[mikeeastman]

I'm building a corner bass trap above a cabinet and was going to use 1/4" oak ply with a couple coats of clear, will this work or would something else work better? Also should I put sound material on bottom as well as the sides? The ceiling is wood slats over 12" air gap, should I cover it or leave it?

[Ethan Winer]

You need to describe what you intend - "1/4" oak ply" doesn't really explain much. I can tell you that most bass traps are made from rigid fiberglass, with any wood used only as a frame.

--Ethan

[mikeeastman]

Sorry for lack of info. I'm coming out 3ft from the corner and covering walls with rigid fiberglass and was going to cover opening diagonally with rigid fiberglass with an 1" air gap and then cover that with the 1/4" ply, I also was going to put a layer of rigid fiberglass on the top and bottom of the inside of the trap. As I'm a beginner at all this any help would be appreciated.

[steve2701]

A couple of things come to my mind here - I'm sure Ethan will say if this is wrong though:-
If these are corner traps in front of your listening position then I wold think covering them with ply should be ok - but the ply really needs to be lightly glued to the rockwool (carpet spray glue?) as if there is a gap left then it could resonate causing you more problems?
If this is a rear corner trap behind the listening position then I would at least try listening to the trap uncovered first as you dont want to be reflecting mids and highs to your listening position with the plywood.
3' is a great size for the trap.
These are mine - I like oak 



construction:-

[sl_1800]

Those are nice looking traps.   

[Ethan Winer]

I'm coming out 3ft from the corner and covering walls with rigid fiberglass and was going to cover opening diagonally with rigid fiberglass with an 1" air gap and then cover that with the 1/4" ply, I also was going to put a layer of rigid fiberglass on the top and bottom of the inside of the trap.

Again, I don't know what opening you're describing. Bass traps need to be much thicker than one inch. The thick corner traps Steve showed are one great way to do it.

--Ethan

[davidrs]

The thick corner traps Steve showed are one great way to do it.

Ethan,

I am a complete newbie in this area. Came across the thread so asking a quick question, before I do some searches on AC and elsewhere.

Will a couple of rolls of wool-rock, set on top of each other, and covered with cloth (for a simple cosmetic touch) in a corner be a good starting point?

Thanks,

David.

[Cheerwino]

Mike and davidrs:

In addition to the good folks here on AC, I've found these articles on acoustics from RealTraps (Ethan's company) and GIK to be helpful in learning the basics. There are also some good DIY options around, too.

And from what I've read and experienced, rolls of insulation in corners do work, but have a very low WAF.

[bpape]

As an inexpensive solution, you can certainly use just cloth covered bales of insulation.  It's going to be somewhat reflective at high frequencies due to the plastic but will work just fine in the bass.

Bryan

[steve2701]

Yup, worked for me to - obviously. I made sure my bales didn't come un-done by putting pallet tape round them then took the plastic off of them.
Mad really as I put craft over the outer rockwool as these are front traps. Then covered to be rather more appealing than bare yucky rockwool. Why it has been turned that brown colour in the UK is beyond me - it's obviously been made at a hotter temp as the glass strands almost appear burnt. They claim better efficiency as insulating and acoustics though..

[davidrs]

Thanks: Cheerwino, bpape, and steve2701

Can standard Fiberglass wool be substituted for the Rockwool?

Does shape play a role?  Cubes, vs. bales, vs. ?

And is it advisable to remove the plastic, as Steve did?

Thanks,

- David.

