I heard that broadband bass traps are ineffective below 100 hz?

C

crimsonhawk47

New member
I read this on another forum. Why are they ineffective below 100 hz? They were recommended to me by the same guy that said 49 hz was a problem for me.

Also, how do you calculate what a broadband bass absorbs? Because everybody has been telling me.

--Edit-- Sorry that this wasn't in studio design, don't know why I posted it here
 
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Whilst I am not disputing your sources (hard to without knowing where yuo were looking), I would suggest that you view this page first

Helmholtz resonators - John L Sayers

and then come back with more questions - this is the type of construction I was referring to (second diagram)

to achieve low freq absorption over a broad band you may want to limit the depth of the cavity so as to achieve your upper and lower limits.
 
bandcoach said:
Whilst I am not disputing your sources (hard to without knowing where yuo were looking), I would suggest that you view this page first

Helmholtz resonators - John L Sayers

and then come back with more questions - this is the type of construction I was referring to (second diagram)

to achieve low freq absorption over a broad band you may want to limit the depth of the cavity so as to achieve your upper and lower limits.
Click to expand...

I think the particular article I was reading was referring to a specific brand.

1) You did give me the numbers in the previous posts, but you were referring to them as modes. I looked up what axial and tangential modes meant, and they weren't specific corners, so does that mean I just want a broadband absorber that generally covers the frequencies from the lowest to highest?

2) Is that diagram a birds eye view?

3) The place I was talking about was various posts on gear slutz. I realize that they were talking about a specific brand, which is why it's important to take advice like that with grain of salt. One thing I am reading their though is that Helmholtz's are really hard to build to specific frequency (since any variation can knock it off) and I would be better off with broadband (From the sounds of it, they are two different things?). Somebody with similar specs had 4 inches of fiberglass covered In fabric recommended to him.
 
1) the axial, tangential and oblique modes are all resonant modes within the room. When you treat a room, you treat all three of these modes if you can - your tangential and oblique modes will be higher than your axial modes, but add to the colouring of the room and create a range of freqs that need treating generally below 100Hz

2) that diagram is a birds-eye view but can be tipped so it is wide at the bottom and thin at the top - you can even build them across the corner that way/ remember that it must be a sealed cavity (air-tight).

3) the construction is manageable as long as you use a straight edge and use a thicknesser and a jointer to control the straightness of edges and the thickness of individual slats - glue and nail gun them to the external board on the cavity box

Broadband simply means covering a range of frequencies - a Helmholtz resonator can be a single fixed frequency or a broad range of frequencies based on your design paradigm.

Some accurate measurements will allow me to offer some design advice.
 
Unfortunately I don't have the tools/or craftsmanship to pull something like that off.

Could I just treat with 4 inch thick fiber glass?
 
sheggs said:
crimsonhawk47 said:
sheggs said:
Double them up and make them 8 inches thick
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What about Length/width?
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Depends on the dimensions of the room but, floor to ceiling would be recommended (in the corners)
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how about you check out the Helms article and then advise appropriately?

Steven P. Helm: DIY Bass Traps

I say this, only because I know that you mean well, but the 4" thickness of the individual tiles is done via height, not depth and the dimensions of the corner traps are 24"x24"x34" as triangles - making the depth 8" means nothing in this context....
 
bandcoach said:
how about you check out the Helms article and then advise appropriately?

Steven P. Helm: DIY Bass Traps

I say this, only because I know that you mean well, but the 4" thickness of the individual tiles is done via height, not depth and the dimensions of the corner traps are 24"x24"x34" as triangles - making the depth 8" means nothing in this context....
Click to expand...


I wonder if I know how to make DIY traps and superchunks bandcoach ;)

There are obviously two approaches to bass trapping -

Superchunks - Basically filling the entire corner
Panels - Straddling panels in the corners or on the back wall

If you are using superchunks then cutting the slabs into triangles and placing into corners is the way forward
If you are making panels I would recommend 6 inches plus thick Why? -

Bass traps work by providing resistance, generally in the form of an insulation material with the right properties, specifically proper gas flow resistivity. When the energy in the room encounters the insulation material, friction causes the kinetic (motion) energy to be changed to thermal (heat) energy, which results in a loss of amplitude. That reduction in amplitude brings peaks down and valleys up by reducing the strength of one or more interfering waves. We experience that as a reduction in volume as peaks are decreased and an increase in volume when valleys are brought up.

 
I know that you know what to do, but you offered advice that was less than clear - it could be interpreted at so many levels that it needed clarification from you as to your intent - hence my gentle prodding.....
 
No problems bandcoach I was only teasing I understood your prodding :) and hint for more detailed answers
 
Well I got confused. Did you mean depth doesn't matter with superchunks?

Because with depth of just a rectangle straddling a corner, that would make a difference right?

Also, is there any reason not to do super chunks?
 
the depth of a super chunk is variable as it moves from the points where the hypoteneuse of your triangle meets the walls to a maximum at the center point of the hypoteneuse (if working with a 90/45/45 triangle) which in the a case of 24"x24"x34" would be something like 17" (more or less) and as a result the variable depth tunes the frequency trapped/absorbed as it changes - making it another form of broadband trap

whereas a wall-mounted trap/absorber will have a fixed depth and fixed absorption frequency unless you use the layout suggested by John L Sayer (angled along the wall - which changes the frequency upwards as it becomes shallower)
 
bandcoach said:
the depth of a super chunk is variable as it moves from the points where the hypoteneuse of your triangle meets the walls to a maximum at the center point of the hypoteneuse (if working with a 90/45/45 triangle) which in the a case of 24"x24"x34" would be something like 17" (more or less) and as a result the variable depth tunes the frequency trapped/absorbed as it changes - making it another form of broadband trap

whereas a wall-mounted trap/absorber will have a fixed depth and fixed absorption frequency unless you use the layout suggested by John L Sayer (angled along the wall - which changes the frequency upwards as it becomes shallower)
Click to expand...

Sorry for the confusion, to clarify if you have 4 inch slabs of rockwool / fibre glass there are two methods are building effective bass traps which are the most popular -

A) superchunks - basically as bandcoach is saying you cut the slab as per the article to fit into corners. If you follow the article you will get a normal size superchunks. If you use more slabs you can of course make them bigger. Bigger superchunks will be more effective at tackling the lows. Simple fact there is more material to absorb. However unless it is a big room it can be overkill (I.e. take too much liveliness out of the room) and also they take up a lot more room
B) build bass panels for the back wall and for corners. Basically when used in the corner you straddle them across the walls. Basically you are using less material so it is cheaper but not quite so effective. If I was making bass traps panels for back walls or corners I would make at least 6 inches thick
 
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