much tighter in my room but .. i just cant hear anything at 80Hz!!!

I can probably fit all of 3 more for the corners and an additional 2 more that would just be at the sides or behind the mix position between the two speakers.. but ive read that putting bass traps outside of corners are very ineffective and shouldnt even bother..?
If you are going to go with a tube shape I would make them larger.. More like 24 inches.
Old 30th June 2012
  #8
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ludwigvanlee's Avatar
 
🎧 15 years
so would the subwoofer be the most cost effective way at this point to be able to hear 80Hz?

I really don't think adding an additional 3-5 bass tubes would erase that big null right? I mix a lot of hip hop and pop so the low end is critical..

and bass tubes at 24 inches would leave me almost no room left.. :(

so do you think I'm at the point where it wont get much better given the restrictions?

also, are the tubes less absorbant than the flat types like your tritraps and 244 bass traps?
Old 30th June 2012
  #9
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Glenn Kuras's Avatar
 
🎧 15 years
Quote:
so do you think I'm at the point where it wont get much better given the restrictions?
It really does come down to your budget.. If that was my room I would put soffit style trapping in the upper corners around the room and maybe also some tuned trapping. Keep in mind though that within one sentence I just spent a few thousand dollars.
Old 30th June 2012
  #10
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ludwigvanlee's Avatar
 
🎧 15 years
so lets assume my budget left is $1000

would it be best to

1) buy subwoofer to make up for the 80Hz null

2) invest in more bass traps

this is probably a very relevant question for a lot of fellow GSluts on a budget so I hope this gets an answer

and as always thanks for you guys very expert advice..
Old 30th June 2012
  #11
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Glenn Kuras's Avatar
 
🎧 15 years
2
Old 30th June 2012
  #12
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Jens Eklund's Avatar
 
🎧 10 years
Just to clarify: a 4" panel (porous) straddling a corner will result in a lot deeper total depth than 4", especially at the apex of the corner for tangential or oblique modes that might hit it at close to 45 degree incidence. For axial modes, the panel will be deeper at one end and shallower at the other (assuming velocity based absorber).

Also, dips can be the result of different things:

How to treat nulls

I would try to acquire a deeper understanding of the room and then treat using pressure based absorbers (but not the single Helmholtz type, slotted panels or membrane is what I would use), and make sure to target both the destructive interference causing the dip (unless it´s due to a lack of modal support at this frequency range) and also the surrounding peaks in order to even out the response. If a sub helps (due to the different location), by all means; use it. I would avoid EQ if possible and if used, primarily to tame peaks.
Old 30th June 2012
  #13
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matucha's Avatar
 
1 Review written
🎧 15 years
In my expirience, these are mostly placement related. One thing is where you're listening (and I guess you've tried moving around while listening to sine sweeps). Other thing is moving the speakers so they interact with modes so that the low-end is smoother. It's a lot of pushing around (closer/further from the front wall, wider/narrower).

It's a pitty you have to work with small square room, that's very hard.
Old 30th June 2012 | Show parent
  #14
Registered User
 
🎧 10 years
Quote:
Originally Posted by ludwigvanlee ➡️
so lets assume my budget left is $1000

would it be best to

1) buy subwoofer to make up for the 80Hz null

2) invest in more bass traps

this is probably a very relevant question for a lot of fellow GSluts on a budget so I hope this gets an answer

and as always thanks for you guys very expert advice..
You allready have a lot of so called bass traps and you still have not fixed the problem. It will not help you by just putting in some more bass traps.

Only HH resonator properly tuned will fix below 100 Hz.
Old 30th June 2012 | Show parent
  #15
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by Mctwins ➡️
Only HH resonator properly tuned will fix below 100 Hz.
Old 30th June 2012
  #16
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🎧 10 years
Oh, by the way, when using HH resonators you can forget about your room dimension.
Old 30th June 2012 | Show parent
  #17
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🎧 15 years
Quote:
Originally Posted by Mctwins ➡️
Oh, by the way, when using HH resonators you can forget about your room dimension.
Come on now - be honest with us here - are you a professional comedian? Because that was really funny........