[steve2701]

Hi David,
              it is a rather large subject and just trying to take chunks of information is not always easy to do, or easy to give info on as we dont know the application you are going to use it on.
The most important thing to get is that the DENSITY of what is being used is very important. Rockwool and fibreglass are very similar and for the best part can be said to be the same.
OK - lets say you seriously want to improve your listening and want a 'reflection free zone' where you sit. Note we are not trying to kill the room dead, it still needs to maintain life (absolutely vital actually) what we want is a nice even zoom response.
For most this will mean keeping the front part of the room 'live' with mids and highs but trapping bass. The rear will be used to kill highs and mids and also trap bass. First reflection points will trap mids and highs.
Yes, fluffy fibrglass can be used in a bass trap - but it is best to keep it compressed in the roll shaps and not opened out as this is what gives it the required density. For front traps keep the plastic wrapper on as this reflects mids and highs. For rears it really needs to have the plastic removed and be kept compressed somehow.
As above this is a huge subject to get your head around, but the results are fantastic - way better bang for buck than any amount of upgrade electronically. This just needs to be tempered by the fact that most listening spaces are shared with family and need to be treated sympathetically.
http://www.ethanwiner.com/acoustics.html
Reading the above link will set you right - it started me on my journey and it was huge fun along with it.
Good luck - it is worth the effort and experimenting.

[bpape]

Just a clarification.  The need for density in bass absorption goes down as thickness goes up.  Once you get beyond about 6-8", you can use a much lighter density provided the gas flow resistivity is correct.  Thickness is the real key.  If I had a choice of 12" of fluffy wall insulation or 4" of 6-8lb rigid FG or mineral wool, I'll take the 12" of thickness over the thinner but more dense material.

Whether you leave any kind of facing on it really depends on what you want the absorber to do.  The less high frequencies you want absorbed, the more of a facing you want on the material.  Just understand that as the facing gets more dense and the denser the core material, the more you'll get a 'hump' in the absorption curve at a given subset of frequencies (and it's not always at the bottom of the range)

Bryan

[Cheerwino]

You can also check out Ethan's "educational video" Acoustic Treatment Exposed for a more comprehensive "education". 

He has many of the articles he wrote linked from this page.
http://www.ethanwiner.com/articles.html#Audio%20Magic

[davidrs]

Thanks everyone, for your feedback.

I need to start educating myself, so off to bass trap school.

My needs are pretty basic. Low frequency dampening in the corners behind the speakers and perhaps in an offset center position , behind the speakers since the active woofers are side firing, set-up on the inside, and are toed in.

As for cosmetics and compromise around WAF, it's my room - so no issues there.

[mikeeastman]

Ok, finally got some time off, so let me start all over again Here is a floor plan and some pics. I want to put a trap in the left corner above the cabinet, after you comments and suggestions I'm going to put 4 layer of 1/2" fiberglass (that is designed to suppress sound in large air ducts, it is about 70-80% as dense as 703) on the walls then tightly roll up some and fill the space with it then I would run 4 layers across the corner diagonally and cover with same canvas I covered ceiling with. The frequencies I need to handle are 50-65hz and 18-25hz as a newbie I greatly appreciate the help up to now and any further suggestion. Also I was wondering if I could use that pop out window, on the right side, as some kind of trap?

[steve2701]

Mike,
        Not certain just which cabinet you are refering to - but if it's the one right next to the window it would be a waste of time without doing anythng else.
If you are talking about the whole range of cabinets over the kitchen worktops then yes, that will help, but results will be variable as you are not symetrical in your approach here. Are the ceiling mounted speakers used as your main source or the open baffles - or both?
We dont have a lot of info to work with at present.

There appear to be plenty of corners where traps will work well though.
Fixing a trap in the window space may help - but would you need it to be movable as surely you dont want to lose the outlook? Plus is there a place to put one on the opposite wall - maybe just leave the window as is and put a diffusor on the opposite wall directly opposite the window? This will give symetry?

[mikeeastman]

Here is pic of bass trap. The window I was talking about is the one that is popped out ( see floor plan and new pics ) on right side of room.  I thought I could make something that was removable, but as window is for light only, no real view, it could be left in most of the time  The ceiling mounted speakers are not used in the main system they are for my wife's system.

[bmckenney]

That trap above the kitchen cabinets looks like a waste of time to me, as in not very effective.  And it will wreck the look of the kitchen cause it looks f-ugly.

[mikeeastman]

Its not a kitchen it's a studio/office/music room. When I finish trimming it out it will be hardly noticeable.It must just be my imagination that it seams to have helped, but I will know more when my system get reEQed.