slot resonator vs panel absorber...my brain hurts

[jordya]

I think my brain is turning to mush from all the info I have absorbed over the last few days...

Ok, according to the SAE site, low-mid frequency absorbers are known as the slot resonator. This can be constructed using strips of wood going across the frame with different spaces between them, if you're looking for broadband absorbtion.

On that same page, it says you can also use pegboard instead, which makes it similar to a panel absorber.

On the next page which discusses low frequency absorbtion, they discuss using either hangers or panel absorbers.

Now, the question is why can't I use panel absorbers with a pegboard front all around my control room including the bass traps in the corner? Or maybe I can and I just dont see it. Is there anything wrong with doing this, or is it "better" to use actual slats on the walls and hangers on the low frequency bass traps? I am trying to find the easiest way to treat a room, and then make it more difficult from there. I just don't know where to start because of all the different ways people do it.

Thanks for the help...

Jordy A.

[AVare]

the question is why can't I use panel absorbers with a pegboard front all around my control room including the bass traps in the corner?

Do the math. Pegboard is too thin to amke an efective low frequency absorber. Double or triple the thickness? Do the math, it may be good.

Andre

[jordya]

Quoted from the SAE website:

"Another form of helmholtz resonator is created using perforated plywood - i.e. plywood with hundreds of holes in it. We call it pegboard in Oz, you see it in hardware stores holding up tools etc. If you place a panel of this over an air cavity like in a panel absorber not only do the little holes act like bottle necks the whole panel acts as a low frequency panel absorber!"

Now, I understand they are talking about a low-mid frequency absorber, but the last sentence states "the whole panel acts as a low frequency panel absorber." I take that as meaning it will work for low frequencies as well as low-mid frequencies. Is that a mistake?

The only thing I am starting to assume is pegboard panel resonators are good for side wall absorbtion and corner absorbtion can also be a panel resonator, but you need to use plywood instead.

Am I on the right track...?

[AVare]

I am confused. PAnels are sealed and helmholtz absorbers are not. Someone else will to jump in and clarify this.

Andre

[lex]

I think where you are getting confused is thinking the pegboard can replace a flat unperforated panel in a panel trap.

The only reason you would want those holes is if you were making a 'resonator' trap, where the holes would be able to function in some useful way. So, just use pegboard as a replacement for the wood slats in a resonator trap or don't use it. It will probably still resonate but won't absorb much if any lows without a sealed cavity behind it. You also wouldn't get a very broad absorbtion range unless you varied the depth of the cavity behind it since the holes are all the same size. That's what I figure.

Panel traps are more for the overall low frequencies. Resonators, slats resonators for example, are good for taking 'slices' out of the sound spectrum while keeping the frequencies you want intact.

I'm learning too so maybe a more experienced person can clear it up better for you. Give some specifics about your room, the dimensions, and I bet someone here will help you out regarding possible treatments.

Hope that helps mate. Aspirin works well too

[jordya]

Thanks Lex. Yeah, asprin does the trick nicely.

That does answer some of my questions. Mainly, I'm trying to plan the acoustic design for a room the does not exist yet. My control room, once it is built, will be 13'L x 11'W. The ceiling is not yet determined, but I have 12' to work with.

I have gotten some great ideas and drawings on the studio design portion of this forum, but I am still a little confused regarding acoustics. In the drawing of the control room,

http://www.johnlsayers.com/phpBB2/viewt ... c&start=15

the back corners and front corners are thought to have acoustic hangers placed in them. Would that be all I need for a room of this design and size, or do I need other acoustical goodies like resonators, etc. If so, where is a good place to put them?

thanks for the help...

[lex]

http://www.johnlsayers.com/HR/index1.htm

Scroll to the bottom. There is a good basic layout for a rectangular room.

What does your room sound like? Wait till you hear what it sounds like then treat it. In general you want bass trapping for a room that size. I would try basic fibreglass panels stacked 2 high in the corners to start with. If that's not enough try something more elaborate.

I see you have a nice height to work with for your ceiling. Take advantage of that and maybe just trap the top 3 feet with hangers and put a false cloth ceiling like some have done here. If that seems like a lot of work try suspended fibre glass panels. This will only take up about 6 inches at most and the rest is left for the sound to dissipate and move.

Go for a hard reflective floor and absorptive ceiling. Make sure there are no parallel surfaces in your room. Try to design the room so there are few early reflections to the microphone or listening position.

If you're going to get 1 book on acoustics, try
this one: ("Master Handbook of Acoustics" F. Alton Everest)

Take a look at this:

http://www.realtraps.com/articles.htm
http://www.saecollege.de/reference_material/index.html


My room sounds boomy in recordings so I need mostly bass treatment. I also want to angle the walls to avoid standing waves and flutter echo. I was thinking about diffusion for my room but I think the slats will provide that along with the angle. I will design my slats so that they hit problem mode frequencies. The variation in depth behind the slats should broaden the range of frequencies that are tamed.


Here's my room:

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=2997

[lovecow]

Jordy,

Don't know if this will help, but I've been reading the Cox & D'Antonio book a bit lately (Acoustic Absorbers and Diffusers—Theory, Design and Application). Chapter 6 covers "Resonant Absorbers." Most of what they talk about pretty much confirmed what I'd learned from other sources - and from experience - over the years. I.e., panel and/or membrane traps as well as "Helmholtz"-type traps can be effective. The former, if built properly, tend to be a little more effective than the latter (on a per unit area or volume basis). The latter are easier to build and apply. Membrane and panel traps are simply more sensitive to slight variations in mounting, membrane/panel weight, etc. They are also subject to resonate at (non-linear) harmonics above the design frequency and could reradiate energy into the room if designed or built poorly. FWIW, I have found that unless you build them to within about 1/16" tolerances with a very rigid mounting, you are not likely to gain as much from them as slot or perforated absorbers of the same area.

As to your question with pegboard, off-the-shelf stuff tends to be 1/8" to 1/4" thick with 1/4" diameter holes spaced 1" o.c., non-staggered. This type of layout and sizing of the holes typically leads to absorption in the mid-range, as opposed to the low-end, depending on the thickness of the backing, which should - as others have pointed out - be filled with "fuzz." If you are going to build a perforated absorber, I would suggest playing around with Chris Wheatley's spreadsheet, or at least using the design formulae given in the other resources above. (Careful on the slot resonator equation - many sources have printed a bogus version of this equation. There's a thread in this forum that details it.)

Hope this helps!!!

[knightfly]

Lex, I edited your post to get rid of the long link that forces people to scroll sideways for the entire rest of the topic; if you go back and edit your post, you can see the syntax that does this - the way I remember all the crap that's necessary is to keep a small file on my desktop called "tiny URL syntax", then I just cut and paste the parts of that before and after any long links - here is the body of "tiny url" so you can use it next time -

TextYouActuallySee

Thanks... Steve

[lex]

No problem, sorry about that.

[knightfly]