Rod
Old 1st July 2012 | Show parent
  #18
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Tim Farrant's Avatar
 
🎧 20 years
Quote:
Originally Posted by Mctwins ➡️
Only HH resonator properly tuned will fix below 100 Hz.
I do not think this comment is entirely true. I have had great success building limp mass absorbers, easily tuned down to 30Hz. I have several times audibly experienced the change in the sound of a room whilst limp mass absorbers were being installed. It is strange, no one seems to mention them in this forum. Fibreglass panels across corners never seem to do much in my experience.

Tim.
Old 1st July 2012 | Show parent
  #19
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Tim Farrant's Avatar
 
🎧 20 years
Quote:
Originally Posted by Mctwins ➡️
Oh, by the way, when using HH resonators you can forget about your room dimension.
errrrrr, this does not make sense either. The reason why the OP has a problem is due to the room dimension. Perhaps you are trying to say they will fix problems due to room dimension? Is this a language problem?
Old 1st July 2012 | Show parent
  #20
nms
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2 Reviews written
🎧 10 years
Quote:
Originally Posted by Rod Gervais ➡️
Come on now - be honest with us here - are you a professional comedian? Because that was really funny........
Rod
No doubt.

Having "a bunch of traps" isn't what makes the difference.

It's about having the right traps, in the right locations, at a thickness suitable for the range you're trying to target.

16x16" soffits!
Old 1st July 2012 | Show parent
  #21
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Glenn Kuras's Avatar
 
🎧 15 years
Quote:
Originally Posted by Tim Farrant ➡️
I do not think this comment is entirely true. I have had great success building limp mass absorbers, easily tuned down to 30Hz. I have several times audibly experienced the change in the sound of a room whilst limp mass absorbers were being installed. It is strange, no one seems to mention them in this forum. Fibreglass panels across corners never seem to do much in my experience.

Tim.
Limp membrane traps are talked about all the time around here. Also it is recommend to straddle them in corners if panels.
Old 1st July 2012 | Show parent
  #22
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by Tim Farrant ➡️
I do not think this comment is entirely true.
Of course it´s not.

Any type of absorber (deep velocity based or pressure based; perforated panels, membranes etc.) effective at the frequency range of interest will be a solution assuming correctly positioned. Unfortunately, Some are convinced that only one type of pressure based absorber (and only from one manufacturer) works …


Quote:
Originally Posted by Tim Farrant ➡️
errrrrr, this does not make sense either.
It is also unfortunate that some people believes that a cubic room offers better possibilities to get the modal range under control. Let´s just hope they don’t convince anyone that has options regarding room dimensioning, to make the room cubic.
Old 2nd July 2012 | Show parent
  #23
Registered User
 
🎧 10 years
Quote:
Originally Posted by Tim Farrant ➡️
errrrrr, this does not make sense either. The reason why the OP has a problem is due to the room dimension. Perhaps you are trying to say they will fix problems due to room dimension? Is this a language problem?
No language problem here. The room dimension is the least/last problem, if you ask me. The OP can fix his room and still get flat freq reponse.
Old 3rd July 2012
  #24
Gear Guru
 
1 Review written
🎧 15 years
Limp

Quote:
I have several times audibly experienced the change in the sound of a room whilst limp mass absorbers were being installed. It is strange, no one seems to mention them in this forum.
Hi Tim. G.E. has experimented very extensively with pretty much all of the designs for enhanced LF absorption. He achieved the best results in the resonant membrane sub genre using wooden panels. As did the BBC.

It is of note that limp mass membrane or deadsheet type designs are still pretty widely used particularly in the UK. They work fine but evidence suggests wooden panels in the same space should work even better. I reckon many have focussed on the BBC's earlier use of Roofing Felt. They did move on after that.

Gernot has also moved on to his best DIY efforts so far. These are DIY versions of the Fuchs/Fraunhofer VPR, CBA, etc. RPG call their version Modex Plate and Modex Broadband. Gernot's test of just one large simple device in a corner shows amazing results. Perforated Panel with Porous Absorber trap

Observation over time will show Helmholtz and even variable tuned Helmholtz popping up periodically. There is a pattern of pretty damning failure in many of the attempt to persuade these to work.

These are the reasons why Limp and Helm don't get much approval here, i.e. evidence.


As you are here, the prattle visible here from a particular GS is to a totally consistent repeating pattern. Generously, one could be amused, but in reality it is a stream of miscontrued nonsense. Not to mention Shilling a device we have show to be relatively ineffective for it's intended purpose. I, and I am sure many, would welcome a little 'Tightening'. The neck area comes to mind.....


DD
Old 13th July 2013
  #25
Registered User
 
🎧 5 years
use 4 vprs 120\60cm on the corners of the room,use 10 cm basotect.poly,or iso-bond,2-1mm plate and 2 2mm plates use if you want 3cm* foem infront of the plate for 80hz It does wonders
Old 11th August 2013 | Show parent
  #26
Registered User
 
🎧 10 years
Quote:
Originally Posted by Glenn Kuras ➡️
. Needless to say if a room has the highest peak and lowest dip of 15db in the low end it is considered VERY nice and to have a room your shape to get to that point is actually not easy.
I dont understand how 15db could be acceptable. Listening to sine waves at 80, the difference between 15db seems dramatically different.


I have the exact same problem as OP....15db null at 80hz.
Old 12th August 2013 | Show parent
  #27
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1 Review written
🎧 10 years
Quote:
Originally Posted by takman ➡️
I dont understand how 15db could be acceptable. Listening to sine waves at 80, the difference between 15db seems dramatically different.


I have the exact same problem as OP....15db null at 80hz.
Just started working on my new space... 20db null at 90hz

I have a lot of possibilities for bass traps that haven't been explored...but I will be following this thread closely!
Old 12th August 2013 | Show parent
  #28
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1 Review written
🎧 10 years
Quote:
Originally Posted by BigKD ➡️
Just started working on my new space... 20db null at 90hz

I have a lot of possibilities for bass traps that haven't been explored...but I will be following this thread closely!
Gonna quote myself for the 1st time lol. Just did some experimenting to see if I could improve this big null. First I put a bunch of tri traps behind my monitors and measured the effects. The result was a reduction in the 90hz null. OK...so SBIR is very likely. Next, I moved my speakers very close to the front wall. 90hz null pretty much completely gone. So OP...try putting your monitors right up against the front wall if you can.
Old 12th August 2013 | Show parent
  #29
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Quote:
Originally Posted by takman ➡️
I dont understand how 15db could be acceptable. Listening to sine waves at 80, the difference between 15db seems dramatically different.


I have the exact same problem as OP....15db null at 80hz.
I am talking about the highest peak to the lowest null. Honestly though decay time is what you should be really looking at.
Understanding Decay Time and Waterfall Graphs - GIK Acoustics
Old 13th August 2013 | Show parent
  #30
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ludwigvanlee's Avatar
 
🎧 15 years
Quote:
Originally Posted by BigKD ➡️
Gonna quote myself for the 1st time lol. Just did some experimenting to see if I could improve this big null. First I put a bunch of tri traps behind my monitors and measured the effects. The result was a reduction in the 90hz null. OK...so SBIR is very likely. Next, I moved my speakers very close to the front wall. 90hz null pretty much completely gone. So OP...try putting your monitors right up against the front wall if you can.
I'm going to be trying this out today and I will report back the results. The area behind my speakers have a large window behind it as well - and only the right speaker's back is facing it. So I'm sure that affects things as well..
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